Enhanced photoelectrochemical response of reduced-graphene oxide/Zn1−xAgxO nanocomposite in visible-light region

Graphene based nanocomposites have the potential to work as efficiently, multifunctional materials for energy conversion & storage. These composites may exhibit better photocatalytic properties by the improvement of their electronic and structural properties than pure photocatalysts. In the present work, reduced graphene oxide (rGO) & ZnO nanocomposite with 0–5 atom% Ag doping was prepared by electrodeposition method and characterized by XRD, Raman spectroscopy, FE-SEM, EDX, UV–Vis spectroscopy and final photoelectrochemical activity was assessed under 1.5 AM solar simulator in 1 M NaOH as electrolyte. Significant changes in the Raman spectrum for the nanocomposite suggest the possible electronic interaction between rGO and ZnO nanocomposite and its successful fabrication, which improves the charge separation and enhanced photoelectrochemical activity in the nanocomposite. We find a red-shift of 0.35 eV in the UV–vis spectrum and therefore an enhanced photoelectrochemical activity in the visible range on Ag doping in rGO/ZnO nanocomposite. Nanocomposite with 1 atom% Ag doping showed the highest photocurrent density of 2.48 mA/cm² at 0.8 V vs Ag/AgCl over other samples, which was almost five times higher than that for undoped rGO/ZnO composite. Calculated Flat-band potential and donor densities using Mott–Schottky data also supported the better photoelectrochemical response for Ag doping in nanocomposite.     

Hierarchically self-assembled ZnO architectures: Establishing light trapping networks for effective photoelectrochemical water splitting

Here we develop photoanodes based on hierarchical zinc oxide (ZnO) nanostructures such as vertically aligned nanorods (NR), nanorods interconnected by thin nanosheets (NR@TN) and nanorods interconnected by dense nanosheets (NR@DN). The morphological variations were successfully controlled by secondary growth time and the plausible formation mechanisms of these hierarchical ZnO architectures were explained based on the experiment analysis. Under simulated light illumination (AM 1.5, 100 mW cm^?2), NR@TN produced a photocurrent density of 0.62 mA/cm² at 1.23 V vs. reversible hydrogen electrode (vs. RHE). Importantly, 35% enrichment in photoconversion efficiency was observed for NR@TN at much lower bias potential (0.77 V vs. RHE) compared with NR (0.135%) and NR@DN (0.13% at 0.82 V vs. RHE). Key to the improved performance is believed to be synergetic effects of excellent light-trapping characteristics and the large surface-to-volume ratios due to the nanosheet structures. The nanorod connected with thin nanosheet structures improved the efficiency by means of improved charge transfer across the nanostructure/electrolyte interfaces, and efficient charge transport within the material. We believe that the hierarchical ZnO structures can be used in conjunction with doping and/or sensitization to promote the photoelectrochemical (PEC) performance. Further, the ZnO nanorod interconnected with nanosheets morphology presented in this article is extendable to other metal oxide semiconductors to establish a universal protocol for the development of high performance photoanodes in the field of PEC water splitting.     

Facile fabrication and optimization of bowl-like ZnO/CdS nano-composite thin films with hierarchical nanopores and nano-cracks for high-performance photoelectrochemistry

A special nano-structured composite ZnO/CdS thin film with hierarchical nanopores and nano-cracks has been synthesized by a facile two-step method for the first time, in which both loadings of ZnO and CdS are optimized. We first fabricated the hierarchical nanoporous ZnO thin film through rapid gas/liquid interface assembly and layer-by-layer transfers of bowl-like ZnO nanoparticles for thirteen times. The ZnO nanobowls are prepared by a simple solution chemical reaction without using any templates. After annealing, the assembled ZnO film is sensitized with CdS nanoparticles by successive ionic layer adsorption and reactions for six cycles. Nano-cracks form for the ZnO/CdS nano-composite film by calcination, which is due to the different thermal expansion behavior between the ZnO film and the CdS layer. The facilely optimized ZnO/CdS films can serve as a promising photoanode in a photoelectrochemical cell, and it can generate a saturated photocurrent density as high as 7.8 mA cm^?2 at ?0.9 V (vs. Hg|Hg₂SO₄|saturated K₂SO₄) under visible light illumination of 100 mW cm^?2 in an aqueous solution of 0.5 M Na₂S, corresponding to a solar-to-electricity conversion efficiency of 6.6%.     

