Enhanced Photoelectrochemical Performance Research Articles

Dual Functionality of Surface States in Dictating Photocurrent Generation of Au Nanocluster-Sensitized TiO2 Electrodes.

Gold nanoclusters (Au NCs), composed of only a few atoms, exhibit molecule-like behavior due to their distinct electronic structures arising from quantum confinement effects. Unlike their plasmonic nanoparticle counterparts, these nonplasmonic Au NCs possess unique properties with significant potential for photosensitizer applications. While traditional and NC-based electrodes share architectural similarities, the photoelectrochemical (PEC) behavior of the latter diverges significantly. Sensitizing TiO2 with Au NCs introduces additional surface trap states. In contrast to conventional photosensitizers, where surface states typically have a negligible impact on hole transfer, these trap states actively mediate the charge transfer process in Au NC-sensitized TiO2 electrodes. In this study, we employed impedance spectroscopy to elucidate the role of surface trap states in photocurrent generation. Our investigation revealed that these states are critical in determining PEC performance, presenting a dichotomy: they facilitate charge transfer (enhancing PEC performance) while simultaneously promoting carrier recombination (limiting efficiency). We demonstrated that the judicious control of otherwise deleterious surface trap states can significantly boost photocurrent. Our findings highlight that the dual nature of surface trap states demands a comprehensive investigation to fully understand their intricate impact on PEC performance.

A Convenient In Situ Preparation of Cu2ZnSnS4-Anatase Hybrid Nanocomposite for Photocatalysis/Photoelectrochemical Water-Splitting Hydrogen Production.

This study details the rational design and synthesis of Cu2ZnSnS4 (CZTS)-doped anatase (A) heterostructures, utilizing earth-abundant elements to enhance the efficiency of solar-driven water splitting. A one-step hydrothermal method was employed to fabricate a series of CZTS-A heterojunctions. As the concentration of titanium dioxide (TiO2) varied, the morphology of CZTS shifted from floral patterns to sheet-like structures. The resulting CZTS-A heterostructures underwent comprehensive characterization through photoelectrochemical response assessments, optical measurements, and electrochemical impedance spectroscopy analyses. Detailed photoelectrochemical (PEC) investigations demonstrated notable enhancements in photocurrent density and incident photon-to-electron conversion efficiency (IPCE). Compared to pure anatase electrodes, the optimized CZTS-A heterostructures exhibited a seven-fold increase in photocurrent density and reached a hydrogen production efficiency of 1.1%. Additionally, the maximum H2 production rate from these heterostructures was 11-times greater than that of pure anatase and 250-times higher than the original CZTS after 2 h of irradiation. These results underscore the enhanced PEC performance of CZTS-A heterostructures, highlighting their potential as highly efficient materials for solar water splitting. Integrating Cu2ZnSnS4 nanoparticles (NPs) within TiO2 (anatase) heterostructures implied new avenues for developing earth-abundant and cost-effective photocatalytic systems for renewable energy applications.

Systematic Constructing FeOCl/BiVO4 Hetero-Interfacial Hybrid Photoanodes for Efficient Photoelectrochemical Water Splitting.

Bismuth vanadate (BiVO4), as a promising photoanode for photoelectrochemical (PEC) water splitting, suffers from poor charge separation efficiency and light absorption efficiency. Herein, iron oxychloride (FeOCl) is introduced as a novel cocatalyst simply grafted on BiVO4 to construct an integrated photoanode, enhancing PEC performance. The optimized FeOCl/BiVO4 photoanode exhibits a superior photocurrent density value of 5.23mAcm-2 at 1.23V versus reversible hydrogen electrode (RHE) under AM 1.5G illuminations. From experimental analysis, such high PEC performance is ascribed to the unique properties of FeOCl, facilitating charge transport, increasing light absorption efficiency, and promoting water oxidation kinetics. Density functional theory calculations further confirm that FeOCl optimizes the Gibbs free energy of H and O-containing intermediates (OOH*) during PEC processes, boosting the catalytic kinetics of PEC water splitting. This work presents FeOCl as a promising catalyst for constructing high efficient PEC water-splitting photoanodes.

