Customized Photoelectrochemical C-N and C-P Formation Enabled by Tailored Deposition on Photoanodes.

Photoelectrochemistry (PEC) is burgeoning as an innovative solution to organic synthesis. However, the current PEC system suffers limited reaction types and unsatisfactory performances. Herein, we employ efficient BiVO4 photoanode with tailored deposition layers for customizing two PEC approaches toward C-N and C-P formation. Notably, our process proceeds under mild reaction conditions, easily available substrates, and ultra-low potentials. Beyond photocatalysis and electrocatalysis, customized PEC offers high efficiency, good functional group tolerance, and substantial applicability for decorating drug molecules, highlighting its promising potential to enrich the synthetic toolbox for broader organic chemistry of practical applications.

Promoting the Photoelectrochemical Properties of BiVO4 Photoanode via Dual Modification with CdS Nanoparticles and NiFe-LDH Nanosheets.

Bismuth vanadate (BiVO4) has long been considered a promising photoanode material for photoelectrochemical (PEC) water splitting. Despite its potential, significant challenges such as slow surface water evolution reaction (OER) kinetics, poor carrier mobility, and rapid charge recombination limit its application. To address these issues, a triadic photoanode has been fabricated by sequentially depositing CdS nanoparticles and NiFe-layered double hydroxide (NiFe-LDH) nanosheets onto BiVO4, creating a NiFe-LDH/CdS/BiVO4 composite. This newly engineered photoanode demonstrates a photocurrent density of 3.1 mA cm-2 at 1.23 V vs. RHE in 0.1 M KOH under AM 1.5 G illumination, outperforming the singular BiVO4 photoanode by a factor of 5.8 and the binary CdS/BiVO4 and NiFe-LDH/BiVO4 photoanodes by factors of 4.9 and 4.3, respectively. Furthermore, it exhibits significantly higher applied bias photon-to-current efficiency (ABPE) and incident photon-to-current efficiency (ICPE) compared to pristine BiVO4 and its binary counterparts. This enhancement in PEC performance is ascribed to the formation of a CdS/BiVO4 heterojunction and the presence of a NiFe-LDH OER co-catalyst, which synergistically facilitate charge separation and transfer efficiencies. The findings suggest that dual modification of BiVO4 with CdS and NiFe-LDH is a promising approach to enhance the efficiency of photoanodes for PEC water splitting.

Enhanced 1,2-dichloroethane removal using g-C3N4/Blue TiO2 nanotube array photoanode in microbial photoelectrochemical cells.

The compound 1,2-dichloroethane (1,2-DCA), a persistent and ubiquitous pollutant, is often found in groundwater and can strongly affect the ecological environment. However, the extreme bio-impedance of C-Cl bonds means that a high energy input is needed to drive biological dechlorination. Biotechnology techniques based on microbial photoelectrochemical cell (MPEC) could potentially convert solar energy into electricity and significantly reduce the external energy inputs currently needed to treat 1,2-DCA. However, low electricity-generating efficiency at the anode and sluggish bioreaction kinetics at the cathode limit the application of MPEC. In this study, a g-C3N4/Blue TiO2-NTA photoanode was fabricated and incorporated into an MPEC for 1,2-DCA removal. Optimal performance was achieved when Blue TiO2 nanotube arrays (Blue TiO2-NTA) were loaded with graphitic carbon nitride (g-C3N4) 10 times. The photocurrent density of the g-C3N4/Blue TiO2-NTA composite electrode was 2.48-fold higher than that of the pure Blue TiO2-NTA electrode under light irradiation. Furthermore, the MPEC equipped with g-C3N4/Blue TiO2-NTA improved 1,2-DCA removal efficiency by 45.21% compared to the Blue TiO2-NTA alone, which is comparable to that of a microbial electrolysis cell. In the modified MPEC, the current efficiency reached 69.07% when the light intensity was 150 mW cm-2 and the 1,2-DCA concentration was 4.4 mM. The excellent performance of the novel MPEC was attributed to the efficient direct electron transfer process and the abundant dechlorinators and electroactive bacteria. These results provide a sustainable and cost-effective strategy to improve 1,2-DCA treatment using a biocathode driven by a photoanode.

