Investigation of Photo(electro)catalytic water splitting to evolve H2 on Pt-g-C3N4 nanosheets

g-C₃N₄ has shown great potentials in photocatalytic water splitting to produce hydrogen. Herein, we successfully synthesized g-C₃N₄ nanosheets via exfoliating bulk g-C₃N₄. And different metal nanoparticles were photo-deposited onto the surface of g-C₃N₄ nanosheets. The photocatalytic H₂ production activity of g-C₃N₄ nanosheets increased from 0 to 11.2 μmol/h/g_cat. The Pt loaded g-C₃N₄ nanosheets manifested the highest H₂ production activity with a rate of 589.4 μmol/h/g_cat. In addition, the hydrogen evolution rate was further enhanced with addition of external bias to fabricate a photoelectrocatalytic (PEC) system. And the maximum hydrogen production rate (23.1 mmol/h/m²) was obtained at a voltage of 0.6 V (vs. Ag/AgCl). The enhancement in H₂ production may be due to the following reasons: (1) Two-dimensional atomic flakes is beneficial to increase the specific surface area of g-C₃N₄, enhance the mobility of carriers, and improve the energy band structure, (2) Pt nanoparticles play an important role in g-C₃N₄ electron transport, (3) the g-C₃N₄ nanosheets loaded with Pt nanoparticles exhibited significant enhancement in photoelectrocatalytic performance, which may be attributed to its enhanced electronic conductivity and photoelectrochemical surface area, (4) Pt inhibited the recombination of photogenerated carriers and significantly improved the photocatalytic performance. The enhancement mechanism was deeply discussed and explained in this work.     

Boosting the visible-light photoelectrochemical performance of C3N4 by coupling with TiO2 and carbon nanotubes: An organic/inorganic hybrid photocatalyst nanocomposite for photoelectrochemical water spitting

Developing photoanode with proficient sunlight harvesting, stability as well as enhancing the electron injection across the interface remains a major challenge in the photoelectrochemical water splitting strategy to generate hydrogen. Herein, we design and fabricate an organic/inorganic TiO₂/C₃N₄/CNT photoanode by a hydrothermal technique which exhibits much enhanced photoelectrochemical properties. The TiO₂/C₃N₄/CNT photoanode exhibits a photocurrent density of 2.94 mA/cm², which is ~6.4 time higher than pristine graphitic carbon nitride (C₃N₄) at an applied bias potential of 0.6 V vs. Ag/AgCl. The excellent photoelectrochemical performance benefits from the impactful migration of photo-induced electrons at the TiO₂/C₃N₄ interface from C₃N₄ to TiO₂ and their intimate interface contact with CNT. Kelvin probe force microscopy result shows a smaller interface barrier height (~10 meV) between TiO₂ and C₃N₄, suggesting that electrons transport is favored through TiO₂/C₃N₄ interfaces in a ternary photoanode. The TiO₂/C₃N₄/CNT photoanode exhibited an onset potential of 0.25 V vs. Ag/AgCl which is much lower compared to pristine C₃N_4. The electrochemical impedance spectroscopy results also confirmed the enhanced electron injection across the interface in a ternary photoanode. These results demonstrate a promising approach to develop a highly proficient and visible light active photoanode with excellent stability for renewable energy applications.     

High-efficiency photoelectrochemical water splitting with heterojunction photoanode of In2O3-x nanorods/black Ti–Si–O nanotubes

Constructing heterojunction was an efficient way to promote photoelectrochemical (PEC) water splitting performance of TiO₂-based nano-photoanode. In this work, we demonstrated the feasible preparation of oxygen vacancies-induced In₂O₃ (In₂O_3-x) nanorods/black Si-doped TiO₂ (Ti–Si–O) nanotubes heterojunction photoanode for enhanced PEC water splitting. Black Ti–Si–O nanotubes were fabricated through Zn reduction of the as-annealed Ti–Si–O nanotubes, followed by In₂O_3-x nanorods coupling by a facile electrodepositing and Ar heat treatment. Solar to hydrogen conversion efficiency of the heterojunction photoanode reached as high as 1.96%, which was almost 10 times that of undoped TiO₂. The improved PEC properties were mainly attributed to co-doping effects of Si and Ti³⁺/oxygen vacancy as well as In₂O_3-x decoration, which resulted in enhanced optical absorption and facilitated separation-transport process of photogenerated charge carriers. Charge transfer process in the composite system and hydrogen production mechanism were proposed. This work will facilitate designing TiO₂-based nano-photoanodes for promoting water splitting by integrating with elements doping, oxygen vacancies self-doping and semiconductors coupling.     