Work function-tunable graphene/WO3 heterojunctions for high-performance photoelectrochemical cell: UV-treatment effect and defective graphene

Designing hybrid photoelectrodes with graphene capable of efficient charge-carrier transfer and excellent chemical stability is an effective strategy for developing high-performance photoelectrochemical (PEC) cells. However, it remains unclear how the PEC properties are enhanced and how to control the junction properties in graphene/metal oxide heterojunction-based photoelectrodes. Here, we develop a deterministic junction to enhance PEC performance in graphene/tungsten trioxide (WO3)-based photoelectrodes by tuning the work function of graphene. It reveals that the band structure of graphene/WO3 heterojunctions can be modified by ultraviolet (UV) treatment on WO3 thin films. This modification is supported by the observation that a single-layer graphene/UV-treated WO3 photoelectrode exhibits significantly enhanced PEC activities toward the oxygen evolution reaction (OER) (evidenced by features like a threefold increase in photocurrent, an onset potential shift, and improved stability), whereas the single-layer graphene/untreated WO3 electrode demonstrates improved properties for the hydrogen evolution reaction (HER). Additionally, defects in the graphene layer formed during PEC water splitting contribute to high catalytic activities of the graphene/WO3 photoelectrode due to a decrease in the Gibbs free energy for OER and HER. These results emphasize that band structure engineering via work function tuning in graphene/WO3 heterostructures can provide multiple benefits for high PEC performance and long-term stability.

The CuSCN layer between BiVO4 and NiFeOx for facilitating photogenerated carrier transfer and water oxidation kinetics

Modification of oxygen evolution co-catalyst (OEC) on the surface of bismuth vanadate (BiVO4) can effectively improve the kinetics of water oxidation, but it is still limited by the small hole extraction driving force at the BiVO4/OEC interface. Modulating the BiVO4/OEC interface with a hole transfer layer (HTL) is expected to facilitate hole transport from BiVO4 to the OEC surface. Herein, a copper(I) thiocyanate (CuSCN) HTL is inserted between BiVO4 and NiFeOx OEC to create BiVO4/CuSCN/NiFeOx photoanode, resulting in a significant enhancement of photoelectrochemical (PEC) water splitting performance. From electrochemical analyses and density functional theory (DFT) simulations, the markedly enhanced PEC performance is attributed to the insertion of CuSCN as an HTL, which promotes the extraction of holes from BiVO4 surface and boosts the water oxidation kinetics. The optimal photoanode achieves a photocurrent density of 5.6 mA cm−2 at 1.23 V versus the reversible hydrogen electrode (vs. RHE) and an impressive charge separation efficiency of 96.2 %. This work offers valuable insights into the development of advanced photoanodes for solar energy conversion and emphasizes the importance of selecting an appropriate HTL to mitigate recombination at the BiVO4/OEC interface.

Insights on Z-scheme interfacial charge transfer of TiO2-NRAs/BiOI-NFs/Au-NPs nanoheterostructures and unveiling enhanced photoelectrochemical performances

We synthesized TiO2-NRAs/BiOI-NFs/Au-NPs ternary Z-scheme nanoheterostructure using an accessible preparation method. The ternary nanoheterostructureexhibited enhanced photoelectrochemical (PEC) performance compared to other binary nanoheterostructure. The improved performance was attributed to the synergistic effect between enhanced charge separation and improved injection efficiency. An interfacial charge migration mechanism involving plasmon-induced hot electron injection and transition with oxygen vacancies defects was proposed. The triple nanohybrids showed a higher photodegradation rate for methyl orange (MO). Based on the scheme, the TiO2-NRAs/BiOI-NFs/Au-NPs ternary nanohybrids exhibited a photodegradation rate of 96.6% toward degradation of MO irradiated by UV-visible light, 1.47 and 1.19 fold that of BiOI-NFs/Au-NPs and TiO2-NRAs/BiOI-NFs, respectively. Furthermore, the TiO2-NRAs/BiOI-NFs/Au-NPs ternary nanoheterojunction exhibits the best photodegradation performance under near-infrared light irradiation, with a photodegradation rate 4.3 times and 1.2 times that of the binary TiO2-NRAs/BiOI-NFs and BiOI-NFs/Au-NPs nanoheterojunction composites, respectively. These findings provide insights into interfacial charge transfer in TiO2-NRAs/BiOI-NFs/Au-NPs nanoheterostructures and demonstrate their enhanced PEC performances, inspiring the design of high-efficiency and non-toxic Z-scheme heterostructures for various applications.

