Hierarchical carbon nanofiber/NiCo2O4 composites as electrode for high-performance supercapacitors

Hierarchical carbon nanofiber/NiCo2O4 composites as electrode for high-performance 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 Hierarchical carbon nanofiber/NiCo2O4 composites as electrode for high-performance supercapacitors Qiqi Zhuo, Yalou Lv, Hanzhao Wu, Jintian Jiang, Jijun Tang, Chao Yan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4689095/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 Carbon Nanofibers (CNFs)/transition metal oxides (TMOs) composites have obtained much attention as supercapacitor electrode with benefits from the superior electrical conductivity of carbon materials and high capacity of TMOs. However, nano-size TMOs is prone to agglomeration and hard to grow efficiently and uniformly on CNFs due to the surface of CNFs lack effective targets, which limits its performance. In this paper, different hierarchical structures of CNFs-NiCo 2 O 4 were prepared and assembled as supercapacitor electrode. The results showed that CNFs-NiCo 2 O 4 prepared by treatment of potassium permanganate exhibited a high capacitance of 1175 F g − 1 at a current density of 1 A g − 1 and long-term cycling stability, with 93% capacitance retention after 3000 cycles. The excellent electrochemical performance could be attributed to that more active sites were introduced on the CNFs after solvent treatment, which were beneficial for NiCo 2 O 4 to grow uniformly on CNFs. This approach provides a new strategy for controllable design and synthesis of homogeneous hierarchical CNFs/TMOs composites. hierarchical Carbon nanofibers supercapacitors Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Transition metal oxides (TMOs) have attracted great interest for various applications as electrodes, catalysts, sensors, etc., due to their excellent theoretical specific capacitance, high redox reactivity, and environmental friendliness[ 1 – 4 ]. However, TMOs often suffers from low electrical conductivity and poor electrochemical stability which limit their usage[ 5 – 10 ]. To overcome these deficiencies, a large variety of TMOs based materials with various structures including zero, one, two and three dimension nanostructures have been fabricated to improve the performance. Among those, 1D Carbon nanofibers(CNFs) have attracted more and more attention for their advantages of efficient electron transport along one direction, excellent mechanical property, high pore volume, large specific surface area and ease to construct nanodevices[ 11 – 14 ]. In general, there are two methods to prepare CNFs/TMOs composites. In a one-step method, metal precursor and polymers (PAN, PVA or PVP) were mixed in organic solvent and then spun into nanofibers using an electrospinning apparatus[ 12 , 15 – 18 ]. This method is highly efficient and the synthesized TMOs could distribute well. However, the size and morphology of TMOs are hard to control during the electrospinning process, which can affect the performance of the composite. Also, large amounts of TMOs were wrapped in CNFs, thus they were hindered to contact with the electrolyte in the supercapacitor. Another one is a two-step method. Firstly, pure CNFs were obtained by electrospinning. Then TMOs were decorated on CNFs by electro-deposition or hydrothermal method. Compared to the one-step method, the size and morphology of TMOs can be exactly regulated in the two-step method. However, it’s difficult to control the distribution of nano-sized TMOs on CNFs as they are prone to aggregate, which would influence the electrical conductivity and performance. In recent years many efforts have been paid to growing TMOs efficiently and uniformly on CNFs, thus to improve the specific surface area as well as electrical performance. For instance, Balan et.al used hydrogen peroxide to treat CNFs by introducing oxygen containing functional groups. Then RuO 2 nanoparticles in the range of 2–3 nm were decorated around CNFs at room temperature and a hybrid electrode was prepared[ 19 ]. Liu et.al prepared CNFs/nickel-cobalt (Ni-Co) LDH composite by a co-deposition approach, in which CNFs were treated by sulfuric acid to increase its hydrophilicity[ 20 ]. The galvanostatic charge-discharge measurements revealed specific capacitance of CNFs/nickel-cobalt (Ni-Co) LDH was 1195.4 F g − 1 at 1 A g − 1 . Zhang et.al also used sulphuric acid to treat CNFs then MnO 2 were deposited on CNFs to fabricate MnO 2 /CNFs hybrid fibers. A single MnO 2 /CNFs fiber electrode exhibits a specific volumetric capacitance of 58.7 F cm − 3 with a specific gravimetric capacitance of 428 F g − 1 [21] . To the best of our knowledge, there are few reports on the rational design of a homogeneous hierarchical CNFs/TMOs nanocomposite. In our work, different CNFs-NiCo 2 O 4 hierarchical structures were prepared by a two-step method and assembled as supercapacitor electrode. Scanning electron microscope, Raman spectroscopy and X-ray diffraction were used to characterize the morphology and electronic structure of CNFs-NiCo 2 O 4 . Through systematic and detailed evaluation of electrochemistry characteristics, it is proved that more active sites were introduced on the CNFs after solvent treatment, which were beneficial for NiCo 2 O 4 to grow uniformly on CNFs. The present research brings new inspiration to controllable design and synthesis of homogeneous hierarchical CNFs/TMOs composites. 2. Experimental Section 2.1 Materials and chemicals Cobalt chloride hexahydrate, Hydrogen peroxide 30% aqueous solution, potassium hydroxide, urea, methanol, and potassium permanganate were purchased from Sinopharm Chemical Reagent Co. Ltd. Nickel chloride hexahydrate was purchased from Shanghai Macklin Biochemical Co., Ltd. Sulfuric acid, hydrochloric acid and Nitric acid were obtained from Shanghai SuYi Chemical Reagent Co. Ltd. All the chemicals used in the experiments were at analytical grade and without further purification. 2.2 Synthesis CNFs-NiCo 2 O 4 Firstly the CNFs were prepared using an electrospinning method as literature reported[ 22 ]. Five different structured CNFs-NCO composites were developed by using five different solvents: nitric acid, sulfuric acid, 0.5M potassium permanganate, hydrogen peroxide, potassium hydroxide. In this process, the CNFs were immersed in the five solvents for 30 min, respectively. Then the treated CNFs were washed by distilled water until it reached neutral pH and dried at 40 ℃ for 12 h. In a typical process, 0.4 mmol NiCl 2 ·H 2 O, 0.8 mmol CoCl 2 ·H 2 O and 30 mmol urea were added successively into 30 mL methanol with vigorous stirring to form homogeneous solution. The solution was transferred into a 50 mL Teflon autoclave, with a piece of treated CNFs (2 cm × 2 cm) immersed, followed by keeping at 120 ℃ for 6 h. After cooled down, the product was taken out and washed with deionized water and absolute ethanol for 3 times, then dried at 80 ℃ for 12 h. Finally the obtained sample was annealed at 300 ℃ for 2h with a heating rate of 5 ℃ min − 1 . The CNFs-NCO products prepared by immersing CNFs in potassium hydroxide, nitric acid, sulfuric acid, 0.5M potassium permanganate and hydrogen peroxide were named as CNFs-NCO1, CNFs-NCO2, CNFs-NCO3, CNFs-NCO4, CNFs-NCO5, respectively. 2.3 Characterization Scanning electron microscope (SEM, ZEISS) was carried out to characterize the morphology of the samples. X-ray diffraction (XRD, Bruker) patterns were taken on a powder XRD system with Cu Kα radiation, and Raman spectra were taken on a confocal Raman Microscope (Renishaw InVia) with an excitation length of 532 nm. Fourier transform infrared (FTIR, Bruker) spectroscopy was used to investigate the surface functional groups on spectrometer with ATR mode. The surface state and electron structure of the samples were obtained by X-ray photoelectron spectroscopy (XPS) measurement, using Al Ka radiation (1486 eV) as a probe. 