Advancing BiVO4 Photoanode Activity for Ethylene Glycol Oxidation via Strategic pH Control.

The photoelectrochemical (PEC) conversion of organic small molecules offers a dual benefit of synthesizing value-added chemicals and concurrently producing hydrogen (H2). Ethylene glycol, with its dual hydroxyl groups, stands out as a versatile organic substrate capable of yielding various C1 and C2 chemicals. In this study, we demonstrate that pH modulation markedly enhances the photocurrent of BiVO4 photoanodes, thus facilitating the efficient oxidation of ethylene glycol while simultaneously generating H2. Our findings reveal that in a pH = 1 ethylene glycol solution, the photocurrent density at 1.23 V vs. RHE can attain an impressive 7.1 mA cm-2, significantly surpassing the outputs in neutral and highly alkaline environments. The increase in photocurrent is attributed to the augmented adsorption of ethylene glycol on BiVO4 under acidic conditions, which in turn elevates the activity of the oxidation reaction, culminating in the maximal production of formic acid. This investigation sheds light on the pivotal role of electrolyte pH in the PEC oxidation process and underscores the potential of the PEC strategy for biomass valorization into value-added products alongside H2 fuel generation.

Recent Developments in Nickel-Based Layered Double Hydroxides for Photo(-/)electrocatalytic Water Oxidation.

Layered double hydroxides (LDHs), especially those containing nickel (Ni), are increasingly recognized for their potential in photo(-/)electrocatalytic water oxidation due to the abundant availability of Ni, their corrosion resistance, and their minimal toxicity. This review provides a comprehensive examination of Ni-based LDHs in electrocatalytic (EC), photocatalytic (PC), and photoelectrocatalytic (PEC) water oxidation processes. The review delves into the operational principles, highlighting similarities and distinctions as well as the benefits and limitations associated with each method of water oxidation. It includes a detailed discussion on the synthesis of monolayer, ultrathin, and bulk Ni-based LDHs, focusing on the merits and drawbacks inherent to each synthesis approach. Regarding the EC oxygen evolution reaction (OER), strategies to improve catalytic performance and insights into the structural evolution of Ni-based LDHs during the electrocatalytic process are summarized. Furthermore, the review extensively covers the advancements in Ni-based LDHs for PEC OER, including an analysis of semiconductors paired with Ni-based LDHs to form photoanodes, with a focus on their enhanced activity, stability, and underlying mechanisms facilitated by LDHs. The review concludes by addressing the challenges and prospects in the development of innovative Ni-based LDH catalysts for practical applications. The comprehensive insights provided in this paper will not only stimulate further research but also engage the scientific community, thus driving the field of photo(-/)electrocatalytic water oxidation forward.

Structural Refinement and Optoelectrical Properties of Nd2Ru2O7 and Gd2Ru2O7 Pyrochlore Oxides for Photovoltaic Applications.

High-performance photovoltaic devices require active photoanodes with superior optoelectric properties. In this study, we synthesized neodymium ruthenate, Nd2Ru2O7 (NRO), and gadolinium ruthenate pyrochlore oxides, Gd2Ru2O7 (GRO), via the solid-state reaction technique, showcasing their potential as promising candidates for photoanode absorbers to enhance the efficiency of dye-sensitized solar cells. A structural analysis revealed predominantly cubic symmetry phases for both materials within the Fd-3m space group, along with residual orthorhombic symmetry phases (Nd3RuO7 and Gd3RuO7, respectively) refined in the Pnma space group. Raman spectroscopy further confirmed these phases, identifying distinct active modes of vibration in the predominant pyrochlore oxides. Additionally, a scanning electron microscopy (SEM) analysis coupled with energy-dispersive X-ray spectroscopy (EDX) elucidated the morphology and chemical composition of the compounds. The average grain size was determined to be approximately 0.5 µm for GRO and 1 µm for NRO. Electrical characterization via I-V measurements revealed that these pyrochlore oxides exhibit n-type semiconductor behavior, with conductivity estimated at 1.5 (Ohm·cm)-1 for GRO and 4.5 (Ohm·cm)-1 for NRO. Collectively, these findings position these metallic oxides as promising absorber materials for solar panels.

Modulating built-in electric field via Bi-VO4-Fe interfacial bridges to enhance charge separation for efficient photoelectrochemical water splitting.

