Temperature-Tuned Performance of MXene-NiO Nanocomposites for High-Efficiency Supercapacitors

Temperature-Tuned Performance of MXene-NiO Nanocomposites for High-Efficiency Supercapacitors | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Temperature-Tuned Performance of MXene-NiO Nanocomposites for High-Efficiency Supercapacitors Tariq Saeed, Javed Iqbal, Aamir Ahmed This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7309937/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The current study centers on the design and optimization of electroactive materials for energy storage purposes. We present the preparation of a noble series of (MXene) x (NiO) 1−x nanocomposite electrodes (where x = 1, 0.75, 0.50, 0.25, 0), prepared in varying stoichiometric ratios, which exhibit exceptional performance as supercapacitor electrodes. Detailed structural and morphological characterizations were conducted to gain insight into the underlying physical properties of the composites. Electrochemical performance was systematically evaluated using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS). The optimized electrode delivered a high energy density of 17.7 Wh kg − 1 and a power density of 450 W kg − 1 . Additionally, it displayed impressive cyclic stability, retaining 114% of its initial capacitance after 1200 cycles. The improved functionality is assigned to both the synergistic effect of the nanocomposite constituents and the tailored nanostructured architecture of the electrode. Nickel oxide (NiO) MAX phase (Ti3AlC2) MXene (Ti3C2) Supercapacitor Nanostructures Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 1. Introduction Electrical energy is essential to modern life, powering everything from personal devices to industrial and agricultural operations. Historically, fossil fuels have dominated the worldwide energy mix, supplying 81% of primary energy in 2019 (IEA). While critical to economic and technological development, their widespread use has led to significant environmental harm, particularly through CO 2 emissions driving climate change [ 1 ], [ 2 ], [ 3 ]. Despite the promise of renewables, the transition to fully sustainable energy systems remains incomplete. Electrochemical energy storage, particularly lithium-ion batteries, has rapidly advanced due to its high energy density, stable output, and flexibility across regions, outperforming other systems like flow and lead-acid batteries [ 4 ], [ 5 ]. While lithium-ion batteries and other advanced rechargeable batteries provide satisfactory energy densities, they still face shortcomings, including low power density [ 6 ]. Supercapacitors have gained widespread interest due to their distinctive benefits, including superior specific capacitance, speedy charge-discharge rates, and impressive cycling stability [ 7 ]. While supercapacitors offer numerous advantages, their primary limitation is their relatively low energy density, ranging from 5 to 20 Whkg − 1 , which is approximately 20 to 40 times smaller in comparison to lithium-ion batteries (100–265 Whkg − 1 ) [ 8 ]. The charge-storage capacity of supercapacitors (SCs) is heavily affected by the selection of both electrolyte and electrode materials. Although both components affect the operating voltage of SCs, the capacitance is primarily dictated by the properties of the electrode material [ 9 ], [ 10 ], [ 11 ]. Consequently, extensive research efforts are focused on developing innovative, high-performance electrode materials for SCs. Among various electrode materials, two-dimensional (2D) materials have garnered the most attention owing of their enhanced specific surface area (SSA), which enhances specific capacitance in supercapacitors [ 12 ]. MXenes are a novel class of 2D materials with structural similarities to graphene and molybdenum disulfide. The discovery of Ti 3 C 2 in 2011 sparked extensive research into the unique properties of the broader MXene family [ 13 ]. The standard expression for MXenes is M n+1 X n T x , where M signifies an early transition metals (such as Ti, Sc, Mo, Hf, V, Nb, etc.), X signifies carbon or nitrogen, and T x signifies surface terminations, including O, OH, and F [ 14 ]. MAX phases serve as the primary precursors for synthesizing MXenes. These phases are specified by the standard formula M n+1 AX n , where M signifies early transition metals, A is an element from groups IIIA or IVA (13–14), and X represents carbon or nitrogen, with the possibility of forming carbonitride compounds. The value of n extends from 1 to 4 [ 15 ]. However, MXenes face challenges in practical applications due to their tendency to oxidize and restack, which reduces the available surface area and negatively impacts their capacitive performance [ 16 ], [ 17 ]. To overcome these critical challenges for large-scale production, integrating MXene and other materials together such as polymers, carbide-based materials (CNTs, GO/rGO), metal oxides, and layered transition metal dichalcogenides has proven to be an efficient and straightforward approach for developing MXene nanocomposites [ 18 ]. Metal oxides, including NiO [ 19 ], RuO 2 [ 20 ], Fe 3 O 4 [ 21 ], Fe 2 O 3 [ 22 ], MnO 2 [ 23 ], and Co 3 O 4 [ 24 ] are already being investigated as electrode materials for supercapacitors, showing promising potential. Despite extensive research on RuO₂ and IrO₂ as pseudocapacitive electrode materials, their practical applications are constrained by their high cost. In contrast, NiO is regarded as a viable alternative due to its abundance, accessibility, affordability, customizable morphology, high surface area, and comparable electrochemical performance. NiO exhibits a relatively high specific capacitance and is straightforward to produce. However, transition metal oxides (TMOs) like NiO generally demonstrate enhanced resistance at the electrode/electrolyte boundary at high rates, along with reduced electronic conductivity, ionic diffusivity, and cycle life. To effectively address these challenges, an effective strategy is to integrate a flexible and conductive 2D framework that facilitates the uniform distribution of TMO nanostructures. In the context of supercapacitor applications, these electrode materials provide several architectural advantages. Firstly, the specific surface area of stacked MXene sheets is substantial. By alleviating the inactive surface area caused by restacking, the incorporation of NiO onto the nanosheets generates additional active sites. Secondly, MXene enhances the conductivity of the MXene-NiO nanocomposite, thereby improving its electrochemical performance [ 25 ], [ 26 ]. This study demonstrates the synthesis and electrochemical evaluation of (MXene) x (NiO) 1–x nanocomposites as electrode materials for supercapacitors. The research focuses on charge kinetics and enhanced energy storage performance compared to pristine MXene and nickel oxide. These findings offer valuable insights for advancing 2D MXene-based electrode design in energy storage applications. 2. EXPERIMENTAL DETAILS 2.1. Materials For this experiment, analytical reagent grade chemicals were utilized. Nickel chloride hexahydrate (NiCl.6H 2 O), sodium hydroxide (NaOH), polyvinylidene fluoride (PVDF), and carbon black were procured from Sigma Aldrich. Titanium aluminum carbide (Ti 3 AlC 2 ), MAX phase was obtained from Mac Chemicals. Double distilled water was used to prepare all solutions. The compounds were used in their primary form devoid of any additional alteration or purification. 2.2. Synthesis of NiO Nickel oxide (NiO) nanoparticles were synthesized via the hydrothermal method. Precursors of nickel chloride hexahydrate (NiCl.6H 2 O) and sodium hydroxide (NaOH) as well as distilled water as a solvent were utilized. Two separate beakers were used to prepare solutions. In the first beaker, 3.8 grams of NiCl·6H₂O was mixed in 80 ml distilled water. In the second beaker, 50 ml of distilled water was combined with 2 grams of NaOH. The solution from the second beaker was slowly added to the first beaker to maintain a pH of 10, while continuously stirring for one hour at room temperature. Then, the solution was transported into Teflon autoclave and heated at 170℃ for 14 hours. Once the autoclave had cooled to room temperature, distilled water was utilized to rinse the greenish precipitate that had developed, dried at 70℃ for overnight. The resulting sample was grounded and annealed at 600°C for 2 hours in a muffle furnace and schematic diagram shown in Fig. 1 . The NiO nanoparticles were carefully stored in anticipation of their upcoming characterization and utilization. 2.3. Synthesis of MXene To prepare MXene (Ti 3 C 2 ), 30 wt% hydrofluoric acid (HF) was used, into which 1 g of MAX phase (Ti₃AlC₂) was gently added. This mixture was stirred in a Teflon bar for eight hours at 55°C. Afterward, distilled water was added, allowing the Ti₃C₂ MXene to settle at the bottom while the Al layer floated to the top. The MXene was then repeatedly rinsed until it reached a neutral pH and subsequently dried overnight at 60°C, and schematic diagram is shown in Fig. 2 . 2.4. Preparation of MXene/NiO nanocomposites In this research, an ex-situ approach was employed to synthesize composites of MXene and NiO. The nanocomposites' concentrations were controlled by mixing varying ratios: 0.75 of NiO with 0.25 of MXene, equal amounts of 0.50 each, and 0.25 of NiO with 0.75 of MXene. Throughout a one-hour grinding process, acetone is slowly introduced to the mixture prepared in a mortar and pestle. Subsequently, the composite undergoes heating at 70ºC for a duration of 12 hours after thorough grinding, and schematic diagram is shown in Fig. 3. 2.5. Materials characterizations The samples were analyzed for their phase composition and crystallographic structure using an X-ray diffractometer operating with Copper-Kα radiation (λ = 1.5406 Å), providing detailed insights into their structural properties. Additionally, FTIR spectroscopy was conducted over the 4000–400 cm − 1 range to explore the molecular framework and identify key chemical interactions within the materials. UV-Vis spectroscopy was employed to experimentally explore the band gap energy of the materials, offering insight into their optical behavior. The optical band gap was precisely calculated using Tauc plots, allowing for a detailed assessment of electronic transitions. Scanning electron microscopy (SEM) was deployed to analyze the morphology of the nanostructures, providing detailed insights into their size, shape, and surface characteristics. 