2.4 Electrochemical measurements All the electrochemical measurements were carried out by using a Metrohm Autolab 302N electrochemical workstation. The electrochemical behaviors were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) and electrochemical impedance spectroscopy (EIS). The CV and GCD tests were carried out at various scan rates and current densities. The EIS plots were obtained in the frequency ranging from 0.01 Hz to 100 kHz with 5 mV amplitude. CNFs-NCO with mass loading (1∼1.2 mg cm − 2 ) was used as the work electrode and sandwiched between two pieces of foam Ni sheets without any conductive additives. The platinum (Pt) foil and Hg/HgO electrodes were used as the counter and reference electrodes, respectively. Cycling stability tests were performed in the range of 0-0.5 V with a constant current density of 5 A g − 1 for 3000 cycles by using a LANHE Battery Test System (Wuhan Kingnuo Electronic Company, China). All tests were conducted in 2M KOH aqueous electrolyte. The specifc capacitance of single electrode is calculated by the following formula: $$\:{C}_{s}=\left(I\bullet\:\varDelta\:t\right)/\left(m\bullet\:\varDelta\:V\right)$$ 1 where C s (F g − 1 ) is the specific capacitance of the electrode, I (A) is the discharge current, Δ t (s) is the discharge time, Δ V (V) is the voltage range and m is the whole mass of the binder-free electrode. 3. Results and Discussion Figure 1 illustrates the preparation process of NiCo 2 O 4 on CNFs. Firstly, CNFs were obtained by the thermal treatment of electrospun PAN nanofibers. Then CNFs were treated by solvent and NiCo 2 (OH) 6 nanosheets were grown on modified CNFs by a hydrothermal method to form core-shell structures. After annealing, CNFs-NiCo 2 O 4 was finally obtained. As the morphology and thickness of NiCo 2 O 4 grown on CNFs would greatly influence the performance of the composite, it’s necessary to investigate the interface of CNFs. Figure 2 showed the contact angel images of pure CNFs and modified CNFs by different solvents. The contact angle of the pure CNFs was as high as 116–117 。 , which indicated it is hydrophobic (Fig. 2 (a)). That it’s not conducive for NiCo 2 (OH) 6 nanosheets growing uniformly on CNFs by hydrothermal method. Figure 2 (b-e) are the contact angle images of modified CNFs treated with different solvents at different time and table S1 listed the corresponding contact angel value. Compared to CNFs treated by KOH, H 2 SO 4 and H 2 O 2 , the much lower contact angle of CNFs treated by HNO 3 and KMnO 4 presented they had much better hydrophilic performance. The CNFs treated by KMnO 4 could even be totally wetted immediately. FTIR was used to study the surface structure of CNFs and modified CNFs (see Fig S1 ). The result showed CNFs treated by HNO 3 and KMnO 4 have large amount of stretching vibration bands of C − O at around 1135 cm − 1 , which help to improve the surface hydrophilic performance of CNFs and as active sites to beneficial for the NiCo 2 O 4 to grow on. While C − O vibration peak nearly could not be detected in the products treated by KOH, H 2 SO 4 and H 2 O 2 . In order to evaluate the influence of surface treatment on the growing of NiCo 2 O 4 on CNFs, the morphology and microstructure of CNFs-NiCo 2 O 4 were investigated by SEM. As shown in Fig. 3 (a), the surface of pure CNFs was smooth and arranged randomly to form conductive networks. Numerous irregular micrometer-scale pores between the carbon nanofibers could enhance electron transfer rate among cathodes and offer sufficient channels for cathode breathing[ 23 ]. Figure 3 (b-e) showed the SEM images of different structured CNFs-NCO. It can be clearly observed that NiCo 2 O 4 nanosheets can uniformly grow on CNFs modified by HNO 3 (Fig. 3 (c)) and KMnO 4 (Fig. 3 (e)). On the contrary, few NiCo 2 O 4 nanosheets growed on CNFs modified by KOH (Fig. 3 (b)), H 2 SO 4 (Fig. 3 (d)) and H 2 O 2 (Fig. 3 (f)), as the NiCo 2 O 4 was prone to aggregate. All the results proved the growing of NiCo 2 O 4 on CNFs would be greatly influenced by surface treatment of different solvents. Figure 3 (g) was the photo of synthesized CNFs fibrofelt. With the decoration of NiCo 2 O 4 , CNFs-NCO fibrofelt remain the same macrostructure of pure CNFs and exhibited good flexibility, as shown in Fig. 3 (h, i). To further analyze the distribution of NiCo 2 O 4 on CNFs, Energy-dispersive X-ray (EDX) mapping was performed. As shown in Fig. 4 (a-e), the Ni, Co, and O elements are uniformly distributed around CNFs. The core-shell structure could be clearly observed from Fig. 4 (f), NiCo 2 O 4 nanoflakes wrapped uniformly around the CNFs core. The diameter of CNFs is measured to be around 195 nm and the hybrid structure was about 567 nm in width. EDX result of remarked area in CNFs-NCO4 also demonstrated the existence of Ni, Co, O and C elements. XRD was also used to characterize the component of CNFs-NCO composites, as shown in Fig. 5 (a). The XRD pattern of pure CNFs displayed a broad peak at around 22.5 o corresponding to (002) diffraction planes, demonstrating carbon formation in graphite phase during the synthesis process of CNFs. XRD patterns of the CNFs-NCO composite were compared with those of the standard PDF card (JCPDS-20-0781). The diffraction peaks at 30.9, 36.6, 44.5, 58.9 and 64.9° corresponded to the (220), (311), (400), (511) and (440) crystal planes of NiCo 2 O 4 , respectively. To investigate the electronic and structural properties of CNFs and CNFs-NCO composites, Raman spectroscopy was also performed (Fig. 5 (b)). Raman spectra of CNFs displayed two bands including D (1355 cm − 1 ) and G (1597 cm − 1 ): The D band corresponded to the amount of disorder and its intensity indicated the degree of edge chirality and the G band corresponded to the E 2g phonon vibration of sp 2 carbon atom. For the CNFs-NCO composites, both the D and G bands of the carbon material were suppressed, while the peaks at 165, 491 and 644 cm − 1 corresponded to the F 2g , E g and A 1g vibrational modes of NiCo 2 O 4 were also observed. This also demonstrated the surface of the CNFs substrate was covered by the NiCo 2 O 4 . The elemental and chemical bonding states of the CNFs-NCO4 were studied by XPS as well. Figure 6 (a) showed the spectra of CNFs-NCO4, in which there existed characteristic peaks for C, O, Co and Ni elements. The O 1s spectra (Fig. 6 b) showed three peaks with binding energies of 529.2 eV, 531.0 eV and 532.7 eV, which were attributed to metal-oxygen bonds (Ni-O-Co), double-bonded oxygen C = O-C, and single-bonded oxygen C-O-C, respectively. In Ni2p spectrum of CNFs-NCO4 (Fig. 6 c), the binding energies at 854.2 and 871.5 eV belong to Ni 2+ , and those at 855.4 and 872.8 eV belong to Ni 3+ [ 24 , 25 ]. The Co2p spectrum in Fig. 6 (d) showed two spin-orbit doublet peaks, one doublet peak at binding energies of 796.5 and 779.6 eV belong to Co 3+ species, while the other at 798.2 and 781.9 eV is from Co 2+ species. To evaluate the electrochemical properties of the different CNFs-NCO composites, CV and galvanostatic charge-discharge tests were carried out by a three-electrode system in 2.0 M KOH aqueous electrolyte. Figure 7 (a) was CV curve of the various CNFs-NCO electrodes at a scan rate of 20 mV/s. A pair of redox peaks can be observed within the potential range from 0 to 0.6 V, revealing the pseudocapacitive characteristics mainly from the faradaic redox reactions of M-O/M-O-OH (where M refers to Ni or Co). The larger integral area was detected in the CV curve of the CNFs-NCO4 electrode compared with the other four electrodes, indicating its superior specific capacitance. Figure 7 (b) was galvanostatic charge/discharge curves of the various CNFs-NCO electrodes at 1A/g. The CNFs-NCO4 electrode showed longer charging and discharging durations, exhibiting a superior electrochemical performance compared to other electrode systems. Figure 7 (c) showed the CV curve of the CNFs-NCO4 electrode at scan rates from 2 to 50 mV s − 1 . It is noted that the shape of CV curves showed no obvious change and the redox peaks showed a slight shift with the increase of the scan rate, which could be explained as the weak electrode polarization[ 26 ]. The CV curve of the CNFs-NCO1, CNFs-NCO2, CNFs-NCO3 and CNFs-NCO5 electrode at different scan rates as show in Fig. S2. Also the change of specific capacitance with the current density was studied. From Fig. 7 (d), the charge/discharge curves of the CNFs-NCO5 at a current density of 1, 2, 5, 10 and 20 A g − 1 show a stable platform, which correspond to the obvious redox