Crystal Crafting: Controlling Crystallites Orientation and Facet Exposure for Enhanced Electrochemical Properties of Polycrystalline MoO3 Films

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Nowak, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3109838/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 04 Oct, 2023 Read the published version in Scientific Reports → Version 1 posted 8 You are reading this latest preprint version Abstract This study focuses on the development and optimization of MoO 3 films on commercially available FTO substrates using the pulsed laser deposition (PLD) technique. By carefully selecting deposition conditions and implementing post-treatment procedures, precise control over crystallite orientation relative to the substrate is achieved. Deposition at 450°C in O 2 atmosphere results in random crystallite arrangement, while introducing argon instead of oxygen to the PLD chamber during the initial stage of sputtering exposes the (102) and (011) facets. On the other hand, room temperature deposition leads to the formation of amorphous film, but after appropriate post-annealing treatment, the (00k) facets were exposed. The deposited films are studied using SEM and XRD techniques. Moreover, electrochemical properties of FTO/MoO 3 electrodes immersed in 1 M AlCl 3 aqueous solution are evaluated using cyclic voltammetry and electrochemical impedance spectroscopy. The results demonstrate that different electrochemical processes are promoted based on the orientation of crystallites. When the (102) and (011) facets are exposed, the Al 3+ ions intercalation induced by polarization is facilitated, while the (00k) planes exposure leads to the diminished hydrogen evolution reaction overpotential. Physical sciences/Materials science/Materials for energy and catalysis Physical sciences/Materials science/Techniques and instrumentation/Design synthesis and processing Physical sciences/Materials science/Condensed matter physics/Surfaces interfaces and thin films PLD MoO3 FTO substrates crystal facets exposure crystallites orientation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction The orientation of crystallites relative to the substrate, as well as the exposed crystal facets, affect the properties of deposited films. The phenomenon is universal and has been reported for various materials, including BiVO 4 1 , WO 3 2 , TiO 2 3 , ZnO 4 , Bi 2 O 3 5 , and others. The ability to control the exposure of specific crystal facets can be beneficial for applications in photoelectrochemistry 3 , energy storage and conversion 6 , photocatalysis 7 , and sensing 8 . In general, the approach of controlling the crystals' orientation may be advantageous wherever the crystalline material exhibits anisotropic properties or possess active centers on specific facets. In the case of film deposition, the most common way to affect the crystal orientation of sputtered materials is by selecting an appropriate substrate that promotes growth in the desired direction due to lattice matching. This method enables the production of high-quality films, however, such procedures limit the possible applications of the deposited layers due to the properties of those single-crystalline substrates, such as non-conductivity, opaqueness, high price, or instability in operating conditions. Thus, it would be advantageous to develop methods for affecting the crystal orientation on randomly oriented substrates, such as FTO (fluorine-doped tin oxide). An exemplary SEM image and XRD pattern of an FTO substrate that confirms the random arrangement of crystallites is shown in Fig. 1 a and 1 b. FTO glass possesses desirable characteristics such as transparency, conductivity, thermal and chemical stability over a wide range of pH 9 , making it suitable for a wide range of applications. Previous reports have demonstrated that BiVO 4 , when deposited on single crystal YSZ (yttria-stabilized zirconia) substrate due to lattice matching, exhibits (004) facet exposition, which is highly convenient for photoelectrochemical water splitting 10 . However, a similar effect has also been achieved using high-temperature pulsed laser deposition, even on an FTO polycrystalline substrate 11 . The primary objective of this paper is to investigate and customize the properties of MoO 3 films deposited on commercially available FTO substrates. Through the exploration of various deposition techniques and post-treatment methods, the aim is to optimize and tailor the characteristics of the MoO 3 films for specific applications. α-MoO 3 is a metal oxide characterized by a layered structure and is distinguished by the presence of van der Waals (vdW) gaps 12 . These vdW gaps contribute to the unique physical and chemical properties exhibited by α-MoO 3 . Understanding the relationship between crystal structure and anisotropy is crucial for optimizing the functionality and performance of α-MoO 3 in various fields, including energy storage, sensing, and catalysis. Figure 1 c depicts the representation of the crystal unit with highlighted facets, illustrating that the van der Waals gaps are parallel to the (00k) planes. This crystal structure suggests that the material can exhibit anisotropy in properties such as ion conductivity, and demonstrate varying activity on specific crystal facets. And indeed, previous studies have proven that α-MoO 3 exhibits anisotropy, particularly in catalytic properties 13 . Moreover, this material is also commonly investigated as an electrode material for batteries and electrochemical capacitors 14,15 , but also for photocatalysts 16 , electrochromic films 17 , and gas sensing materials 18 . Hence, it is reasonable to develop methods of MoO 3 deposition that enable the control of crystals orientation and exposure of specific crystal facets on the same type of polycrystalline substrate. Until recently, various methods of MoO 3 deposition have been proposed, including PLD 19 , spray pyrolysis 20 , RF sputtering 21 , and electrodeposition 22 . The orientation of the deposited crystals is found to depend on the choice of substrates and deposition parameters, as indicated by the literature. Pulsed laser deposition of MoO 3 on Si (111) wafers results in the formation of α-MoO 3 with exposed (00k) planes. On alumina polycrystalline substrates, the same deposition technique leads to the formation of suboxides, but subsequent post-annealing significantly enhances the intensities of (102) and (011) reflections 23 . On the other hand, spray-pyrolysis of molybdenum trioxide on glass substrates, conducted at an appropriate temperature using MoCl 5 and (NH 4 ) 6 Mo 7 O 24 ·4H 2 O solutions as precursors, allows the exposure of (00k) planes 20,24 , whereas RF sputtering of MoO 3 on glass and silicon substrates results in amorphous film, but a post-annealed film consists of both, α- and β-MoO 3 phases 21 . In this study, we demonstrate the deposition of MoO 3 polycrystalline films with desired orientation on FTO substrates using the PLD system. Experimental part The FTO substrates (7 Ω/sq) were purchased from Merck. The cleaning procedure involved ultrasonic treatment of the substrates in acetone, ethanol, and isopropanol (all from POCH) for approximately 20 minutes each. Subsequently, the substrates were dried using a stream of air. Prior to deposition, the FTO pieces underwent treatment with oxygen plasma using plasma cleaner (Femto, Diener). The deposition process was conducted in a developed PLD chamber, where the laser beam was directed perpendicularly onto the metallic molybdenum target, while the substrates were positioned parallel to the beam at a distance of 10 mm from the target. A 266nm, 6ns pulse-duration Nd:YAG laser (Brilliant B, Quantel) with an FHG module was employed for the ablation process. The laser’s energy density was set at approximately 2.5 J cm 2 . Further technical details about the deposition system can be found in our previous paper 25 . Samples deposited at room temperature were subsequently annealed in oven (FCF 1SP, Czylok) under an air atmosphere. The metallic Mo thin film was deposited using magnetron sputtering system (Q150T, Quorum). The morphology of the deposited films was examined using scanning microscope (SU3500, Hitachi) at a 10 kV accelerating voltage. XRD patterns were collected using a Rigaku Intelligent X-ray diffraction system Smartlab with Cu Kα radiation. The patterns were recorded in a range of 10–40°. All electrochemical experiments were performed using a potentiostat (Vertex, Ivium) in a three-electrode cell, where FTO/MoO 3 , Ag/AgCl (3 M KCl), and platinum mesh served as working electrode, reference electrode, and counter electrode, respectively. The measurements were performed in 1 M AlCl 3 (AlCl 3 ·6H 2 O, 99%, Alfa Aesar) aqueous solution. The geometric surface area of the electrode in contact with the electrolyte was approximately ~ 0.2 cm 2 . Results and discussion Deposition of MoO 3 with (011) and (102) planes exposed First, the MoO 3 material was deposited at 450°C in O 2 atmosphere (0.5 mbar) for 120 minutes. The resulting MoO 3 film uniformly covered the entire surface of the FTO substrate. The SEM micrograph of the deposited film is presented in Fig. 2 a. The polycrystalline film consisted of thin plates with sizes up to 500 nm. The crystallites appeared to be predominantly oriented