A transition metal-doped copper oxide nanoparticle film fabrication system for the production of photoelectrochemical hydrogen

Abstract

A transition metal-doped copper oxide (CuO) nanoparticle film synthesis system (100) for the photoelectrochemical production of hydrogen, wherein the system (100) comprises: a heating vessel (102) configured for heating and mixing an ethanolamine-stabilized solution of copper acetate monohydrate in 2-methoxyethanol at 50-70 °C for 1-3 hours; an additive dispenser (104) connected to the heating vessel (102) and configured to introduce concentrated iron(III) chloride and cobalt nitrate into the heating vessel (102) to form a solution; a storage unit (106) connected to the additive dispenser (104), which is configured to age the prepared solutions at ambient temperature for 22-26 hours; a spin coater unit (108) connected to the storage unit (106) and configured to apply the prepared solutions to well-cleaned and dried glass substrates, i.e., CuO thin films, to form the CuO thin films doped with iron(III) chloride and cobalt nitrate; a drying unit (110) integrated with a heating plate (110a) and connected to the spin coater unit (108) configured to dry the coated layers at 130-170 °C, the coating and drying of the solution being repeated for six cycles to obtain a film of defined thickness using a multilayer deposition control unit; and a calcination chamber (112) connected to the drying unit (110) and configured to heat the obtained films to 350-450 °C in air for 1-3 hours to crystallize the CuO thin films doped with iron chloride and cobalt nitrate for the production of photoelectrochemical hydrogen.

Description

FIELD OF THE INVENTIONThe present invention relates to the field of photoelectrochemical energy conversion systems. In particular, the present invention is focused on the development of copper oxide (CuO) based photocatalysts for solar hydrogen production. More particularly, the present invention relates to a transition metal doped copper oxide nanoparticle film system for generating photoelectrochemical hydrogen.BACKGROUND OF THE INVENTIONTransition metal oxides (TMOs) have attracted great attention because of their many possible applications in various technological fields, including gas sensor systems, energy saving applications, optoelectronic devices and hydrogen generation. Among the TMOs, copper oxide (CuO) is prominent as abundant, environmentally friendly material having a direct optical energy band gap of 1.2 - 2.2 eV. This property allows CuO to absorb a broad spectrum of visible light, making it particularly attractive for use in photoelectrochemical (PEC) cells, lithium ion batteries, and infrared photodetectors.The properties of CuO, in particular in its nanostructured form, are significantly influenced by the production method, morphology, composition and the type of dopants introduced into the material. Doping CuO with transition metals (TMs) such as iron (Fe) and cobalt (Co) has shown that the band structure of the material is altered, thereby improving its optoelectronic and semiconducting properties. These dopants also contribute to improvements in material photocurrent, sensitivity in photodetectors, and overall stability under operating conditions.Several studies have studied various techniques for preparing thin CuO films and the effects of doping. For example, the improved photocatalytic activity of CuO films produced by DC magnetron sputtering and decomposed organic dyes such as methyl orange (MO) and methyl blue (MB) has been demonstrated. Other studies have shown that doping CuO films with elements such as zinc (Zn), barium (Ba), and ruthenium (Ru) further improves their performance in certain applications including hydrogen generation, supercapacitors, and thin film transistors.The incorporation of Fe and Co as dopants into CuO has proven to be a promising strategy for further optimizing its functionality. These dopants have different oxidation states, ionic radii and electronegativity compared to copper, which leads to a change in the crystallographic structure and the charge transport properties of the CuO films. Co-doped CuO exhibited superior catalytic activity for the oxygen evolution reaction (OER) as compared to undoped CuO, while the Fe-doped CuO improved photoelectrochemical performance with a marked increase in photocurrent density. Moreover, Fe and Co doping improved the supercapacitive performance and long term stability of CuO electrodes, making them suitable for energy storage applications.Despite the numerous advantages of CuO-based films, one of the greatest challenges remains their relatively short charge carrier lifetime, which limits their efficiency in applications such as hydrogen production by water splitting. It has been found that doping CuO with Fe and Co increases the charge carrier