Melamine Cyanaurate Microrods Decorated with SnO2 Quantum Dots for Photoelectrochemical Applications

This study employs a simple and cost-effective technique to enhance the photoelectrochemical (PEC) water-splitting performance of melamine cyanaurate microrods (M), SnO2 nanostructures (S), and melamine cyanaurate microrods decorated with SnO2 quantum dots (MS) by optimizing NaOH and Na2SO3 electrolytes. Notably, the MS electrode demonstrates a remarkable improvement in PEC efficiency in Na2SO3 solution associated with NaOH solution. Specifically, the induced currents of the MS anode in the Na2SO3 electrolyte are approximately 6.28 mAcm−2 more than those observed in the NaOH electrolyte solution. It is revealed that SO32− anions effectively consume the holes, leading to improved separation of the generated charge pairs. This effective charge separation mechanism significantly contributes to the enhanced PEC performance observed in Na2SO3 electrolytes. The findings of this study suggest a capable approach for improving the PEC activity of the materials through the careful optimization of the supported electrolytes.

In situ polymerised polyaniline films over multi-walled carbon nanotubes coatings for enhanced photoelectrochemical performance

Polyaniline (PANI), which is a π-conjugated polymer, has stood out as a promising candidate for dihydrogen generation in photoelectrochemical (PEC) cells owing to its suitable optoelectronic properties and excellent stability. Nevertheless, the PEC performance of this material is still far from adequate for technological applications. Herein, we have focused on improving the PEC performance of PANI films by combining this polymer with multi-walled carbon nanotubes (MWCNTs) layers. Specifically, we have assessed the PEC activity of the in situ polymerised PANI films onto FTO substrates coated with different amounts of MWCTNs for the hydrogen evolution reaction (HER). The FTO/MWCNTs/PANI films with the optimum deposited amount of MWCNTs (i.e., 30 μL) featured a 2.4-fold increase of the cathodic photocurrent density response for the HER compared to that of FTO/PANI film. Moreover, the FTO/(30 μL)-MWCNTs/PANI films exhibited good PEC stability, as observed by the relatively low cathodic photocurrent density decay of up to 7% during 3720 s of stability test. Based on joint analyses of physical and PEC characterisation, the improved PEC performance for the FTO/(30 μL)-MWCNTs/PANI films were assigned to the combined contribution of the following factors: (i) enhancement of light absorption; (ii) possible improvement of excitons dissociation; (iii) minimisation of the electron-hole recombination process; and (iv) facilitation of electrons transfer at the PANI|electrolyte interface for the HER. The enhancement of PEC performance achieved in this work for the fully organic photocathode composed of MWCNTs/PANI paves the way to invest in additional modifications seeking to further improve the dissociation of excitons and the interfacial transfer of charge carriers for the light-driven HER.

Synergistic Effect of Co3(HPO4)2(OH)2 Cocatalyst and Al2O3 Passivation Layer on BiVO4 Photoanode for Enhanced Photoelectrochemical Water Oxidation

Bismuth vanadate (BVO) is regarded as an exceptional photoanode material for photoelectrochemical (PEC) water splitting, but it is restricted by the severe photocorrosion and slow water oxidation kinetics. Herein, a synergistic strategy combined with a Co3(HPO4)2(OH)2 (CoPH) cocatalyst and an Al2O3 (ALO) passivation layer was proposed for enhanced PEC performance. The CoPH/ALO/BVO photoanode exhibits an impressive photocurrent density of 4.9 mA cm−2 at 1.23 VRHE and an applied bias photon-to-current efficiency (ABPE) of 1.47% at 0.76 VRHE. This outstanding PEC performance can be ascribed to the suppressed surface charge recombination, facilitated interfacial charge transfer, and accelerated water oxidation kinetics with the introduction of the CoPH cocatalyst and ALO passivation layer. This work provides a novel and synergistic approach to design an efficient and stable photoanode for PEC applications by combining an oxygen evolution cocatalyst and a passivation layer.