perpendicular to the substrate, although a mixture of different orientations was observed. The XRD pattern showed that the most intense reflexes originated from the (102) and (011) planes, while the (002), (004), and (006) planes were also clearly visible (see Fig. 2 b, PLD_450°C(O 2 )). Additionally, deposition was performed at different temperatures, and deposition at 400°C also resulted in a random orientation of crystallites, while deposition at 500°C did not lead to the formation of a distinct layer (see Fig. S1 a and 1b , respectively). In order to achieve a more ordered arrangement of α-MoO 3 crystallites, slight modifications were made to the deposition parameters. The deposition process commenced at room temperature in an argon atmosphere. After 10 minutes, oxygen was introduced into the chamber, and the temperature was raised to 450°C (sample labeled as PLD_450°C(Ar,O 2 )). The SEM image of resulting layer is presented in Fig. 2 c. The morphology of the layer was relatively similar, consisting of crystallites with a similar appearance. However, upon closer examination, it was observed that the majority of crystallites were perpendicular to the FTO substrate. Moreover, the intensities of the reflections from the (00k) planes were significantly diminished, and the peaks appear broader in comparison with the conventionally deposited film pattern (Fig. 2 b). Based on this results, it can be concluded that the exposed facets observed in the SEM image were (011) and (102), while the (00k) planes were oriented perpendicular to the substrate. Considering this findings, it can be inferred that vdW gaps are also perpendicular to FTO and the direction of crystallites growth is related to the initial stage of the process when metallic Mo is deposited in argon atmosphere. To validate this hypothesis, a 20 nm layer of metallic Mo was deposited on FTO using a magnetron sputtering machine, and then the FTO/Mo was used as a substrate for MoO 3 deposition using PLD (O 2 atmosphere, 120 min, 450°C). The resulting layer exhibited a similar morphology and exposed (102) and (011) facets (SEM micrograph is shown in Fig. S1 c ). Thus, the presence of a thin Mo film during the initial stage of MoO 3 deposition is crucial for obtaining a film with exposed (011) and (102) facets. Deposition of MoO 3 with (00k) planes exposed The same PLD system, substrates, and target were used to obtain a MoO 3 film with differently oriented crystallites and exposed (00k) planes. The deposition process was performed at room temperature for the same duration (120 minutes) and under the same oxygen pressure (0.5 mbar). The SEM image of the as-deposited film is presented in Fig. 3 a, where no distinguishable crystallites can be observed, indicating an amorphous nature of as-deposited film. To crystallize the layer, the sample was annealed in an air atmosphere. However, conventional annealing at 450°C for 4 hours with a slow heating rate resulted in the formation of relatively large crystallites that poorly covered the substrate and exhibited completely random arrangement, see Fig. S2a . Nevertheless, through optimization of the crystallization procedure, it was possible to obtain a film with exposed (00k) facets. The amorphous films were directly placed in a heated oven and annealed at 575°C for varying periods of time (0–20 minutes). The selected temperature was limited by thermal stability of the FTO substrates (lower temperatures did not yield the expected effect). The SEM images of the post-annealed films are presented in Fig. 3 b-f. The morphology of the films underwent significant changes with increasing annealing time. After 0.5 and 1 minute of heating, there can be found epitaxial-like areas. Prolonging the annealing time resulted in fully polycrystalline layers, with larger crystallites formed as the heating duration increased. Notably, after 20 minutes, the crystal size expanded to several micrometers, causing partial exposure of the FTO substrate surface, as it is shown in Fig. S2b . In the studied case, where the aim is to obtain a film of deposited material, the observed effect of patchy layer formation is unfavorable. Extending the annealing time to 60 minutes at a temperature of 575°C revealed an intriguing phenomenon concerning the behavior of MoO 3 . It appeared that the material underwent sublimation from the FTO substrate, as evidenced by the absence of MoO 3 on part of the FTO surface ( Fig. S3a ). This sublimation phenomenon was unexpected since it is generally claimed that the sublimation temperature of MoO 3 is higher than 780°C 26 . However, it has been reported that in the case of the MoO 3 nanoplates, the sublimation occurred even at prolonged heating at about 400°C 27 . This sublimation phenomenon highlights the sensitivity of MoO 3 in a form of thin films to elevated temperatures and emphasizes the importance of carefully controlling the annealing conditions to achieve the desired layer deposition and maintain film integrity. Based on these findings, a post-annealing duration of 5 minutes was determined to be optimal for the sample, labeled as PLD_RT(575°C,5). A digital photo of the sample is shown in Fig. S3b for comparison with the sample annealed for 60 minutes. The morphology of the films presented in Fig. 3 differs significantly from the morphology of MoO 3 deposited at 450°C. In contrast to the crystallites deposited at high temperatures, the crystallites in post-annealed samples after room temperature deposition appeared to be oriented parallel to the FTO substrate. The XRD patterns of the films after annealing at 575°C are shown in Fig. 3 g. As expected, the as-deposited layer was amorphous, with only reflexes originating from the FTO substrate. After 30 seconds of heating, low-intensity reflections characteristic of α-MoO 3 appeared and as the heating time increased, the intensity of these signals grew, indicating a more crystalline material. Moreover, after 5 minutes of annealing, the intensity of the MoO 3 peaks exceeded that of the peaks originating from the FTO substrate. Notably, the intensities of the peaks did not increase uniformly as the reflexes originating from the (002), (004), and (006) planes exhibited much higher intensity compared to the (011) plane, while the peak from (102) plane nearly disappeared. On the basis of XRD results, it can be inferred that the majority of the crystallites is arranged in such a way that the (00k) planes are exposed. Considering the crystal structure of α-MoO 3 (see Fig. 1 a), the vdW gaps for this type of samples were parallel to the substrate. The post-annealing of amorphous MoO 3 was also performed at lower temperatures (400 and 450°C) using the same method of directly placing the samples in the hot oven for 60 minutes. The obtained films were polycrystalline and uniformly covered the substrate (no sublimation of MoO 3 was observed), see Fig. S4a and S4b . However, the XRD results demonstrated that exposure of the (00k) plane was not achieved at this temperature ( Fig. S4c ). Therefore, to obtain a MoO 3 film with the (00k) planes exposed, the “rapid” annealing at 575°C for a short period of time was required. Two samples, labeled as PLD_450°C(Ar,O 2 ) and PLD_RT(575°C,5), were selected for further comparison of their properties using electrochemical methods Electrochemical properties Both types of samples were subjected to investigation using electrochemical methods in a 1 M AlCl 3 aqueous electrolyte. Previous studies have already reported the satisfactory electrochemical properties of MoO 3 in such an electrolyte 28 . First, cyclic voltammetry curves were recorded to compare the behavior of the PLD_450°C(Ar,O 2 ) and PLD_RT(575°C,5) electrode materials, as shown in Fig. 4 a and 4 b. Generally, during the first scan, both samples exhibited cathodic peaks occurring at the same potentials. Notably, the current density for the PLD_450°C(Ar,O 2 ) sample was higher than that of the PLD_RT(575°C,5) one. These cathodic peaks correspond to the reduction of Mo(VI) centers and simultaneous cation insertion. The complexity of the AlCl 3 aqueous solution chemistry, including hydrolysis, makes it unclear which form of ion is being intercalated. However, the ex-situ EDX measurements confirms the presence of Al in the sample after cathodic polarization (-0.1 V vs Ag/AgCl (3 M KCl) as it is shown in Fig.S5 , indicating that the observed electroactivity is related to the insertion of Al-containing cations into the MoO 3 structure. The presence of chlorides was also detected, suggesting that the electrolyte was simply adsorbed on the electrode surface, however, the excess of Al (considering the stoichiometry of AlCl 3 ) clearly indicates the incorporation of Al-containing ions into the structure. Regarding the shape of the cyclic voltammetry curves, both samples exhibited clear irreversibility of the electrochemical processes. MoO 3 is sensitive to the potential range during polarization 29 , indicating that cations are likely irreversibly intercalated into the electrode material structure. The cathodic peak observed during the 1st scan at around E = 0.05 V vs. Ag/AgCl (3 M KCl) disappeared and was not seen during the 2nd scan. Similar behavior has already been reported for MoO 3 -based electrodes tested in Mg 2+ -containing electrolytes 30 . In the case of the sample with (011) and (102) facets exposed, the electrochemical activity related to cation intercalation/deintercalation was clearly observed also during 2nd scan, as well. The peaks registered for the electrode material with (00k) planes exposed almost disappeared, but a similar shape of cyclic voltammogram has been reported before 31 . This suggests that the PLD_450°C(Ar,O 2 ) sample, with vdW gaps perpendicular to the substrate, is a more suitable electrode material for energy storage due to the occurrence of intercalation/deintercalation processes during subsequent scans. However, as shown in the CV curves, the PLD_RT(575°C,5) sample exhibited a significantly lower overpotential for the hydrogen evolution reaction (HER). The Tafel parameters determined based on polarization curves are presented in Fig. 4 c. The results prove that the MoO 3 sample with exposed (00k) planes was characterized by higher electrocatalytic activity and faster kinetics in promoting the HER. The electrocatalytic properties of MoO 3 towards HER have already been reported 32 . Moreover, it has been presented that MoO 3 in the form of nanobelts, with (00k) planes exposed, exhibits superior properties for H 2 evolution compared to commercially available MoO 3 33 . Additionally, electrochemical impedance spectroscopy measurements were performed and the comparison of spectra recorded during cathodic polarization (E = -0.1 V vs Ag/AgCl (3 M KCl)) is shown in Fig. 5 a. The measurements were performed at the potential that Al-containing ions are intercalated to the electrode material. As expected, due to the mechanism of charge storage in MoO 3 34 , there is a range of frequencies where the spectra exhibit diffusional behavior. Thus, the Warburg coefficients were estimated as the slope of Z = f(ω −0.5 ) function, as shown in Fig. 5 b. This analysis suggests that apparent diffusion coefficient of cations (it is assumed that it is Al 3+ diffusion) is higher for the PLD_450°C(Ar,O 2 ) electrode material compared to the PLD_RT(575°C,5) one. In order to compare the electrical properties of the electrodes, an electric equivalent circuit was proposed, as shown in the inset of Fig. 5 a. The simple model consist of 4 elements: R1 – electrolyte resistance, R2 – charge transfer resistance on the electrode/electrolyte interface, CPE1 – capacitive properties of the electrode material, and W1 – Warburg element (diffusional processes). The goodness of fitting of about 3–5·10 − 5 was achieved and the results are shown in Fig. 5 c. The values of R1 are comparable due to the electrochemical setup, which ensures constant distances between the electrodes. However, a significant difference was observed for the R2 values, with 261 and 3 Ωcm 2 for the PLD_RT(575°C,5) and the PLD_450°C(Ar,O 2 ) electrode, respectively. Assuming that this value is related to cation insertion from the electrolyte to the electrode material, results indicate that exposing the (001) and (102) planes to the electrolyte facilitates the intercalation phenomenon. The values of the constant phase element parameters are related to the capacitive properties of the electrode materials. The “n” values close to 0.7 suggest that it is not “pure” double-layer capacitance, but rather a more complex modeled process 35 , thus the electric equivalent circuit used is simplified. Nevertheless, the higher “P” value indicated a higher capacitance of the PLD_450°C(Ar,O 2 ) material. The values of the Warburg coefficients obtained from modeling are not exactly the same as those from the analysis shown in Fig. 5 b, however, the trend remains consistent. The apparent diffusion coefficient of Al 3+ ions was estimated using a formula derived by rearranging the definition of the Warburg coefficient, assuming that the diffusion coefficients of intercalation and deintercalation are the same: $${D}_{{Al}^{3+}}={\left(\frac{RT}{\sqrt{2}{n}^{2}\sigma c{F}^{2}}\right)}^{2}$$ 1 where R – gas constant [J·K − 1 ·mol − 1 ], T – temperature [K], n – charge of ion, σ – Warburg coefficient [Ωcm 2 s − 0.5 ], c – concentration of ions [mol·cm − 3 ] (it is assumed that c = 1 M), F - Faraday constant [C·mol − 1 ]. The apparent diffusion coefficient of Al 3+ ions estimated using the Warburg coefficient from modeling was found to be 1.9·10 − 14 and 3.9·10 − 15 cm 2 s − 1 for PLD_450°C(Ar,O 2 ) and PLD_RT(575°C,5), respectively. Notably, different diffusion coefficients were determined for electrodeposited MoO 3 , depending on the size and charge of the cation; for instance, D Na+ was higher than D Al3+ 36 . Moreover, the values of D Al3+ are in good agreement with values presented here. In this work, the diffusion coefficients of the same cation were compared for polycrystalline films with differently oriented crystallites. Moreover, it can be expected that intercalated ions are mobile in vdW gaps. According to the results, in the case of the polycrystalline film with vdW gaps perpendicular to the substrate, diffusion is facilitated, resulting in a higher diffusion coefficient compared to the material with vdW gaps parallel to the substrate. Furthermore, the values of charge transfer resistance suggest that the intercalation phenomenon occurs on the (011) and (102) facets, while the mobility of the cation through the (00k) plane is hindered. On the other hand, the electrode material with exposed (00k) planes exhibits enhanced electrocatalytic properties towards the hydrogen evolution reaction. The presented conclusions are schematically shown in Fig. 6 . Summary The pulsed laser deposition technique enables the deposition of MoO 3 polycrystalline films onto FTO substrates. By adjusting the procedure parameters, the orientation of the crystallites in relation to the substrate can be controlled, without altering the substrate itself. In order to expose the (011) and (102) facets, the deposition process was carried out at 450°C, while filling the deposition chamber with argon during the initial minutes of sputtering. Thus, the pre-deposited thin layer of metallic molybdenum promote the growth of MoO 3 crystallites in a manner that exposes the desired facets. On the other hand, the deposition of amorphous layers followed by rapid heating at 575°C for a short duration resulted in layers with exposed (00k) planes. In conclusion, the deposition of α-MoO 3 on commercially available polycrystalline FTO substrates is achievable, and the orientation of the crystallites, as well as the exposure of specific crystal facets can be controlled by adjusting the deposition and post-treatment conditions. Electrochemical findings indicated that the intercalation of cations is facilitated when the vdW gaps are perpendicular to the substrate and the (011) and (102) facets are exposed to the electrolyte. However, when (00k) planes are exposed, electrode material exhibited improved electrocatalytic properties for hydrogen evolution. The apparent diffusion coefficient value also strictly depends on the deposition conditions, with the highest value of 1.9·10 − 14 cm 2 s − 1 observed for PLD_450°C(Ar,O 2 ) material. Furthermore, these results show promise and warrant further exploration of the proposed procedures to assess their universality and applicability to different materials and substrates. Such investigation would provide significant benefits by enabling the study of the influence of crystallite orientation on layer properties, independent of substrate variations. This comprehensive approach would facilitate a deeper understanding of the fundamental relationships between crystallographic orientation and material functionality, fostering advancements in materials science and providing opportunity for innovative applications across various fields. Declarations Acknowledgements Financial support provided by the Gdańsk University of Technology by the DEC-3/2020/IDUB/I.3.3 grant under the Argentum - ‘Excellence Initiative - Research University’ program is gratefully acknowledged. The visualization of crystal structures was accomplished using Vesta software. We extend our thanks to dr Jakub Karczewski from Gdansk University of Technology for conducting the EDX analysis. Data availability XRD patterns and polarization curves are available in the BRIDGE OF KNOWLEDGE repository: https://mostwiedzy.pl/pl/open-research-data/xrd-and-electrochemical-results-for-moo3-films-deposited-using-pulsed-laser-deposition-system,703093455755919-0 Additional information Correspondence and requests for materials should be addressed to K.T. Competing interests The authors declare no competing interests. Author contributions Conceptualization: K.T., M.S.; Investigation: K.T., Z.Z., M.Sz.,M.S.; Methodology: K.T., M.S; Formal Analysis: K.T., Z.Z., M.Sz., A.P.N. M.S.; Writing – Original Draft: K.T.; Review & Editing: Z.Z., M.Sz., A.P.N. M.S., Visualization: K.T.; Project administration: K.T., Funding acquisition: K.T. References Rather, R. A. et al. Influence of exposed facets, morphology and hetero-interfaces of BiVO 4 on photocatalytic water oxidation: A review. Int. J. Hydrogen Energy 46 , 21866–21888 (2021). Jia, Q. Q. et al. 