peaks in CV curves. The charge/discharge curves of the CNFs-NCO1, CNFs-NCO2, CNFs-NCO3 and CNFs-NCO5 electrode at different current density as show in Fig. S3. Figure 7 (e) shows the specific capacitance of the different CNFs-NCO electrodes at different current densities. The specific capacitances of the CNFs-NCO4 electrodes at different currents of 1, 2, 5, 10, and 20 A g − 1 , were calculated using above equation to be 1175, 1145, 1067, 983, and 912 F g − 1 , respectively. Cycling stability performance is also highly required in supercapacitors. Figure 7 (f) shows the specific capacitance and coulombic efficiency at current density of 5 A g − 1 . After 3000 continuous cycles, the capacitance of CNFs-NCO4 electrode could maintain 93% of initial value, indicating good cycling stability. The coulombic efficiency of electrode is around 94%, demonstrating high reversibility of the flexible carbon-based electrode. The inset of Fig. 7 (f) shows the GCD curves of the first and last five cycles with a current density of 5A g − 1 . It can be observed that the last five cycles charge-discharge time maintained as long as 93% of the first 5 cycles, also demonstrating high capacitance after 3000 cycles. All of these indicate the CNFs-NCO4 electrode exhibited good cycling stability, which could be attributed to the uniform distribution of NiCo 2 O 4 nanosheets on the surface of CNFs. 4. Conclusions In summary, different CNFs-NiCo 2 O 4 hierarchical structures were prepared and assembled as supercapacitor electrode. The surface structure of CNFs greatly influenced the morphology and electrochemical performance of composite. CNFs-NiCo 2 O 4 prepared by treatment of potassium permanganate exhibited a capacity of 1175 F g − 1 at a current density of 1 A g − 1 , much higher than products treated by potassium hydroxide, nitric acid, sulfuric acid and hydrogen peroxide. It also showed good cycle performance that maintained 93% of initial capacitance up to 3000 cycles. The excellent electrochemical performance could be attributed to that more active sites were introduced on the CNFs after treatment of potassium permanganate, which were beneficial for NiCo 2 O 4 to grow uniformly on CNFs. Our results provide a new strategy for controllable design and synthesis of homogeneous hierarchical CNFs/TMOs composite. Declarations Conflicts of interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgment This research was funded by Jiangsu Province industry-university-research cooperation project (No. BY2022533). Appendix A. Supplementary data Supplementary data to this article can be found. References Kang L, Qiao DH, Zhang Q, Zou JX, Ai J, Jun SC, et al. Oxygen Vacancy-Induced Low-Valence reactive species enabling High-Efficient nonenzymatic glucose detection. Appl Surf Sci. 2024;669:160355. https:// doi. org/10.1016/j.apsusc.2024.160355. Huang MT, Wang M, Yang LM, Wang ZH, Yu HX, Chen KC, et al. Direct Regeneration of Spent Lithium-Ion Battery Cathodes: From Theoretical Study to Production Practice. Nano-Micro Letters. 2024;16:225. https:// doi. org/10.1007/s40820-024-01434-0. Parveen N, Ansari MO, Ansari SA, Kumar P. Nanostructured Titanium Nitride and Its Composites as High-Performance Supercapacitor Electrode Material. Nanomaterials. 2023;13:105. https:// doi. org/10.3390/nano13010105. Zhou ZQ, Yang LB, Ma C, Wang JT, Qiao WM, Ling LC. A review of the use of metal oxide/carbon composite materials to inhibit the shuttle effect in lithium-sulfur batteries. New Carbon Materials. 2024;39:201-22. https:// doi. org/10.1016/s1872-5805(24)60838-3. Lu X, Wang C, Favier F, Pinna N. Electrospun Nanomaterials for Supercapacitor Electrodes: Designed Architectures and Electrochemical Performance. Adv Energy Mater. 2017;7:1601301. https:// doi. org/10.1002/aenm.201601301. Salunkhe RR, Kaneti YV, Yamauchi Y. Metal-Organic Framework-Derived Nanoporous Metal Oxides toward Supercapacitor Applications: Progress and Prospects. ACS Nano. 2017;11:5293-308. https:// doi. org/10.1021/acsnano.7b02796. Chen SG, Wu BX, Qian H, Wu ZX, Liu P, Li FJ, et al. An asymmetric supercapacitor using sandwich-like NiS/NiTe/Ni positive electrode exhibits a super-long cycle life exceeding 200 000 cycles. J Power Sources. 2019;438:227000. https:// doi. org/10.1016/j.jpowsour.2019.227000. Feng X, Ning J, Wang D, Zhang JC, Dong JG, Zhang C, et al. All-solid-state planner micro-supercapacitor based on graphene/NiOOH/Ni (OH)(2) via mask-free patterning strategy. J Power Sources. 2019;418:130-7. https:// doi. org/10.1016/j.jpowsour.2019.01.093. Zhu J, Shen XP, Kong LR, Zhu GX, Ji ZY, Xu KQ, et al. MOF derived CoP-decorated nitrogen-doped carbon polyhedrons/reduced graphene oxide composites for high performance supercapacitors. Dalton Trans. 2019;48:10661-8. https:// doi. org/10.1039/c9dt01629e. Wang P, Shen M, Zhou H, Meng C, Yuan A. MOF-Derived CuS@Cu-BTC Composites as High-Performance Anodes for Lithium-Ion Batteries. Small (Weinheim an der Bergstrasse, Germany). 2019;e1903522. https:// doi. org/10.1002/smll.201903522. Zhuo QQ, Tang JJ, Sun J, Yan C. High Efficient Reduction of Graphene Oxide via Nascent Hydrogen at Room Temperature. Materials. 2018;11:340. https:// doi. org/10.3390/ma11030340. Zhuo QQ, Zhang YP, Du QC, Yan C. Facile reduction of graphene oxide at room temperature by ammonia borane via salting out effect. J Colloid Interface Sci. 2015;457:243-7. https:// doi. org/10.1016/j.jcis.2015.07.029. Havigh RS, Yildirim F, Chenari HM, Türüt A, Aydogan S. Self-powered stable high-performance UV-Vis-NIR broadband photodetector based on PVP-Cobalt@Carbon nanofibers/n-GaAs heterojunction. Nanotechnology. 2024;35:335201. https:// doi. org/10.1088/1361-6528/ad4973. Seo JW, Park JH, Jung JW, Choi SJ. Dual-catalytic activation of Pt and MoS x O y on carbon nanofibers for NO 2 sensors. Sensors and Actuators B-Chemical. 2024;412:135750. https:// doi. org/10.1016/j.snb.2024.135750. Han J, Wang S, Zhu S, Huang C, Yue Y, Mei C, et al. Electrospun Core-Shell Nanofibrous Membranes with Nanocellulose-Stabilized Carbon Nanotubes for Use as High-Performance Flexible Supercapacitor Electrodes with Enhanced Water Resistance, Thermal Stability and Mechanical Toughness. ACS Appl Mater Interfaces. 2019;11:44624-35. https:// doi. org/10.1021/acsami.9b16458. Dai Z, Ren PG, An YL, Zhang H, Ren F, Zhang Q. Nitrogen-sulphur Co-doped graphenes modified electrospun lignin/polyacrylonitrile-based carbon nanofiber as high performance supercapacitor. J Power Sources. 2019;437:226937. https:// doi. org/10.1016/j.jpowsour.2019.226937. Guo YQ, Hong XF, Wang Y, Li Q, Meng JS, Dai RT, et al. Multicomponent Hierarchical Cu-Doped NiCo-LDH/CuO Double Arrays for Ultralong-Life Hybrid Fiber Supercapacitor. Advanced Functional Materials. 2019;29:1809004. https:// doi. org/10.1002/adfm.201809004. Zhuo QQ, Gao J, Peng MF, Bai LL, Deng JJ, Xia YJ, et al. Large-scale synthesis of graphene by the reduction of graphene oxide at room temperature using metal nanoparticles as catalyst. Carbon. 2013;52:559-64. https:// doi. org/10.1016/j.carbon.2012.10.014. Balan BK, Chaudhari HD, Kharul UK, Kurungot S. Carbon nanofiber-RuO2-poly(benzimidazole) ternary hybrids for improved supercapacitor performance. RSC Advances. 2013;3:2428-36. https:// doi. org/10.1039/c2ra22776b. Lai F, Huang Y, Miao Y-E, Liu T. Controllable preparation of multi-dimensional hybrid materials of nickel-cobalt layered double hydroxide nanorods/nanosheets on electrospun carbon nanofibers for high-performance supercapacitors. Electrochimica Acta. 2015;174:456-63. https:// doi. org/10.1016/j.electacta.2015.06.031. Zhang JX, Zhao X, Huang ZL, Xu T, Zhang QH. High-performance all-solid-state flexible supercapacitors based on manganese dioxide/carbon fibers. Carbon. 2016;107:844-51. https:// doi. org/10.1016/j.carbon.2016.06.064. Lin S-C, Lu Y-T, Chien YA, Wang J-A, You T-H, Wang Y-S, et al. Asymmetric supercapacitors based on functional electrospun carbon nanofiber/manganese oxide electrodes with high power density and energy density. J Power Sources. 