Enhancing photoelectrochemical performance and stability of Ti-doped hematite photoanode via pentanuclear Co-based MOF modification.

Modifying photoanodes with metal-organic frameworks (MOFs) as oxygen evolution reaction (OER) cocatalysts has emerged as a promising approach to enhance the efficiency of photoelectrochemical (PEC) water oxidation. However, designing OER-active MOFs with both high photo- and electrochemical stability remains a challenge, limiting the advancement of this research. Herein, we present a facile method to fabricate a MOF-modified photoanode by directly loading a pentanuclear Co-based MOF (Co-MOF) onto the surface of a Ti-doped hematite photoanode (Ti:Fe2O3). The resulting Co-MOF/Ti:Fe2O3 modified photoanode exhibits an enhanced photocurrent density of 1.80mA∙cm-2 at 1.23V, surpassing those of the Ti:Fe2O3 (1.53mA∙cm-2) and bare Fe2O3 (0.59mA∙cm-2) counterparts. Additionally, significant enhancements in charge injection and separation efficiencies, applied bias photon-to-current efficiency (ABPE), incident photon to current conversion efficiency (IPCE), and donor density (Nd) were observed. Notably, a minimal photocurrent decay of only 5% over 10h demonstrates the extraordinary stability of the Co-MOF/Ti:Fe2O3 photoanode. This work highlights the efficacy of polynuclear Co-based MOFs as OER cocatalysts in designing efficient and stable photoanodes for PEC water splitting applications.

Enhancing photoelectrochemical surface reactivity through interface grafting of g-C3N4 quantum dots with BiVO4

Due to the high photosensitivity, quantum dots (QDs) offer promise in establishing heterojunctions to improve the photoelectrochemical (PEC) water oxidation process and enhance the solar-to-hydrogen conversion efficiency. However, apart from their catalytic capacity, additional protection strategies should be considered to eliminate the destruction of QDs from electrolytes and photo-corrosion. Here, we present a facile strategy to fabricate heterojunction by employing graphitic carbon nitride QDs (g-C3N4 QDs) coupled with BiVO4, referred to CNQDs/BiVO4. With the help of CNQDs, a gradient energy band alignment has been established in CNQDs/BiVO4, leading to facilitated hole migration driven by an upward force. The optimal CNQDs/BiVO4 sample shows significantly enhanced PEC performance for water oxidation, with a photocurrent of 2.2 mA/cm2 at 1.23 V vs. RHE (reversible hydrogen electrode), which is about 2.26 times better than that of BiVO4 (0.97 mA/cm2). The enhanced PEC performance could be attributed to the increased surface-active area and facilitated surface oxidation kinetics.

CuO photocathode enhancement through ultra-thin carbon coating layer for photoelectrochemical water splitting

In this research, we introduce a facile approach utilizing a glucose solution as a precursor to form a protective carbon layer on inherently unstable semiconductor nanostructures, addressing the pervasive issue of photo-corrosion. We focused on CuO photocathode, employing a straightforward technique to envelop them with an ultra-thin, amorphous carbon layer, rendering them suitable for photoelectrochemical (PEC) water-splitting application for hydrogen production. The results demonstrated exceptional photo-stability and significantly improved photocurrent density of CuO arrays equipped with the carbon protective layer. This transformative modification led to a substantial enhancement in PEC performance, yielding a photocurrent density up to 2.19 mA.cm−2 at 0 V vs. RHE. Furthermore, the maximum photo-to-current conversion efficiency reached 0.12 % at 0.1 V vs. RHE under AM 1.5G illumination condition (100 mW cm−2). In-depth investigations revealed that these enhancements results from accelerated electrochemical charge transfer at the electrode/electrolyte interface and concurrent mitigation of photo-corrosion rates. This approach has the potential to address stability concerns among a broad range of non-stable photoelectrodes, offering significant contributions to the field of energy conversion and the advancement of renewable energy technologies.