Electrochemically active and robust cobalt doped copper phosphosulfide electro-catalysts for hydrogen evolution reaction in electrolytic and photoelectrochemical water splitting

The area of non-noble metals based electro-catalysts with electrochemical activity and stability similar or superior to that of noble metal electro-catalyst for efficient hydrogen production from electrolytic and photoelectrochemical (PEC) water splitting is a subject of intense research. In the current study, exploiting theoretical first principles study involving determination of hydrogen binding energy to the surface of the electro-catalyst, we have identified the (Cu_0.83Co_0.17)₃P: x at. % S system displaying excellent electrochemical activity for hydrogen evolution reaction (HER). Accordingly, we have experimentally synthesized (Cu_0.83Co_0.17)₃P: x at. % S (x = 10, 20, 30) demonstrating excellent electrochemical activity with an onset overpotential for HER similar to Pt/C in acidic, neutral as well as basic media. The highest electrochemical activity is exhibited by (Cu_0.83Co_0.17)₃P:30 at. % S nanoparticles (NPs) displaying overpotential to reach 100 mA cm^?2 in acidic, neutral and basic media similar to Pt/C. The (Cu_0.83Co_0.17)₃P:30 at. % S NPs also display excellent electrochemical stability in acidic media for long term electrolytic and PEC water splitting process [using our previously reported (Sn_0.95Nb_0.05) O₂: N-600 nanotubes (NTs) as the photoanode]. The applied bias photon-to-current efficiency obtained using (Cu_0.83Co_0.17)₃P:30 at. % S NPs as the cathode electro-catalyst for HER in an H-type PEC water splitting cell (～4%) is similar to that obtained using Pt/C (～4.1%) attesting to the promise of this exciting non-noble metal containing system.     

Multilayered large‐area WO3 films on sheet and mesh‐type stainless steel substrates for photoelectrochemical hydrogen generation

The objective of this study is to demonstrate the significant improvement in the photoelectrochemical (PEC) hydrogen generation by a photoanode owing to the increased surface area of the substrate. In this work, multilayered tungsten oxide (WO₃) films have been successfully synthesized onto the large‐area sheet (9 × 9cm²) and mesh (1 × 20cm²) ‐type stainless steel (SS) substrates using screen printing and brush painting methods, respectively. All the WO₃ films are porous and nanocrystalline (30–80 nm) in nature with a monoclinic crystal structure as revealed from X‐ray diffraction and scanning electron microscopy studies. The PEC water splitting study is performed under simulated 1 SUN illumination (AM1.5 G) in a typical two‐electrode cell configuration with WO₃ photoanode and Pt wire immersed in 0.5 M H₂SO₄ electrolyte. The photocurrent as well as hydrogen generation rate for WO₃ photoanodes coated on the plane SS sheet substrate is relatively low and showed minimal change with increasing film thickness. On the other hand, the photocurrent as well as the hydrogen generation is enhanced by a 3–4 fold degree for the WO₃ photoanodes coated on SS mesh. We attribute such efficient water splitting to the increment in the filling factor of the WO₃ material due to the large effective surface area of the SS mesh as compared to the SS sheet substrate. Copyright © 2011 John Wiley & Sons, Ltd.     

A novel photoelectrochemical cell with self-organized TiO2 nanotubes as photoanodes for hydrogen generation

A photoelectrochemical (PEC) cell with an innovative design for hydrogen generation via photoelectrocatalytic water splitting is proposed and investigated. It consisted of a TiO₂ nanotube photoanode, a Pt/C cathode and a commercial asbestos diaphragm. The PEC could generate hydrogen under ultraviolet (UV) light-excitation with applied bias in KOH solution. The Ti mesh was used as the substrate to synthesize the self-organized TiO₂ nanotubular array layers. The effect of the morphology of the nanotubular array layers on the photovoltaic performances was investigated. When TiO₂ photocatalyst was irradiated with UV-excitation, it prompted the water splitting under applied bias (0.6 V vs. Normal Hydrogen Electrode, NHE.). Photocurrent generation of 0.58 mA/cm² under UV-light irradiation showed good performance on hydrogen production.     