2017;362:258-69. https:// doi. org/10.1016/j.jpowsour.2017.07.052. Liu G, Zhang L, Wang S, Ding L-X, Wang H. Hierarchical NiCo2O4 nanosheets on carbon nanofiber films for high energy density and long-life Li-O-2 batteries. Journal of Materials Chemistry A. 2017;5:14530-6. https:// doi. org/10.1039/c7ta03703a. Xu J, Zhang L, Xu G, Sun Z, Zhang C, Ma X, et al. Facile synthesis of NiS anchored carbon nanofibers for high-performance supercapacitors. Appl Surf Sci. 2018;434:112-9. https:// doi. org/10.1016/j.apsusc.2017.09.233. Parveen N, Al-Jaafari AI, Han JI. Robust cyclic stability and high-rate asymmetric supercapacitor based on orange peel-derived nitrogen-doped porous carbon and intercrossed interlinked urchin-like NiCo2O4@3DNF framework. Electrochimica Acta. 2019;293:84-96. https:// doi. org/10.1016/j.electacta.2018.08.157. Tian D, Lu XF, Nie GD, Gao M, Wang C. Direct growth of Ni-Mn-O nanosheets on flexible electrospun carbon nanofibers for high performance supercapacitor applications. Inorg Chem Front. 2018;5:635-42. https:// doi. org/10.1039/c7qi00696a. Additional Declarations No competing interests reported. Supplementary Files SupportingMaterials.docx 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. 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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-4689095","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":335216588,"identity":"6a738abb-8b70-4310-a02b-349f0944775a","order_by":0,"name":"Qiqi Zhuo","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABEUlEQVRIiWNgGAWjYHACxgcfKmzs+NmbDz6QgIgYENLCbDjjTFqyZM+xZAOgFglitLBJ87YdYtxww8cMpJywFvn25M2GM9gOMDPcYEursGyrq2Ngb94mwVBzB7dHep4VPvjAc4ePcXbzsRuSbYclGHiOlUkwHHuG2yMSOcaGMySeMTPLHEsDajkgwSCRYybB2HAYt0eACqR5DA4ztgEZBZJtdRIM8m/wa+EBa0k4zNgDZDBItjEDbeHBr0WC51mx4YwDackSPMeSJSTOHZZs40krtkg4hlsLMMQ2Pvj4z8bO/njzwc8SZXX8/OyHN974UINbCwNDAiIWmEGRwgYWxKMBRQvjB7wqR8EoGAWjYKQCABnKU6ATJzf0AAAAAElFTkSuQmCC","orcid":"","institution":"Jiangsu University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Qiqi","middleName":"","lastName":"Zhuo","suffix":""},{"id":335216589,"identity":"ccadb896-15bc-4328-a94b-f525fabe2184","order_by":1,"name":"Yalou Lv","email":"","orcid":"","institution":"Jiangsu University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Yalou","middleName":"","lastName":"Lv","suffix":""},{"id":335216590,"identity":"ac3082e4-d1d3-417b-8fad-d420204088f3","order_by":2,"name":"Hanzhao Wu","email":"","orcid":"","institution":"Jiangsu University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Hanzhao","middleName":"","lastName":"Wu","suffix":""},{"id":335216591,"identity":"9ca6cafa-1635-4a5c-8246-d914ed0f0d1d","order_by":3,"name":"Jintian Jiang","email":"","orcid":"","institution":"Jiangsu University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Jintian","middleName":"","lastName":"Jiang","suffix":""},{"id":335216592,"identity":"07a4dae5-8454-491a-afc3-c089c6f97fc0","order_by":4,"name":"Jijun Tang","email":"","orcid":"","institution":"Jiangsu University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Jijun","middleName":"","lastName":"Tang","suffix":""},{"id":335216593,"identity":"60abc45a-ae94-431b-b313-53e854e459c5","order_by":5,"name":"Chao Yan","email":"","orcid":"","institution":"Jiangsu University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Chao","middleName":"","lastName":"Yan","suffix":""}],"badges":[],"createdAt":"2024-07-05 02:21:51","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4689095/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4689095/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":61851845,"identity":"1172b6b1-2a20-41bc-bc3f-993770fa98a6","added_by":"auto","created_at":"2024-08-06 09:10:05","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":116283,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic of growing process of NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e on CNFs.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4689095/v1/5661ec0ba03b77fd0312ec83.png"},{"id":61852737,"identity":"44809fec-112f-46e8-9a83-99aa42beecd3","added_by":"auto","created_at":"2024-08-06 09:18:05","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":82512,"visible":true,"origin":"","legend":"\u003cp\u003eContact angel images of (a) pure CNFs and modified CNFs by (b) KOH; (c) HNO\u003csub\u003e3\u003c/sub\u003e; (d) H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e; (e) KMNO\u003csub\u003e4\u003c/sub\u003e; (f) H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4689095/v1/bedb5c6d656f9cf4d487e614.png"},{"id":61851847,"identity":"d7b75efa-2573-40bb-8783-a0a103ec8bd7","added_by":"auto","created_at":"2024-08-06 09:10:05","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":504479,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of (a) pure CNFs and CNFs-NCO composite grown from CNFs modified by (b) KOH; (c) HNO\u003csub\u003e3\u003c/sub\u003e; (d) H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e; (e) KMNO\u003csub\u003e4\u003c/sub\u003e; (f) H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e; Photos of (g) CNFs fibrofelt and (h) CNFs-NCO fibrofelt; (i) bended CNFs-NCO fibrofelt.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4689095/v1/ed9aaee9b8bd9a5402e608e7.png"},{"id":61852738,"identity":"448d100d-1bdb-4627-a583-6efb3fe2bd46","added_by":"auto","created_at":"2024-08-06 09:18:05","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":368631,"visible":true,"origin":"","legend":"\u003cp\u003e(a) SEM image of CNFs-NCO4 and the corresponding elemental mappings of (b) carbon; (c) oxygen; (d) cobalt; (e) Nickel; (f) SEM image of CNFs with and without NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e; (g) SEM image CNFs-NCO4; (h) EDX of\u0026nbsp; remark area in (g).\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4689095/v1/e2e871e3e1744dd5e8863966.png"},{"id":61851849,"identity":"6f459f2c-5e45-41fa-bbce-8c68c44edbc0","added_by":"auto","created_at":"2024-08-06 09:10:05","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":201450,"visible":true,"origin":"","legend":"\u003cp\u003e(a) XRD patterns of CNFs and CNFs-NCO; (b) Raman spectra of CNFs and CNFs-NCO.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-4689095/v1/bd71cce1aa22c2323f8e17fa.png"},{"id":61851846,"identity":"64296dad-97b2-4f2a-bedc-0ad247e9e485","added_by":"auto","created_at":"2024-08-06 09:10:05","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":173478,"visible":true,"origin":"","legend":"\u003cp\u003eXPS spectra of CNFs-NCO4. (a) survey spectra of CNFs-NCO4; (b) O1s of CNFs-NCO4; (c)\u003cstrong\u003e \u003c/strong\u003eNi2p\u003cstrong\u003e \u003c/strong\u003eof CNFs-NCO4; (d) Co2p of CNFs-NCO4.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-4689095/v1/ac6b9505bb9786c494b3b984.png"},{"id":61851851,"identity":"4b953972-b8b9-4de8-8b60-46c028e1fa06","added_by":"auto","created_at":"2024-08-06 09:10:05","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":241612,"visible":true,"origin":"","legend":"\u003cp\u003e(a) CV curves of the different CNFs-NCO at scan rate of 20 mV/s; (b) Galvanostatic charge/discharge curves of the different CNFs-NCO at 1A/g; (c) CV curves of the CNFs-NCO4 electrode at different scan rates; (d) Charge/discharge curves of the CNFs-NCO4 at different current density; (e) Specific capacitance of the different CNFs-NCO electrode at different current densities; (f) Cycling stability and coulombic efficiency of the CNFs-NCO4, the inset shows GCD curves of the first and last five cycles with a current density of 5A g\u003csup\u003e-1\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-4689095/v1/90ff53caec1fa2e839e1c09f.png"},{"id":86299089,"identity":"c8f1d590-f083-4068-93b1-028530c3c6d3","added_by":"auto","created_at":"2025-07-09 06:02:29","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2194593,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4689095/v1/b8f97eef-3ccb-4a32-8994-1bacf619e7d1.pdf"},{"id":61851853,"identity":"724b1a04-5e30-4515-ae8b-e93b1eb0c4db","added_by":"auto","created_at":"2024-08-06 09:10:05","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":2629404,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingMaterials.docx","url":"https://assets-eu.researchsquare.com/files/rs-4689095/v1/c8f66002a085fc33b2444ae7.