Enhancement of photoelectrochemical performance for nitrogen-doped titanium dioxide-based thin films produced by a facile air-based sputtering deposition

This work explores the use of air as a reactive gas in the sputtering deposition of N-doped TiO2-based bilayer, gradient, and multilayer thin films for photoelectrochemical evaluations. By merely adjusting the air/Ar flow ratio, crystalline phases, nitrogen doping contents, electrical properties, optical bandgaps, and valence band maximum (VBM) positions of N–TiO2 films were tailored. The N–TiO2/TiN(O) bilayer on the glass substrates exhibited a peak photocurrent density of 776 μA cm−2 at an air/Ar ratio of 1.60, which may be due to suitable bandgap and carrier mobility of the TiO2 overlayer as the bandgap was affected by the nitrogen content and rutile fraction in the TiO2 overlayer. To further improve the performance of N–TiO2, stepwise and sequential gradient structures with gradient bandgaps and nitrogen contents were produced, which could reach photocurrent densities of 805 ± 4 and 837 ± 3 μA cm−2, respectively. The gradient structures lead to enhanced light absorption efficiency and reduce carrier recombination. The N–TiO2/TiN(O) multilayer structures were also designed and revealed the highest photocurrent density of 865 ± 7 μA cm−2. Such evident enhancement is mainly due to the thin conductive while translucent TiN(O) layers between the photoelectrochemical-active N–TiO2 layers provide multiple low-impedance channels in enhancing carrier transport.

Fast Interfacial Carrier Dynamics Modulated by Bidirectional Charge Transport Channels in ZnIn2 S4 -based Composite Photoanodes Probed by Scanning Photoelectrochemical Microscopy.

Limited charge separation/transport efficiency remains the primary obstacle of achieving satisfying photoelectrochemical (PEC) water splitting performance. Therefore, it is essential to develop diverse interfacial engineering strategies to mitigate charge recombination. Despite obvious progress having been made, most works only considered a single-side modulation in either the electrons of conduction band or the holes of valence band in a semiconductor photoanode, leading to a limited PEC performance enhancement. Beyond this conventional thinking, we developed a novel coupling modification strategy to achieve a composite electrode with bidirectional carrier transport for a better charge separation, in which Ti2 C3 Tx MXene quantum dots (MQDs) and α-Fe2 O3 nanodots (FO) are anchored on the surface of ZnIn2 S4 (ZIS) nanoplates, resulting in markedly improved PEC water splitting of pure ZIS photoanode. Systematic studies indicated that the bidirectional charge transfer pathways were stimulated due to MQDs as "electron extractor" and S-O bonds as carriers transport channels, which synergistically favors significantly enhanced charge separation. The enhanced kinetic behavior at the FO/MQDs/ZIS interfaces was systematically and quantitatively evaluated by a series of methods, especially scanning photoelectrochemical microscopy. This work may deepen our understanding of interfacial charge separation, and provide valuable guidance for the rational design and fabrication of high-performance composite electrodes.

Fast Interfacial Carrier Dynamics Modulated by Bidirectional Charge Transport Channels in ZnIn2S4‐based Composite Photoanodes Probed by Scanning Photoelectrochemical Microscopy