Photoelectrochemical (PEC) water splitting on semiconductor electrodes is considered to be one of the important ways to produce clean and sustainable hydrogen fuel, which is a great help in solving energy and environmental problems. Bismuth vanadate (BiVO4) as a promising photoanode for photoelectrochemical water splitting still suffers from poor charge separation efficiency and photo-induced self-corrosion. Herein, we develop heterojunction-rich photoanodes composed of BiVO4 and iron vanadate (FeVO4), coated with nickel iron oxide (NiFeOx/FeVO4/BiVO4). The formation of the interface between BiVO4 and FeVO4 (Bi-VO4-Fe bridges) enhances the interfacial interaction, resulting in improved performance. Meanwhile, high-conductivity FeVO4 and NiFeOx oxygen evolution co-catalysts effectively enhance bulk electron/hole separation, interface water's kinetics and photostability. Concurrently, the optimized NiFeOx/FeVO4/BiVO4 possesses a remarkable photocurrent density of 5.59 mA/cm2 at 1.23 V versus reversible hydrogen electrode (vs RHE) under AM 1.5G (Air Mass 1.5 Global) simulated sunlight, accompanied by superior stability without any decreased of its photocurrent density after 14 h. This work not only reveals the crucial role of built-in electric field in BiVO4-based photoanode during PEC water splitting, but also provides a new guide to the design of efficient photoanode for PEC.

Rapid Surface Reconstruction of In2S3 Photoanode via Flame Treatment for Enhanced Photoelectrochemical Performance.

Surface reconstruction, reorganizing the surface atoms or structure, is a promising strategy to manipulate materials' electrical, electrochemical, and surface catalytic properties. Herein, a rapid surface reconstruction of indium sulfide (In2S3) is demonstrated via a high-temperature flame treatment to improve its charge collection properties. The flame process selectively transforms the In2S3 surface into a diffusionless In2O3 layer with high crystallinity. Additionally, it controllably generates bulk sulfur vacancies within a few seconds, leading to surface-reconstructed In2S3 (sr-In2S3). When using those sr-In2S3 as photoanode for photoelectrochemical water splitting devices, these dual functions of surface In2O3/bulk In2S3 reduce the charge recombination in the surface and bulk region, thus improving photocurrent density and stability. With optimized surface reconstruction, the sr-In2S3 photoanode demonstrates a significant photocurrent density of 8.5 mA cm-2 at 1.23 V versus a reversible hydrogen electrode (RHE), marking a 2.5-fold increase compared to pristine In2S3 (3.5 mA cm-2). More importantly, the sr-In2S3 photoanode exhibits an impressive photocurrent density of 7.3 mA cm-2 at 0.6 V versus RHE for iodide oxidation reaction. A practical and scalable surface reconstruction is also showcased via flame treatment. This work provides new insights for surface reconstruction engineering in sulfide-based semiconductors, making a breakthrough in developing efficient solar-fuel energy devices.

Unveiling Enhanced PEC Water Oxidation: Morphology Tuning and Interfacial Phase Change in α-Fe2O3@K-OMS-2 Branched Core-Shell Nanoarrays.

A simple fabrication method that involves two steps of hydrothermal reaction has been demonstrated for the growth of α-Fe2O3@K-OMS-2 branched core-shell nanoarrays. Different reactant concentrations in the shell-forming step led to different morphologies in the resultant composites, denoted as 0.25 OC, 0.5 OC, and 1.0 OC. Both 0.25 OC and 0.5 OC formed perfect branched core-shell structures, with 0.5 OC possessing longer branches, which were observed by SEM and TEM. The core K-OMS-2 and shell α-Fe2O3 were confirmed by grazing incidence X-ray diffraction (GIXRD), EDS mapping, and atomic alignment from high-resolution STEM images. Further investigation with high-resolution HAADF-STEM, EELS, and XPS indicated the existence of an ultrathin layer of Mn3O4 sandwiched at the interface. All composite materials offered greatly enhanced photocurrent density at 1.23 VRHE, compared to the pristine Fe2O3 photoanode (0.33 mA/cm2), and sample 0.5 OC showed the highest photocurrent density of 2.81 mA/cm2. Photoelectrochemical (PEC) performance was evaluated for the samples by conducting linear sweep voltammetry (LSV), applied bias photo-to-current efficiency (ABPE), electrochemical impedance spectroscopy (EIS), incident-photo-to-current efficiency (IPCE), transient photocurrent responses, and stability tests. The charge separation and transfer efficiencies, together with the electrochemically active surface area, were also investigated. The significant enhancement in sample 0.5 OC is ascribed to the synergetic effect brought by the longer branches in the core-shell structure, the conductive K-OMS-2 core, and the formation of the Mn3O4 thin layer formed between the core and shell.