A ternary Ag/TiO2/CNT photoanode for efficient photoelectrochemical water splitting under visible light irradiation

A ternary Ag/TiO₂/CNT photoanode was prepared by grafting Ag nanoparticles on the surface of as-synthesized TiO₂/CNT nanocomposite for the photoelectrochemical (PEC) water splitting under visible light irradiance. The ternary composite photoanode was observed to generate four times higher photocurrent density compared to binary TiO₂/CNT nanocomposite under visible light irradiance. The Ag nanoparticles on the surface of nanocomposite act as a surface plasmon resonance (SPR) photosensitizer under visible light. The enhanced photocurrent density of Ag/TiO₂/CNT ternary photoanode is attributed to the increased light absorption in the visible region, decrease in band-bending and effective interfacial electron transfer due to the synergetic effect of Ag nanoparticles and CNTs. The enhanced charge transfer within the Ag/TiO₂/CNT was also confirmed by the electrochemical impedance spectroscopy. This work demonstrates a feasible route to improve the PEC performance of TiO₂ towards water splitting under sunlight irradiation.     

Construction of g-C3N4/BCN two-dimensional heterojunction photoanode for enhanced photoelectrochemical water splitting

Two-dimensional heterojunction g-C₃N₄/BCN was constructed via thermal polymerization process. The formed two-dimensional heterostructure could enhance the interfacial contact area between BCN and porous g-C₃N₄ as well as shorten the photogenerated charge carriers transfer time and distance. The two-dimensional g-C₃N₄/BCN heterojunction photoanode shows enhanced photoelectrochemical (PEC) performance for water splitting under visible-light irradiation, which primarily originates from the improved charge transfer and separation, and prolonged lifetime of electrons. Under the visible light irradiation, the g-C₃N₄/BCN heterojunction sample yields a photocurrent density of ∼0.62 mA cm⁻² at 1.23 V vs. RHE, which is about eight times as many as that of CN (0.08 mA cm⁻²) electrode at the same conditions. In addition, the possible electron transfer model and mechanism of PEC water splitting for H₂ evolution have been discussed.     

Membrane electrode assembly-based photoelectrochemical cell for hydrogen generation

A novel photoelectrochemical cell (PEC) for generation of hydrogen via photocatalytic water splitting is proposed and investigated. At the heart of the PEC is a membrane electrode assembly (MEA) integrated with Degussa P25 TiO₂ powder as a model photocatalyst for the photoanode and Pt catalyst powder for the dark cathode, respectively. It serves as a compact photocatalytic reactor for water splitting as well as an effective separator for the generated hydrogen and oxygen. The unique characteristic of the MEA-based PEC is that the use of co-catalyst, sacrificial reagent and supporting electrolyte in the cell is totally not required. The novel PEC can be operated without addition of water in the cathode compartment resulting in improved photo conversion efficiency. In addition, the application of a Degussa P25/BiVO₄ mixed photocatalyst was found to significantly enhance the hydrogen generation. Further improvements for the MEA-based PEC utilizing solar energy are also proposed.     

Enhanced photoelectrochemical water splitting using zinc selenide/graphitic carbon nitride type-II heterojunction interface

The objective of this research is to construct a type-II heterojunction interface for effective photoelectrochemical (PEC) water splitting for hydrogen generation. A series of ZnSe/g-C₃N₄ heterojunctions is prepared by ultrasonication procedure and tested for PEC water splitting for the first time. The successful formation of ZnSe/g-C₃N₄ is confirmed by phase, morphological and optical analysis. Linear sweep voltammetry of 0.05 ZG (0.05% ZnSe/g-C₃N₄) showed a six-fold higher photocurrent density of 500 μA than g-C₃N₄. These results are supported by the Tafel slopes and PL (photoluminescence spectroscopy) studies by showing the smallest slope and lesser electron-hole recombination for 0.05 ZG. Increased lifetime of 107 ms and a higher donor density of 3.6 × 10¹⁹ cm^?3 for 0.05 ZG is observed. The smallest semicircle for 0.05 ZG in EIS implies the least charge transfer resistance among the prepared heterojunctions. All the results comply with each other showing the successful formation of type-II heterojunction for enhanced PEC water splitting.     

Photoelectrochemical performance of bismuth vanadate photoanode for water splitting under concentrated light irradiation

Photoelectrochemical (PEC) water splitting is a promising way to convert solar energy into hydrogen energy. It is typically carried out at room temperature (RT) and 1 sun illumination. The PEC water splitting under concentrated light is expected to be an effective route to improve PEC performance, but there are few studies on it. Herein, CoPi/Mo:BiVO₄ photoanode was selected to investigate the effect of concentrated light and the reaction temperature on its PEC performance. It was revealed that CoPi/Mo:BiVO₄ showed enhanced PEC performance under concentrated light. The photocurrent density was enhanced with increased light intensity and increased reaction temperature. At a high temperature (60 °C), the normalized photocurrent density (3.31 mA cm⁻² at 1.23 V vs. RHE) was found to be optimal at 4 suns, which was attributed to the synergistic effect of concentrating light and heating. It is proved that concentrated light can effectively improve the PEC performance, which has important guiding significance to realize the low-cost and efficient PEC water splitting.     