Surface modification of the p-type Cu2ZnSnS4 photocathode with n-type zinc oxide nanorods for photo-driven salt water splitting

The sulfurization of co-sputtering Cu–Zn–Sn metal precursors was employed to prepare the quaternary copper-zinc-tin-sulphide (Cu₂ZnSnS₄, CZTS) photocathodes on substrates. Influence of [Zn]/[Sn] ratios in CZTS photocathodes on their phases, morphologies, and the efficiencies of photo-driven salt-water splitting was examined. Pristine p-type CZTS photocathodes showed the highest photo-driven performance of 0.61 mA cm^?2 in an electrolyte containing 1 M sodium chloride with the external bias kept at ?1.0 V vs. Ag/AgCl. An n-type zinc oxide (ZnO) nanorod arrays layer was then coated on the CZTS photocathode to improve its photo-driven salt-water splitting performance. The CZTS/ZnO photoelectrode had the best photo-driven performance of 1.87 mA cm^?2 in the 1 M NaCl solution under illumination with the external bias set at ?1.0 V vs. Ag/AgCl. From results of electrochemical impedance spectra measurements for the samples in the electrolyte, the CZTS/ZnO sample had good photo-driven salt-water splitting performance due to its lowest charge transfer resistance and p-n junction formed at the sample. Intensity modulated photocurrent spectroscopy and electrochemical impedance spectra results of samples indicated that the surface states at the CZTS/ZnO interface were the recombination centers with the electrons from the CZTS sample and holes from the ZnO and therefore improved its photo-driven salt-water splitting performance.     

The effect of varying N/C ratios of nitrogen precursors during non-metal graphene catalyst synthesis

Nitrogen-doped carbon materials have great potential as metal-free catalysts in a variety of applications, including batteries, supercapacitors and fuel cells. In this paper, nitrogen-doped graphene (NG) catalysts were synthesized via thermal annealing with varying ratios of graphite oxide and melamine precursors. The NG catalysts were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The prepared NG catalysts were folded transparent films with wrinkles. The nitrogen content of the NG catalysts calculated from XPS varied from approximately 4.18%–7.40%. NG1 displayed the highest performance, with a remarkable reduction peak of 0.39 mA cm^?2 at ?0.21 V vs. Ag/AgCl in alkaline media. A direct correlation between total nitrogen content and catalytic activity was not observed, but catalytic activity was dependent on the nature of the nitrogen configurations. XPS analysis revealed that the high catalytic activity of NG1 is attributable to the configuration of the graphitic N-type nitrogen.     

Electrospun Co-TiC nanoparticles embedded on carbon nanofibers: Active and chemically stable counter electrode for methanol fuel cells and dye-sensitized solar cells

Cobalt-titanium carbide nanoparticles (Co-TiC NPs) embedded on carbon nanofibers (composite) were prepared by electrospinning of a solution containing cobalt acetate tetrahydrate (CoAc), titanium (IV) isopropoxide (TIIP) and polyvinylpyrrolidone (PVP) in acetic acid and ethanol. It was then subjected to a carbonation process at a low temperature (850 °C) since the composite contains metal carbide. The obtained composite, as an efficient electrode, was used as an alternative to Pt-free counter electrode (CE) for fuel cells (FCs) and dye-sensitized solar cells (DSSCs). Cyclic voltammetry (CV) and chronoamperatory (CA) tests were used to measure the composite electrode's performance in methanol oxidation. The results showed that the introduced composite could enhance both methanol electro-oxidation and electrochemical stability as the low onset potential and high current density of the composite electrode were obtained at 189 mV and ～90 mA cm^?2 vs. Ag/AgCl, respectively. The composite also was examined in dye-sensitized solar cells as counter electrode (CE). The results showed that the composite electrode was effective, providing stable electrocatalytic activity (ECA) and conductivity, indicating the composite can improve catalytic activity in triiodide reduction. The short-circuit current density (J_sc), open circuit voltage (V_OC), fill factor (FF), and energy conversion efficiency (η) were found to be ～9.98 mA cm^?2, 0.758 V, 0.507 and 3.87%, respectively. The high ECA could be attributed to the synergic effects from all the pristine components.     