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Hierarchical carbon nanofiber/NiCo2O4 composites as electrode for high-performance supercapacitors","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eTransition metal oxides (TMOs) have attracted great interest for various applications as electrodes, catalysts, sensors, etc., due to their excellent theoretical specific capacitance, high redox reactivity, and environmental friendliness[\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. However, TMOs often suffers from low electrical conductivity and poor electrochemical stability which limit their usage[\u003cspan additionalcitationids=\"CR6 CR7 CR8 CR9\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. To overcome these deficiencies, a large variety of TMOs based materials with various structures including zero, one, two and three dimension nanostructures have been fabricated to improve the performance. Among those, 1D Carbon nanofibers(CNFs) have attracted more and more attention for their advantages of efficient electron transport along one direction, excellent mechanical property, high pore volume, large specific surface area and ease to construct nanodevices[\u003cspan additionalcitationids=\"CR12 CR13\" citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn general, there are two methods to prepare CNFs/TMOs composites. In a one-step method, metal precursor and polymers (PAN, PVA or PVP) were mixed in organic solvent and then spun into nanofibers using an electrospinning apparatus[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan additionalcitationids=\"CR16 CR17\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. This method is highly efficient and the synthesized TMOs could distribute well. However, the size and morphology of TMOs are hard to control during the electrospinning process, which can affect the performance of the composite. Also, large amounts of TMOs were wrapped in CNFs, thus they were hindered to contact with the electrolyte in the supercapacitor. Another one is a two-step method. Firstly, pure CNFs were obtained by electrospinning. Then TMOs were decorated on CNFs by electro-deposition or hydrothermal method. Compared to the one-step method, the size and morphology of TMOs can be exactly regulated in the two-step method. However, it\u0026rsquo;s difficult to control the distribution of nano-sized TMOs on CNFs as they are prone to aggregate, which would influence the electrical conductivity and performance. In recent years many efforts have been paid to growing TMOs efficiently and uniformly on CNFs, thus to improve the specific surface area as well as electrical performance. For instance, Balan et.al used hydrogen peroxide to treat CNFs by introducing oxygen containing functional groups. Then RuO\u003csub\u003e2\u003c/sub\u003e nanoparticles in the range of 2\u0026ndash;3 nm were decorated around CNFs at room temperature and a hybrid electrode was prepared[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Liu et.al prepared CNFs/nickel-cobalt (Ni-Co) LDH composite by a co-deposition approach, in which CNFs were treated by sulfuric acid to increase its hydrophilicity[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The galvanostatic charge-discharge measurements revealed specific capacitance of CNFs/nickel-cobalt (Ni-Co) LDH was 1195.4 F g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 1 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Zhang et.al also used sulphuric acid to treat CNFs then MnO\u003csub\u003e2\u003c/sub\u003e were deposited on CNFs to fabricate MnO\u003csub\u003e2\u003c/sub\u003e/CNFs hybrid fibers. A single MnO\u003csub\u003e2\u003c/sub\u003e/CNFs fiber electrode exhibits a specific volumetric capacitance of 58.7 F cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e with a specific gravimetric capacitance of 428 F g\u003csup\u003e\u0026minus;\u0026thinsp;1 [21]\u003c/sup\u003e. To the best of our knowledge, there are few reports on the rational design of a homogeneous hierarchical CNFs/TMOs nanocomposite.\u003c/p\u003e \u003cp\u003eIn our work, different CNFs-NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e hierarchical structures were prepared by a two-step method and assembled as supercapacitor electrode. Scanning electron microscope, Raman spectroscopy and X-ray diffraction were used to characterize the morphology and electronic structure of CNFs-NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e. Through systematic and detailed evaluation of electrochemistry characteristics, it is proved that more active sites were introduced on the CNFs after solvent treatment, which were beneficial for NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e to grow uniformly on CNFs. The present research brings new inspiration to controllable design and synthesis of homogeneous hierarchical CNFs/TMOs composites.\u003c/p\u003e"},{"header":"2. Experimental Section","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials and chemicals\u003c/h2\u003e \u003cp\u003eCobalt chloride hexahydrate, Hydrogen peroxide 30% aqueous solution, potassium hydroxide, urea, methanol, and potassium permanganate were purchased from Sinopharm Chemical Reagent Co. Ltd. Nickel chloride hexahydrate was purchased from Shanghai Macklin Biochemical Co., Ltd. Sulfuric acid, hydrochloric acid and Nitric acid were obtained from Shanghai SuYi Chemical Reagent Co. Ltd. All the chemicals used in the experiments were at analytical grade and without further purification.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Synthesis CNFs-NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/h2\u003e \u003cp\u003eFirstly the CNFs were prepared using an electrospinning method as literature reported[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Five different structured CNFs-NCO composites were developed by using five different solvents: nitric acid, sulfuric acid, 0.5M potassium permanganate, hydrogen peroxide, potassium hydroxide. In this process, the CNFs were immersed in the five solvents for 30 min, respectively. Then the treated CNFs were washed by distilled water until it reached neutral pH and dried at 40 ℃ for 12 h. In a typical process, 0.4 mmol NiCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;H\u003csub\u003e2\u003c/sub\u003eO, 0.8 mmol CoCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;H\u003csub\u003e2\u003c/sub\u003eO and 30 mmol urea were added successively into 30 mL methanol with vigorous stirring to form homogeneous solution. The solution was transferred into a 50 mL Teflon autoclave, with a piece of treated CNFs (2 cm \u0026times; 2 cm) immersed, followed by keeping at 120 ℃ for 6 h. After cooled down, the product was taken out and washed with deionized water and absolute ethanol for 3 times, then dried at 80 ℃ for 12 h. Finally the obtained sample was annealed at 300 ℃ for 2h with a heating rate of 5 ℃ min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The CNFs-NCO products prepared by immersing CNFs in potassium hydroxide, nitric acid, sulfuric acid, 0.5M potassium permanganate and hydrogen peroxide were named as CNFs-NCO1, CNFs-NCO2, CNFs-NCO3, CNFs-NCO4, CNFs-NCO5, respectively.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Characterization\u003c/h2\u003e \u003cp\u003eScanning electron microscope (SEM, ZEISS) was carried out to characterize the morphology of the samples. X-ray diffraction (XRD, Bruker) patterns were taken on a powder XRD system with Cu Kα radiation, and Raman spectra were taken on a confocal Raman Microscope (Renishaw InVia) with an excitation length of 532 nm. Fourier transform infrared (FTIR, Bruker) spectroscopy was used to investigate the surface functional groups on spectrometer with ATR mode. The surface state and electron structure of the samples were obtained by X-ray photoelectron spectroscopy (XPS) measurement, using Al Ka radiation (1486 eV) as a probe.