Photoelectrochemical Hydrogen Evolution Research Articles

Enhanced photoelectrochemical performance of P-doped g‑C3N4/Zn0.5Cd0.5S heterojunction photocathode for water splitting

Photoelectrochemical (PEC) hydrogen evolution reaction at semiconductor photocathode in the presence of visible light is a promising way to harvest renewable energy. Graphitic carbon nitride (g-C3N4) has intriguing properties, making it highly favorable for photoelectrode engineering. This work demonstrated P-doped g-C3N4 nanosheets (PCN-Nss) and Zn0.5Cd0.5S heterojunction (PCN-Nss/ZCS-40) for PEC hydrogen evolution reaction using simulated sunlight. A facile and simple two-step strategy developed PCN-Nss/ZCS-40 photocathode; including co-precipitation of ZnCdS in the highly dispersed suspension of PCN-Nss and then drop-casting it on the surface of a conductive substrate. The intimate contact between PCN-Nss and ZnCdS at the molecular level due to the formation of heterojunction efficiently triggers charge separation, suppressing electron-hole pair recombination and easing the movement of photo-generated holes towards the conductive substrate. PCN-Nss/ZCS-40 (40% P-C3N4 by weight) showed substantially improved photocurrent response (−12 µA cm−2) at −0.6 V vs Ag/AgCl reference electrode in 0.2 M Na2S solution, which is almost 40 times greater than simple P-C3N4 nanosheets under the same conditions. This work will expose new applications for P-doped graphitic carbon nitride-based heterostructures for PEC water splitting.

Facile low temperature ammonolysis synthesis of CeO2-xNx for enhanced photoelectrochemical H2 generation

A facile solid–gas interface method for anionic substitution of nitrogen in CeO2 lattice is reported. In this study, a low temperature ammonolysis method is developed as an alternate to high temperature ammonolysis of CeO2. Cerium nitrate precursor is thermally treated directly by ammonia gas at 550 °C to prepare cerium-oxy-nitride samples which are tested for photoelectrochemical hydrogen evolution activity (HER). The CeO2-xNx material synthesized by low temperature ammonolysis of cerium nitrate shows lower onset potential ηlight = -1.04 V vs Ag/AgCl under light, large photocurrent density of 0.2 µA/cm2 at −0.4 V applied potential. The proposed method of ammonolysis of salt precursors is an excellent method for the synthesis of oxy-nitrides at low temperatures without residual carbon impurities for higher photocatalytic efficiencies.

Band engineering enables highly efficient and stable photoelectrochemical hydrogen evolution

Colloidal quantum dots (QDs) are promising photosensitizers for the conversion of solar energy into electric energy or chemical fuels. Particularly, they are potentially used in photoelectrochemical (PEC) devices for the realization of solar-driven hydrogen (H2) generation because their optoelectronic properties could be tunable by controlling their size/shape/composition. However, the long-term operation stability of the PEC devices based on QDs is not good, which is strongly prohibited the potential of the QDs based PEC hydrogen production. Here, we engineer the band structure of the CdSe QDs via a Zn dopant and demonstrate a highly stable PEC devices based on CdSe/Cd1-xZnxSe QDs. Through controlling the molar ratio of Cd/Zn precursors, the Zn concentration in the shell can be finely controlled to form an alloyed shell of Cd1-xZnxSe. The alloyed shell enables the efficient hole transfer from the QDs to TiO2, benefiting from the optimization of the valence energy alignment between the core and shell. As a proof-of-concept, the PEC device based on alloyed-shell QDs achieves a current density of ∼ 13.5 mA/cm2, which is comparable to the best reported PEC devices. More importantly, the PEC devices maintained 99% of its initial current density after 10 h of continuous H2 generation under one sun illumination. Even after 50 h operation, the PEC device still keeps 65% of initial current density. The excellent long-term operation stability paves the way for the design and use of doped QDs for potential H2 production.

Building Directional Charge Transport Channel in CdTe-Based Multilayered Photocathode for Efficient Photoelectrochemical Hydrogen Evolution

Building Directional Charge Transport Channel in CdTe-Based Multilayered Photocathode for Efficient Photoelectrochemical Hydrogen Evolution

Multistage charge redistribution constructing heterostructured WO3@RuSe2 on Si for enhanced photoelectrochemical hydrogen evolution

Producing green hydrogen by photoelectrocatalytic water splitting is one of the most promising approaches to conversion of renewable energy to chemical energy, which is restricted by the unsuitable energy barrier between the conduction band of the semiconductor and the H+/H2 level as well as the unsuitable binding energy of active sites with the intermediates in hydrogen evolution reaction. Herein, we rationally construct an n+p-Si/Ti/WO3@RuSe2 heterostructured photocatalyst, which significantly improves the photovoltage and photocurrent by charge redistribution between p-Si and heterostructured WO3@RuSe2. The representative n+p-Si/Ti/WO3@RuSe2 exhibits a photovoltage of 0.54 VRHE with a high short-circuit photocurrent density of −36 mA cm−2 and solar-to-hydrogen conversion efficiency of 9.43%, which is much higher than that of n+p-Si/Ti (0.45 VRHE, −0.22 mA cm−2, 0.015%). The characterizations and density functional theory calculations reveal that the heterostructured interface moves the d-band center of WO3@RuSe2 (−0.699 eV) to the Fermi level through the multistaged charge redistribution, thus reducing the barrier between the conduction band of p-Si and H+/H2 level as well as improving the charge separation efficiency.