2.6. Electrochemical characterizations Electrochemical characterizations were conducted at room temperature, low temperature and high temperature through a Gamry (Interface 5000 E) Electrochemical Workstation. A three-electrode system was employed, with nickel foam serving for the working electrode, Ag/AgCl for reference, and platinum wire for the counter. A 1M KOH solution served as the electrolyte. To assess the electrochemical performance, electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge (GCD), cyclic voltammetry (CV), coulombic efficiency, and retentivity curves were recorded. Cyclic voltammetry (CV) scans were recorded at scan rates between 10 mVs − 1 and 100 mVs − 1 , within a potential window of 0.2 V to 0.6 V. Galvanostatic charge-discharge cycling was executed at current densities spanning from 0.2 Ag − 1 to 0.8 Ag − 1 . Using CV and GCD, the specific capacitance was assessed using Eqs. ( 1 ) and ( 2 ). Additionally, the energy density and power density were elegantly figured out using Eqs. ( 3 ) and ( 4 ), respectively. $$\:{C}_{s}=\frac{A}{mK\varDelta\:V}\:\left(F{g}^{-1}\right)$$ 1 $$\:{C}_{s}=I\frac{\varDelta\:t}{m\varDelta\:V}\:\left(F{g}^{-1}\right)$$ 2 $$\:{E}_{g}=\frac{1}{2}{C}_{s}\varDelta\:V\:\left(Wh{Kg}^{-1}\right)$$ 3 $$\:{P}_{g}=\frac{{E}_{g}}{\varDelta\:t}\:\left(W{Kg}^{-1}\right)$$ 4 where A is the area of the CV curve, m is the mass of active materials, k is the scan rate, ∆V is the potential window, Δt is the discharge time and I denotes the response current [ 25 ]. 3. RESULTS AND DISCUSSIONS 3.1. Structural Studies The distinctive diffraction peaks of Ti 3 AlC 2 observed at approximately 10.2° and 39.2° are associated with the (002) and (104) planes, respectively [ 27 ]. After HF etching, the reduced intensity of these peaks indicated a significant loss of crystallinity and structural deformation [ 28 ]. For Ti 3 C 2 MXene, diffraction peaks were identified at 2θ values of 9.6°, 18.5°, and 60.5°, associated to the (002), (006), and (110) planes [ 28 ]. The characteristic peaks of the MXene/NiO composites, located at 37.3°, 43.2°, 62.4°, 75.4°, and 79.1°, can be indexed to the NiO phase, specifically the (111), (200), (220), (311), and (222) planes (JCPDS Card No. 00-001-1239) [ 29 ]. The XRD pattern of the MXene/NiO composites also displayed the distinctive peaks attributed to MXene, indicating the NiO has been successfully incorporated into MXene [ 30 ]. The (002) peaks of all MXene and MXene/NiO composites exhibit a shift toward lower 2θ values compared to the MAX phase, primarily due to the increased interlayer spacing between the MXene sheets, which is occupied by intercalants such as water and NiO. During the etching process, the removal of Al layers not only etches the MXene but also causes delamination, resulting in an expanded interlayer gap. The broadening of the (006) plane indicates increased interlayer spacing, confirming NiO nanoparticle intercalation within MXene layers. This expansion introduces more active edge sites and open channels, enhancing ion transport and structural stability. The average crystallite size of the MXene/NiO nanocomposite was determined from XRD data using Debye Scherrer formula. The average crystallite size of the MXene/NiO nanocomposite was found to be approximately 268Å. The measured crystallite size of (MXene) 0.75 (NiO) 0.25 is smaller than that of the other composites listed in Table 1 . The lowering of average crystalline size reflects the effect of NiO on MXene, which improves the electrochemical performance over that of pure MXene. Figure 4 depicts the XRD diffractograms of the MAX phase, MXene, and nanocomposites with NiO. f) (MXene) 0.50 (NiO) 0.50 g) (MXene) 0.25 (NiO) 0.75 Table 1 The various structural parameter values Sample Crystallite Size (Å) a \(\:=\) b (Å) c (Å) Volume (Å 3 ) Strain(%) NiO 295 4.171 4.171 72.56 0.293 (MXene) 0.25 (NiO) 0.75 315 4.171 4.171 72.56 0.685 (MXene) 0.50 (NiO) 0.50 284 4.171 4.171 72.56 0.566 (MXene) 0.75 (NiO) 0.25 268 4.171 4.171 72.56 0.653 MXene 332 3.071 20.51 164.8 0.680 Scanning Electron Microscopy (SEM) is utilized to investigate the surface morphology and assess the structural integrity of the synthesized samples. High-magnification SEM images, presented in Fig. 5 (a–f), reveal distinct structural characteristics: NiO exhibits nanograin-like morphology, MXene forms nanosheets, and the NiO/MXene composite showcases nanosheets elegantly adorned with nanograins. In Fig. 5 a, the delaminated multilayered MXene nanosheets appear smooth and pristine, with well-defined edges. Meanwhile, Fig. 5 b illustrates the uniform dispersion and slight aggregation of NiO nanograins, highlighting their structural integrity. Due to their high surface energy and strong surface tension, NiO nanoparticles have a natural tendency to agglomerate, leading to the formation of larger nanoparticle clusters[ 31 ]. After the synthesis of the nanocomposite, NiO nanoparticles uniformly coat the Ti 3 C 2 surface and intercalate between its layers (Fig. 5 e, f), providing clear evidence of the successful formation of the Ti 3 C 2 /NiO nanocomposite which validates the XRD results. The intercalation of NiO nanoparticles between the MXene layers effectively inhibits their restacking, thereby boosting electrolyte accessibility and elevating the electrochemical response of the composite. The vibrational modes of NiO, MXene and its nanocomposites were identified through FTIR study. FTIR spectra were recorded in the limit of 400–4000 cm − 1 using Fourier mapping, with a KBr pellet serving as a reference. Figure 6 presents the FTIR spectra highlighting various vibrational modes for NiO, MXene, and (MXene) 0.75 (NiO) 0.25 . The absorption band at 472 cm⁻¹ was linked with the Ni-O vibrational bond. The distinctive peaks at 1741 cm − 1 , 1375cm − 1 and 1015cm − 1 were due to C = O, OH and C-O respectively. For pure MXene, the absorption bands at 460 cm − 1 and 1738 cm − 1 were due to the Ti–C and C = O vibrations, respectively. The broad peak between 3000 and 3500 cm⁻¹ corresponds to an OH bond. Common bands of both appeared in (MXene) 0.75 (NiO) 0.25 nanocomposite. The downward movement of peaks suggests the strong interaction between NiO and MXene [ 25 ], [ 32 ], [ 33 ], [ 34 ]. The nonexistence of extra modes validates the cleanliness of the electrode surface and aligns well with the XRD results, reinforcing the material's structural purity. The optical properties of (MXene) x (NiO) 1−x nanocomposites have been examined by UV-vis absorption spectroscopy. The absorption peaks for pure MXene and NiO were recorded at 310 nm and 225 nm, respectively. For the (MXene)ₓ(NiO) 1−x composites, a pronounced red shift in the absorption peaks was observed, occurring at 317 nm, 320 nm, and 325 nm for x = 0.75, 0.50, and 0.25, respectively, as the MXene content decreased. The presence of a single absorption peak in all spectra indicates the synthesis of a single phase in the nanocomposites, further corroborating the phase purity results obtained from XRD and SEM analyses. The optical energy gap of the nanocomposites was figured out using the Tauc relation, \(\:{\left(\varvec{\alpha\:}\mathbf{h}\varvec{\nu\:}\right)}^{\mathbf{n}}=\varvec{\beta\:}(\mathbf{h}\varvec{\nu\:}-{\mathbf{E}}_{\mathbf{g}})\) . By plotting \(\:{\left({\alpha\:}\text{h}{\nu\:}\right)}^{\text{n}}\) versus photon energy ( \(\:\text{h}{\nu\:}\) ) with \(\:n=2\) , the band gap energy \(\:{E}_{g}\) ​ was determined by drawing a tangent to the curve at the onset of the linear region [ 35 ]. The estimated band gap energy for NiO is 3.40 eV and for MXene is 1.46eV. For the (MXene)ₓ(NiO) 1−x nanocomposites, the energies gap was figured out to be 3.28 eV, 3.19 eV, and 3.08 eV for x = 0.75, 0.50, and 0.25, respectively. The band gap energy of NiO decreased with the incorporation of MXene, which may be associated with numerous factors, including the lowering of crystallite size and the formation of localized states of the oxides between the band gap as apparent from XRD, FTIR as well as SEM data. Figure 7 corresponding Tauc plots and variation in the band gap energy is depicted in the Ragone plot. 3.2. ELECTROCHEMICAL STUDIES The cyclic voltammograms shown in Fig. 8 reveal the electrochemical characteristics of NiO, MXene, and their composites. All CV profiles display two well-defined Faradaic peaks, indicating active redox reactions taking place at the electrode surface during both forward and reverse sweeps. Interestingly, as the scan rate increases, a noticeable shift is observed in the voltammograms reduction peaks drift toward the cathodic side, while oxidation peaks shift anodically highlighting the dynamic electrochemical response of the material [ 36 ]. Moreover, the symmetrical shape of the voltammograms reflects the high reversibility of the electrochemical processes, suggesting efficient charge-discharge behavior and rapid ion diffusion within the electrolyte. This symmetry is a clear indication of a well-balanced redox mechanism occurring at the electrode surface. Notably, the specific capacitance (C s ) reaches its peak value at the lowest scan rate of 10 mV s − 1 , as the ions have ample time to penetrate deeply into the porous structure of the electrode material. As the scan rate rises, there is a continuous reduction in specific capacitance. This drop is assigned to the limited time available for ions to fully diffuse into the inner active sites, resulting in reduced electrochemical utilization of the material at higher scan rates [ 37 ]. The current response observed in the voltammograms serves as a clear reflection of the electrochemical activity of the samples. Among them, pure MXene exhibits the lowest response current, indicating minimal electrochemical activity. However, as the concentration of NiO increases, a noticeable enhancement in activity is observed. At a scan rate of 10 mVs − 1 , the (MXene) 0.75 (NiO) 0.25 nanocomposite exhibited a significantly higher specific capacitance of 482 Fg − 1 , compared to pristine MXene (137 Fg − 1 ), NiO (326 Fg − 1 ), and all other nanocomposites listed in Table 2 . As shown in Fig. 8 , the cyclic voltammetry (CV) data indicate a significantly larger CV area for the Ti 3 C 2 /NiO composites, highlighting the synergistic interaction between NiO and Ti₃C₂ as a key factor contributing to the enhanced capacitance of the composite due to addition of NiO, which hinders the restacking of MXene layers. Table 2 Specific capacitance values determined through CV Sample Specific Capacitance (C s ) Fg − 1 10mVs − 1 20mVs − 1 40mVs − 1 60mVs − 1 80mVs − 1 100mVs − 1 NiO 326 270 218 181 155 147 (MXene) 0.25 (NiO) 0.75 216 208 201 175 162 151 (MXene) 0.50 (NiO) 0.50 309 267 221 201 185 171 (MXene) 0.75 (NiO) 0.25 482 457 402 359 325 295 MXene 137 119 96 72 46 23 Figure 9 presents the charge–discharge profiles, showing the variation of potential with time at current densities