AbstractLimited charge separation/transport efficiency remains the primary obstacle of achieving satisfying photoelectrochemical (PEC) water splitting performance. Therefore, it is essential to develop diverse interfacial engineering strategies to mitigate charge recombination. Despite obvious progress having been made, most works only considered a single‐side modulation in either the electrons of conduction band or the holes of valence band in a semiconductor photoanode, leading to a limited PEC performance enhancement. Beyond this conventional thinking, we developed a novel coupling modification strategy to achieve a composite electrode with bidirectional carrier transport for a better charge separation, in which Ti2C3Tx MXene quantum dots (MQDs) and α‐Fe2O3 nanodots (FO) are anchored on the surface of ZnIn2S4 (ZIS) nanoplates, resulting in markedly improved PEC water splitting of pure ZIS photoanode. Systematic studies indicated that the bidirectional charge transfer pathways were stimulated due to MQDs as “electron extractor” and S−O bonds as carriers transport channels, which synergistically favors significantly enhanced charge separation. The enhanced kinetic behavior at the FO/MQDs/ZIS interfaces was systematically and quantitatively evaluated by a series of methods, especially scanning photoelectrochemical microscopy. This work may deepen our understanding of interfacial charge separation, and provide valuable guidance for the rational design and fabrication of high‐performance composite electrodes.

In-situ zinc vanadate layer derived from highly hydrophilic substrate for PEC performance enhancement of Zn-doped BiVO4 photoanode

Owing to serious concerns regarding environmental issues, extensive research is being conducted to develop eco-friendly and sustainable energy sources. One promising solution is the utilization of solar energy for energy production using photoelectrochemical (PEC) methods. However, the performance of photoanodes is frequently hindered by high recombination rates and inadequate charge transport. To address these issues, we designed an approach that incorporates an ultrathin hydrophilic carbon (UTHC) film on a substrate. The UTHC film enhanced the hydrophilicity of the FTO surface and enabled the synthesis of a zinc vanadate layer for efficient charge transfer. As a conductive bridge, the zinc vanadate layer promotes effective charge transfer for excellent PEC performance. The resulting carbon film/Zn-doped BiVO4 (CZB) photoanode exhibited significantly improved PEC performance, achieving a remarkable photocurrent density of 1.515 mA∙cm−2 and a separation efficiency of 9.58 % at 1.23 VRHE. This study demonstrates a potential method for enhancing PEC performance for sustainable energy conversion using a highly hydrophilic metal oxide layer on an FTO substrate.

In-situ growth of CuI/Porphyrin-based graphdiyne (PDY) p-n heterojunction for high-performance cathodic photoelectrochemical sensing

Cathodic photoelectrochemical (PEC) bioanalysis has been attracting great interest due to its excellent anti-interference capability. As a p-type wide energy band gap semiconductor, CuI is regarded as an ideal material for the construction of photocathodes, while its poor stability and narrow light absorption range limit its application as a photoelectrode in PEC sensing. Herein, we report a simple in-situ growth strategy to synthesize CuI/Porphyrin-based graphdiyne (PDY) p-n heterojunction as a photocathode. CuI crystals were firstly deposited on the ITO glass surface via the electrochemical deposition, and CuI could catalyze the in-situ Glaser coupling reaction of 5,10,15,20-tetra(4-ethynylphenyl) porphyrin (TEPP), allowing the growth of PDY film on the CuI crystal surface and forming the p-n heterojunction photocathode. The as-prepared PDY film plays a crucial role in the significant enhancement of PEC performance because of its intense light absorption, and the formation of CuI/PDY p-n heterojunction can efficiently promote the transportation of photogenerated carriers between CuI and PDY thanks to the excellent electrical conductivity and high carrier mobility of highly π-conjugated PDY. After the growth of PDY, the photocurrent response of PDY/CuI/ITO is almost seven folds higher compared to that of CuI/ITO. Owing to the selective Cu–S bond interaction between l-cysteine (L-Cys) and Cu+, a PEC sensor for the L-Cys determination is developed with a broad linear range from 0.05 to 1.2 μM and a limit of detection (LOD) of 0.03 μM.