Graphene Quantum Dots as Hole Extraction and Transfer Layer Empowering Solar Water Splitting of Catalyst-Coupled Zinc Ferrite Nanorods.

Despite the narrow band gap energy, the performance of zinc ferrite (ZnFe2O4) as a photoharvester for solar-driven water splitting is significantly hindered due to its sluggish charge transfer and severe charge recombination. This work reports the fabrication of a hybrid nanostructured hydrogenated ZnFe2O4 (ZFO) photoanode with enhanced photoelectrochemical water-oxidation activity through coupling N-doped graphene quantum dots (GQDs) as a hole transfer layer and Co-Pi as a catalyst. The GQDs not only reduce the surface-mediated nonradiative electron-hole pair recombination but also induce a built-in interfacial electric field leading to a favorable band alignment at the ZFO/GQDs interface, helping rapid photogenerated hole separation and serving as a conducting hole transfer highway, improve the hole transportation into the Co-Pi catalyst for enhanced water oxidation reaction kinetics. The optimized ZFO/GQD/Co-Pi hybrid photoanode delivers a 23-fold photocurrent enhancement at 1.23 V versus the reversible hydrogen electrode (RHE) and a significant 360 mV reduction in the onset potential, reaching 0.65 VRHE compared with the ZFO photoanode under 1 sun illumination in a neutral electrolytic environment. This investigation underscores the mechanism of synergistic interplay between the hole transport layer and cocatalyst in boosting the solar-illuminated water-splitting activity of the ZFO photoanode.

BiVO4 Photoanode with NiV2O6 Back Contact Interfacial Layer for Improved Hole-Diffusion Length and Photoelectrochemical Water Oxidation Activity.

The short hole diffusion length (HDL) and high interfacial recombination are among the main drawbacks of semiconductor-based solar energy systems. Surface passivation and introducing an interfacial layer are recognized for enhancing HDL and charge carrier separation. Herein, we introduced a facile recipe to design a pinholes-free BiVO4 photoanode with a NiV2O6 back contact interfacial (BCI) layer, marking a significant advancement in the HDL and photoelectrochemical activity. The fabricated BiVO4 photoanode with NiV2O6 BCI layer exhibits a 2-fold increase in the HDL compared to pristine BiVO4. Despite this improvement, we found that the front surface recombination still hinders the water oxidation process, as revealed by photoelectrochemical (PEC) studies employing Na2SO3 electron donors and by intensity-modulated photocurrent spectroscopy measurements. To address this limitation, the surface of the NiV2O6/BiVO4 photoanode was passivated with a cobalt phosphate electrocatalyst, resulting in a dramatic enhancement in the PEC performance. The optimized photoanode achieved a stable photocurrent density of 4.8 mA cm-2 at 1.23 VRHE, which is 12-fold higher than that of the pristine BiVO4 photoanode. Density Functional Theory (DFT) simulations revealed an abrupt electrostatic potential transition at the NiV2O6/BiVO4 interface with BiVO4 being more negative than NiV2O6. A strong built-in electric field is thus generated at the interface and drifts photogenerated electrons toward the NiV2O6 BCI layer and photogenerated holes toward the BiVO4 top layer. As a result, the back-surface recombination is minimized, and ultimately, the HDL is extended in agreement with the experimental findings.

Enhanced ammonia oxidation by a photoelectrocatalysis­chlorine system: The role of ClO• and free chlorine.