lifetime and reduces the charge transfer resistance, thereby improving the performance of the material in such energy conversion applications.In order to overcome these limitations, therefore, a composition must be developed with which improved CuO thin films can be produced by a solution-based process. This is followed by spin coating on glass substrates and subsequent calcination by incorporating Fe and Co as dopants which may have improved optical, electronic and semiconducting properties and are therefore suitable for applications such as hydrogen generation, PEC cells, gas sensor systems and energy storage devices.The technical advances disclosed by the present invention overcome the limitations and disadvantages of existing and conventional systems and methods.SUMMARY OF THE INVENTIONThe present invention relates to a transition metal-doped copper oxide nanoparticle film system for photoelectrochemical generation of hydrogen. The system uses copper oxide (CuO) thin films doped with accurate amounts of iron (Fe) and cobalt (Co) to improve their hydrogen power generation properties. X-ray diffraction (XRD) analysis confirms that Fe and Co successfully replace Cu sites and induce tensile stresses in the CuO lattice. Fe doping increases dislocation density and changes crystallinity, while codoping exhibits non-systematic behavior. Scanning electron micrographs (SEM) show that the films have smooth surfaces with uniform particle distribution. Energy dispersive X-ray analysis (EDX) confirms the presence of Fe and Co in the desired ratios. Optical measurements show that increasing Fe content increases the absorption coefficient and narrows the optical band gap of CuO from 1.7 to 1.55 eV. The CuO-6%Fe film has a significantly improved photocatalytic performance for hydrogen generation by water splitting and achieves a photocurrent density 155 times higher than pure CuO. The film has long term photostability, with photon-to-current efficiency (IPCE) of 5.98% at 307 nm and solar-to-hydrogen efficiency (ηST) of 0.94% under xenon irradiation, making it a highly efficient photoelectrode for solar hydrogen generation. An object of the present invention is to provide a transition metal doped copper oxide (CuO) nanoparticle film system for photoelectrochemical generation of hydrogen.Another object of the present invention is to analyze structural changes caused by Fe and Co doping in CuO with emphasis on lattice stress, dislocation density and crystallinity using X-ray diffraction (XRD) techniques.Another object of the present invention is to examine the effects of Fe and Co doping on the optical band gap and the absorption coefficient of CuO to improve its solar energy detection efficiency for conversion of solar energy to hydrogen energy.Another object of the present invention is to characterize the surface morphology of doped CuO films by scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX) to confirm uniform doping and determine particle distribution.Another object of the present invention is to make photoelectrochemical (PEC) measurements for evaluating photocurrent density, photon-to-current efficiency (IPCE), and solar-to-hydrogen efficiency (STH) of Fe and Co doped CuO thin films for solar hydrogen production andAnother object of the present invention is to examine photostability of the optimized CuO-6%Fe thin films under prolonged solar radiation, thus ensuring uniform hydrogen evolution over a prolonged period of time.The present invention aims to provide a transition metal doped copper oxide (CuO) nanoparticle film system for generating photoelectrochemical hydrogen, the system comprising a heating vessel (102) for heating and stirring a 0.5 M solution of copper acetate monohydrate in 2-methoxyethanol stabilized with ethanolamine at 60°C for 2 hours; an additive dispenser connected to the heating vessel and configured for introducing concentrated iron (III) chloride and cobalt nitrate into the heating vessel to form solutions; a storage unit connected to the additive dispenser and configured for aging the prepared solutions at ambient temperature for 24 hours; a spin coater unit that rotates at 2000 rpm for 45 seconds and is connected to the storage unit and configured to apply the solutions to well cleaned and dried glass substrates, i.e., CuO thin films, to form the iron(III) chloride and cobalt nitrate doped CuO thin films; a hot plate integrated drying unit that is connected to the spin coater unit and configured to dry the coated layers at 150° C., wherein the coating and drying of the solution are repeated for six cycles to achieve the required film thickness by using a multilayer deposition controller; and a calcination chamber connected to the drying unit and configured to heat the films to 400° C. in air for 2 hours to crystallize the iron chloride and cobalt