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Al 3+ ion intercalation in MoO 3 for aqueous aluminum-ion battery. J. Power Sources 413 , 134–138 (2019). Mendoza-Sánchez, B., Brousse, T., Ramirez-Castro, C., Nicolosi, V. & S. Grant, P. An investigation of nanostructured thin film α-MoO 3 based supercapacitor electrodes in an aqueous electrolyte. Electrochim. Acta 91 , 253–260 (2013). Das, T., Tosoni, S. & Pacchioni, G. Structural and electronic properties of bulk and ultrathin layers of V 2 O 5 and MoO 3 . Comput. Mater. Sci. 163 , 230–240 (2019). Thangasamy, P., Ilayaraja, N., Jeyakumar, D. & Sathish, M. Electrochemical cycling and beyond: unrevealed activation of MoO 3 for electrochemical hydrogen evolution reactions. Chem. Commun. 53 , 2245–2248 (2017). Phuruangrat, A., Ham, D. J., Thongtem, S. & Lee, J. S. Electrochemical hydrogen evolution over MoO 3 nanowires produced by microwave-assisted hydrothermal reaction. Electrochem. commun. 11 , 1740–1743 (2009). Sinaim, H. et al. Free-polymer controlling morphology of α-MoO 3 nanobelts by a facile hydrothermal synthesis, their electrochemistry for hydrogen evolution reactions and optical properties. J. Alloys Compd. 516 , 172–178 (2012). Elkholy, A. E., Duignan, T. T., Knibbe, R. & Zhao, X. S. Electrosynthesis of polypyrrole-reinforced helical α-MoO 3 microribbons for high-energy aqueous Al 3+ -ion pseudocapacitors. Electrochim. Acta 429 , 141050 (2022). Drewniak, Ł. & Kochowski, S. The origin of constant phase element in equivalent circuit of MIS (n) GaAs structures. J. Mater. Sci. Mater. Electron. 31 , 19106–19118 (2020). Elkholy, A. E., Duignan, T. T., Hussain, T., Knibbe, R. & Zhao, X. S. Charge Storage Behaviour of α-MoO 3 in Aqueous Electrolytes – Effect of Charge Density of Electrolyte Cations. ChemElectroChem 9 , 1–13 (2022). Additional Declarations No competing interests reported. Supplementary Files SI.docx Cite Share Download PDF Status: Published Journal Publication published 04 Oct, 2023 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Major revision 25 Jul, 2023 Reviews received at journal 10 Jul, 2023 Reviewers agreed at journal 10 Jul, 2023 Reviewers invited by journal 09 Jul, 2023 Editor assigned by journal 09 Jul, 2023 Editor invited by journal 09 Jul, 2023 Submission checks completed at journal 09 Jul, 2023 First submitted to journal 26 Jun, 2023 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-3109838","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":217006560,"identity":"06e1b8d5-daba-4e2b-bb35-e67f67798b9e","order_by":0,"name":"Konrad Trzciński","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA0klEQVRIiWNgGAWjYBACCSjNww+m2ICYnbAWxgaQFskGmBZmIrUwGBwgVotke+/xxxV/7GSMb7dfYPhQdpjBnJAWaZ5ziY1neJJ5zO6cKWCcce4wg2UzAS1yEjmGjQ0SB3jMbuQkMPO2HWYwOEyUFoMDPMYzgFr+EqNFGqwl4QCPgUT6AWZGYrRI9pwxnNlwIJlH4s4ZhoM959J5CPpF4niPwceGP3b2/LPbHz74UWYtZ87eQEAPQjMPOGp4DIjVANTC/gBMk6BlFIyCUTAKRggAACZ+P3VMVBHwAAAAAElFTkSuQmCC","orcid":"","institution":"Gdańsk University of Technology","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Konrad","middleName":"","lastName":"Trzciński","suffix":""},{"id":217006561,"identity":"8efa963a-4d3f-47fe-82af-d6929a517d83","order_by":1,"name":"Zuzanna Zarach","email":"","orcid":"","institution":"Gdańsk University of Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zuzanna","middleName":"","lastName":"Zarach","suffix":""},{"id":217006562,"identity":"460cf2c1-b394-4c0d-b7e7-4200350764b7","order_by":2,"name":"Mariusz Szkoda","email":"","orcid":"","institution":"Gdańsk University of Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Mariusz","middleName":"","lastName":"Szkoda","suffix":""},{"id":217006563,"identity":"9e6920bd-c4f9-4b27-87b2-689ccb2d1116","order_by":3,"name":"Andrzej P. Nowak","email":"","orcid":"","institution":"Gdańsk University of Technology","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Andrzej","middleName":"P.","lastName":"Nowak","suffix":""},{"id":217006564,"identity":"d8fc72cd-b33c-44aa-aded-0f50c9c766a2","order_by":4,"name":"Mirosław Sawczak","email":"","orcid":"","institution":"The Szewalski Institute of Fluid Flow Machinery","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Mirosław","middleName":"","lastName":"Sawczak","suffix":""}],"badges":[],"createdAt":"2023-06-26 09:14:21","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3109838/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3109838/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s41598-023-43800-9","type":"published","date":"2023-10-04T15:02:49+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":39993547,"identity":"31d7c5dd-59b4-4706-95ae-32180e42010f","added_by":"auto","created_at":"2023-07-13 16:07:54","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":183542,"visible":true,"origin":"","legend":"\u003cp\u003ea) SEM micrograph and b) XRD pattern of the FTO substrate; c) α-MoO\u003csub\u003e3\u003c/sub\u003e crystal structure with (002), (102), and (011) planes highlighted.\u003c/p\u003e","description":"","filename":"floatimage1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3109838/v1/7471b21186aaaea7f1a5aa3d.jpg"},{"id":39994285,"identity":"ba96a4d7-3360-4ca1-9516-7021f136fe6f","added_by":"auto","created_at":"2023-07-13 16:15:54","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":268107,"visible":true,"origin":"","legend":"\u003cp\u003ea) SEM micrograph of the PLD_450°C(O\u003csub\u003e2\u003c/sub\u003e) film; b) XRD patterns of the PLD_450°C(O\u003csub\u003e2\u003c/sub\u003e) and PLD_450°C(Ar,O\u003csub\u003e2\u003c/sub\u003e) materials (reflections labeled with “*” origin from FTO); c) SEM micrograph of the PLD_450°C(Ar,O\u003csub\u003e2\u003c/sub\u003e) film.\u003c/p\u003e","description":"","filename":"floatimage2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3109838/v1/ae4d81be9f09b3afafd44f78.jpg"},{"id":39993543,"identity":"e4fbcecd-e8e4-403e-8350-1dc3e8985977","added_by":"auto","created_at":"2023-07-13 16:07:54","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":392350,"visible":true,"origin":"","legend":"\u003cp\u003ea-f) SEM micrographs and g) XRD patterns of MoO\u003csub\u003e3\u003c/sub\u003e films deposited on the FTO substrate at room temperature for 120 minutes, followed by “rapid” post-annealing for various durations.\u003c/p\u003e","description":"","filename":"floatimage3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3109838/v1/1bfa18b65969eecd18f262ca.jpg"},{"id":39993548,"identity":"19046f8f-f523-4c8c-8a82-adcc415c8efa","added_by":"auto","created_at":"2023-07-13 16:07:54","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":155890,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of a) the 1\u003csup\u003est\u003c/sup\u003e and\u0026nbsp; b) the 2\u003csup\u003end\u003c/sup\u003e cyclic voltammetry scans of PLD_450°C(Ar,O\u003csub\u003e2\u003c/sub\u003e) and PLD_RT(575°C,5) electrodes; c) Linear voltammetry curves recorded at potential range suitable for hydrogen evolution reaction (inset: corresponding Tafel slopes), all measurements were performed in a 1 M AlCl\u003csub\u003e3\u003c/sub\u003e electrolyte with a scan rate of 2.5 mVs\u003csup\u003e-1\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"floatimage4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3109838/v1/86d0fbcd333d24ad0d2cabaa.jpg"},{"id":39994284,"identity":"389af616-1973-4fcf-a7bd-6d6ee1f747a4","added_by":"auto","created_at":"2023-07-13 16:15:54","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":154703,"visible":true,"origin":"","legend":"\u003cp\u003ea) Nyquist plots and b) Z = f(ω\u003csup\u003e-0.5\u003c/sup\u003e) plots for the PLD_450°C(Ar,O\u003csub\u003e2\u003c/sub\u003e) and PLD_RT(575°C,5) electrode materials, recorded at E = -0.1 V vs. Ag/AgCl (3 M KCl);\u0026nbsp; c) The results of EIS fitting for both electrodes.\u003c/p\u003e","description":"","filename":"floatimage5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3109838/v1/885ba30aa0a35741ffb6aa6d.jpg"},{"id":39993544,"identity":"a1988d48-b279-4bf5-80a9-7000c482681c","added_by":"auto","created_at":"2023-07-13 16:07:54","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":78435,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic representation of the electrochemical properties of MoO\u003csub\u003e3\u003c/sub\u003e films based on the orientation of the crystallites.\u003c/p\u003e","description":"","filename":"floatimage6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3109838/v1/ddcd0e561c39315046e3f7de.jpg"},{"id":44302345,"identity":"cec74102-0487-4380-97ad-85c7159f5b39","added_by":"auto","created_at":"2023-10-09 15:10:16","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":826418,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3109838/v1/0d7e78dd-a6e9-43cf-97a0-a310997ac42b.pdf"},{"id":39993549,"identity":"c8162359-895e-487a-a518-aa45cc208614","added_by":"auto","created_at":"2023-07-13 16:07:54","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":2897014,"visible":true,"origin":"","legend":"","description":"","filename":"SI.docx","url":"https://assets-eu.researchsquare.com/files/rs-3109838/v1/26f923ec201d30ac37521b90.