between 0.2 A g − 1 and 0.8 A g − 1 . The nonlinear voltage–time characteristics of NiO, MXene, and (MXene) x (NiO) 1−x align with the expected behavior of pseudocapacitance [ 38 ]. Results revealed that (MXene) 0.75 (NiO) 0.25 exhibited the highest specific capacitance of 255 Fg − 1 at 0.2 Ag − 1 . The subsequent specific capacitances were 198 Fg − 1 for (MXene) 0.50 (NiO) 0.50 , 193 Fg − 1 for (MXene) 0.25 (NiO) 0.75 , 30 Fg − 1 for NiO, and 68 Fg − 1 for MXene. The composite (MXene) 0.75 (NiO) 0.25 exhibits a calculated energy density of 17.7 Whkg − 1 and a power density of 450 Wkg − 1 , representing a significant advancement for supercapacitor applications. At higher current densities, both charge and discharge times are reduced, leading to a lower capacitance. This reduction occurs because, at elevated current densities, the charge/discharge rates increase, limiting the time available for electrolyte ions to entirely diffuse onto the electroactive surface area [ 39 ].Conversely, at lower current densities, the ions have sufficient time to fully access and replenish the electroactive surface, optimizing capacitance. Electrical impedance spectroscopy (EIS), conducted over a broad frequency range of 1–100 kHz, was employed to comprehensively analyze various physical and electrochemical parameters. To further interpret the data, Nyquist plots were utilized, offering valuable insights into the material's resistive and capacitive behavior. In a typical Nyquist plot, the real part of impedance (Z ’ ) on the x-axis represents the resistive characteristics of the electrode material, while the imaginary part (Z ’’ ) on the y-axis reflects its reactive or capacitive nature. As the applied frequency varies, the impedance response transitions between resistive and capacitive behavior capturing the dynamic performance of the material within a supercapacitor system. [ 40 ]. In a Nyquist plot, the high-frequency region reflects resistive behavior, while the mid-to-high frequency zone reveals key physical properties like electroactive layer thickness, morphology, and pore size critical for assessing electrode performance[ 41 ]. The solution resistance (Rs), determined from the x-axis intercept of the Nyquist plot, represents the resistance offered by the porous electrode to electrolyte penetration. A lower Rs value signifies enhanced ion accessibility and more efficient electrolyte diffusion into the electrode’s porous network[ 42 ]. Figure 10 displays the Nyquist plots for different concentrations of (MXene) x (NiO) 1−x (x = 1, 0.75, 0.50, 0.25, 0). In electrochemical impedance spectroscopy, the solution resistance Rs is expressed by the intercept on the Z ’ -axis and comprises the resistance of the electrolyte solution along with the contact resistance at the interface between the electroactive material and the current collector. The diameter of the semicircle is approximately corresponding to the charge transfer resistance R ct across the electrode/electrolyte interface. R s of the (MXene) x (NiO) 1−x (x = 0.25, 0.50, 0.75) electrodes can be calculated to be 0.19 \(\:{\Omega\:}\) , 0.25 \(\:{\Omega\:}\) and 0.22 \(\:{\Omega\:}\) respectively, lying between the MXene (0.28 \(\:{\Omega\:}\) ) and NiO (0.10 \(\:{\Omega\:}\) ) electrodes. A negligible diameter suggests lower Rct resistance in the material. Consequently, reduced resistance, or higher conductivity, of electrode materials makes them more suitable for supercapacitor applications, as less energy is lost during the charge/discharge cycle. The inclusion of NiO is suggested to enhance charge transfer efficiency within the composite electrode. To evaluate cycling stability, the samples were subjected to 1200 charge-discharge cycles at a current density of 1Ag − 1 . Notably, the (MXene) 0.75 (NiO) 0.25 composite demonstrated superior capacitance retention compared to pure MXene, with respective retention values of 97% and 114%. Both pure MXene and its composite exhibited similar coulombic efficiencies of approximately 96%. The MXene-NiO composite thus presents a compelling candidate for electrochemical storage devices (ESDs), delivering an advantageous balance of enhanced capacitance retention and nearly unchanged coulombic efficiency qualities essential for high-capacity, high efficiency applications. The electrode's capacitance increased during the initial cycles as a consequence of the activation process [ 43 ]. Figure 11 represents the cyclic stability and coulombic efficiency different samples. 3.3. Effect of temperature When the (MXene) x (NiO) 1−x ( \(\:x=0.75\) ) composite was tested in a 1M KOH electrolyte at 0°C, a significant decrease in capacitance was observed, dropping to 44 Fg −1 compared to room temperature. This substantial reduction, as indicated by the CV curves, suggests that the lower temperature adversely affects the material's ability to store and release charge. At 0°C, the kinetic processes that facilitate charge transfer and ion diffusion are hindered, leading to a much lower capacitance. Furthermore, galvanostatic charge-discharge (GCD) tests revealed a noticeable decrease in discharge time at 0°C compared to room temperature. This shorter discharge time is indicative of a reduced energy storage capability, as the material's ability to sustain a charge under lower temperatures is compromised. Electrochemical impedance spectroscopy (EIS) further supported these findings by showing an increase in solution resistance to 1.12 ohms at 0°C, compared to the sample's resistance at room temperature. The increased resistance highlights the challenges in charge transfer and ionic movement within the electrolyte and composite material at lower temperatures. This rise in resistance is likely to contribute to the overall decrease in electrochemical performance, as higher resistance impedes the efficient flow of electrons and ions, leading to diminished capacitance and faster discharge rates. These results collectively underscore the critical impact of temperature on the electrochemical performance of the MXene/NiO composite, particularly highlighting the challenges faced at lower operating temperatures. When the (MXene) x (NiO) 1−x ( \(\:x=0.75)\) composite was tested at 60°C in a 1M KOH electrolyte, the capacitance was measured at 261 Fg −1 . Although this value is lower than the 482 Fg − 1 observed at room temperature. Up to 60°C, water evaporation from the electrolytes is observed, with this phenomenon becoming more pronounced at lower electrolyte concentrations. The evaporation alters the physicochemical properties of the electrolytes and the internal environment of the supercapacitors, leading to an increase in the equivalent series resistance (ESR) of the supercapacitors and a subsequent deterioration in their electrochemical performance. However, the MXene/NiO composite still outperforms pure MXene at this elevated temperature, likely due to the synergistic effect of NiO. NiO, known for its pseudocapacitive properties, contributes to the overall charge storage ability of the composite, helping to maintain a higher capacitance despite the adverse effects of increased temperature. Figure 12 represents the electrochemical characterization of (MXene) 0.75 (NiO) 0.25 composite. Conclusions In conclusion, (MXene) x (NiO) 1−x nanocomposites were successfully implemented as supercapacitor electrodes. Structural parameters including average crystallite size, phase purity, and density were evaluated using X-ray diffraction (XRD), while FTIR spectroscopy confirmed the presence of theoretical phonon modes, reinforcing the compositional integrity of the synthesized materials. UV–Vis spectroscopy revealed a tunable optical band gap in intermediate compositions, which resulted enhanced electrical conductivity. Scanning electron microscopy (SEM) unveiled agglomerated morphologies with well-defined nanoporous structures and uniform particle size distribution. Electrochemical characterizations revealed the superior performance of the (MXene) 0.75 (NiO) 0.25 composition. This sample exhibited an excellent specific capacitance of 482 F g − 1 at a scan rate of 10 mV s − 1 and 255 F g − 1 at a current density of 0.2 A g − 1 , along with a high energy density of 17.7 Wh kg − 1 at a power density of 450 W kg − 1 . EIS analysis highlighted the beneficial role of intermediate compositions in reducing solution resistance and facilitating efficient electrolyte diffusion through the porous electrode matrix. Furthermore, the reduced impedance in nanocomposite samples underscores the enhancement in electroconductivity due to synergistic material integration. Overall, the findings convincingly establish the (MXene) 0.75 (NiO) 0.25 nanocomposite as a leading electrode material for advanced, next-generation supercapacitor technologies. Declarations Author Contribution Tariq Saeed wrote the manuscript. Aamir Ahmed prepared the figures.Javid Iqbal is the corresponding author and supervised the research. Data Availability The data supporting the findings of this study are not publicly available but can be obtained from the corresponding author upon reasonable request. References R. P. Kumar and G. 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Naikoo et al. , “Electrochemical performance of Co3O4/Ag/CuO electrodes for supercapacitor applications,” J. Energy Storage , vol. 85, p. 111047, Apr. 2024, doi: 10.1016/j.est.2024.111047. H. Liu, W. Zhu, D. Long, J. Zhu, and G. Pezzotti, “Porous V2O5 nanorods/reduced graphene oxide composites for high performance symmetric supercapacitors,” Appl. Surf. Sci. , vol. 478, pp. 383–392, 2019. D. D. Macdonald, “Reflections on the history of electrochemical impedance spectroscopy,” Electrochimica Acta , vol. 51, no. 8–9, pp. 1376–1388, 2006. V. F. Lvovich, Impedance spectroscopy: applications to electrochemical and dielectric phenomena . John Wiley & Sons, 2012. Accessed: Apr. 14, 2025. C. Du and N. Pan, “High power density supercapacitor electrodes of carbon nanotube films by electrophoreticdeposition,” Nanotechnology , vol. 17, no. 21, p. 5314, 2006. K. Sambath Kumar, J. Cherusseri, and J. Thomas, “Two-Dimensional Mn 3 O 4 Nanowalls Grown on Carbon Fibers as Electrodes for Flexible Supercapacitors,” ACS Omega , vol. 4, no. 2, pp. 4472–4480, Feb. 2019, doi: 10.1021/acsomega.8b03309. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7309937","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":498517007,"identity":"c2b4a5f2-cb58-404f-bb1f-bec2a04618ba","order_by":0,"name":"Tariq Saeed","email":"","orcid":"","institution":"Quaid-i-Azam University","correspondingAuthor":false,"prefix":"","firstName":"Tariq","middleName":"","lastName":"Saeed","suffix":""},{"id":498517012,"identity":"f2afd24f-f9ec-4345-beac-56939a0a2ae7","order_by":1,"name":"Javed Iqbal","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABBElEQVRIiWNgGAWjYBACxgYgwQNlP4DQCUB8gDgtzAZEaQEDqBY2CaK0MLefMXzwhqFOXt5/jVnFm5rDDPzsOQbMBWfwOKwnx9hwDsNhw4033pjdnHPsMINkzxsD5hk38PklLU2ah+EA48YZZ8xu87AdZjC4AbSF5wMeLf3P0n/zMNTZg7QU8/w7zGBPUMuM5GPMPAzMifP5e8yYeduAtkiAtOBz2IzHhyXnGBxO3iDBViw5ty+dR+LMs4LDM/B437A/sfHDm4o62/n9hzd+ePPNWo6/PXnj44JjeLQ0gEhgHBrcSABHEDiODuPWwMAgD2f0H4DHKQMzPi2jYBSMglEw4gAAn1RUdSeq3EYAAAAASUVORK5CYII=","orcid":"","institution":"Quaid-i-Azam University","correspondingAuthor":true,"prefix":"","firstName":"Javed","middleName":"","lastName":"Iqbal","suffix":""},{"id":498517014,"identity":"d1a0ed98-06ab-4361-956c-d3d4a88988dc","order_by":2,"name":"Aamir Ahmed","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Aamir","middleName":"","lastName":"Ahmed","suffix":""}],"badges":[],"createdAt":"2025-08-06 12:53:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7309937/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7309937/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":89070261,"identity":"80796577-68cf-4c8e-917a-fdc3ecbf6f44","added_by":"auto","created_at":"2025-08-14 10:59:04","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":232312,"visible":true,"origin":"","legend":"\u003cp\u003eSynthesis of NiO nanoparticles\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7309937/v1/58b2e54facd7150b1b5a6551.png"},{"id":89070688,"identity":"f90b402b-b5c4-45bf-b667-9a2d53a38c7f","added_by":"auto","created_at":"2025-08-14 11:07:03","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":192711,"visible":true,"origin":"","legend":"\u003cp\u003eSynthesis of MXene\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7309937/v1/bf7ce776bc69455f3429eb14.png"},{"id":89070241,"identity":"728a9e00-87cd-477e-8529-dff317416685","added_by":"auto","created_at":"2025-08-14 10:59:03","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":344200,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of MXene/NiO nanocomposites and electrode fabrication.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7309937/v1/ef4562eeeff7599f336a7fe4.png"},{"id":89070247,"identity":"64e17de7-8f7f-4cbb-abd5-466bc524ff29","added_by":"auto","created_at":"2025-08-14 10:59:03","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":107894,"visible":true,"origin":"","legend":"\u003cp\u003eXRD spectrum a) MAX phase b) MXene c) NiO e) (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e\u003c/p\u003e\n\u003cp\u003ef) (MXene)\u003csub\u003e0.50\u003c/sub\u003e(NiO)\u003csub\u003e0.50 \u003c/sub\u003eg) (MXene)\u003csub\u003e0.25\u003c/sub\u003e(NiO)\u003csub\u003e0.75\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7309937/v1/afd3b7240bbfcce7cc0db89e.png"},{"id":89070242,"identity":"e34f2e5b-2bb5-4990-b054-601cc1797d96","added_by":"auto","created_at":"2025-08-14 10:59:03","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":774062,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of a-b) MXene c-d) NiO e-f) MXene/NiO nanocomposite\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7309937/v1/4870c372c5ae09876739c455.png"},{"id":89070240,"identity":"66efad0d-5bfd-44e9-91a3-4c6378a25fcc","added_by":"auto","created_at":"2025-08-14 10:59:03","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":40364,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra of a) NiO b) (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25 \u003c/sub\u003ec) MXene\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7309937/v1/3e661c6e86227cd61f76ad0d.png"},{"id":89070246,"identity":"5db5fc52-ba0a-42e9-ba56-bbf18a3a64db","added_by":"auto","created_at":"2025-08-14 10:59:03","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":78055,"visible":true,"origin":"","legend":"\u003cp\u003eTauc’s plots of (a) NiO (b) (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e (c) (MXene)\u003csub\u003e0.50\u003c/sub\u003e(NiO)\u003csub\u003e0.50\u003c/sub\u003e (d) (MXene)\u003csub\u003e0.25\u003c/sub\u003e(NiO)\u003csub\u003e0.75\u003c/sub\u003e (e) MXene\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7309937/v1/6f917d085cf1fe6c64678fd5.png"},{"id":89070691,"identity":"3b794c44-69d2-44d9-a467-eec181fe4741","added_by":"auto","created_at":"2025-08-14 11:07:03","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":97864,"visible":true,"origin":"","legend":"\u003cp\u003eCyclic Voltammetry curve of (a) NiO (b) MXene (c) (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e (d) (MXene)\u003csub\u003e0.50\u003c/sub\u003e(NiO)\u003csub\u003e0.50\u003c/sub\u003e (e) (MXene)\u003csub\u003e0.25\u003c/sub\u003e(NiO)\u003csub\u003e0.75 \u003c/sub\u003ef) Graphical comparison\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7309937/v1/fc31d05b3f67627f6b60cec5.png"},{"id":89070693,"identity":"cf4dfb7c-8dfe-4192-a57c-05eebc628a21","added_by":"auto","created_at":"2025-08-14 11:07:04","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":84878,"visible":true,"origin":"","legend":"\u003cp\u003eCharge/ discharge curves of\u003cstrong\u003e \u003c/strong\u003e(a) NiO (b) MXene (c) (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e (d) (MXene)\u003csub\u003e0.50\u003c/sub\u003e(NiO)\u003csub\u003e0.50\u003c/sub\u003e (e) (MXene)\u003csub\u003e0.25\u003c/sub\u003e(NiO)\u003csub\u003e0.75 \u003c/sub\u003ef) Comparison among all samples\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-7309937/v1/8c8a060fad16214b4a8bd53b.png"},{"id":89070259,"identity":"6f095637-b40b-4eee-9f07-31e1b43b58d3","added_by":"auto","created_at":"2025-08-14 10:59:04","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":44985,"visible":true,"origin":"","legend":"\u003cp\u003eNyquist plots of all prepared samples\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-7309937/v1/256258daa83d7fda42aedabf.png"},{"id":89070277,"identity":"0dc3c738-d817-46e5-915c-47384dfb3725","added_by":"auto","created_at":"2025-08-14 10:59:04","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":49201,"visible":true,"origin":"","legend":"\u003cp\u003eCyclic stability and Coulombic efficiency of a prepared sample\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-7309937/v1/30da155fbba8f41ade814cde.png"},{"id":89070288,"identity":"3549ae60-3df7-46c6-be66-c4dcb752ad9f","added_by":"auto","created_at":"2025-08-14 10:59:05","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":67135,"visible":true,"origin":"","legend":"\u003cp\u003eElectrochemical characterization at different temperatures\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-7309937/v1/96985a9b10c835449d01cbb9.png"},{"id":94859799,"identity":"d84833ef-d17c-4164-b189-e4c97febe8c6","added_by":"auto","created_at":"2025-10-31 12:53:56","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2707497,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7309937/v1/9189fcac-76c6-4629-ad5f-51953605f4d4.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Temperature-Tuned Performance of MXene-NiO Nanocomposites for High-Efficiency Supercapacitors","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eElectrical energy is essential to modern life, powering everything from personal devices to industrial and agricultural operations. Historically, fossil fuels have dominated the worldwide energy mix, supplying 81% of primary energy in 2019 (IEA). While critical to economic and technological development, their widespread use has led to significant environmental harm, particularly through CO\u003csub\u003e2\u003c/sub\u003e emissions driving climate change [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Despite the promise of renewables, the transition to fully sustainable energy systems remains incomplete. Electrochemical energy storage, particularly lithium-ion batteries, has rapidly advanced due to its high energy density, stable output, and flexibility across regions, outperforming other systems like flow and lead-acid batteries [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e], [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. While lithium-ion batteries and other advanced rechargeable batteries provide satisfactory energy densities, they still face shortcomings, including low power density [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Supercapacitors have gained widespread interest due to their distinctive benefits, including superior specific capacitance, speedy charge-discharge rates, and impressive cycling stability [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. While supercapacitors offer numerous advantages, their primary limitation is their relatively low energy density, ranging from 5 to 20 Whkg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which is approximately 20 to 40 times smaller in comparison to lithium-ion batteries (100\u0026ndash;265 Whkg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe charge-storage capacity of supercapacitors (SCs) is heavily affected by the selection of both electrolyte and electrode materials. Although both components affect the operating voltage of SCs, the capacitance is primarily dictated by the properties of the electrode material [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Consequently, extensive research efforts are focused on developing innovative, high-performance electrode materials for SCs. Among various electrode materials, two-dimensional (2D) materials have garnered the most attention owing of their enhanced specific surface area (SSA), which enhances specific capacitance in supercapacitors [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. MXenes are a novel class of 2D materials with structural similarities to graphene and molybdenum disulfide. The discovery of Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e in 2011 sparked extensive research into the unique properties of the broader MXene family [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The standard expression for MXenes is M\u003csub\u003en+1\u003c/sub\u003eX\u003csub\u003en\u003c/sub\u003eT\u003csub\u003ex\u003c/sub\u003e, where M signifies an early transition metals (such as Ti, Sc, Mo, Hf, V, Nb, etc.), X signifies carbon or nitrogen, and T\u003csub\u003ex\u003c/sub\u003e signifies surface terminations, including O, OH, and F [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. MAX phases serve as the primary precursors for synthesizing MXenes. These phases are specified by the standard formula M\u003csub\u003en+1\u003c/sub\u003eAX\u003csub\u003en\u003c/sub\u003e, where M signifies early transition metals, A is an element from groups IIIA or IVA (13\u0026ndash;14), and X represents carbon or nitrogen, with the possibility of forming carbonitride compounds. The value of n extends from 1 to 4 [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. However, MXenes