The decomposition of ammonia-N to environmental-friendly N2 remains a fundamental problem for water treatment. We proposed a way to selectively and efficiently oxidize ammonia to N2 through an integrated photoeletrocatalysis­chlorine reactions (PECCl) system based on a bifunctional TiO2 nanotube photoanode. The ·OH and HClO can be simultaneously generated on the TiO2 nanotube photoanode in this system, which can in situ form ClO· for efficient ammonia removal. Compared with electrochemical­chlorine (EC-Cl), photocatalysis­chlorine (PC-Cl) and photoelectrocatalysis (PEC) systems, the PEC-Cl system exhibited much higher electrocatalytic activity due to the synergetic effect of photoelectrocatalyst and electrocatalyst in bifunctional TiO2 nanotube electrode. The removal efficiency of ammonia-N and total-N reached 100.0 % and 93.3 % at 0.3 V (vs Ag/AgCl) in the PEC-Cl system. Moreover, the system was efficient under various pH conditions. The reactions between ClO-/ClO· and the N-containing intermediates contributed to the high performance of the system, which expanded the reactions from the electrode surface to the electrolyte. Furthermore, radical scavenging and free chlorine determination experiments confirmed that ClO· and free chlorine were the main active species that enabled the ammonia oxidation. This study presents new understanding on the role of active species for ammonia removal in wastewater.

Bias distribution and regulation in photoelectrochemical overall water-splitting cells.

The water oxidation half-reaction at anodes is always considered the rate-limiting step of overall water splitting (OWS), but the actual bias distribution between photoanodes and cathodes of photoelectrochemical (PEC) OWS cells has not been investigated systematically. In this work, we find that, for PEC cells consisting of photoanodes (nickel-modified n-Si [Ni/n-Si] and α-Fe2O3) with low photovoltage (Vph < 1 V), a large portion of applied bias is exerted on the Pt cathode for satisfying the hydrogen evolution thermodynamics, showing a thermodynamics-controlled characteristic. In contrast, for photoanodes (TiO2 and BiVO4) with Vph > 1 V, the bias required for cathode activation can be significantly reduced, exhibiting a kinetics-controlled characteristic. Further investigations show that the bias distribution can be regulated by tuning the electrolyte pH and using alternative half-reaction couplings. Accordingly, a volcano plot is presented for the rational design of the overall reactions and unbiased PEC cells. Motivated by this, an unbiased PEC cell consisting of a simple Ni/n-Si photoanode and Pt cathode is assembled, delivering a photocurrent density of 5.3 ± 0.2 mA cm-2.

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.

Strong Interactions between Au Nanoparticles and BiVO4 Photoanode Boosts Hole Extraction for Photoelectrochemical Water Splitting.

Strong metal-support interaction (SMSI) is widely proposed as a key factor in tuning catalytic performances. Herein, the classical SMSI between Au nanoparticles (NPs) and BiVO4 (BVO) supports (Au/BVO-SMSI) is discovered and used innovatively for photoelectrochemical (PEC) water splitting. Owing to the SMSI, the electrons transfer from V4+ to Au NPs, leading to the formation of electron-rich Au species (Auδ-) and strong electronic interaction (i.e., Auδ--Ov-V4+), which readily contributes to extract photogenerated holes and promote charge separation. Benefitted from the SMSI effect, the as-prepared Au/BVO-SMSI photoanode exhibits a superior photocurrent density of 6.25 mA cm-2 at 1.23 V versus the reversible hydrogen electrode after the deposition of FeOOH/NiOOH cocatalysts. This work provides a pioneering view for extending SMSI effect to bimetal oxide supports for PEC water splitting, and guides the interfacial electronic and geometric structure modulation of photoanodes consisting of metal NPs and reducible oxides for improved solar energy conversion efficiency.

BiVO4-Based Heterojunction Photocathode for High-Performance Photoelectrochemical Hydrogen Peroxide Production.