nitrate doped CuO thin films to produce photoelectrochemical hydrogen.In order to further clarify the advantages and features of the present disclosure, a more detailed description of the invention will be given with reference to specific embodiments thereof illustrated in the accompanying drawings. It should be noted that these drawings illustrate only typical embodiments of the invention and are therefore not to be considered as limiting the scope thereof. The invention will be described and explained with additional details and details with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE FIGURESThese and other features, aspects, and advantages of the present disclosure will become more fully understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout. The following applies here: FIG. 1 is a block diagram of a transition metal doped copper oxide (CuO) nanoparticle film system for generating photoelectrochemical hydrogen according to an embodiment of the present disclosure; and FIG. 2 illustrates X-ray diffraction of Fe-doped CuO and (Co, Fe)-doped CuO films according to an embodiment of the present disclosure.Moreover, those skilled in the art will appreciate that elements are shown in the drawings for simplicity and need not necessarily be drawn to scale. For example, the flowcharts illustrate the method using the major steps to improve understanding of aspects of the present disclosure. Moreover, with respect to the construction of the apparatus, one or more components of the apparatus may have been represented in the drawings by conventional symbols, and the drawings may only show the specific details relevant to understanding the embodiments of the present disclosure so as not to obscure the drawings with details readily apparent to those skilled in the art having the benefit of the description herein.DETAILED DESCRIPTION:In order to aid in the understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and described in specific language. It is to be understood, however, that no limitation of the scope of the invention is intended, since such changes and further modifications to the illustrated system and such further applications of the principles of the invention as illustrated therein are contemplated, as would normally occur to one skilled in the art to which the invention pertains.It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be limiting thereof.References throughout this specification to "one aspect," "another aspect," or similar language mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrase "in one embodiment," "in another embodiment," and similar language in this specification may or may not all refer to the same embodiment.The terms "comprises," "comprising," or other variations thereof are intended to cover a non-exclusive inclusion, such that a process or method comprising a list of steps not only comprises those steps, but may also comprise other steps not expressly listed or inherent in such a process or method. Likewise, one or more devices or subsystems or elements or structures or components preceded by "comprises..." do not exclude, without further limitations, the existence of other devices or other subsystems or other elements or other structures or other components or additional devices or additional subsystems or additional elements or additional structures or additional components.Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The system, methods, and examples provided herein are illustrative only and are not to be considered limiting.Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.FIG. 1 shows a block diagram of a transition metal doped copper oxide (CuO) nanoparticle film system (100) for photoelectrochemical generation of hydrogen, the system (100) comprising: a heating vessel (102) configured to heat and mix a solution of copper acetate monohydrate in 2-methoxyethanol stabilized with ethanolamine at 50-70° C. for 1-3 hours; an additive dispenser (104) connected to the heating vessel (102) and configured to introduce concentrated iron (III) chloride and cobalt nitrate into the heating vessel (102) to form a solution; a storage unit (106) connected to the additive dispenser (104) and configured to age the prepared solutions at ambient temperature for 22-26 hours; a spin coater unit (108) connected to the storage unit (106) and configured to apply the prepared solutions to well cleaned and dried glass substrates, i.e., CuO thin films, to form the CuO thin films doped with iron (III) chloride and cobalt nitrate; a drying unit (110) integrated with a hot plate (110a) and connected to the spin coater unit (108) and configured to dry the applied layers at 130-170°C, wherein the application and drying of the solution is repeated for six cycles to obtain a film of defined thickness using a multilayer deposition control