BiVO4 photoanode decorated with cobalt-manganese layered double hydroxides for enhanced photoelectrochemical water oxidation

Bismuth vanadate (BiVO₄) is being widely identified as a leading n-type semiconductor material for photoelectrochemical (PEC) water splitting. Nevertheless, achieving efficient PEC water oxidation process through BiVO₄ photoanode still faces serious challenge such as severe electron-hole recombination. In this case, PEC activity of BiVO₄ photoanode was enhanced by decoration of three-dimensional CoMn-layered double hydroxide (CoMn-LDH) nanoflakes on the BiVO₄ surface via a facile electrodeposition process. It was suggested that CoMn-LDH played a synergistic effect on broadening internal light absorption, which accelerated injection of holes carrier to electrolyte and alleviated the electron-hole recombination, resulting in expediting faster PEC water oxidation reaction kinetics. Consequently, the photocurrent density of BiVO₄/CoMn-LDH photoanode achieved 2.69 mA cm⁻² at 1.23 V_RHE, 2.45 times higher than the pristine BiVO₄. What's more, 220 mV negative-shift took place on onset potential that was further decreased to 0.31 V_RHE. The vastly enhanced PEC performance was also prioritized to those of Co and Mn single relatives. This work demonstrated that the synergistic BiVO₄/CoMn-LDH as a capable candidate material, can be utilized for effective PEC water splitting.     

Rational design of W-doped BiVO4 photoanode coupled with FeOOH for highly efficient photoelectrochemical catalyzing water oxidation

Developments of promising photocatalyst for PEC water oxidation gain significant interest in the research field of PEC water splitting. The BiVO₄ has been envisioned as suitable photocatalyst material for the PEC water oxidation due to suitable bandgap with favorable band edge positions. Nevertheless, the poor electron-hole separation and low charge transfer efficiency of BiVO₄ yield sluggish surface catalysis reaction. Herein, facile electrodeposition and annealing techniques are proposed to fabricate W-doped BiVO₄ photoanode coupled with FeOOH (W–BiVO₄/FeOOH) for efficient photocatalytic water oxidation. This synthesis is simple, cost-effective and less time consuming. The doping concentration of W and deposition time of FeOOH are optimized to improve photocatalytic ability of BiVO₄. At 1.23 V vs. reversible hydrogen electrode (RHE) under 1 sun illumination, the W–BiVO₄/FeOOH photoanode exhibits a high photocurrent density of 2.2 mA/cm², which is seven folds higher than that of the pristine BiVO₄ photoanode (0.31 mA/cm² 1.23 V vs. RHE). The enhanced photocatalytic ability of W–BiVO₄/FeOOH photoanode is due to the enhanced charge transport properties and synergistic effects of W doping and FeOOH deposition. The excellent long-term stability with the photocurrent density retention of 90% after continuous light illumination for 1000 s is also achieved for the W–BiVO₄/FeOOH photoanode.     

Simultaneously efficient light absorption and charge transport of CdS/TiO2 nanotube array toward improved photoelectrochemical performance

CdS has been widely used to modify TiO₂-based photoanodes for photoelectrochemical (PEC) water splitting. Due to the poor interface contact between chalcogenides and oxides, however, such CdS modified TiO₂ materials usually exhibit inefficient separation and transport of charges, leading to an unsatisfactory efficiency during the PEC water splitting process. Addressing this issue, we herein report a CdS/TiO₂ nanotube array (CdS/TNA) photoanode that was fabricated through a successive ion layer absorption and reaction (SILAR) method with an additional subsequent annealing. This post-annealing process is essential to enhance the interface contact between the CdS and the TNAs, resulting in an accelerated transfer of photogenerated electrons from the CdS to the TNAs. In addition, the post-annealing also improves the light absorption capability of the CdS/TNA photoanode. The simultaneous enhancement of charge transport and light absorption provided by the post-annealing is essential for improving the PEC performance of the CdS/TNA photoanode. The CdS/TNA photoanode obtained by this strategy exhibits a much enhanced PEC performance in water splitting, and its photocurrent density and solar-to-hydrogen conversion efficiency could reach 4.56 mA cm⁻² at 1.23 V vs. reversible hydrogen electrode and 5.61%, respectively. This simple but effective route can provide a general strategy for obtaining high-performance oxide-based photoelectrodes.     