Photoelectrochemical (PEC) cells provide a promising solution for the synthesis of hydrogen peroxide (H2O2). Herein, an integrated photocathode of p-type BiVO4 (p-BVO) array with tetragonal zircon structure coupled with different metal oxide (MOx, M = Sn, Ti, Ni, and Zn) heterostructure and NiNC cocatalyst (p-BVO/MOx/NiNC) was synthesized for the PEC oxygen reduction reaction (ORR) in production of H2O2. The p-BVO/SnO2/NiNC array achieves the production rate 65.46 µmol L-1 h-1 of H2O2 with a Faraday efficiency (FE) of 76.12%. Combined with the H2O2 generation of water oxidation from the n-type Mo-doped BiVO4 (n-Mo:BVO) photoanode, the unbiased photoelectrochemical cell composed of a p-BVO/SnO2/NiNC photocathode and n-Mo:BVO photoanode achieves a total FE of 97.67% for H2O2 generation. The large area BiVO4-based tandem cell of 3 × 3 cm2 can reach a total H2O2 production yield of 338.84 µmol L-1. This work paves the way for the rational design and fabrication of artificial photosynthetic cells for the production of liquid solar fuel.

Bioelectricity and CO2-to-butyrate production using photobioelectrochemical cells with bio-hydrogel.

Bio-photoelectrochemical cell (BPEC) is an emerging technology that can convert the solar energy into electricity or chemicals. However, traditional BPEC depending on abiotic electrodes is challenging for microbial/enzymatic catalysis because of the inefficient electron exchange. Here, electroactive bacteria (Shewanella loihica PV-4) were used to reduce graphene oxide (rGO) nanosheets and produce co-assembled rGO/Shewanella biohydrogel as a basic electrode. By adsorbing chlorophyll contained thylakoid membrane, this biohydrogel was fabricated as a photoanode that delivered maximum photocurrent 126 µA/cm3 under visible light. Impressively, the biohydrogel could be served as a cathode in BPEC by forming coculture system with genetically edited Clostridium ljungdahlii. Under illumination, the BPEC with above photoanode and cathode yielded âˆ¼ 5.4 mM butyrate from CO2 reduction, 169 % increase compared to dark process. This work provided a new strategy (nanotechnology combined with synthetic biology) to achieve efficient bioelectricity and valuable chemical production in PBEC.

Deposition of FeOOH Layer on Ultrathin Hematite Nanoflakes to Promote Photoelectrochemical Water Splitting.

Hematite is one of the most promising photoanode materials for the study of photoelectrochemical (PEC) water splitting because of its ideal bandgap with sufficient visible light absorption and stability in alkaline electrolytes. However, owing to the intrinsically high electron-hole recombination, the PEC performance of hematite is still far below that expected. The efficient charge separation can be achieved via growth of FeOOH on hematite photoanode. In this study, hematite nanostructures were successfully grown on the surface of iron foil by the simple immersion deposition method and thermal oxidation treatment. Furthermore, cocatalyst FeOOH was successfully added to the hematite nanostructure surface to improve charge separation and charge transfer, and thus promote the photoelectrochemical water splitting. By utilizing the FeOOH overlayer as a cocatalyst, the photocurrent density of hematite exhibited a substantial 86% increase under 1.5 VRHE, while the onset potential showed an apparent shift towards the cathodic direction. This can be ascribed to the high reaction area for the nanostructured morphology and high electrocatalytic activity of FeOOH that enhanced the amount of photogenerated holes and accelerated the kinetics of water splitting.

Quantum Dots Mediated Heterojunction Coupling MoSe2 Photoanode for Photoelectrochemical Water Splitting.

Graphene quantum dots (GQDs) possess the photosensitive absorption for photoelectrochemical hydrogen evolution owing to special band structures, whereas they usually confront with photo-corrosion or undesired charge recombination during photoelectrochemical reactions. Hence, we establish the heterojunction between GQDs and MoSe2 sheets via a hydrothermal process for improved stability and performance. Photoanodic water splitting with hydrogen evolution boosted by the heteroatom doped N,S-GQDs/MoSe2 heterojunction has been attained due to the abundant active sites, promoted charge separation and transfer kinetics with reduced energy barriers. Diphasic 1T and 2H MoSe2 sheet-hybridized quantum dots contribute to the Schottky heterojunction, which can play a key role in expedited carrier transport to inhibit accumulative photo-corrosion and increase photocurrent. Heteroatom dopants lead to favored energy band matching, bandgap narrowing, stronger light absorption and high photocurrent density. The external quantum efficiency of the doped heterojunction has been elevated twofold over that of the non-doped pristine heterojunction. Modification of the graphene quantum dots and MoSe2 heterojunction demonstrate a viable and adaptable platform toward photoelectrochemical hydrogen evolution processes.

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.