unit; and a calcination chamber (112) connected to the drying unit (110) and configured to heat the obtained films at 350-450°C in air for 1-3 hours to crystallize the CuO thin films doped with iron(III) chloride and cobalt nitrate to produce photoelectrochemical hydrogen.In one embodiment, the spin coater unit (108) is operated at 2000 revolutions / min for 45 seconds and includes an adjustable unit (108a) for adjusting the rotational speed and the operating time, which provides flexibility in achieving different film thicknesses.In one embodiment, the calcination chamber (112) is equipped with a temperature control unit (112a) that precisely controls the temperature to 400°C to ensure uniform crystallization of the doped films.In one embodiment, a stirrer is arranged in the heating vessel (102) in order to stir and mix the solution of copper acetate monohydrate in 2-methoxyethanol at 60° C. for 2 hours.In one embodiment, the solutions are aged for 24 hours and applied to well cleaned and dried glass substrates to ensure that any dust and moisture has been removed.In one embodiment, the CuO thin films doped with iron chloride and cobalt nitrate have the following structures: CuO, 2.0% Fe-doped CuO, 4.0% Fe-doped CuO, 6.0% Fe-doped CuO, (2.0% Co+6.0% Fe)-doped CuO, (4.0% Co+6.0% Fe)-doped CuO.In one embodiment, the Fe-doped CuO film exhibits long-term photostability with increased absorption over a wide wavelength range during hydrogen generation under sunlight.In one embodiment, the Fe doping concentration is precisely controlled to 6%, resulting in maximum photocatalytic performance for hydrogen generation compared to lower Fe doping concentrations of 2% or 4%.The proposed system is characterized by X-ray diffraction (XRD, Philips X'PertPro MRD) at a wavelength of λ=1.546 Å for Cu Kα with a pitch of 0.021 to examine the crystal structure and purity of the film. The surface morphology, thickness and chemical composition of the films are examined with a field emission scanning electron microscope (FE-SEM; ZEISS SUPRA 55 VP) and energy dispersive X-ray spectroscopy (EDX; ZEISS LEO). UV170 spectra in the wavelength range of 200-1100 nm are recorded with the Shimadzu double-beam spectrophotometer (UV / VIS / NIR 3700).In one embodiment, the photoelectrochemical (PEC) properties of the films are measured in a three electrode cell using an electrochemical workstation (OrigaFlex, OrigaLys ElectroChem., OGF01A, France). The prepared sample (1 cm 2) serves as the working electrode, while a platinum plate serves as the counter electrode. For the electrochemical measurements, Ag / AgCl (in 3 M KCl) is used as reference electrode, with a voltage range of -1 V to +1 V compared to Ag / AgCl. The measured potentials relative to Ag / AgCl are then converted into the reversible hydrogen electrode (RHE) scale using the Nernst equation: V_RH=V_(Ag / AgCl)+0.059×pH+0.1976. The performance of the PEC process is estimated by measuring linear sweep voltammetry (LSV), cyclic voltammetry (CV), and chronoamperometry (CA) at room temperature. The PEC cell is illuminated with a xenon arc lamp (Newport, UK) at a power density of about 100 mW·cm -2. The supporting electrolyte medium used is a 100 ml solution of 0.3 M Na 2 S 2 O 3 having a pH of 7.0.FIG. 2 illustrates X-ray diffraction of Fe-doped CuO and (Co, Fe)-doped CuO films according to an embodiment of the present disclosure. According to XRD patterns of the sol-gel spin coated films, the broad peak around 2θ≈22.5° is due to the amorphous nature of the glass slides. Various diffraction peaks appear at 2θ=32.5°, 35.5°, 38.7°, 48.8°, 53.3° and 58.2°, which corresponds to tenorite-CuO having a monoclinic crystal structure and a C2 / c space group. According to JCPDS card No. 48-1548, the associated crystal planes are (110), (002), (200), (-202), (020) and (202), respectively. There are no other peaks associated with Cu(OH) 2, Fe, Co, or their oxides, indicating that (i) annealing the films at 400°C is sufficient to fully oxidize copper acetate to crystalline CuO, and (ii) Fe and Co are successfully inserted into the Cu sites in the lattice without altering the crystalline nature of CuO, meaning that the defects caused by Fe and Co are substitutable. A similar result is reported for spray deposited CuO films. Cu 2 Y 2 O 5 is recognized, however, as a secondary phase in the XRD of 2.0% Y-doped CuO films. Because of the differences in atomic radii between Fe (0.083 Å for Fe 2+), Co (0.074 Å for Co 2+) and Cu (0.073 Å for Cu 2+) doping with 2.0% to 6.0% Fe shifts the (002) and (200) peaks to higher 2θ values as shown in the insert of Figure 1. However, simultaneous doping with Fe-Co will restore the (002) peaks to their original position probably due to the narrow ionic radii of Fe and Co. This indicates successful substitution of Fe and Co at the Cu sites