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eCrystal Crafting: Controlling Crystallites Orientation and Facet Exposure for Enhanced Electrochemical Properties of Polycrystalline MoO\u003csub\u003e3\u003c/sub\u003e Films\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe orientation of crystallites relative to the substrate, as well as the exposed crystal facets, affect the properties of deposited films. The phenomenon is universal and has been reported for various materials, including BiVO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e1\u003c/sup\u003e, WO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u003c/sup\u003e, TiO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e3\u003c/sup\u003e, ZnO \u003csup\u003e4\u003c/sup\u003e, Bi\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e5\u003c/sup\u003e, and others. The ability to control the exposure of specific crystal facets can be beneficial for applications in photoelectrochemistry \u003csup\u003e3\u003c/sup\u003e, energy storage and conversion \u003csup\u003e6\u003c/sup\u003e, photocatalysis \u003csup\u003e7\u003c/sup\u003e, and sensing \u003csup\u003e8\u003c/sup\u003e. In general, the approach of controlling the crystals' orientation may be advantageous wherever the crystalline material exhibits anisotropic properties or possess active centers on specific facets. In the case of film deposition, the most common way to affect the crystal orientation of sputtered materials is by selecting an appropriate substrate that promotes growth in the desired direction due to lattice matching. This method enables the production of high-quality films, however, such procedures limit the possible applications of the deposited layers due to the properties of those single-crystalline substrates, such as non-conductivity, opaqueness, high price, or instability in operating conditions. Thus, it would be advantageous to develop methods for affecting the crystal orientation on randomly oriented substrates, such as FTO (fluorine-doped tin oxide). An exemplary SEM image and XRD pattern of an FTO substrate that confirms the random arrangement of crystallites is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb. FTO glass possesses desirable characteristics such as transparency, conductivity, thermal and chemical stability over a wide range of pH \u003csup\u003e9\u003c/sup\u003e, making it suitable for a wide range of applications. Previous reports have demonstrated that BiVO\u003csub\u003e4\u003c/sub\u003e, when deposited on single crystal YSZ (yttria-stabilized zirconia) substrate due to lattice matching, exhibits (004) facet exposition, which is highly convenient for photoelectrochemical water splitting \u003csup\u003e10\u003c/sup\u003e. However, a similar effect has also been achieved using high-temperature pulsed laser deposition, even on an FTO polycrystalline substrate \u003csup\u003e11\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe primary objective of this paper is to investigate and customize the properties of MoO\u003csub\u003e3\u003c/sub\u003e films deposited on commercially available FTO substrates. Through the exploration of various deposition techniques and post-treatment methods, the aim is to optimize and tailor the characteristics of the MoO\u003csub\u003e3\u003c/sub\u003e films for specific applications. α-MoO\u003csub\u003e3\u003c/sub\u003e is a metal oxide characterized by a layered structure and is distinguished by the presence of van der Waals (vdW) gaps \u003csup\u003e12\u003c/sup\u003e. These vdW gaps contribute to the unique physical and chemical properties exhibited by α-MoO\u003csub\u003e3\u003c/sub\u003e. Understanding the relationship between crystal structure and anisotropy is crucial for optimizing the functionality and performance of α-MoO\u003csub\u003e3\u003c/sub\u003e in various fields, including energy storage, sensing, and catalysis. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec depicts the representation of the crystal unit with highlighted facets, illustrating that the van der Waals gaps are parallel to the (00k) planes. This crystal structure suggests that the material can exhibit anisotropy in properties such as ion conductivity, and demonstrate varying activity on specific crystal facets. And indeed, previous studies have proven that α-MoO\u003csub\u003e3\u003c/sub\u003e exhibits anisotropy, particularly in catalytic properties \u003csup\u003e13\u003c/sup\u003e. Moreover, this material is also commonly investigated as an electrode material for batteries and electrochemical capacitors \u003csup\u003e14,15\u003c/sup\u003e, but also for photocatalysts \u003csup\u003e16\u003c/sup\u003e, electrochromic films \u003csup\u003e17\u003c/sup\u003e, and gas sensing materials \u003csup\u003e18\u003c/sup\u003e. Hence, it is reasonable to develop methods of MoO\u003csub\u003e3\u003c/sub\u003e deposition that enable the control of crystals orientation and exposure of specific crystal facets on the same type of polycrystalline substrate. Until recently, various methods of MoO\u003csub\u003e3\u003c/sub\u003e deposition have been proposed, including PLD \u003csup\u003e19\u003c/sup\u003e, spray pyrolysis \u003csup\u003e20\u003c/sup\u003e, RF sputtering \u003csup\u003e21\u003c/sup\u003e, and electrodeposition \u003csup\u003e22\u003c/sup\u003e. The orientation of the deposited crystals is found to depend on the choice of substrates and deposition parameters, as indicated by the literature. Pulsed laser deposition of MoO\u003csub\u003e3\u003c/sub\u003e on Si (111) wafers results in the formation of α-MoO\u003csub\u003e3\u003c/sub\u003e with exposed (00k) planes. On alumina polycrystalline substrates, the same deposition technique leads to the formation of suboxides, but subsequent post-annealing significantly enhances the intensities of (102) and (011) reflections \u003csup\u003e23\u003c/sup\u003e. On the other hand, spray-pyrolysis of molybdenum trioxide on glass substrates, conducted at an appropriate temperature using MoCl\u003csub\u003e5\u003c/sub\u003e and (NH\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e6\u003c/sub\u003eMo\u003csub\u003e7\u003c/sub\u003eO\u003csub\u003e24\u003c/sub\u003e\u0026middot;4H\u003csub\u003e2\u003c/sub\u003eO solutions as precursors, allows the exposure of (00k) planes \u003csup\u003e20,24\u003c/sup\u003e, whereas RF sputtering of MoO\u003csub\u003e3\u003c/sub\u003e on glass and silicon substrates results in amorphous film, but a post-annealed film consists of both, α- and β-MoO\u003csub\u003e3\u003c/sub\u003e phases \u003csup\u003e21\u003c/sup\u003e. In this study, we demonstrate the deposition of MoO\u003csub\u003e3\u003c/sub\u003e polycrystalline films with desired orientation on FTO substrates using the PLD system.\u003c/p\u003e "},{"header":"Experimental part","content":"\u003cp\u003eThe FTO substrates (7 Ω/sq) were purchased from Merck. The cleaning procedure involved ultrasonic treatment of the substrates in acetone, ethanol, and isopropanol (all from POCH) for approximately 20 minutes each. Subsequently, the substrates were dried using a stream of air. Prior to deposition, the FTO pieces underwent treatment with oxygen plasma using plasma cleaner (Femto, Diener). The deposition process was conducted in a developed PLD chamber, where the laser beam was directed perpendicularly onto the metallic molybdenum target, while the substrates were positioned parallel to the beam at a distance of 10 mm from the target. A 266nm, 6ns pulse-duration Nd:YAG laser (Brilliant B, Quantel) with an FHG module was employed for the ablation process. The laser\u0026rsquo;s energy density was set at approximately 2.5 J cm\u003csup\u003e2\u003c/sup\u003e. Further technical details about the deposition system can be found in our previous paper \u003csup\u003e25\u003c/sup\u003e. Samples deposited at room temperature were subsequently annealed in oven (FCF 1SP, Czylok) under an air atmosphere. The metallic Mo thin film was deposited using magnetron sputtering system (Q150T, Quorum). The morphology of the deposited films was examined using scanning microscope (SU3500, Hitachi) at a 10 kV accelerating voltage. XRD patterns were collected using a Rigaku Intelligent X-ray diffraction system Smartlab with Cu Kα radiation. The patterns were recorded in a range of 10\u0026ndash;40\u0026deg;. All electrochemical experiments were performed using a potentiostat (Vertex, Ivium) in a three-electrode cell, where FTO/MoO\u003csub\u003e3\u003c/sub\u003e, Ag/AgCl (3 M KCl), and platinum mesh served as working electrode, reference electrode, and counter electrode, respectively. The measurements were performed in 1 M AlCl\u003csub\u003e3\u003c/sub\u003e (AlCl\u003csub\u003e3\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, 99%, Alfa Aesar) aqueous solution. The geometric surface area of the electrode in contact with the electrolyte was approximately\u0026thinsp;~\u0026thinsp;0.2 cm\u003csup\u003e2\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003eDeposition of MoO\u003csub\u003e3\u003c/sub\u003e with (011) and (102) planes exposed\u003c/h2\u003e\n \u003cp\u003eFirst, the MoO\u003csub\u003e3\u003c/sub\u003e material was deposited at 450\u0026deg;C in O\u003csub\u003e2\u003c/sub\u003e atmosphere (0.5 mbar) for 120 minutes. The resulting MoO\u003csub\u003e3\u003c/sub\u003e film uniformly covered the entire surface of the FTO substrate. The SEM micrograph of the deposited film is presented in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ea. The polycrystalline film consisted of thin plates with sizes up to 500 nm. The crystallites appeared to be predominantly oriented perpendicular to the substrate, although a mixture of different orientations was observed. The XRD pattern showed that the most intense reflexes originated from the (102) and (011) planes, while the (002), (004), and (006) planes were also clearly