Molybdenum doped bilayer photoanode nanotubes for enhanced photoelectrochemical water splitting

Conversion of solar energy into hydrogen energy via photoelectrochemical (PEC) water splitting is one of the most promising approaches for generation of clean and sustainable hydrogen energy in order to address the alarming global energy crisis and environmental problems. To achieve superior PEC performance and solar to hydrogen efficiency (STH), identification, synthesis, and development of efficient photoelectrocatalysts with suitable band gap and optoelectronic properties along with high PEC activity and durability is highly imperative. With the aim of improving the performance of our previously reported bilayer photoanode of WO₃ and Nb and N co-doped SnO₂ nanotubes i.e. WO₃-(Sn_0.95Nb_0.05)O₂:N NTs, herein, we report a simple and efficient strategy of molybdenum (Mo) doping into the WO₃ lattice to tailor the optoelectronic properties such as band gap, charge transfer resistance, and carrier density, etc. The Mo doped bilayer i.e. (W_0.98Mo_0.02)O_3-(Sn_0.95Nb_0.05)O₂:N revealed a higher light absorption ability with reduced band gap (1.88 eV) in comparison to that of the undoped bilayer (1.94 eV). In addition, Mo incorporation offered improvements in charge carrier density, photocurrent density, with reduction in charge transfer resistance, contributing to a STH (～3.12%), an applied bias photon-to-current efficiency (ABPE ～ 8% at 0.4 V), including a carrier density (N_d ～ 7.26 × 10²² cm^?3) superior to that of the undoped bilayer photoanode (STH ～2%, ABPE ～ 5.76%, and N_d ～5.11 × 10²² cm^?3, respectively). The substitution of Mo⁶⁺ for W⁶⁺ in the monoclinic lattice, forming the W–O–Mo bonds altered the band structure, realizing further enchantments in the PEC reaction and charge transfer kinetics. Additionally, doped bilayer photoanode revealed excellent long term PEC stability under illumination, suggesting its robustness for PEC water splitting. The present work herein provides a simple and effective Mo doping approach for generation of high performance photoanodes for PEC water splitting.     

Three-dimensional plasmonic photoanode of Co3O4 nanosheets coated onto TiO2 nanorod arrays for visible-light-driven water splitting

In this work, we report for the first time a plasmonic photoanode by decorating Au nanoparticles (NPs) onto two-dimensional (2D) Co₃O₄ nanosheets (NSs)/one-dimensional (1D) TiO₂ nanorod arrays (NRAs) (Au/Co₃O₄/TiO₂-NRAs) for enhanced visible-light photoelectrochemical (PEC) water splitting. In this plasmonic photoanode, TiO₂ NRAs act as an electron acceptor, plasmonic Au NPs and hierarchical Co₃O₄ NSs serve as visible-light harvesters. Light absorption shows that Au/Co₃O₄/TiO₂-NRAs heterojunction architectures exhibit greatly improved ability to harvest visible light due to the surface plasmon resonance (SPR) absorption of Au NPs and visible light harvesting ability of Co₃O₄ NSs. Spectroscopic measurements demonstrate that a type II band alignment is formed between Co₃O₄ and TiO₂. Benefiting from the SPR effect, type II band alignment and novel hierarchical architecture, plasmonic Au/Co₃O₄/TiO₂-NRAs photoanode shows remarkably enhanced visible-light PEC water splitting activity compared with Co₃O₄/TiO₂-NRAs and pristine TiO₂-NRAs photoanodes. Photocurrent density achieved by plasmonic photoanode is 37 and 1.2 times higher than those of TiO₂-NRAs and Co₃O₄/TiO₂-NRAs photoanodes, respectively. This work provides a promising strategy to highly enhance visible-light PEC water splitting activity of wide band-gap semiconductor-based photoelectrode materials.     