Synergistic effect of Co doping and borate impregnation on BiVO4 photoanode for efficient photoelectrochemical water splitting

The performance of photoelectrochemical (PEC) water splitting is hindered by high overpotential and significant recombination of photogenerated charges occurring within the bulk and on the surface of the photoanodes. In this study, we propose a nanoporous photoelectrode, B–Co:BVO, which combines ex-situ Co-doping and surface borate impregnation treatments through simple electrodeposition and immersion methods. As a result, the optimized photocurrent densities of B-BVO and Co:BVO exhibit 1.58 mA/cm2 and 1.9 mA/cm2, respectively, showing a 1.3 and 1.6-fold increase compared to the bare BVO sample (1.2 mA/cm2) at 1.23 VRHE. Moreover, the synergistic effect of Co doping and borate impregnation on the BiVO4 photoanode (B–Co:BVO) achieves the photocurrent density of 2.27 mA/cm2, accompanied by a lower onset potential (0.23 VRHE) and highest IPCE value (42.6 %) at 1.23 VRHE, maintaining 80.4 % of initial current density value for 18 h in KBi + V electrolyte solution with the enhancement of PEC performance. The proposed charge transfer mechanism in optimum B–Co:BVO photoanodes during the photoelectrochemical water splitting was also studied.

Construction of type-II SnO2/InGaN nanorods heterostructure toward high photoelectrochemical performance

Exploring highly efficient and stable photoelectrode material is essential for high-performance photoelectrochemical (PEC) water-splitting applications. III-nitride semiconductors, particularly InGaN, have been considered as prospective materials for PEC hydrogen evolution. However, their surface states and other recombination centers, which enhance the charge recombination kinetics, are bottlenecks for the high PEC performance. In this work, we report the construction of type-II heterojunction by sputter depositing SnO2 on InGaN nanorods (NRs) to promote interfacial carrier transport and thereby enhance PEC performance. The energy band offsets at the SnO2/InGaN NRs interface were analyzed by x-ray photoelectron spectroscopy. Type-II heterojunction was defined at the SnO2/InGaN NRs interface with a valence band offset of 0.77 eV and conduction band offset of 0.25 eV. The photocurrent density of the SnO2/InGaN NRs photoanode is 7.09 mA/cm2 at 0.77 V vs Ag/AgCl electrode with 80 nm SnO2 thickness, which is ∼14-fold higher than that of the pristine InGaN NRs photoanode. Furthermore, the applied bias photo-to-current efficiency of SnO2/InGaN NRs photoanode records 3.36% at 0.77 V vs Ag/AgCl electrode. The enhanced PEC performance is mainly ascribed to the formation of high-quality SnO2/InGaN NRs heterojunction that enforces the directional charge transfer and substantially boosts the separation of photogenerated electron–hole pairs at the interface of InGaN NRs and SnO2. Overall, this work sheds light on the promising strategy to design and fabricate III-nitride nanostructures-based photoelectrodes for feasible PEC water-splitting applications.

Photoelectrochemical Properties of Pulse‐Reverse Electrodeposited Sb2Se3/TiO2 Nanotube Photoanodes’ Controlled Sb2Se3 Overlayer

Constructing heterostructures is a promising strategy to improve the photoelectrochemical (PEC) performance of photoanodes in PEC water‐splitting systems. The effect on PEC performance is dependent on the deposition conditions of the overlayer in the heterostructured photoanode. Herein, the deposition condition of the antimony selenide (Sb2Se3) overlayer by adjusting the duty cycle and cycle number during pulse‐reverse electrodeposition. This aims to assess its impact on the PEC characteristics of the Sb2Se3 overlayered titanium dioxide (Sb2Se3/TiO2) nanotube photoanode. Adequate pulse‐off time in the duty cycle ensures sufficient permeation of deposition electrolyte into the inner wall of TiO2 nanotube, leading to uniform Sb2Se3 deposition. On the other hand, an excessive cycle number negatively affects PEC performance, as Sb2Se3 agglomeration blocks the pores of the TiO2 nanotube. Consequently, the Sb2Se3/TiO2 nanotube photoanode, when fabricated with the optimal pulse‐off time and cycle number, exhibits enhanced PEC performance. This is due to efficient charge transfer/separation facilitated by the p–n heterojunction and improved light absorption. These insights offer valuable guidance in choosing the appropriate fabrication processes for heterostructured photoanodes in efficient PEC water‐splitting systems.