visible (see Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eb, PLD_450\u0026deg;C(O\u003csub\u003e2\u003c/sub\u003e)). Additionally, deposition was performed at different temperatures, and deposition at 400\u0026deg;C also resulted in a random orientation of crystallites, while deposition at 500\u0026deg;C did not lead to the formation of a distinct layer (see \u003cstrong\u003eFig. \u003cspan class=\"InternalRef\"\u003eS1\u003c/span\u003ea\u003c/strong\u003e and \u003cstrong\u003e1b\u003c/strong\u003e, respectively). In order to achieve a more ordered arrangement of \u0026alpha;-MoO\u003csub\u003e3\u003c/sub\u003e crystallites, slight modifications were made to the deposition parameters. The deposition process commenced at room temperature in an argon atmosphere. After 10 minutes, oxygen was introduced into the chamber, and the temperature was raised to 450\u0026deg;C (sample labeled as PLD_450\u0026deg;C(Ar,O\u003csub\u003e2\u003c/sub\u003e)). The SEM image of resulting layer is presented in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ec. The morphology of the layer was relatively similar, consisting of crystallites with a similar appearance. However, upon closer examination, it was observed that the majority of crystallites were perpendicular to the FTO substrate. Moreover, the intensities of the reflections from the (00k) planes were significantly diminished, and the peaks appear broader in comparison with the conventionally deposited film pattern (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eb). Based on this results, it can be concluded that the exposed facets observed in the SEM image were (011) and (102), while the (00k) planes were oriented perpendicular to the substrate. Considering this findings, it can be inferred that vdW gaps are also perpendicular to FTO and the direction of crystallites growth is related to the initial stage of the process when metallic Mo is deposited in argon atmosphere. To validate this hypothesis, a 20 nm layer of metallic Mo was deposited on FTO using a magnetron sputtering machine, and then the FTO/Mo was used as a substrate for MoO\u003csub\u003e3\u003c/sub\u003e deposition using PLD (O\u003csub\u003e2\u003c/sub\u003e atmosphere, 120 min, 450\u0026deg;C). The resulting layer exhibited a similar morphology and exposed (102) and (011) facets (SEM micrograph is shown in \u003cstrong\u003eFig. \u003cspan class=\"InternalRef\"\u003eS1\u003c/span\u003ec\u003c/strong\u003e). Thus, the presence of a thin Mo film during the initial stage of MoO\u003csub\u003e3\u003c/sub\u003e deposition is crucial for obtaining a film with exposed (011) and (102) facets.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003eDeposition of MoO\u003csub\u003e3\u003c/sub\u003e with (00k) planes exposed\u003c/h2\u003e\n \u003cp\u003eThe same PLD system, substrates, and target were used to obtain a MoO\u003csub\u003e3\u003c/sub\u003e film with differently oriented crystallites and exposed (00k) planes. The deposition process was performed at room temperature for the same duration (120 minutes) and under the same oxygen pressure (0.5 mbar). The SEM image of the as-deposited film is presented in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ea, where no distinguishable crystallites can be observed, indicating an amorphous nature of as-deposited film. To crystallize the layer, the sample was annealed in an air atmosphere. However, conventional annealing at 450\u0026deg;C for 4 hours with a slow heating rate resulted in the formation of relatively large crystallites that poorly covered the substrate and exhibited completely random arrangement, see \u003cstrong\u003eFig. S2a\u003c/strong\u003e. Nevertheless, through optimization of the crystallization procedure, it was possible to obtain a film with exposed (00k) facets. The amorphous films were directly placed in a heated oven and annealed at 575\u0026deg;C for varying periods of time (0\u0026ndash;20 minutes). The selected temperature was limited by thermal stability of the FTO substrates (lower temperatures did not yield the expected effect). The SEM images of the post-annealed films are presented in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eb-f. The morphology of the films underwent significant changes with increasing annealing time. After 0.5 and 1 minute of heating, there can be found epitaxial-like areas. Prolonging the annealing time resulted in fully polycrystalline layers, with larger crystallites formed as the heating duration increased. Notably, after 20 minutes, the crystal size expanded to several micrometers, causing partial exposure of the FTO substrate surface, as it is shown in \u003cstrong\u003eFig. S2b\u003c/strong\u003e. In the studied case, where the aim is to obtain a film of deposited material, the observed effect of patchy layer formation is unfavorable. Extending the annealing time to 60 minutes at a temperature of 575\u0026deg;C revealed an intriguing phenomenon concerning the behavior of MoO\u003csub\u003e3\u003c/sub\u003e. It appeared that the material underwent sublimation from the FTO substrate, as evidenced by the absence of MoO\u003csub\u003e3\u003c/sub\u003e on part of the FTO surface (\u003cstrong\u003eFig. S3a\u003c/strong\u003e). This sublimation phenomenon was unexpected since it is generally claimed that the sublimation temperature of MoO\u003csub\u003e3\u003c/sub\u003e is higher than 780\u0026deg;C \u003csup\u003e26\u003c/sup\u003e. However, it has been reported that in the case of the MoO\u003csub\u003e3\u003c/sub\u003e nanoplates, the sublimation occurred even at prolonged heating at about 400\u0026deg;C \u003csup\u003e27\u003c/sup\u003e. This sublimation phenomenon highlights the sensitivity of MoO\u003csub\u003e3\u003c/sub\u003e in a form of thin films to elevated temperatures and emphasizes the importance of carefully controlling the annealing conditions to achieve the desired layer deposition and maintain film integrity. Based on these findings, a post-annealing duration of 5 minutes was determined to be optimal for the sample, labeled as PLD_RT(575\u0026deg;C,5). A digital photo of the sample is shown in \u003cstrong\u003eFig. S3b\u003c/strong\u003e for comparison with the sample annealed for 60 minutes. The morphology of the films presented in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e differs significantly from the morphology of MoO\u003csub\u003e3\u003c/sub\u003e deposited at 450\u0026deg;C. In contrast to the crystallites deposited at high temperatures, the crystallites in post-annealed samples after room temperature deposition appeared to be oriented parallel to the FTO substrate. The XRD patterns of the films after annealing at 575\u0026deg;C are shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eg. As expected, the as-deposited layer was amorphous, with only reflexes originating from the FTO substrate. After 30 seconds of heating, low-intensity reflections characteristic of \u0026alpha;-MoO\u003csub\u003e3\u003c/sub\u003e appeared and as the heating time increased, the intensity of these signals grew, indicating a more crystalline material. Moreover, after 5 minutes of annealing, the intensity of the MoO\u003csub\u003e3\u003c/sub\u003e peaks exceeded that of the peaks originating from the FTO substrate. Notably, the intensities of the peaks did not increase uniformly as the reflexes originating from the (002), (004), and (006) planes exhibited much higher intensity compared to the (011) plane, while the peak from (102) plane nearly disappeared. On the basis of XRD results, it can be inferred that the majority of the crystallites is arranged in such a way that the (00k) planes are exposed. Considering the crystal structure of \u0026alpha;-MoO\u003csub\u003e3\u003c/sub\u003e (see Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea), the vdW gaps for this type of samples were parallel to the substrate. The post-annealing of amorphous MoO\u003csub\u003e3\u003c/sub\u003e was also performed at lower temperatures (400 and 450\u0026deg;C) using the same method of directly placing the samples in the hot oven for 60 minutes. The obtained films were polycrystalline and uniformly covered the substrate (no sublimation of MoO\u003csub\u003e3\u003c/sub\u003e was observed), see \u003cstrong\u003eFig. S4a\u003c/strong\u003e and \u003cstrong\u003eS4b\u003c/strong\u003e. However, the XRD results demonstrated that exposure of the (00k) plane was not achieved at this temperature (\u003cstrong\u003eFig. S4c\u003c/strong\u003e). Therefore, to obtain a MoO\u003csub\u003e3\u003c/sub\u003e film with the (00k) planes exposed, the \u0026ldquo;rapid\u0026rdquo; annealing at 575\u0026deg;C for a short period of time was required. Two samples, labeled as PLD_450\u0026deg;C(Ar,O\u003csub\u003e2\u003c/sub\u003e) and PLD_RT(575\u0026deg;C,5), were selected for further comparison of their properties using electrochemical methods\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003eElectrochemical properties\u003c/h2\u003e\n \u003cp\u003eBoth types of samples were subjected to investigation using electrochemical methods in a 1 M AlCl\u003csub\u003e3\u003c/sub\u003e aqueous electrolyte. Previous studies have already reported the satisfactory electrochemical properties of MoO\u003csub\u003e3\u003c/sub\u003e in such an electrolyte \u003csup\u003e28\u003c/sup\u003e. First, cyclic voltammetry