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Electrochemical measurements\u003c/h2\u003e \u003cp\u003eAll the electrochemical measurements were carried out by using a Metrohm Autolab 302N electrochemical workstation. The electrochemical behaviors were investigated by cyclic voltammetry (CV), galvanostatic charge\u0026ndash;discharge (GCD) and electrochemical impedance spectroscopy (EIS). The CV and GCD tests were carried out at various scan rates and current densities. The EIS plots were obtained in the frequency ranging from 0.01 Hz to 100 kHz with 5 mV amplitude. CNFs-NCO with mass loading (1\u0026sim;1.2 mg cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) was used as the work electrode and sandwiched between two pieces of foam Ni sheets without any conductive additives. The platinum (Pt) foil and Hg/HgO electrodes were used as the counter and reference electrodes, respectively. Cycling stability tests were performed in the range of 0-0.5 V with a constant current density of 5 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for 3000 cycles by using a LANHE Battery Test System (Wuhan Kingnuo Electronic Company, China). All tests were conducted in 2M KOH aqueous electrolyte.\u003c/p\u003e \u003cp\u003eThe specifc capacitance of single electrode is calculated by the following formula:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:{C}_{s}=\\left(I\\bullet\\:\\varDelta\\:t\\right)/\\left(m\\bullet\\:\\varDelta\\:V\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere \u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e (F g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) is the specific capacitance of the electrode, \u003cem\u003eI\u003c/em\u003e (A) is the discharge current, Δ\u003cem\u003et\u003c/em\u003e (s) is the discharge time, Δ\u003cem\u003eV\u003c/em\u003e (V) is the voltage range and \u003cem\u003em\u003c/em\u003e is the whole mass of the binder-free electrode.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e illustrates the preparation process of NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e on CNFs. Firstly, CNFs were obtained by the thermal treatment of electrospun PAN nanofibers. Then CNFs were treated by solvent and NiCo\u003csub\u003e2\u003c/sub\u003e(OH)\u003csub\u003e6\u003c/sub\u003e nanosheets were grown on modified CNFs by a hydrothermal method to form core-shell structures. After annealing, CNFs-NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e was finally obtained. As the morphology and thickness of NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e grown on CNFs would greatly influence the performance of the composite, it\u0026rsquo;s necessary to investigate the interface of CNFs. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e showed the contact angel images of pure CNFs and modified CNFs by different solvents. The contact angle of the pure CNFs was as high as 116\u0026ndash;117\u003csup\u003e。\u003c/sup\u003e, which indicated it is hydrophobic (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(a)). That it\u0026rsquo;s not conducive for NiCo\u003csub\u003e2\u003c/sub\u003e(OH)\u003csub\u003e6\u003c/sub\u003e nanosheets growing uniformly on CNFs by hydrothermal method. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b-e) are the contact angle images of modified CNFs treated with different solvents at different time and table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e listed the corresponding contact angel value. Compared to CNFs treated by KOH, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e, the much lower contact angle of CNFs treated by HNO\u003csub\u003e3\u003c/sub\u003e and KMnO\u003csub\u003e4\u003c/sub\u003e presented they had much better hydrophilic performance. The CNFs treated by KMnO\u003csub\u003e4\u003c/sub\u003e could even be totally wetted immediately. FTIR was used to study the surface structure of CNFs and modified CNFs (see Fig \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). The result showed CNFs treated by HNO\u003csub\u003e3\u003c/sub\u003e and KMnO\u003csub\u003e4\u003c/sub\u003e have large amount of stretching vibration bands of C\u0026thinsp;\u0026minus;\u0026thinsp;O at around 1135 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which help to improve the surface hydrophilic performance of CNFs and as active sites to beneficial for the NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e to grow on. While C\u0026thinsp;\u0026minus;\u0026thinsp;O vibration peak nearly could not be detected in the products treated by KOH, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn order to evaluate the influence of surface treatment on the growing of NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e on CNFs, the morphology and microstructure of CNFs-NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e were investigated by SEM. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(a), the surface of pure CNFs was smooth and arranged randomly to form conductive networks. Numerous irregular micrometer-scale pores between the carbon nanofibers could enhance electron transfer rate among cathodes and offer sufficient channels for cathode breathing[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(b-e) showed the SEM images of different structured CNFs-NCO. It can be clearly observed that NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanosheets can uniformly grow on CNFs modified by HNO\u003csub\u003e3\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(c)) and KMnO\u003csub\u003e4\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(e)). On the contrary, few NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanosheets growed on CNFs modified by KOH (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(b)), H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(d)) and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(f)), as the NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e was prone to aggregate. All the results proved the growing of NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e on CNFs would be greatly influenced by surface treatment of different solvents. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e (g) was the photo of synthesized CNFs fibrofelt. With the decoration of NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e, CNFs-NCO fibrofelt remain the same macrostructure of pure CNFs and exhibited good flexibility, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e (h, i).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo further analyze the distribution of NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e on CNFs, Energy-dispersive X-ray (EDX) mapping was performed. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(a-e), the Ni, Co, and O elements are uniformly distributed around CNFs. The core-shell structure could be clearly observed from Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(f), NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanoflakes wrapped uniformly around the CNFs core. The diameter of CNFs is measured to be around 195 nm and the hybrid structure was about 567 nm in width. EDX result of remarked area in CNFs-NCO4 also demonstrated the existence of Ni, Co, O and C elements.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eXRD was also used to characterize the component of CNFs-NCO composites, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(a). The XRD pattern of pure CNFs displayed a broad peak at around 22.5\u003csup\u003eo\u003c/sup\u003e corresponding to (002) diffraction planes, demonstrating carbon formation in graphite phase during the synthesis process of CNFs. XRD patterns of the CNFs-NCO composite were compared with those of the standard PDF card (JCPDS-20-0781). The diffraction peaks at 30.9, 36.6, 44.5, 58.9 and 64.9\u0026deg; corresponded to the (220), (311), (400), (511) and (440) crystal planes of NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e, respectively. To investigate the electronic and structural properties of CNFs and CNFs-NCO composites, Raman spectroscopy was also performed (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(b)). Raman spectra of CNFs displayed two bands including D (1355 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and G (1597 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e): The D band corresponded to the amount of disorder and its intensity indicated the degree of edge chirality and the G band corresponded to the E\u003csub\u003e2g\u003c/sub\u003e phonon vibration of sp\u003csup\u003e2\u003c/sup\u003e carbon atom. For the CNFs-NCO composites, both the D and G bands of the carbon material were suppressed, while the peaks at 165, 491 and 644 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponded to the F\u003csub\u003e2g\u003c/sub\u003e, E\u003csub\u003eg\u003c/sub\u003e and A\u003csub\u003e1g\u003c/sub\u003e vibrational modes of NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e were also observed. This also demonstrated the surface of the CNFs substrate was covered by the NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe elemental and chemical bonding states of the CNFs-NCO4 were studied by XPS as well. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(a) showed the spectra of CNFs-NCO4, in which there existed characteristic peaks for C, O, Co and Ni elements. The O 1s spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb) showed three peaks with binding energies of 529.2 eV, 531.0 eV and 532.7 eV, which were attributed to metal-oxygen bonds (Ni-O-Co), double-bonded oxygen C\u0026thinsp;=\u0026thinsp;O-C, and single-bonded oxygen C-O-C, respectively. In Ni2p spectrum of CNFs-NCO4 (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec), the binding energies at 854.2 and 871.5 eV belong to Ni\u003csup\u003e2+\u003c/sup\u003e, and those at 855.4 and 872.8 eV belong to Ni\u003csup\u003e3+\u003c/sup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The Co2p spectrum in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(d) showed two spin-orbit doublet peaks, one doublet peak at binding energies of 796.5 and 779.6 eV belong to Co\u003csup\u003e3+\u003c/sup\u003e species, while the other at 798.2 and 781.9 eV is from Co\u003csup\u003e2+\u003c/sup\u003e species.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo evaluate the electrochemical properties of the different CNFs-NCO composites, CV and galvanostatic charge-discharge tests were carried out by a three-electrode system in 2.0 M KOH aqueous electrolyte. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(a) was CV curve of the various CNFs-NCO electrodes at a scan rate of 20 mV/s. A pair of redox peaks can be observed within the potential range from 0 to 0.6 V, revealing the pseudocapacitive characteristics mainly from the faradaic redox reactions of M-O/M-O-OH (where M refers to Ni or Co). The larger integral area was detected in the CV curve of the CNFs-NCO4 electrode compared with the other four electrodes, indicating its superior specific capacitance. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(b) was galvanostatic charge/discharge curves of the various CNFs-NCO electrodes at 1A/g. The CNFs-NCO4 electrode showed longer charging and discharging durations, exhibiting a superior electrochemical performance compared to other electrode systems. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(c) showed the CV curve of the CNFs-NCO4 electrode at scan rates from 2 to 50 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. It is noted that the shape of CV curves showed no obvious change and the redox peaks showed a slight shift with the increase of the scan rate, which could be explained as the weak electrode polarization[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. The CV curve of the CNFs-NCO1, CNFs-NCO2, CNFs-NCO3 and CNFs-NCO5 electrode at different scan rates as show in Fig. S2. Also the change of specific capacitance with the current density was studied. From Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(d), the charge/discharge curves of the CNFs-NCO5 at a current density of 1, 2, 5, 10 and 20 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e show a stable platform, which correspond to the obvious redox peaks in CV curves. The charge/discharge curves of the CNFs-NCO1, CNFs-NCO2, CNFs-NCO3 and CNFs-NCO5 electrode at different current density as show in Fig. S3.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(e) shows the specific capacitance of the different CNFs-NCO electrodes at different current densities. The specific capacitances of the CNFs-NCO4 electrodes at different currents of 1, 2, 5, 10, and 20 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, were calculated using above equation to be 1175, 1145, 1067, 983, and 912 F g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. Cycling stability performance is also highly required in supercapacitors. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(f) shows the specific capacitance and coulombic efficiency at current density of 5 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. After 3000 continuous cycles, the capacitance of CNFs-NCO4 electrode could maintain 93% of initial value, indicating good cycling stability. The coulombic efficiency of electrode is around 94%, demonstrating high reversibility of the flexible carbon-based electrode. The inset of Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e(f) shows the GCD curves of the first and last five cycles with a current density of 5A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. It can be observed that the last five cycles charge-discharge time maintained as long as 93% of the first 5 cycles, also demonstrating high capacitance after 3000 cycles. All of these indicate the CNFs-NCO4 electrode exhibited good cycling stability, which could be attributed to the uniform distribution of NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanosheets on the surface of CNFs.\u003c/p\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eIn summary, different CNFs-NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e hierarchical structures were prepared and assembled as supercapacitor electrode. The surface structure of CNFs greatly influenced the morphology and electrochemical performance of composite. CNFs-NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e prepared by treatment of potassium permanganate exhibited a capacity of 1175 F g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at a current density of 1 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, much higher than products treated by potassium hydroxide, nitric acid, sulfuric acid and hydrogen peroxide. It also showed good cycle performance that maintained 93% of initial capacitance up to 3000 cycles. The excellent electrochemical performance could be attributed to that more active sites were introduced on the CNFs after treatment of potassium permanganate, which were beneficial for NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e to grow uniformly on CNFs. Our results provide a new strategy for controllable design and synthesis of homogeneous hierarchical CNFs/TMOs composite.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eConflicts of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp; \u0026nbsp; The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eThis research was funded by Jiangsu Province industry-university-research cooperation project\u0026nbsp;(No. BY2022533).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAppendix A. Supplementary data\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSupplementary data to this article can be found.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eKang L, Qiao DH, Zhang Q, Zou JX, Ai J, Jun SC, et al. Oxygen Vacancy-Induced Low-Valence reactive species enabling High-Efficient nonenzymatic glucose detection. Appl Surf Sci. 2024;669:160355. https:// doi. org/10.1016/j.apsusc.2024.160355.\u003c/li\u003e\n\u003cli\u003eHuang MT, Wang M, Yang LM, Wang ZH, Yu HX, Chen KC, et al. Direct Regeneration of Spent Lithium-Ion Battery Cathodes: From Theoretical Study to Production Practice. Nano-Micro Letters. 2024;16:225. https:// doi. org/10.1007/s40820-024-01434-0.\u003c/li\u003e\n\u003cli\u003eParveen N, Ansari MO, Ansari SA, Kumar P. Nanostructured Titanium Nitride and Its Composites as High-Performance Supercapacitor Electrode Material. Nanomaterials. 2023;13:105. https:// doi. org/10.3390/nano13010105.\u003c/li\u003e\n\u003cli\u003eZhou ZQ, Yang LB, Ma C, Wang JT, Qiao WM, Ling LC. A review of the use of metal oxide/carbon composite materials to inhibit the shuttle effect in lithium-sulfur batteries. New Carbon Materials. 2024;39:201-22. https:// doi. org/10.1016/s1872-5805(24)60838-3.\u003c/li\u003e\n\u003cli\u003eLu X, Wang C, Favier F, Pinna N. Electrospun Nanomaterials for Supercapacitor Electrodes: Designed Architectures and Electrochemical Performance. Adv Energy Mater. 2017;7:1601301. https:// doi. org/10.1002/aenm.201601301.