in the CuO lattice. Charging Zn 2+ into CuO nanoparticles with doping ratios of 0.0% to 6.0% shifts the (002) and (200) peaks to lower 2θ values, but at 6.0% to 10.0%, these planes shift slightly higher. Our results show that the incorporation of Fe and Co does not cause significant changes in the lattice parameters of CuO. According to Bragg's law, peak shift induces compressive stresses (tensile stresses) in the grating at higher (lower) θ. The variation of the 2θ values indicates that the d-spacing, lattice parameters and unit cell volume are affected by the introduction of Fe and Co atoms.The crystal size (D) of the films is determined using the Scherer equation (D=0.9λ / FWHM cos θ), where FWHM is the half width of the XRD peak and θ is the Bragg diffraction angle. The average D value for pure CuO calculated from the planes (002) and (200) is 23.45 nm and decreases to 15.14 nm with 6.0% Fe doping. However, codoping with Co up to 4.0% increases D as listed in Table 1. A higher dopant content may result in more lattice asymmetry by replacing Cu-O bonds with Fe-O and Co-O bonds, resulting in larger crystal sizes. Similarly, a 20-40% Ni loading increases the D-value of solution processed CuO films from 45.5 nm to 39.4 and 37.7 nm, respectively. Doping with 2.0% Co or Mn increases the D value of CuO nanoparticles from 15 nm to 22 nm or 27 nm. In addition, an Fe loading of up to 6.0% improves the crystallinity of electrophoretically deposited CuO films. Dislocation density (δ=1 / (D 2)) is also calculated and is shown in Table 1. The δ values increase from 2.54×10 -3 for CuO:2.0% Fe film to 4.36×10 -3 nm -2 for CuO:6.0% Fe and then decrease to 3.02×10 -3 nm -2. after codoping with 4.0% Co. These results show that codoping with Co improves CuO crystal growth by reducing defects. This indicates the possibility of controlling the crystallinity and defects of the CuO film by double doping with Fe and Co.Specific surface area (SSA) is used for analysis of surface reactions, adsorption and film heterogenity. High SSA is favorable for the diffusion and transport of reactive molecules. The SSA is predicted from XRD by inverting the crystal size (D_avg) and the film density (ρ) using the Sauter formula (SSA=6000 / D ρ). The calculated SSA value for CuO-6%Fe is higher than that of other films as shown in Table 1 below:Undoped CuO23.451.824.051.702.0 Atomic % Fe-doped CuO19.852.544.781.654.0 Atomic % Fe-doped CuO17.693.205.371.606.0 Atomic % Fe-doped CuO15.144.366.271.55CuO: (6% Fe+2% Co)20.782.324.571.70CuO: (6% Fe + 4% Co)18.213.025.211.65The pure CuO film has irregular compact grains with a small number of surface voids. The CuO film doped with 6% Fe has surfaces consisting of agglomerated spherical nanoparticles having diameters of less than 15 nm, which have a narrow size distribution and a high particle density per unit area, as shown in the insert of Fig. 2(B). Moreover, the presence of numerous porous features allows electrolyte flow and facilitates PEC reactions. The CuO film doped with (4.0% Co, 4.0% Fe) has a smooth flat surface with thin, irregular cracks as seen in Fig. 2(C). These morphological characteristics make the films suitable for applications in photocatalytic and hydrogen production. The average thickness of the films as indicated by the cross-sectional images in Figure S1 (supplemental data) is between 1.80 and 1.86 μm.The chemical composition of the CuO, 4.0% Fe-doped and (4.0% Co, 4.0% Fe)-doped CuO films is additionally determined by EDX analysis. For the pure CuO film, the spectrum confirms the presence of Cu (at ~1.0 and 8 keV) and O (at ~0.523 keV). Quantitative analysis shows a composition of 79% Cu and 21% O, indicating the high purity of the spin-coated CuO film. It is important to note that the O peak originates from both the CuO material and the glass substrate. In addition, the peaks of Ca, Mg, Si and Na originate from the substrate. The determined [Cu] / [O] ratio depends on the synthesis method and the production conditions. If, for example, a Cu substrate is immersed in an ammonia solution (0.075 M, pH=11) for 1.5 days, a ratio [Cu] / [O] of 53.8 / 46.2 results, which changes to 50.7 / 49.3 after 9.0 days.In the doped films, the spectra show the same peaks but with relatively lower intensity, together with additional peaks corresponding to Fe and Co. Quantitative analysis shows an Fe content of 4% in the Fe-doped film and a Co content of just below 4% in the Fe-Coco-doped film. These results confirm the presence of Fe and Co atoms in the CuO films, consistent with the XRD results.In the UV range, α has high values with an absorption band around 338 nm. In the visible region, α decreases strongly with increasing incident wavelength. Moreover, α seems to be constant in the IR region. 2.0-6.0 at.