curves were recorded to compare the behavior of the PLD_450\u0026deg;C(Ar,O\u003csub\u003e2\u003c/sub\u003e) and PLD_RT(575\u0026deg;C,5) electrode materials, as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ea and \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eb. Generally, during the first scan, both samples exhibited cathodic peaks occurring at the same potentials. Notably, the current density for the PLD_450\u0026deg;C(Ar,O\u003csub\u003e2\u003c/sub\u003e) sample was higher than that of the PLD_RT(575\u0026deg;C,5) one. These cathodic peaks correspond to the reduction of Mo(VI) centers and simultaneous cation insertion. The complexity of the AlCl\u003csub\u003e3\u003c/sub\u003e aqueous solution chemistry, including hydrolysis, makes it unclear which form of ion is being intercalated. However, the ex-situ EDX measurements confirms the presence of Al in the sample after cathodic polarization (-0.1 V vs Ag/AgCl (3 M KCl) as it is shown in \u003cstrong\u003eFig.S5\u003c/strong\u003e, indicating that the observed electroactivity is related to the insertion of Al-containing cations into the MoO\u003csub\u003e3\u003c/sub\u003e structure. The presence of chlorides was also detected, suggesting that the electrolyte was simply adsorbed on the electrode surface, however, the excess of Al (considering the stoichiometry of AlCl\u003csub\u003e3\u003c/sub\u003e) clearly indicates the incorporation of Al-containing ions into the structure. Regarding the shape of the cyclic voltammetry curves, both samples exhibited clear irreversibility of the electrochemical processes. MoO\u003csub\u003e3\u003c/sub\u003e is sensitive to the potential range during polarization \u003csup\u003e29\u003c/sup\u003e, indicating that cations are likely irreversibly intercalated into the electrode material structure. The cathodic peak observed during the 1st scan at around E\u0026thinsp;=\u0026thinsp;0.05 V vs. Ag/AgCl (3 M KCl) disappeared and was not seen during the 2nd scan. Similar behavior has already been reported for MoO\u003csub\u003e3\u003c/sub\u003e-based electrodes tested in Mg\u003csup\u003e2+\u003c/sup\u003e-containing electrolytes \u003csup\u003e30\u003c/sup\u003e. In the case of the sample with (011) and (102) facets exposed, the electrochemical activity related to cation intercalation/deintercalation was clearly observed also during 2nd scan, as well. The peaks registered for the electrode material with (00k) planes exposed almost disappeared, but a similar shape of cyclic voltammogram has been reported before \u003csup\u003e31\u003c/sup\u003e. This suggests that the PLD_450\u0026deg;C(Ar,O\u003csub\u003e2\u003c/sub\u003e) sample, with vdW gaps perpendicular to the substrate, is a more suitable electrode material for energy storage due to the occurrence of intercalation/deintercalation processes during subsequent scans. However, as shown in the CV curves, the PLD_RT(575\u0026deg;C,5) sample exhibited a significantly lower overpotential for the hydrogen evolution reaction (HER). The Tafel parameters determined based on polarization curves are presented in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ec. The results prove that the MoO\u003csub\u003e3\u003c/sub\u003e sample with exposed (00k) planes was characterized by higher electrocatalytic activity and faster kinetics in promoting the HER. The electrocatalytic properties of MoO\u003csub\u003e3\u003c/sub\u003e towards HER have already been reported \u003csup\u003e32\u003c/sup\u003e. Moreover, it has been presented that MoO\u003csub\u003e3\u003c/sub\u003e in the form of nanobelts, with (00k) planes exposed, exhibits superior properties for H\u003csub\u003e2\u003c/sub\u003e evolution compared to commercially available MoO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e33\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eAdditionally, electrochemical impedance spectroscopy measurements were performed and the comparison of spectra recorded during cathodic polarization (E = -0.1 V vs Ag/AgCl (3 M KCl)) is shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea. The measurements were performed at the potential that Al-containing ions are intercalated to the electrode material. As expected, due to the mechanism of charge storage in MoO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e34\u003c/sup\u003e, there is a range of frequencies where the spectra exhibit diffusional behavior. Thus, the Warburg coefficients were estimated as the slope of Z\u0026thinsp;=\u0026thinsp;f(\u0026omega;\u003csup\u003e\u0026minus;0.5\u003c/sup\u003e) function, as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003eb. This analysis suggests that apparent diffusion coefficient of cations (it is assumed that it is Al\u003csup\u003e3+\u003c/sup\u003e diffusion) is higher for the PLD_450\u0026deg;C(Ar,O\u003csub\u003e2\u003c/sub\u003e) electrode material compared to the PLD_RT(575\u0026deg;C,5) one. In order to compare the electrical properties of the electrodes, an electric equivalent circuit was proposed, as shown in the inset of Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea. The simple model consist of 4 elements: R1 \u0026ndash; electrolyte resistance, R2 \u0026ndash; charge transfer resistance on the electrode/electrolyte interface, CPE1 \u0026ndash; capacitive properties of the electrode material, and W1 \u0026ndash; Warburg element (diffusional processes). The goodness of fitting of about 3\u0026ndash;5\u0026middot;10\u003csup\u003e\u0026minus;\u0026thinsp;5\u003c/sup\u003e was achieved and the results are shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ec. The values of R1 are comparable due to the electrochemical setup, which ensures constant distances between the electrodes. However, a significant difference was observed for the R2 values, with 261 and 3 Ωcm\u003csup\u003e2\u003c/sup\u003e for the PLD_RT(575\u0026deg;C,5) and the PLD_450\u0026deg;C(Ar,O\u003csub\u003e2\u003c/sub\u003e) electrode, respectively. Assuming that this value is related to cation insertion from the electrolyte to the electrode material, results indicate that exposing the (001) and (102) planes to the electrolyte facilitates the intercalation phenomenon. The values of the constant phase element parameters are related to the capacitive properties of the electrode materials. The \u0026ldquo;n\u0026rdquo; values close to 0.7 suggest that it is not \u0026ldquo;pure\u0026rdquo; double-layer capacitance, but rather a more complex modeled process \u003csup\u003e35\u003c/sup\u003e, thus the electric equivalent circuit used is simplified. Nevertheless, the higher \u0026ldquo;P\u0026rdquo; value indicated a higher capacitance of the PLD_450\u0026deg;C(Ar,O\u003csub\u003e2\u003c/sub\u003e) material. The values of the Warburg coefficients obtained from modeling are not exactly the same as those from the analysis shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003eb, however, the trend remains consistent. The apparent diffusion coefficient of Al\u003csup\u003e3+\u003c/sup\u003e ions was estimated using a formula derived by rearranging the definition of the Warburg coefficient, assuming that the diffusion coefficients of intercalation and deintercalation are the same:\u003c/p\u003e\n \u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\n \u003cdiv id=\"FileID_Equ1\" class=\"mathdisplay\"\u003e$${D}_{{Al}^{3+}}={\\left(\\frac{RT}{\\sqrt{2}{n}^{2}\\sigma c{F}^{2}}\\right)}^{2}$$\u003c/div\u003e\n \u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003ewhere R \u0026ndash; gas constant [J\u0026middot;K\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u0026middot;mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e], T \u0026ndash; temperature [K], n \u0026ndash; charge of ion, \u0026sigma; \u0026ndash; Warburg coefficient [Ωcm\u003csup\u003e2\u003c/sup\u003es\u003csup\u003e\u0026minus;\u0026thinsp;0.5\u003c/sup\u003e], c \u0026ndash; concentration of ions [mol\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e] (it is assumed that c\u0026thinsp;=\u0026thinsp;1 M), F - Faraday constant [C\u0026middot;mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e].