face challenges in practical applications due to their tendency to oxidize and restack, which reduces the available surface area and negatively impacts their capacitive performance [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. To overcome these critical challenges for large-scale production, integrating MXene and other materials together such as polymers, carbide-based materials (CNTs, GO/rGO), metal oxides, and layered transition metal dichalcogenides has proven to be an efficient and straightforward approach for developing MXene nanocomposites [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Metal oxides, including NiO [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], RuO\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], MnO\u003csub\u003e2\u003c/sub\u003e [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], and Co\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] are already being investigated as electrode materials for supercapacitors, showing promising potential. Despite extensive research on RuO₂ and IrO₂ as pseudocapacitive electrode materials, their practical applications are constrained by their high cost. In contrast, NiO is regarded as a viable alternative due to its abundance, accessibility, affordability, customizable morphology, high surface area, and comparable electrochemical performance. NiO exhibits a relatively high specific capacitance and is straightforward to produce. However, transition metal oxides (TMOs) like NiO generally demonstrate enhanced resistance at the electrode/electrolyte boundary at high rates, along with reduced electronic conductivity, ionic diffusivity, and cycle life. To effectively address these challenges, an effective strategy is to integrate a flexible and conductive 2D framework that facilitates the uniform distribution of TMO nanostructures. In the context of supercapacitor applications, these electrode materials provide several architectural advantages. Firstly, the specific surface area of stacked MXene sheets is substantial. By alleviating the inactive surface area caused by restacking, the incorporation of NiO onto the nanosheets generates additional active sites. Secondly, MXene enhances the conductivity of the MXene-NiO nanocomposite, thereby improving its electrochemical performance [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThis study demonstrates the synthesis and electrochemical evaluation of (MXene)\u003csub\u003ex\u003c/sub\u003e(NiO)\u003csub\u003e1\u0026ndash;x\u003c/sub\u003e nanocomposites as electrode materials for supercapacitors. The research focuses on charge kinetics and enhanced energy storage performance compared to pristine MXene and nickel oxide. These findings offer valuable insights for advancing 2D MXene-based electrode design in energy storage applications.\u003c/p\u003e"},{"header":"2. EXPERIMENTAL DETAILS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Materials\u003c/h2\u003e\u003cp\u003eFor this experiment, analytical reagent grade chemicals were utilized. Nickel chloride hexahydrate (NiCl.6H\u003csub\u003e2\u003c/sub\u003eO), sodium hydroxide (NaOH), polyvinylidene fluoride (PVDF), and carbon black were procured from Sigma Aldrich. Titanium aluminum carbide (Ti\u003csub\u003e3\u003c/sub\u003eAlC\u003csub\u003e2\u003c/sub\u003e), MAX phase was obtained from Mac Chemicals. Double distilled water was used to prepare all solutions. The compounds were used in their primary form devoid of any additional alteration or purification.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Synthesis of NiO\u003c/h2\u003e\u003cp\u003eNickel oxide (NiO) nanoparticles were synthesized via the hydrothermal method. Precursors of nickel chloride hexahydrate (NiCl.6H\u003csub\u003e2\u003c/sub\u003eO) and sodium hydroxide (NaOH) as well as distilled water as a solvent were utilized. Two separate beakers were used to prepare solutions. In the first beaker, 3.8 grams of NiCl\u0026middot;6H₂O was mixed in 80 ml distilled water. In the second beaker, 50 ml of distilled water was combined with 2 grams of NaOH. The solution from the second beaker was slowly added to the first beaker to maintain a pH of 10, while continuously stirring for one hour at room temperature. Then, the solution was transported into Teflon autoclave and heated at 170℃ for 14 hours. Once the autoclave had cooled to room temperature, distilled water was utilized to rinse the greenish precipitate that had developed, dried at 70℃ for overnight. The resulting sample was grounded and annealed at 600\u0026deg;C for 2 hours in a muffle furnace and schematic diagram shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The NiO nanoparticles were carefully stored in anticipation of their upcoming characterization and utilization.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Synthesis of MXene\u003c/h2\u003e\u003cp\u003eTo prepare MXene (Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e), 30 wt% hydrofluoric acid (HF) was used, into which 1 g of MAX phase (Ti₃AlC₂) was gently added. This mixture was stirred in a Teflon bar for eight hours at 55\u0026deg;C. Afterward, distilled water was added, allowing the Ti₃C₂ MXene to settle at the bottom while the Al layer floated to the top. The MXene was then repeatedly rinsed until it reached a neutral pH and subsequently dried overnight at 60\u0026deg;C, and schematic diagram is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e2.4. Preparation of MXene/NiO nanocomposites\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn this research, an ex-situ approach was employed to synthesize composites of MXene and NiO. The nanocomposites' concentrations were controlled by mixing varying ratios: 0.75 of NiO with 0.25 of MXene, equal amounts of 0.50 each, and 0.25 of NiO with 0.75 of MXene. Throughout a one-hour grinding process, acetone is slowly introduced to the mixture prepared in a mortar and pestle. Subsequently, the composite undergoes heating at 70\u0026ordm;C for a duration of 12 hours after thorough grinding, and schematic diagram is shown in \u003cb\u003eFig.\u0026nbsp;3.\u003c/b\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.5. Materials characterizations\u003c/h2\u003e\u003cp\u003eThe samples were analyzed for their phase composition and crystallographic structure using an X-ray diffractometer operating with Copper-Kα radiation (λ\u0026thinsp;=\u0026thinsp;1.5406 \u0026Aring;), providing detailed insights into their structural properties. Additionally, FTIR spectroscopy was conducted over the 4000\u0026ndash;400 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e range to explore the molecular framework and identify key chemical interactions within the materials. UV-Vis spectroscopy was employed to experimentally explore the band gap energy of the materials, offering insight into their optical behavior. The optical band gap was precisely calculated using Tauc plots, allowing for a detailed assessment of electronic transitions. Scanning electron microscopy (SEM) was deployed to analyze the morphology of the nanostructures, providing detailed insights into their size, shape, and surface characteristics.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.6. Electrochemical characterizations\u003c/h2\u003e\u003cp\u003eElectrochemical characterizations were conducted at room temperature, low temperature and high temperature through a Gamry (Interface 5000 E) Electrochemical Workstation. A three-electrode system was employed, with nickel foam serving for the working electrode, Ag/AgCl for reference, and platinum wire for the counter. A 1M KOH solution served as the electrolyte. To assess the electrochemical performance, electrochemical impedance spectroscopy (EIS), galvanostatic charge-discharge (GCD), cyclic voltammetry (CV), coulombic efficiency, and retentivity curves were recorded. Cyclic voltammetry (CV) scans were recorded at scan rates between 10 mVs\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 100 mVs\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, within a potential window of 0.2 V to 0.6 V. Galvanostatic charge-discharge cycling was executed at current densities spanning from 0.2 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 0.8 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eUsing CV and GCD, the specific capacitance was assessed using Eqs.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) and (\u003cspan refid=\"Equ2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Additionally, the energy density and power density were elegantly figured out using Eqs.\u0026nbsp;(\u003cspan refid=\"Equ3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) and (\u003cspan refid=\"Equ4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), respectively.\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:{C}_{s}=\\frac{A}{mK\\varDelta\\:V}\\:\\left(F{g}^{-1}\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:{C}_{s}=I\\frac{\\varDelta\\:t}{m\\varDelta\\:V}\\:\\left(F{g}^{-1}\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\:{E}_{g}=\\frac{1}{2}{C}_{s}\\varDelta\\:V\\:\\left(Wh{Kg}^{-1}\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equ4\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ4\" name=\"EquationSource\"\u003e\n$$\\:{P}_{g}=\\frac{{E}_{g}}{\\varDelta\\:t}\\:\\left(W{Kg}^{-1}\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e4\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003ewhere A is the area of the CV curve, m is the mass of active materials, k is the scan rate, ∆V is the potential window, Δt is the discharge time and I denotes the response current [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e"},{"header":"3. RESULTS AND DISCUSSIONS","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Structural Studies\u003c/h2\u003e\u003cp\u003eThe distinctive diffraction peaks of Ti\u003csub\u003e3\u003c/sub\u003eAlC\u003csub\u003e2\u003c/sub\u003e observed at approximately 10.2\u0026deg; and 39.2\u0026deg; are associated with the (002) and (104) planes, respectively [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. After HF etching, the reduced intensity of these peaks indicated a significant loss of crystallinity and structural deformation [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. For Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e MXene, diffraction peaks were identified at 2θ values of 9.6\u0026deg;, 18.5\u0026deg;, and 60.5\u0026deg;, associated to the (002), (006), and (110) planes [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. The characteristic peaks of the MXene/NiO composites, located at 37.3\u0026deg;, 43.2\u0026deg;, 62.4\u0026deg;, 75.4\u0026deg;, and 79.1\u0026deg;, can be indexed to the NiO phase, specifically the (111), (200), (220), (311), and (222) planes (JCPDS Card No. 00-001-1239) [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. The XRD pattern of the MXene/NiO composites also displayed the distinctive peaks attributed to MXene, indicating the NiO has been successfully incorporated into MXene [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. The (002) peaks of all MXene and MXene/NiO composites exhibit a shift toward lower 2θ values compared to the MAX phase, primarily due to the increased interlayer spacing between the MXene sheets, which is occupied by intercalants such as water and NiO. During the etching process, the removal of Al layers not only etches the MXene but also causes delamination, resulting in an expanded interlayer gap. The broadening of the (006) plane indicates increased interlayer spacing, confirming NiO nanoparticle intercalation within MXene layers. This expansion introduces more active edge sites and open channels, enhancing ion transport and structural stability. The average crystallite size of the MXene/NiO nanocomposite was determined from XRD data using Debye Scherrer formula. The average crystallite size of the MXene/NiO nanocomposite was found to be approximately 268\u0026Aring;. The measured crystallite size of (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e is smaller than that of the other composites listed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The lowering of average crystalline size reflects the effect of NiO on MXene, which improves the electrochemical performance over that of pure MXene. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e depicts the XRD diffractograms of the MAX phase, MXene, and nanocomposites with NiO.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003ef) (MXene)\u003csub\u003e0.50\u003c/sub\u003e(NiO)\u003csub\u003e0.50\u003c/sub\u003e g) (MXene)\u003csub\u003e0.25\u003c/sub\u003e(NiO)\u003csub\u003e0.75\u003c/sub\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThe various structural parameter values\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCrystallite Size (\u0026Aring;)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ea\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:=\\)\u003c/span\u003e\u003c/span\u003eb\u003c/p\u003e\u003cp\u003e(\u0026Aring;)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ec\u003c/p\u003e\u003cp\u003e(\u0026Aring;)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eVolume\u003c/p\u003e\u003cp\u003e(\u0026Aring;\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eStrain(%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eNiO\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e295\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.171\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.171\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e72.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.293\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e(MXene)\u003c/b\u003e\u003csub\u003e\u003cb\u003e0.25\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e(NiO)\u003c/b\u003e\u003csub\u003e\u003cb\u003e0.75\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e315\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.171\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.171\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e72.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.685\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e(MXene)\u003c/b\u003e\u003csub\u003e\u003cb\u003e0.50\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e(NiO)\u003c/b\u003e\u003csub\u003e\u003cb\u003e0.50\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e284\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.171\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.171\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e72.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.566\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e(MXene)\u003c/b\u003e\u003csub\u003e\u003cb\u003e0.75\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e(NiO)\u003c/b\u003e\u003csub\u003e\u003cb\u003e0.25\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e268\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.171\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e4.171\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e72.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.653\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eMXene\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e332\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3.071\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e20.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e164.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.680\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eScanning Electron Microscopy (SEM) is utilized to investigate the surface morphology and assess the structural integrity of the synthesized samples. High-magnification SEM images, presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e(a\u0026ndash;f), reveal distinct structural characteristics: NiO exhibits nanograin-like morphology, MXene forms nanosheets, and the NiO/MXene composite showcases nanosheets elegantly adorned with nanograins. In Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003ea, the delaminated multilayered MXene nanosheets appear smooth and pristine, with well-defined edges. Meanwhile, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003eb illustrates the uniform dispersion and slight aggregation of NiO nanograins, highlighting their structural integrity. Due to their high surface energy and strong surface tension, NiO nanoparticles have a natural tendency to agglomerate, leading to the formation of larger nanoparticle clusters[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. After the synthesis of the nanocomposite, NiO nanoparticles uniformly coat the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e surface and intercalate between its layers (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003ee, f), providing clear evidence of the successful formation of the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e/NiO nanocomposite which validates the XRD results. The intercalation of NiO nanoparticles between the MXene layers effectively inhibits their restacking, thereby boosting electrolyte accessibility and elevating the electrochemical response of the composite.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe vibrational modes of NiO, MXene and its nanocomposites were identified through FTIR study. FTIR spectra were recorded in the limit of 400\u0026ndash;4000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e using Fourier mapping, with a KBr pellet serving as a reference. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e presents the FTIR spectra highlighting various vibrational modes for NiO, MXene, and (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e. The absorption band at 472 cm⁻\u0026sup1; was linked with the Ni-O vibrational bond. The distinctive peaks at 1741 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1375cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1015cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e were due to C\u0026thinsp;=\u0026thinsp;O, OH and C-O respectively. For pure MXene, the absorption bands at 460 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1738 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e were due to the Ti\u0026ndash;C and C\u0026thinsp;=\u0026thinsp;O vibrations, respectively. The broad peak between 3000 and 3500 cm⁻\u0026sup1; corresponds to an OH bond. Common bands of both appeared in (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e nanocomposite. The downward movement of peaks suggests the strong interaction between NiO and MXene [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The nonexistence of extra modes validates the cleanliness of the electrode surface and aligns well with the XRD results, reinforcing the material's structural purity.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe optical properties of (MXene)\u003csub\u003ex\u003c/sub\u003e(NiO)\u003csub\u003e1\u0026minus;x\u003c/sub\u003e nanocomposites have been examined by UV-vis absorption spectroscopy. The absorption peaks for pure MXene and NiO were recorded at 310 nm and 225 nm, respectively. For the (MXene)ₓ(NiO)\u003csub\u003e1\u0026minus;x\u003c/sub\u003e composites, a pronounced red shift in the absorption peaks was observed, occurring at 317 nm, 320 nm, and 325 nm for x\u0026thinsp;=\u0026thinsp;0.75, 0.50, and 0.25, respectively, as the MXene content decreased. The presence of a single absorption peak in all spectra indicates the synthesis of a single phase in the nanocomposites, further corroborating the phase purity results obtained from XRD and SEM analyses. The optical energy gap of the nanocomposites was figured out using the Tauc relation, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\left(\\varvec{\\alpha\\:}\\mathbf{h}\\varvec{\\nu\\:}\\right)}^{\\mathbf{n}}=\\varvec{\\beta\\:}(\\mathbf{h}\\varvec{\\nu\\:}-{\\mathbf{E}}_{\\mathbf{g}})\\)\u003c/span\u003e\u003c/span\u003e. By plotting \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\left({\\alpha\\:}\\text{h}{\\nu\\:}\\right)}^{\\text{n}}\\)\u003c/span\u003e\u003c/span\u003e versus photon energy (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{h}{\\nu\\:}\\)\u003c/span\u003e\u003c/span\u003e) with \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:n=2\\)\u003c/span\u003e\u003c/span\u003e, the band gap energy \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{E}_{g}\\)\u003c/span\u003e\u003c/span\u003e​ was determined by drawing a tangent to the curve at the onset of the linear region [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. The estimated band gap energy for NiO is 3.40 eV and for MXene is 1.46eV. For the (MXene)ₓ(NiO)\u003csub\u003e1\u0026minus;x\u003c/sub\u003e nanocomposites, the energies gap was figured out to be 3.28 eV, 3.19 eV, and 3.08 eV for x\u0026thinsp;=\u0026thinsp;0.75, 0.50, and 0.25, respectively. The band gap energy of NiO decreased with the incorporation of MXene, which may be associated with numerous factors, including the lowering of crystallite size and the formation of localized states of the oxides between the band gap as apparent from XRD, FTIR as well as SEM data. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e corresponding Tauc plots and variation in the band gap energy is depicted in the Ragone plot.