% Fe doping increases the α-value, while Co doping with Co decreases it. Similar results were reported for the (Ni, La) doped CuO and CuO × films deposited by physical vapor deposition.According to Taucs theory, α is linked to the incident photon energy hv by the following relationship: αhv = B(hv - E g)n / 2, where B is a constant and n = 1 in the case of semiconductors with direct allowed junctions. The E g- value of each film is obtained from the linear part of the plots (αhv) 2 vs. hv by extension to α=0 as shown in FIG. 4B. The E g- Wert of CuO is 1.7 eV and, after loading with 6.0% Fe, decreases to 1.55 eV. However, when codoped with Co, it increased to 1.65 eV. Similarly, RF sputtered CuO films have an E g- value of 1.68 eV, which decreases to 1.48 eV after doping with 4.0% Co. Introduction of Zn 2+ into CuO at 0.0-10.0% reduced E g from 1.42 to 1.20 eV. However, mixing 20% and 40% Ni with the spin coated CuO increases its E g from 1.87 eV to 1.95 and 2.1 eV, respectively. Moreover, it was found that an increase in Fe content from 0-6 at % increases E g of CuO films from 1.23 to 1.42 eV. The reduction of E g by doping indicates an increase in the charge carrier concentration by the introduction of Fe / Co ions. Our results indicate possible manipulation of the E g of CuO by double doping with Fe and Co.Practical PEC requires photoelectrodes that use a broad spectrum of solar radiation, efficiently use charge carriers, have high photostability against corrosion for long term operation, and are cost effective for efficient production of hydrogen as solar fuel. The performance of the PEC process was estimated by measuring linear sweep voltammetry (LSV) and cyclic voltammetry (CV) for pure and doped CuO films in complete darkness and under irradiation with light (100 mW.cm -2, λ>200 nm).The photocurrent density for all films increases with increasing applied voltage due to the tunneling process, which enhances the driving force for electron transfer from CuO to water. The photocurrent density improves as the Fe doping proportion increases from 0% to 6%, but decreases with the addition of Co. The CuO-6%Fe film has a photocurrent density 155 times higher than pure CuO, with a Jph of -1556 μA / cm 2 at -38 V vs. RHE.On irradiation with light, a significantly higher photocurrent (-1556 μA / cm 2) is generated than in the dark (-21.3 μA / cm 2), which points to the role of the photogenerated electrons in PEC water splitting. Cyclic voltammetry (CV) shows that CuO-6%Fe has a much greater surface area (1058,9 μA.V / cm 2), as compared to pure CuO (220.5 μA.V / cm 2) indicating better catalytic activity. This is due to Fe doping, which improves light absorption, reduces the band gap (1.55 eV), and improves charge separation and charge transport.The CuO-6%Fe film has a smaller crystal size, a larger surface area and a longer lifetime of electron-hole pairs, which promotes more active sites for PEC reactions, accelerates charge transport and reduces recombination. These properties improve catalytic efficiency, allow for more rapid water oxidation and ultimately increase hydrogen production efficiency.The Table equation is an important tool in electrochemistry for analysis of the kinetics of electrochemical reactions. It describes the relationship between the current through an electrode and the voltage difference between the electrode and the electrolyte. The Table curve is represented as an overvoltage versus logarithmic current density. In electrochemical systems, the charge transfer rate (the rate of electron exchange) and the mass transfer rate (the transport of reactants and products) affect the current-voltage relationship.In hydrogen evolution reactions (HER), two important parameters are used for the evaluation of electrocatalysts: the Table slope and the exchange current density. The Table slope indicates how much overvoltage is needed to increase the current density ten times, while the exchange current density reflects the electron transfer rate at equilibrium. Lower panel slopes and higher exchange current densities are desirable for efficient reactions. A low Table slope means a faster reaction rate and a high exchange current density indicates efficient electron transfer. The Table slope may also help determine the rate-determining step in the HER process, such as in the Volmer, Heyrovsky, or Table reactions.For CuO photocatalysts doped with 6.0 atomic percent Fe, the anodic table slope (βa) and the cathodic table slope (βc) are lower than for pure CuO. This suggests that Fe doping lowers the energy requirement for hydrogen generation. The Fe-doped CuO also has a lower corrosion current, which indicates better photocorrosion resistance. The cyclic reproducibility of the CuO-6%Fe photoelectrode is tested in 10 cycles of LSV experiments. Cycle sustain photocurrent (CRJ10) is ~84.3%, showing good repeatability and degradation