In2O3:Sn/TiO2/CdS heterojunction nanowire array photoanode in photoelectrochemical cells

The design of photoanode with highly efficient light harvesting and charge collection properties is important in photoelectrochemical (PEC) cell performance for hydrogen production. Here, we report the hierarchical In₂O₃:Sn/TiO₂/CdS heterojunction nanowire array photoanode (ITO/TiO₂/CdS-nanowire array photoanode) as it provides a short travel distance for charge carrier and long light absorption pathway by scattering effect. In addition, optical properties and device performance of the ITO/TiO₂/CdS-nanowire array photoanode were compared with the TiO₂ nanoparticle/CdS photoanode. The photocatalytic properties for water splitting were measured in the presence of sacrificial agent such as SO₃²⁻ and S²⁻ ions. Under illumination (AM 1.5G, 100 mW/cm²), ITO/TiO₂/CdS-nanowire array photoanode exhibits a photocurrent density of 8.36 mA/cm² at 0 V versus Ag/AgCl, which is four times higher than the TiO₂ nanoparticle/CdS photoanode. The maximum applied bias photon-to-current efficiency for the ITO/TiO₂/CdS-nanowire array and the TiO₂ nanoparticle/CdS photoanode were 3.33% and 2.09%, respectively. The improved light harvesting and the charge collection properties due to the increased light absorption pathway and reduced electron travel distance by ITO nanowire lead to enhancement of PEC performance.     

Photodeposited CoOx as highly active phases to boost water oxidation on BiVO4/WO3 photoanode

Surface decoration of photoanodes with oxygen evolution cocatalysts is an efficient approach to improve the photoelectrochemical water splitting performance. Herein, ultrafine CoO_x was selectively immobilized on the surface of BiVO₄/WO₃ photoanode by using the photogenerated holes to in-situ oxidize Co₄O₄ cubane. The composited photoanode (CoO_x/BiVO₄/WO₃) displayed an enhanced photoelectrochemical (PEC) water oxidation performance, with a photocurrent density of 2.3 mA/cm² at 1.23 V_RHE under the simulated sunlight irradiation, which was 2 times higher than that of bare BiVO₄/WO₃. The characterization results for the morphological, optical and electrochemical properties of the photoelectrodes revealed that, the enhanced PEC performances could be attributed to the improved charge carrier separation/transport behaviors and the promoted water oxidation kinetics when the photoelectrodes were loaded with CoO_x.     

A heterostructured catalyst composed of poly-2,6-diaminopyridine and TiO2 microspheres used as a photoanode for efficient water splitting

Photoelectrocatalytic (PEC) water splitting provides an alternative to direct solar-to-fuel production. In this study, a novel heterostructure formed between a conjugated polymer [poly-2,6-diaminopyridine (PDAP)] and three-dimensional TiO₂ microspheres was grown in situ on a Ti substrate (PDAP-3DTiO₂MSs/Ti) and used as photoanode for water oxidation in alkaline media under AM 1.5G illumination. The PDAP-3DTiO₂MSs/Ti can produce applied bias photon-to-current efficiency of 0.85% at 0.44 V vs. Pt and a photocurrent density of 1.56 mA cm⁻² at 1.23 V vs. RHE. Moreover, PDAP-3DTiO₂MSs/Ti displays impressive photoelectrochemical stability with 93% of its initial photocurrent being retained after 4 h of reaction. Based on physical-chemical characterization and photo-/electro-chemical measurements, the superior PEC water splitting performance of PDAP-3DTiO₂MSs/Ti should benefit from the coexistence of Ti³⁺ and Ti⁴⁺ in 3DTiO₂MSs, the light harvest capability of PDAP and the type II heterojunction formed between 3DTiO₂MSs and PDAP, which result in the enhanced generation and separation of photocarriers.     

Hierarchical mesoporous SnO2/BiVO4 photoanode decorated with Ag nanorods for efficient photoelectrochemical water splitting

Bismuth vanadate has been extensively investigated as a potential visible light photoanode for PEC water splitting. The performance of BiVO₄ is restricted by fast charge recombination and slow oxygen evolution reaction kinetic. To address these issues, hierarchical SnO₂ (HSN) mesoporous support is developed via a novel sol-electrophoretic approach, and BiVO₄ film is decorated with silver nanorods (Ag NRs). The photocurrent density of HSN/BiVO₄ photoanode is 3.98 mA/cm² at 1.23 V vs. reversible hydrogen electrode (RHE) and onset potential (V_onset) of 0.5 V vs. RHE. The PEC performance is attributed to the appropriate band alignment between SnO₂ and BiVO₄, as well as the hierarchical structure of SnO₂. Ag-HSN/BiVO₄ photoanode shows photocurrent density of 4.30 mA/cm² at 1.23 V vs. RHE and V_onset of 0.28 V vs. RHE. The enhanced photocurrent and negatively shifted V_onset can be attributed to radiative localized surface plasmon resonance decay and catalytic effect of Ag NRs, respectively.