Efficient solar photo-electrochemical hydrogen generation using nanocrystalline CeFeO3 synthesized by a modified microwave assisted method

Pure phase of CeFeO₃ perovskite was synthesized by using a modified microwave-assisted method and was systematically studied by photo-electrochemical (PEC) investigations for water splitting reaction. Characterization studies confirm the formation of crystalline orthorhombic single phase perovskite structure with space group Pbnm and having agglomerated sponge-like morphology with nano size grains. DRS shows broad absorption in UV–Visible region, while tauc plot also inferred estimated band gap of 1.9 eV. The photo-activity of their screen printed thin film was analyzed by PEC studies, which includes photocurrent, EIS spectra, MS-plot, J-V plots. On illumination, EIS analysis of CeFeO₃ reveals improved charge transfer at interfaces of semiconductor/electrolyte. The photocurrent density difference of CeFeO₃ was increased to 6.9 mA cm^?2 at an applied bias of 1.5 V vs (Ag/AgCl). PEC H₂ evolution shows significant cumulative hydrogen rate of 12.3 μmol cm^?2 h^?1. All these results reveal that the microwave-synthesized CeFeO₃ is a potential candidate for PEC application under the visible light illumination.     

In situ fabrication of porous graphene electrodes for high-performance lithiumoxygen batteries

These years, LiO₂ batteries attract wide interest because of its high theoretical energy density. However, the catalytic activity and porous structure of cathode remains a great challenge. In this work, we developed a hierarchical porous graphene foam to serve as a battery cathode, which has much richer active sites for cathodic reaction and channels for Li⁺ transfer and O₂ diffusion. The cathode exhibits a superior specific capacity as high as 9559 mAh g^?1 at 57 mA g^?1 and remains a high-rate capability of 3988 mAh g^?1 at an increased current density of 285 mA g^?1. Benefiting from the well-designed cathode structure, the battery can be stably operated for 150 cycles with a stable voltage profile and voltage efficiency up to 65%. The well-designed graphene has a potential to be a superior free-standing cathode to other carbon-based materials due to its good combination of its hierarchical and porous structure, large surface area, abundant defects and excellent mechanical stability.     

Three-dimensional structure of WS2/graphene/Ni as a binder-free electrocatalytic electrode for highly effective and stable hydrogen evolution reaction

Tungsten disulfide (WS₂) has attracted much attention as the promising electrocatalyst for hydrogen evolution reaction (HER). Herein, the three-dimensional (3D) structure electrode composed of WS₂ and graphene/Ni foam has been demonstrated as the binder-free electrode for highly effective and stable HER. The overpotential of 3D WS₂/graphene/Ni is 87 mV at 10 mA cm^?2, and the current density is 119.1 mA cm^?2 at 250 mV overpotential, indicating very high HER activity. Moreover, the current density of 3D WS₂/graphene/Ni at 250 mV only decreases from 119.1 to 110.1 mA cm^?2 even after 3000 cycles, indicating a good stability. The high HER performance of 3D WS₂/graphene/Ni binder-free electrode is superior than mostly previously reported WS₂-based catalysts, which is attributed to the unique graphene-based porous and conductive 3D structure, the high loading of WS₂ catalysts and the robust contact between WS₂ and 3D graphene/Ni backbones. This work is expected to be beneficial to the fundamental understanding of both the electrocatalytic mechanisms and, more significantly, the potential applications in hydrogen economy for WS₂.     

High electrocatalytic performance of a graphene-supported PtAu nanoalloy for methanol oxidation

Homogeneously distributed PtAu nanoalloy anchored to graphene (PtAuNA/G) was synthesized via a simple one-step electrochemical deposition process, in which Pt and Au ions and graphene oxide was simultaneously electro-reduced on the glassy carbon electrode. The morphology evolution of PtAuNA/G synthesized with different deposition times was characterized via field-emission scanning electron microscopy. X-ray diffraction and transmission electron microscopy was applied to confirm the alloy structure. The electrodeposition conditions, including the deposition time, were further optimized to explore the morphological evolution of PtAuNA/G. Based on cyclic voltammetry and chronoamperometry results, it was found that PtAuNA/G can efficiently catalyze the oxidation of methanol in alkaline media with dramatically enhanced electrocatalytic activity (7.268 mA cm^?2, 3.83 times higher than that of commercial carbon-supported Pt nanoparticles, 1.894 mA cm^?2), along with a considerably improved tolerance to poisoning (current decline: 69% vs 99.89%). These results indicate a great potential for PtAuNA/G in fabricating high-performance direct methanol fuel cells.     