resistance. Chronoamperometry tests additionally confirm photostability. After prolonged operation, the photocurrent decreases only by 10%. The H2 generation rate is calculated according to Faraday's law. The solar-to-hydrogen efficiency (STH) of the CuO-6%Fe electrode is ~0.94%. Photon Current Efficiency (IPCE) values decrease with increasing wavelength, with strong absorption occurring at wavelengths below 350 nm, confirming the potential of the H2generating material over a broad spectrum of sunlight. XRD, SEM and EDX analyses of the 6.0 at% Fe doped CuO electrode after PEC tests show no significant changes in crystal structure or composition, indicating excellent stability after repeated cycles.In one embodiment, the CuO photoelectrode doped with 6.0% Fe exhibited higher efficiency and photogenerated current density than the reported electrodes. These results emphasize the intrinsic potential of this photoelectrode in the areas of photocatalytic and renewable energy generation.The drawings and the foregoing description provide examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be divided into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of the processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow chart need not be implemented in the order shown; nor do all actions necessarily need to be performed. Also, those actions that are not dependent on other actions may be performed in parallel with the other actions. The scope of the embodiments is in no way limited by these specific examples. Numerous variations, whether or not explicitly stated in the specification, such as differences in structure, dimension, and material usage, are possible. The scope of the embodiments is at least as broad as recited in the following claims.Advantages, other advantages, and solutions to problems have been described above with respect to certain embodiments. However, the advantages, benefits, solutions to problems, and any components that may result in an advantage, solution occurring or becoming clearer are not to be construed as a critical, required, or essential feature or component of any or all claims.REFERENCES100 A nanoparticulate layer system of copper oxide (Cuo) doped with transition metals for generating photoelectrochemical hydrogen. 102 Heating vessel 104 Additive dispenser 106 Storage unit 108 Spin coater unit 108 a Unit 110 Drying unit 110 a Koch plate 112 Calcination chamber 112 aTemperature control unit

Claims

A transition metal doped copper oxide (CuO) nanoparticle film synthesis system (100) for photoelectrochemical generation of hydrogen, the system (100) comprising: a heating vessel (102) configured to heat and mix an ethanolamine stabilized solution of copper acetate monohydrate in 2-methoxyethanol at 50-70°C for 1-3 hours; an additive dispenser (104) connected to the heating vessel (102) and configured to introduce concentrated iron (III) chloride and cobalt nitrate into the heating vessel (102) to form a solution; a storage unit (106) connected to the additive dispenser (104) and configured to age the prepared solutions at ambient temperature for 22-26 hours; a spin coater unit (108) connected to the storage unit (106) and configured to apply the prepared solutions to well cleaned and dried glass substrates, i.e., CuO thin films, to form the CuO thin films doped with iron (III) chloride and cobalt nitrate; a drying unit (110) integrated with a hot plate (110a) and connected to the spin coater unit (108) configured to dry the coated layers at 130-170°C, wherein the coating and drying of the solution is repeated for six cycles to obtain a film of defined thickness using a multilayer deposition control unit; and a calcination chamber (112) connected to the drying unit (110) and configured to heat the obtained films to 350-450° C. in air for 1-3 hours to crystallize the CuO thin films doped with iron chloride and cobalt nitrate to generate photoelectrochemical hydrogen.The system of claim 1, wherein the spin coater unit (108) is operated at 2000 revolutions / min for 45 seconds and comprises an adjustable unit (108a) for adjusting the speed of rotation and the duration of operation, which provides flexibility in achieving different film thicknesses.The system according to claim 1, wherein the calcination chamber (112) is equipped with a temperature control unit (112a) that controls the temperature precisely to 400°C to ensure uniform crystallization of the doped films.The system of claim 1, wherein a stirrer is disposed in the heating vessel (102) to stir and mix the solution of copper acetate monohydrate in 2-methoxyethanol at 60°C for 2 hours.The system of claim 1, wherein the solutions are aged for 24 hours and applied to well cleaned and dried glass substrates to ensure removal of dust and moisture.

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