\u003c/li\u003e\n\u003cli\u003eSalunkhe RR, Kaneti YV, Yamauchi Y. Metal-Organic Framework-Derived Nanoporous Metal Oxides toward Supercapacitor Applications: Progress and Prospects. ACS Nano. 2017;11:5293-308. https:// doi. org/10.1021/acsnano.7b02796.\u003c/li\u003e\n\u003cli\u003eChen SG, Wu BX, Qian H, Wu ZX, Liu P, Li FJ, et al. An asymmetric supercapacitor using sandwich-like NiS/NiTe/Ni positive electrode exhibits a super-long cycle life exceeding 200 000 cycles. J Power Sources. 2019;438:227000. https:// doi. org/10.1016/j.jpowsour.2019.227000.\u003c/li\u003e\n\u003cli\u003eFeng X, Ning J, Wang D, Zhang JC, Dong JG, Zhang C, et al. All-solid-state planner micro-supercapacitor based on graphene/NiOOH/Ni (OH)(2) via mask-free patterning strategy. J Power Sources. 2019;418:130-7. https:// doi. org/10.1016/j.jpowsour.2019.01.093.\u003c/li\u003e\n\u003cli\u003eZhu J, Shen XP, Kong LR, Zhu GX, Ji ZY, Xu KQ, et al. MOF derived CoP-decorated nitrogen-doped carbon polyhedrons/reduced graphene oxide composites for high performance supercapacitors. Dalton Trans. 2019;48:10661-8. https:// doi. org/10.1039/c9dt01629e.\u003c/li\u003e\n\u003cli\u003eWang P, Shen M, Zhou H, Meng C, Yuan A. MOF-Derived CuS@Cu-BTC Composites as High-Performance Anodes for Lithium-Ion Batteries. Small (Weinheim an der Bergstrasse, Germany). 2019;e1903522. https:// doi. org/10.1002/smll.201903522.\u003c/li\u003e\n\u003cli\u003eZhuo QQ, Tang JJ, Sun J, Yan C. High Efficient Reduction of Graphene Oxide via Nascent Hydrogen at Room Temperature. Materials. 2018;11:340. https:// doi. org/10.3390/ma11030340.\u003c/li\u003e\n\u003cli\u003eZhuo QQ, Zhang YP, Du QC, Yan C. Facile reduction of graphene oxide at room temperature by ammonia borane via salting out effect. J Colloid Interface Sci. 2015;457:243-7. https:// doi. org/10.1016/j.jcis.2015.07.029.\u003c/li\u003e\n\u003cli\u003eHavigh RS, Yildirim F, Chenari HM, T\u0026uuml;r\u0026uuml;t A, Aydogan S. Self-powered stable high-performance UV-Vis-NIR broadband photodetector based on PVP-Cobalt@Carbon nanofibers/n-GaAs heterojunction. Nanotechnology. 2024;35:335201. https:// doi. org/10.1088/1361-6528/ad4973.\u003c/li\u003e\n\u003cli\u003eSeo JW, Park JH, Jung JW, Choi SJ. Dual-catalytic activation of Pt and MoS x O y on carbon nanofibers for NO 2 sensors. Sensors and Actuators B-Chemical. 2024;412:135750. https:// doi. org/10.1016/j.snb.2024.135750.\u003c/li\u003e\n\u003cli\u003eHan J, Wang S, Zhu S, Huang C, Yue Y, Mei C, et al. Electrospun Core-Shell Nanofibrous Membranes with Nanocellulose-Stabilized Carbon Nanotubes for Use as High-Performance Flexible Supercapacitor Electrodes with Enhanced Water Resistance, Thermal Stability and Mechanical Toughness. ACS Appl Mater Interfaces. 2019;11:44624-35. https:// doi. org/10.1021/acsami.9b16458.\u003c/li\u003e\n\u003cli\u003eDai Z, Ren PG, An YL, Zhang H, Ren F, Zhang Q. Nitrogen-sulphur Co-doped graphenes modified electrospun lignin/polyacrylonitrile-based carbon nanofiber as high performance supercapacitor. J Power Sources. 2019;437:226937. https:// doi. org/10.1016/j.jpowsour.2019.226937.\u003c/li\u003e\n\u003cli\u003eGuo YQ, Hong XF, Wang Y, Li Q, Meng JS, Dai RT, et al. Multicomponent Hierarchical Cu-Doped NiCo-LDH/CuO Double Arrays for Ultralong-Life Hybrid Fiber Supercapacitor. Advanced Functional Materials. 2019;29:1809004. https:// doi. org/10.1002/adfm.201809004.\u003c/li\u003e\n\u003cli\u003eZhuo QQ, Gao J, Peng MF, Bai LL, Deng JJ, Xia YJ, et al. Large-scale synthesis of graphene by the reduction of graphene oxide at room temperature using metal nanoparticles as catalyst. Carbon. 2013;52:559-64. https:// doi. org/10.1016/j.carbon.2012.10.014.\u003c/li\u003e\n\u003cli\u003eBalan BK, Chaudhari HD, Kharul UK, Kurungot S. Carbon nanofiber-RuO2-poly(benzimidazole) ternary hybrids for improved supercapacitor performance. RSC Advances. 2013;3:2428-36. https:// doi. org/10.1039/c2ra22776b.\u003c/li\u003e\n\u003cli\u003eLai F, Huang Y, Miao Y-E, Liu T. Controllable preparation of multi-dimensional hybrid materials of nickel-cobalt layered double hydroxide nanorods/nanosheets on electrospun carbon nanofibers for high-performance supercapacitors. Electrochimica Acta. 2015;174:456-63. https:// doi. org/10.1016/j.electacta.2015.06.031.\u003c/li\u003e\n\u003cli\u003eZhang JX, Zhao X, Huang ZL, Xu T, Zhang QH. High-performance all-solid-state flexible supercapacitors based on manganese dioxide/carbon fibers. Carbon. 2016;107:844-51. https:// doi. org/10.1016/j.carbon.2016.06.064.\u003c/li\u003e\n\u003cli\u003eLin S-C, Lu Y-T, Chien YA, Wang J-A, You T-H, Wang Y-S, et al. Asymmetric supercapacitors based on functional electrospun carbon nanofiber/manganese oxide electrodes with high power density and energy density. J Power Sources. 2017;362:258-69. https:// doi. org/10.1016/j.jpowsour.2017.07.052.\u003c/li\u003e\n\u003cli\u003eLiu G, Zhang L, Wang S, Ding L-X, Wang H. Hierarchical NiCo2O4 nanosheets on carbon nanofiber films for high energy density and long-life Li-O-2 batteries. Journal of Materials Chemistry A. 2017;5:14530-6. https:// doi. org/10.1039/c7ta03703a.\u003c/li\u003e\n\u003cli\u003eXu J, Zhang L, Xu G, Sun Z, Zhang C, Ma X, et al. Facile synthesis of NiS anchored carbon nanofibers for high-performance supercapacitors. Appl Surf Sci. 2018;434:112-9. https:// doi. org/10.1016/j.apsusc.2017.09.233.\u003c/li\u003e\n\u003cli\u003eParveen N, Al-Jaafari AI, Han JI. Robust cyclic stability and high-rate asymmetric supercapacitor based on orange peel-derived nitrogen-doped porous carbon and intercrossed interlinked urchin-like NiCo2O4@3DNF framework. Electrochimica Acta. 2019;293:84-96. https:// doi. org/10.1016/j.electacta.2018.08.157.\u003c/li\u003e\n\u003cli\u003eTian D, Lu XF, Nie GD, Gao M, Wang C. Direct growth of Ni-Mn-O nanosheets on flexible electrospun carbon nanofibers for high performance supercapacitor applications. Inorg Chem Front. 2018;5:635-42. https:// doi. org/10.1039/c7qi00696a.\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":"hierarchical, Carbon nanofibers, supercapacitors","lastPublishedDoi":"10.21203/rs.3.rs-4689095/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4689095/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCarbon Nanofibers (CNFs)/transition metal oxides (TMOs) composites have obtained much attention as supercapacitor electrode with benefits from the superior electrical conductivity of carbon materials and high capacity of TMOs. However, nano-size TMOs is prone to agglomeration and hard to grow efficiently and uniformly on CNFs due to the surface of CNFs lack effective targets, which limits its performance. In this paper, different hierarchical structures of CNFs-NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e were prepared and assembled as supercapacitor electrode. The results showed that CNFs-NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e prepared by treatment of potassium permanganate exhibited a high capacitance of 1175 F g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at a current density of 1 A g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and long-term cycling stability, with 93% capacitance retention after 3000 cycles. The excellent electrochemical performance could be attributed to that more active sites were introduced on the CNFs after solvent treatment, which were beneficial for NiCo\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e to grow uniformly on CNFs. This approach provides a new strategy for controllable design and synthesis of homogeneous hierarchical CNFs/TMOs composites.\u003c/p\u003e","manuscriptTitle":"Hierarchical carbon nanofiber/NiCo2O4 composites as electrode for high-performance supercapacitors","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-06 09:10:00","doi":"10.21203/rs.3.rs-4689095/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":"aa81717c-29cc-4ad1-abb5-7c62d870f16c","owner":[],"postedDate":"August 6th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-07-09T05:54:17+00:00","versionOfRecord":[],"versionCreatedAt":"2024-08-06 09:10:00","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4689095","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4689095","identity":"rs-4689095","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}