Electrocatalytic hydrogen production on GCE/RGO/Au hybrid electrode

We have prepared a nanocomposite hybrid film to produce a collaborative network of gold (Au) nanoparticles that are highly dispersed on reduced graphene oxide (RGO) sheets, and tested it for electrocatalytic hydrogen production. The RGO/Au nanocomposite film synthesized on glassy carbon electrode (GCE) allows significant improvements to the electron-transfer process. The Au nanoparticles decorated on the surface of graphene increases the electron density, which synergistically promote the adsorption of hydrogen atoms on the graphene sheets and consequently enhance the hydrogen evolution reaction (HER) activity. The surface properties of the composite was characterized by field-emission scanning electron microscopy (FE-SEM) and the electrocatalytical performances evaluated as-prepared electrocatalyst toward (HER) by linear sweep voltammetry (LSV), Tafel polarization curves and electrochemical impedance spectroscopy (EIS) analyses. The GCE/RGO/Au nanohybrid electrode exhibited good catalytic activity for HER with an onset potential of ?0.3 V and a Tafel slope of 136 mV dec^?1, achieving a current density of 10 mA cm^?2 at an overpotential of ?0.43 V.     

Construction of ZnO@NiO heterostructure photoelectrodes for improved photoelectrochemical performance

In this report, a p-n junction has been constructed using ZnO/NiO heterostructured photoelectrode by spin coating NiO layers over vertically aligned ZnO nanorod arrays to demonstrate its potential in water splitting applications. Before investigating their PEC performance, we thoroughly studied the introduction of NiO layers on the structure, morphology and light absorption property of ZnO nanorods. 9 layered NiO coated ZnO nanorods exhibited optimum photocurrent density of 0.251 mA/cm² at 0.8 V vs. Ag/AgCl which is attributed to its high absorbance and better charge transfer as recorded from UV–Vis and EIS data. Furthermore, we also studied the effect of (cation (Mg) and anion (Cl)) doping in PEC performance of ZnO nanorods on this optimized sample. Cl_ZnO/NiO showed high J_ph of 1.282 mA/cm² at 1.2 V vs. Ag/AgCl under visible light illumination. The reason behind better photoresponse is its enhanced absorption and well-defined p-n heterojunction between Cl_ZnO and NiO which favoured the separation and transfer of the photocarriers. The results displayed in this work provides a suitable approach of building p-n junction for high performance PEC water oxidation.     

Highly active nanostructured water oxidation catalyst electrodeposited from Co(cyclam) complex

The water soluble molecular complex [Co(cyclam)(ClO₄)]ClO₄ (cyclam = 1,4,8,11-tetraazacyclotetradecane) is utilized as a precursor for deposition of highly active cobalt based nanostructured material on the electrode surface upon electrooxidation. The electrolysis of the complex at +1.1 V vs Ag/AgCl in 0.1 M potassium phosphate at pH 12 leads to the formation of a nanoporous Co(II) hydroxide/phosphate thin film on the printed carbon electrode. The deposited surface was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). The modified electrode (Co-PCE-12) is stable for more than 34 h during the continuous electrolysis. The modified electrode exhibits a high water oxidation catalytic activity of 6.5 mA cm^?2 at an overpotential of 580 mV (0.9 V vs Ag/AgCl (3 M KCl) at pH 12) with 98% Faradaic yield.     