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.2. ELECTROCHEMICAL STUDIES\u003c/h2\u003e\u003cp\u003eThe cyclic voltammograms shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e reveal the electrochemical characteristics of NiO, MXene, and their composites. All CV profiles display two well-defined Faradaic peaks, indicating active redox reactions taking place at the electrode surface during both forward and reverse sweeps. Interestingly, as the scan rate increases, a noticeable shift is observed in the voltammograms reduction peaks drift toward the cathodic side, while oxidation peaks shift anodically highlighting the dynamic electrochemical response of the material [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Moreover, the symmetrical shape of the voltammograms reflects the high reversibility of the electrochemical processes, suggesting efficient charge-discharge behavior and rapid ion diffusion within the electrolyte. This symmetry is a clear indication of a well-balanced redox mechanism occurring at the electrode surface. Notably, the specific capacitance (C\u003csub\u003es\u003c/sub\u003e) reaches its peak value at the lowest scan rate of 10 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, as the ions have ample time to penetrate deeply into the porous structure of the electrode material. As the scan rate rises, there is a continuous reduction in specific capacitance. This drop is assigned to the limited time available for ions to fully diffuse into the inner active sites, resulting in reduced electrochemical utilization of the material at higher scan rates [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. The current response observed in the voltammograms serves as a clear reflection of the electrochemical activity of the samples. Among them, pure MXene exhibits the lowest response current, indicating minimal electrochemical activity. However, as the concentration of NiO increases, a noticeable enhancement in activity is observed. At a scan rate of 10 mVs\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e nanocomposite exhibited a significantly higher specific capacitance of 482 Fg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, compared to pristine MXene (137 Fg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), NiO (326 Fg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), and all other nanocomposites listed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e, the cyclic voltammetry (CV) data indicate a significantly larger CV area for the Ti\u003csub\u003e3\u003c/sub\u003eC\u003csub\u003e2\u003c/sub\u003e/NiO composites, highlighting the synergistic interaction between NiO and Ti₃C₂ as a key factor contributing to the enhanced capacitance of the composite due to addition of NiO, which hinders the restacking of MXene layers.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eSpecific capacitance values determined through CV\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"7\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"6\" nameend=\"c7\" namest=\"c2\"\u003e\u003cp\u003eSpecific Capacitance (C\u003csub\u003es\u003c/sub\u003e) Fg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e10mVs\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e20mVs\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e40mVs\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003e60mVs\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003e80mVs\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003e100mVs\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eNiO\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e326\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e270\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e218\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e181\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e155\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e147\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e(MXene)\u003c/b\u003e\u003csub\u003e\u003cb\u003e0.25\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e(NiO)\u003c/b\u003e\u003csub\u003e\u003cb\u003e0.75\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e216\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e208\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e201\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e175\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e162\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e151\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e(MXene)\u003c/b\u003e\u003csub\u003e\u003cb\u003e0.50\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e(NiO)\u003c/b\u003e\u003csub\u003e\u003cb\u003e0.50\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e309\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e267\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e221\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e201\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e185\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e171\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003e(MXene)\u003c/b\u003e\u003csub\u003e\u003cb\u003e0.75\u003c/b\u003e\u003c/sub\u003e\u003cb\u003e(NiO)\u003c/b\u003e\u003csub\u003e\u003cb\u003e0.25\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e482\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e457\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e402\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e359\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e325\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e295\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eMXene\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e137\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e119\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e23\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e9\u003c/span\u003e presents the charge\u0026ndash;discharge profiles, showing the variation of potential with time at current densities between 0.2 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 0.8 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The nonlinear voltage\u0026ndash;time characteristics of NiO, MXene, and (MXene)\u003csub\u003ex\u003c/sub\u003e(NiO)\u003csub\u003e1\u0026minus;x\u003c/sub\u003e align with the expected behavior of pseudocapacitance [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Results revealed that (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e exhibited the highest specific capacitance of 255 Fg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 0.2 Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The subsequent specific capacitances were 198 Fg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for (MXene)\u003csub\u003e0.50\u003c/sub\u003e(NiO)\u003csub\u003e0.50\u003c/sub\u003e, 193 Fg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for (MXene)\u003csub\u003e0.25\u003c/sub\u003e(NiO)\u003csub\u003e0.75\u003c/sub\u003e, 30 Fg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for NiO, and 68 Fg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for MXene. The composite (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e exhibits a calculated energy density of 17.7 Whkg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and a power density of 450 Wkg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, representing a significant advancement for supercapacitor applications. At higher current densities, both charge and discharge times are reduced, leading to a lower capacitance. This reduction occurs because, at elevated current densities, the charge/discharge rates increase, limiting the time available for electrolyte ions to entirely diffuse onto the electroactive surface area [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e].Conversely, at lower current densities, the ions have sufficient time to fully access and replenish the electroactive surface, optimizing capacitance.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eElectrical impedance spectroscopy (EIS), conducted over a broad frequency range of 1\u0026ndash;100 kHz, was employed to comprehensively analyze various physical and electrochemical parameters. To further interpret the data, Nyquist plots were utilized, offering valuable insights into the material's resistive and capacitive behavior. In a typical Nyquist plot, the real part of impedance (Z\u003csup\u003e\u0026rsquo;\u003c/sup\u003e) on the x-axis represents the resistive characteristics of the electrode material, while the imaginary part (Z\u003csup\u003e\u0026rsquo;\u0026rsquo;\u003c/sup\u003e) on the y-axis reflects its reactive or capacitive nature. As the applied frequency varies, the impedance response transitions between resistive and capacitive behavior capturing the dynamic performance of the material within a supercapacitor system. [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. In a Nyquist plot, the high-frequency region reflects resistive behavior, while the mid-to-high frequency zone reveals key physical properties like electroactive layer thickness, morphology, and pore size critical for assessing electrode performance[\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. The solution resistance (Rs), determined from the x-axis intercept of the Nyquist plot, represents the resistance offered by the porous electrode to electrolyte penetration. A lower Rs value signifies enhanced ion accessibility and more efficient electrolyte diffusion into the electrode\u0026rsquo;s porous network[\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. Figure\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e10\u003c/span\u003e displays the Nyquist plots for different concentrations of (MXene)\u003csub\u003ex\u003c/sub\u003e(NiO)\u003csub\u003e1\u0026minus;x\u003c/sub\u003e (x\u0026thinsp;=\u0026thinsp;1, 0.75, 0.50, 0.25, 0). In electrochemical impedance spectroscopy, the solution resistance Rs is expressed by the intercept on the Z\u003csup\u003e\u0026rsquo;\u003c/sup\u003e-axis and comprises the resistance of the electrolyte solution along with the contact resistance at the interface between the electroactive material and the current collector. The diameter of the semicircle is approximately corresponding to the charge transfer resistance R\u003csub\u003ect\u003c/sub\u003e across the electrode/electrolyte interface. R\u003csub\u003es\u003c/sub\u003e of the (MXene)\u003csub\u003ex\u003c/sub\u003e(NiO)\u003csub\u003e1\u0026minus;x\u003c/sub\u003e (x\u0026thinsp;=\u0026thinsp;0.25, 0.50, 0.75) electrodes can be calculated to be 0.19\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\Omega\\:}\\)\u003c/span\u003e\u003c/span\u003e, 0.25\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\Omega\\:}\\)\u003c/span\u003e\u003c/span\u003e and 0.22\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\Omega\\:}\\)\u003c/span\u003e\u003c/span\u003e respectively, lying between the MXene (0.28\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\Omega\\:}\\)\u003c/span\u003e\u003c/span\u003e) and NiO (0.10\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\Omega\\:}\\)\u003c/span\u003e\u003c/span\u003e) electrodes. A negligible diameter suggests lower Rct resistance in the material. Consequently, reduced resistance, or higher conductivity, of electrode materials makes them more suitable for supercapacitor applications, as less energy is lost during the charge/discharge cycle. The inclusion of NiO is suggested to enhance charge transfer efficiency within the composite electrode.