\u003c/p\u003e\n \u003cp\u003eThe apparent diffusion coefficient of Al\u003csup\u003e3+\u003c/sup\u003e ions estimated using the Warburg coefficient from modeling was found to be 1.9\u0026middot;10\u003csup\u003e\u0026minus;\u0026thinsp;14\u003c/sup\u003e and 3.9\u0026middot;10\u003csup\u003e\u0026minus;\u0026thinsp;15\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003es\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for PLD_450\u0026deg;C(Ar,O\u003csub\u003e2\u003c/sub\u003e) and PLD_RT(575\u0026deg;C,5), respectively. Notably, different diffusion coefficients were determined for electrodeposited MoO\u003csub\u003e3\u003c/sub\u003e, depending on the size and charge of the cation; for instance, D\u003csub\u003eNa+\u003c/sub\u003e was higher than D\u003csub\u003eAl3+\u003c/sub\u003e\u003csup\u003e36\u003c/sup\u003e. Moreover, the values of D\u003csub\u003eAl3+\u003c/sub\u003e are in good agreement with values presented here. In this work, the diffusion coefficients of the same cation were compared for polycrystalline films with differently oriented crystallites. Moreover, it can be expected that intercalated ions are mobile in vdW gaps. According to the results, in the case of the polycrystalline film with vdW gaps perpendicular to the substrate, diffusion is facilitated, resulting in a higher diffusion coefficient compared to the material with vdW gaps parallel to the substrate. Furthermore, the values of charge transfer resistance suggest that the intercalation phenomenon occurs on the (011) and (102) facets, while the mobility of the cation through the (00k) plane is hindered. On the other hand, the electrode material with exposed (00k) planes exhibits enhanced electrocatalytic properties towards the hydrogen evolution reaction. The presented conclusions are schematically shown in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Summary","content":"\u003cp\u003eThe pulsed laser deposition technique enables the deposition of MoO\u003csub\u003e3\u003c/sub\u003e polycrystalline films onto FTO substrates. By adjusting the procedure parameters, the orientation of the crystallites in relation to the substrate can be controlled, without altering the substrate itself. In order to expose the (011) and (102) facets, the deposition process was carried out at 450\u0026deg;C, while filling the deposition chamber with argon during the initial minutes of sputtering. Thus, the pre-deposited thin layer of metallic molybdenum promote the growth of MoO\u003csub\u003e3\u003c/sub\u003e crystallites in a manner that exposes the desired facets. On the other hand, the deposition of amorphous layers followed by rapid heating at 575\u0026deg;C for a short duration resulted in layers with exposed (00k) planes. In conclusion, the deposition of \u0026alpha;-MoO\u003csub\u003e3\u003c/sub\u003e on commercially available polycrystalline FTO substrates is achievable, and the orientation of the crystallites, as well as the exposure of specific crystal facets can be controlled by adjusting the deposition and post-treatment conditions. Electrochemical findings indicated that the intercalation of cations is facilitated when the vdW gaps are perpendicular to the substrate and the (011) and (102) facets are exposed to the electrolyte. However, when (00k) planes are exposed, electrode material exhibited improved electrocatalytic properties for hydrogen evolution. The apparent diffusion coefficient value also strictly depends on the deposition conditions, with the highest value of 1.9\u0026middot;10\u003csup\u003e\u0026minus;\u0026thinsp;14\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003es\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e observed for PLD_450\u0026deg;C(Ar,O\u003csub\u003e2\u003c/sub\u003e) material. Furthermore, these results show promise and warrant further exploration of the proposed procedures to assess their universality and applicability to different materials and substrates. Such investigation would provide significant benefits by enabling the study of the influence of crystallite orientation on layer properties, independent of substrate variations. This comprehensive approach would facilitate a deeper understanding of the fundamental relationships between crystallographic orientation and material functionality, fostering advancements in materials science and providing opportunity for innovative applications across various fields.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFinancial support provided by the Gdańsk University of Technology by the DEC-3/2020/IDUB/I.3.3 grant under the Argentum - \u0026lsquo;Excellence Initiative - Research University\u0026rsquo; program is gratefully acknowledged. The visualization of crystal structures was accomplished using Vesta software. We extend our thanks to dr Jakub Karczewski from Gdansk University of Technology for conducting the EDX analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eXRD patterns and polarization curves are available in the BRIDGE OF KNOWLEDGE repository: https://mostwiedzy.pl/pl/open-research-data/xrd-and-electrochemical-results-for-moo3-films-deposited-using-pulsed-laser-deposition-system,703093455755919-0\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCorrespondence and requests for materials should be addressed to K.T.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization: K.T., M.S.; Investigation: K.T., Z.Z., M.Sz.,M.S.; Methodology: K.T., M.S; Formal Analysis: K.T., Z.Z., M.Sz., A.P.N. M.S.; Writing \u0026ndash; Original Draft: K.T.; Review \u0026amp; Editing: Z.Z., M.Sz., A.P.N. M.S., Visualization: K.T.; Project administration: K.T., Funding acquisition: K.T.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eRather, R. A. \u003cem\u003eet al.\u003c/em\u003e Influence of exposed facets, morphology and hetero-interfaces of BiVO\u003csub\u003e4\u003c/sub\u003e on photocatalytic water oxidation: A review. \u003cem\u003eInt. J. Hydrogen Energy\u003c/em\u003e \u003cstrong\u003e46\u003c/strong\u003e, 21866\u0026ndash;21888 (2021).\u003c/li\u003e\n\u003cli\u003eJia, Q. Q. \u003cem\u003eet al.\u003c/em\u003e Exposed facets induced enhanced acetone selective sensing property of nanostructured tungsten oxide. \u003cem\u003eJ. Mater. Chem. A\u003c/em\u003e \u003cstrong\u003e2\u003c/strong\u003e, 13602\u0026ndash;13611 (2014).\u003c/li\u003e\n\u003cli\u003eKim, C. W., Yeob, S. J., Cheng, H. M. \u0026amp; Kang, Y. S. 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Charge Storage Behaviour of \u0026alpha;-MoO\u003csub\u003e3\u003c/sub\u003e in Aqueous Electrolytes \u0026ndash; Effect of Charge Density of Electrolyte Cations. \u003cem\u003eChemElectroChem\u003c/em\u003e \u003cstrong\u003e9\u003c/strong\u003e, 1\u0026ndash;13 (2022).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"PLD, MoO3, FTO substrates, crystal facets exposure, crystallites orientation","lastPublishedDoi":"10.21203/rs.3.rs-3109838/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3109838/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study focuses on the development and optimization of MoO\u003csub\u003e3\u003c/sub\u003e films on commercially available FTO substrates using the pulsed laser deposition (PLD) technique. By carefully selecting deposition conditions and implementing post-treatment procedures, precise control over crystallite orientation relative to the substrate is achieved. Deposition at 450\u0026deg;C in O\u003csub\u003e2\u003c/sub\u003e atmosphere results in random crystallite arrangement, while introducing argon instead of oxygen to the PLD chamber during the initial stage of sputtering exposes the (102) and (011) facets. On the other hand, room temperature deposition leads to the formation of amorphous film, but after appropriate post-annealing treatment, the (00k) facets were exposed. The deposited films are studied using SEM and XRD techniques. Moreover, electrochemical properties of FTO/MoO\u003csub\u003e3\u003c/sub\u003e electrodes immersed in 1 M AlCl\u003csub\u003e3\u003c/sub\u003e aqueous solution are evaluated using cyclic voltammetry and electrochemical impedance spectroscopy. The results demonstrate that different electrochemical processes are promoted based on the orientation of crystallites. When the (102) and (011) facets are exposed, the Al\u003csup\u003e3+\u003c/sup\u003e ions intercalation induced by polarization is facilitated, while the (00k) planes exposure leads to the diminished hydrogen evolution reaction overpotential.\u003c/p\u003e","manuscriptTitle":"Crystal Crafting: Controlling Crystallites Orientation and Facet Exposure for Enhanced Electrochemical Properties of Polycrystalline MoO3 Films","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-07-13 16:07:49","doi":"10.21203/rs.3.rs-3109838/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revision","date":"2023-07-25T04:17:55+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2023-07-10T09:09:27+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"29c0f23f-c5dc-47a9-8399-22e6ab91fc3c","date":"2023-07-10T05:58:44+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2023-07-09T17:13:46+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2023-07-09T16:28:54+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2023-07-09T14:55:58+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2023-07-09T14:41:41+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2023-06-26T09:04:13+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"c572659c-d9f5-40c9-8e10-382879682069","owner":[],"postedDate":"July 13th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":23237602,"name":"Physical sciences/Materials science/Materials for energy and catalysis"},{"id":23237603,"name":"Physical sciences/Materials science/Techniques and instrumentation/Design synthesis and processing"},{"id":23237604,"name":"Physical sciences/Materials science/Condensed matter physics/Surfaces interfaces and thin films"}],"tags":[],"updatedAt":"2023-10-09T15:08:35+00:00","versionOfRecord":{"articleIdentity":"rs-3109838","link":"https://doi.org/10.1038/s41598-023-43800-9","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2023-10-04 15:02:49","publishedOnDateReadable":"October 4th, 2023"},"versionCreatedAt":"2023-07-13 16:07:49","video":"","vorDoi":"10.1038/s41598-023-43800-9","vorDoiUrl":"https://doi.org/10.1038/s41598-023-43800-9","workflowStages":[]},"version":"v1","identity":"rs-3109838","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3109838","identity":"rs-3109838","version":["v1"]},"buildId":"cBFmMYwuxLRRLfASyISRj","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}