Three-dimensional graphene promoted by palladium nanoparticles,an efficient electrocatalyst for energy production and storage

Three-dimensional (3D) graphene was easily obtained by a simple hydrothermal method from two-dimensional (2D) graphene to create the interspace sites and active surface area. So, the fabrication of the 3D-graphene nanocomposite is promising for advanced energy production and storage application. The structure of the 3D-graphene nanocomposite was characterized by various techniques. Then, 3D-graphene was decorated with Pd nanoparticles. Morphological characterization shows the porous structure of 3D-Pd/rGO, so it has a high electroactive surface area. The function of the electrocatalyst toward the supercapacitor, hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) were investigated. The obtained results as a supercapacitor displayed that the supercapacitor on 3D-Pd/rGO has a high specific capacitance of 582.0 F g^?1, the high energy density of 180 (W h Kg^?1), high power density of 3750 (W Kg^?1), long potential window of 1.00 V and long life. The electrocatalyst shows the small onset potential of ?0.08 V (vs. RHE), Tafel slope of 29 mV dec^?1 and high durability. Also, in the electroanalytical application of the nanocompound as an electrocatalyst for ORR shows an excellent onset potential of 0.90 V (vs. RHE), slow drop in the current density (34% in the presence of MeOH) and the reduction process via a four electrons pathway.     

Co(OH)2 nanoparticles deposited on reduced graphene oxide nanoflake as a suitable electrode material for supercapacitor and oxygen evolution reaction in alkaline media

In this work, cobalt hydroxide nanoparticles are simply synthesized (size is about 50 nm) and deposited on the reduced graphene oxide nanoflake by the hydrothermal method. Then, the ability of glassy carbon electrode modified with this low-cost nanocomposite is examined as a supercapacitor and oxygen evolution electrocatalysts in 2.0 mol L^?1 KOH by a three-electrode system. The modified electrode as a pseudocapacitor with potential windows of 0.35 V, exhibits a powerful specific capacitance (235.20 F g^?1 at 0.1 A g^?1 current density), energy density, stability (about 90% of the initial capacitance value maintain after 2000 cycles at 1.0 A g^?1) and fast charge/discharge ability. Furthermore, the modified electrode displays a good electrocatalytic activity for oxygen evolution reaction with a current density of 10.0 mA cm^?2 at 1.647 V, small Tafel slope of 56.5 mV dec^?1, good onset potential of 1.521 V vs. RHE and suitable durability.     

ZnS/ZnO heterojunction as photoelectrode: Type II band alignment towards enhanced photoelectrochemical performance

Heterojunction structures are attracting lots of attention for enhancing the electron injection across the interface. The ZnS/ZnO one-dimensional heterojunction film was firstly prepared via a chemical sulfidization following hydrothermal reaction. The heterostructure was characterized as ZnS(blende)/ZnO(wurtzite) shell–core nanorods via XRD, SEM and TEM. A type II band alignment structure of ZnS/ZnO composite was synthesized via a temperate condition proved by PLS and XPS. The values for valence band offset (VBO) and conduction band offset (CBO) were calculated to be 0.96 eV and 1.25 eV, respectively. The special electron structure in the heterojunction helped reduce the energy barrier height at the interface and enhance the separation of photo-generated carriers. Thus, the photoelectrochemical performance was highly improved, and a photocurrent density of 380 μA/cm² at 0.9 V (vs. Ag/AgCl) was obtained.     

Application of CuS–ZnS PN junction for photoelectrochemical water splitting

A CuS thin film was prepared by the sulfurization of the electrodeposited copper layer on the FTO substrate using sulfur powder at 400 °C. Surface morphology and structure of the CuS thin film were investigated by scanning electron microscopy and X-ray diffraction. The surface morphology of the CuS thin film was worm-like with the diameter of 70 nm and its crystal structure was hexagonal. Band gap energy of the CuS thin film was obtained as 1.5 eV using absorption spectra. Photoelectrochemical response of the CuS thin film was analyzed under chopped illumination at negative and positive potentials. It showed photoelectrochemical response at negative potentials (ca. 2.6 μA cm^?2 at ?0.4 V vs. Ag/AgCl), but not at positive potentials, which confirmed its p-type semiconductivity. A ZnS thin film was synthesized by spray pyrolysis method and characterized using field emission scanning electron microscopy, X-ray diffraction and UV–vis spectrometer. It was shown that the surface morphology was smooth with the grain size of about 50–150 nm. Also, its crystal structure and band gap energy were hexagonal and 3.72 eV, respectively. In order to obtain PN (positive–negative) junction and increase photoelectrochemical response, the ZnS (n-type semiconductor) thin film was deposited on CuS (p-type semiconductor). Linear scan of elemental composition confirmed the presence of FTO, CuS and ZnS layers. Photoelectrochemical characterization showed more photoresponse than the CuS thin film at negative potentials (13.6 μA cm^?2 at ?0.4 V vs. Ag/AgCl) and no photoresponse at positive potentials. The results confirmed the synthesizing of PN junction at the interface of CuS and ZnS.     