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTo evaluate cycling stability, the samples were subjected to 1200 charge-discharge cycles at a current density of 1Ag\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Notably, the (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e composite demonstrated superior capacitance retention compared to pure MXene, with respective retention values of 97% and 114%. Both pure MXene and its composite exhibited similar coulombic efficiencies of approximately 96%. The MXene-NiO composite thus presents a compelling candidate for electrochemical storage devices (ESDs), delivering an advantageous balance of enhanced capacitance retention and nearly unchanged coulombic efficiency qualities essential for high-capacity, high efficiency applications. The electrode's capacitance increased during the initial cycles as a consequence of the activation process [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. Figure\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e11\u003c/span\u003e represents the cyclic stability and coulombic efficiency different samples.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Effect of temperature\u003c/h2\u003e\u003cp\u003eWhen the (MXene)\u003csub\u003ex\u003c/sub\u003e(NiO)\u003csub\u003e1\u0026minus;x\u003c/sub\u003e (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:x=0.75\\)\u003c/span\u003e\u003c/span\u003e) composite was tested in a 1M KOH electrolyte at 0\u0026deg;C, a significant decrease in capacitance was observed, dropping to 44 Fg\u003csup\u003e\u0026minus;1\u003c/sup\u003e compared to room temperature. This substantial reduction, as indicated by the CV curves, suggests that the lower temperature adversely affects the material's ability to store and release charge. At 0\u0026deg;C, the kinetic processes that facilitate charge transfer and ion diffusion are hindered, leading to a much lower capacitance. Furthermore, galvanostatic charge-discharge (GCD) tests revealed a noticeable decrease in discharge time at 0\u0026deg;C compared to room temperature. This shorter discharge time is indicative of a reduced energy storage capability, as the material's ability to sustain a charge under lower temperatures is compromised. Electrochemical impedance spectroscopy (EIS) further supported these findings by showing an increase in solution resistance to 1.12 ohms at 0\u0026deg;C, compared to the sample's resistance at room temperature. The increased resistance highlights the challenges in charge transfer and ionic movement within the electrolyte and composite material at lower temperatures. This rise in resistance is likely to contribute to the overall decrease in electrochemical performance, as higher resistance impedes the efficient flow of electrons and ions, leading to diminished capacitance and faster discharge rates. These results collectively underscore the critical impact of temperature on the electrochemical performance of the MXene/NiO composite, particularly highlighting the challenges faced at lower operating temperatures.\u003c/p\u003e\u003cp\u003eWhen the (MXene)\u003csub\u003ex\u003c/sub\u003e(NiO)\u003csub\u003e1\u0026minus;x\u003c/sub\u003e (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:x=0.75)\\)\u003c/span\u003e\u003c/span\u003e composite was tested at 60\u0026deg;C in a 1M KOH electrolyte, the capacitance was measured at 261 Fg\u003csup\u003e\u0026minus;1\u003c/sup\u003e. Although this value is lower than the 482 Fg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e observed at room temperature. Up to 60\u0026deg;C, water evaporation from the electrolytes is observed, with this phenomenon becoming more pronounced at lower electrolyte concentrations. The evaporation alters the physicochemical properties of the electrolytes and the internal environment of the supercapacitors, leading to an increase in the equivalent series resistance (ESR) of the supercapacitors and a subsequent deterioration in their electrochemical performance. However, the MXene/NiO composite still outperforms pure MXene at this elevated temperature, likely due to the synergistic effect of NiO. NiO, known for its pseudocapacitive properties, contributes to the overall charge storage ability of the composite, helping to maintain a higher capacitance despite the adverse effects of increased temperature. Figure\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e12\u003c/span\u003e represents the electrochemical characterization of (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e composite.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn conclusion, (MXene)\u003csub\u003ex\u003c/sub\u003e(NiO)\u003csub\u003e1\u0026minus;x\u003c/sub\u003e nanocomposites were successfully implemented as supercapacitor electrodes. Structural parameters including average crystallite size, phase purity, and density were evaluated using X-ray diffraction (XRD), while FTIR spectroscopy confirmed the presence of theoretical phonon modes, reinforcing the compositional integrity of the synthesized materials. UV\u0026ndash;Vis spectroscopy revealed a tunable optical band gap in intermediate compositions, which resulted enhanced electrical conductivity. Scanning electron microscopy (SEM) unveiled agglomerated morphologies with well-defined nanoporous structures and uniform particle size distribution. Electrochemical characterizations revealed the superior performance of the (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e composition. This sample exhibited an excellent specific capacitance of 482 F g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at a scan rate of 10 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 255 F g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at a current density of 0.2 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, along with a high energy density of 17.7 Wh kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at a power density of 450 W kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. EIS analysis highlighted the beneficial role of intermediate compositions in reducing solution resistance and facilitating efficient electrolyte diffusion through the porous electrode matrix. Furthermore, the reduced impedance in nanocomposite samples underscores the enhancement in electroconductivity due to synergistic material integration. Overall, the findings convincingly establish the (MXene)\u003csub\u003e0.75\u003c/sub\u003e(NiO)\u003csub\u003e0.25\u003c/sub\u003e nanocomposite as a leading electrode material for advanced, next-generation supercapacitor technologies.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eTariq Saeed wrote the manuscript. Aamir Ahmed prepared the figures.Javid Iqbal is the corresponding author and supervised the research.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data supporting the findings of this study are not publicly available but can be obtained from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eR. P. Kumar and G. Karthikeyan, \u0026ldquo;A multi-objective optimization solution for distributed generation energy management in microgrids with hybrid energy sources and battery storage system,\u0026rdquo; \u003cem\u003eJ. Energy Storage\u003c/em\u003e, vol. 75, p. 109702, 2024.\u003c/li\u003e\n\u003cli\u003e\u0026ldquo;World Energy Outlook 2019 \u0026ndash; Analysis - IEA.\u0026rdquo; Accessed: Oct. 12, 2024. [Online]. Available: https://www.iea.org/reports/world-energy-outlook-2019\u003c/li\u003e\n\u003cli\u003eQ. 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Cherusseri, and J. Thomas, \u0026ldquo;Two-Dimensional Mn\u003csub\u003e3\u003c/sub\u003e O\u003csub\u003e4\u003c/sub\u003e Nanowalls Grown on Carbon Fibers as Electrodes for Flexible Supercapacitors,\u0026rdquo; \u003cem\u003eACS Omega\u003c/em\u003e, vol. 4, no. 2, pp. 4472\u0026ndash;4480, Feb. 2019, doi: 10.1021/acsomega.8b03309.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Nickel oxide (NiO), MAX phase (Ti3AlC2), MXene (Ti3C2), Supercapacitor, Nanostructures","lastPublishedDoi":"10.21203/rs.3.rs-7309937/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7309937/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe current study centers on the design and optimization of electroactive materials for energy storage purposes. We present the preparation of a noble series of (MXene)\u003csub\u003ex\u003c/sub\u003e(NiO)\u003csub\u003e1\u0026minus;x\u003c/sub\u003e nanocomposite electrodes (where x\u0026thinsp;=\u0026thinsp;1, 0.75, 0.50, 0.25, 0), prepared in varying stoichiometric ratios, which exhibit exceptional performance as supercapacitor electrodes. Detailed structural and morphological characterizations were conducted to gain insight into the underlying physical properties of the composites. Electrochemical performance was systematically evaluated using cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS). The optimized electrode delivered a high energy density of 17.7 Wh kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and a power density of 450 W kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Additionally, it displayed impressive cyclic stability, retaining 114% of its initial capacitance after 1200 cycles. The improved functionality is assigned to both the synergistic effect of the nanocomposite constituents and the tailored nanostructured architecture of the electrode.\u003c/p\u003e","manuscriptTitle":"Temperature-Tuned Performance of MXene-NiO Nanocomposites for High-Efficiency Supercapacitors","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-14 10:58:58","doi":"10.21203/rs.3.rs-7309937/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5f684528-37d8-412e-b588-e6dd8c7238af","owner":[],"postedDate":"August 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-01-21T21:08:17+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-14 10:58:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7309937","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7309937","identity":"rs-7309937","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}