The effect of 3D silver nanodome size on hydrogen evolution activity in alkaline solution

Three-dimensional (3D) Ag nanodomes (AgNDs) having different sizes (400, 800, 1200 and 1600 nm) were fabricated using combination of nanosphere lithography and soft lithography. The surface structures of 3D assembled latex particles, nanovoids and metal nanodomes (ND) were examined using scanning electron microscopy (SEM). Their heights and widths analyses were performed with the help of atomic force microscopy (AFM). The effect of diameter of the NDs on their hydrogen evolution activity was examined in 6 M KOH solution at 298 K using electrochemical techniques. Their activities were compared with the activity of bulk Ag electrode. The preparation of 3D-AgNDs having various diameters and examination of their size effects on the water splitting activity have not been studied yet and are being reported firstly. It was found that very well-structured and very uniformly distributed NDs can be fabricated using this procedure. AgNDs exhibit higher hydrogen evolution activity with respect to bulk Ag. Their hydrogen evolution activity depends on their diameters; 1200 nm NDs were the best among them. The current density at ?1.40 V(Ag/AgCl) which is proportional to the rate of hydrogen releasing reaction increases from 0.70 mA cm^?2 to 44.13 mA cm^?2 at this ND electrode with respect to the bulk Ag electrode. At the same 3D-AgNDs electrode and potential, the resistance against the HER reduces from 148.7 Ω cm² to 1.12 Ω cm² (99.6%) by comparing with the bulk Ag electrode. The average surface roughness factors of bulk Ag, 400 nm, 800 nm, 1200 nm and 1600 nm AgNDs are 8, 123, 100, 291 and 176, respectively. The superior hydrogen evolution performance of this electrode is related to its well-structured surface and large real surface area.     

Reduction of carbon dioxide to methanol on the surface of adenine functionalized reduced graphene oxide at a low potential

In this study, the surface of reduced graphene oxide (rGO) was modified with adenine via diazonium reaction. Then, to prepare Pt@Adenine-rGO, Pt was deposited on the surface of adenine-rGO, using cyclic voltammetry in the range of ?0.30 to +1.30 V at a scan rate of 100 mV s^?1 in a solution containing Pt salt. Afterward, it was characterized by various techniques such as scanning electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. Electrochemical studies showed the efficient electrocatalytic behavior of Pt@Adenine-rGO for the reduction of CO₂ to methanol at ?0.30 V. The products formed on the surface of Pt@Adenine-rGO were monitored using different techniques including Raman spectroscopy, gas chromatography, gas chromatography-mass spectrometry, and ¹³C NMR spectroscopy. Our findings indicated that methanol with a reasonably high Faradaic efficiency up to 85% and a current density of 0.5 mA cm^?2 as the main product of CO₂ reduction on the surface of Pt@Adenine-rGO.     

Photoelectrochemical hydrogen generation with nanostructured CdS/Ti–Ni–O composite photoanode

Composite photocatalysts have aroused great interest due to combination of favorable electronic and optical properties. Herein, novel CdS/Ti–Ni–O composite photoanodes were constructed through anodic fabrication of nanostructured Ni-doped TiO₂ (Ti–Ni–O) oxide films and CdS deposition by successive ionic layer adsorption and reaction (SILAR). The morphology and composition evolution, optical properties and photoelectrochemical (PEC) performance of the photoanodes were investigated. The composite nanofilms mainly consisted of micropores and nanotubes. The CdS/Ti–Ni–O composite photoanode demonstrated remarkable PEC hydrogen generation properties with a high photocurrent density (6.72 mA·cm^?2 at 0 V vs Ag/AgCl) which was 18.2 times to that of the bare Ti–Ni–O photoanode. The synergy of Ni-doping and CdS-coupling on the enhancement of PEC performance offers useful ideas to the exploitation of effective photocatalysts and contributes to the development of solar-driven PEC hydrogen generation.