Covalent Organic Framework Nanoplates Enable Solution-Processed Crystalline Nanofilms for Photoelectrochemical Hydrogen Evolution.

As covalent organic frameworks (COFs) are coming of age, the lack of effective approaches to achieve crystalline and centimeter-scale-homogeneous COF films remains a significant bottleneck toward advancing the application of COFs in optoelectronic devices. Here, we present the synthesis of colloidal COF nanoplates, with lateral sizes of ∼200 nm and average heights of 35 nm, and their utilization as photocathodes for solar hydrogen evolution. The resulting COF nanoplate colloid exhibits a unimodal particle-size distribution and an exceptional colloidal stability without showing agglomeration after storage for 10 months and enables smooth, homogeneous, and thickness-tunable COF nanofilms via spin coating. Photoelectrodes comprising COF nanofilms were fabricated for photoelectrochemical (PEC) solar-to-hydrogen conversion. By rationally designing multicomponent photoelectrode architectures including a polymer donor/COF heterojunction and a hole-transport layer, charge recombination in COFs is mitigated, resulting in a significantly increased photocurrent density and an extremely positive onset potential for PEC hydrogen evolution (over +1 V against the reversible hydrogen electrode), among the best of classical semiconductor-based photocathodes. This work thus paves the way toward fabricating solution-processed large-scale COF nanofilms and heterojunction architectures and their use in solar-energy-conversion devices.

Photoelectrolysis of TiO2 is highly localized and the selectivity is affected by the light

On the way to sustainable prosperity for future generations, photoelectrochemistry is becoming a key area for energy conversion and the environmentally friendly generation of chemical resources because it combines the advantages of electrochemical and photochemical processes. Highly active catalyst materials with excellent selectivity towards the desired reaction are certainly required for efficient processes. Understanding the underlying processes, including detailed in situ information, facilitates the design and development of catalyst materials. In this work, we utilize the scanning photoelectrochemical microscopy for the spatially resolved in situ investigation of the electrochemical and photoelectrochemical evolution of hydrogen, oxygen, reactive oxygen species, and chlorine for energy conversion. Herein, we demonstrate that the activity and the selectivity of the TiO2 photoelectrocatalyst are highly localized despite their apparently uniform composition based on regular morphological characterization. Furthermore, the results suggest that the illumination dramatically changes the selectivity in electrolysis reactions, which is demonstrated on the competing oxygen- and chlorine- evolution reaction. Consequently, this leads to the critical implication that the activity and selectivity should not be considered uniform per se, especially under the illumination. This implies that light might be used for controlling the selectivity in electrolysis reactions. Such discovery shall dramatically impact the optimization of photoelectrocatalysts in general.

Two-Step Process of a Crystal Facet-Modulated BiVO4 Photoanode for Efficiency Improvement in Photoelectrochemical Hydrogen Evolution.

The photoactivity of nanoporous bismuth vanadate (BiVO4, BVO) photoanodes that were fabricated by a two-step process (electrodeposition and then thermal conversion) in photoelectrochemical (PEC) hydrogen (H2) evolution can be enhanced about 1.44-fold by improving the constitutive ratio of (111̅), (061), and (242̅) crystal facets. The PEC characterization was carried out to investigate the factors altering the performance, which revealed that the crystal facet modulation could improve the photoactivity of the BVO photoanodes. In addition, the orientation-controlled BVO thin-film electrodes are introduced as evidence that the present crystal facet modulation is the positive effect for BVO photoanodes in PEC. The investigation of energy band structures and interfacial charge carrier dynamics of the BVO photoanodes reveals that the crystal facet modulation could result in a shorter lifetime of charge carrier recombination and larger band bending at the interface between BVO and electrolytes. This outcome could improve the charge separation and charge transfer efficiencies of BVO photoanodes, promoting the efficiency of PEC H2 evolution. Moreover, this crystal facet modulation can combine with co-catalyst decoration to further improve the solar-to-hydrogen efficiency of BVO photoanodes in PEC. This study presents a potential strategy to promote the PEC activity by crystal facet modulation and important insights into the interfacial charge transfer properties of semiconductor photoelectrodes for the application in solar fuel generation.

Double-defect-induced polarization enhanced OV-BiOBr/Cu2−xS high-low junction for boosted photoelectrochemical hydrogen evolution

In order to improve the carrier transfer driving force and separation efficiency, OV-BiOBr/Cu2−xS high-low junction with double defects (Oxygen vacancy and Copper vacancy) was successfully prepared by a facile two-step solvothermal in situ growth technique. OV-BiOBr/Cu2−xS-0.2 showed the highest hydrogen evolution rate (509.75 μmol·cm−2·h−1), which was 12.45, 6.94 and 3.44 times that of pure BiOBr, OV-BiOBr and BiOBr/Cu2−xS composite, respectively. Obvious free radicals (·OH and ·O2-) were observed in the dark state for the first time. Theoretical and experimental results demonstrate that the charge imbalance within OV-BiOBr/Cu2−xS intensifies after the introduction of the double defects, resulting in enhanced interfacial polarization phenomena. Boosted photoelectrochemical hydrogen evolution activities were achieved with the synergistic effect of the internal electric field and polarization electric field. This study will lay a scientific and experimental foundation for the preparation of high-performance photoelectrochemical anode materials with double defect heterojunction.

Transient Surface Photovoltage Spectroscopy of (NH4)2Mo3S13/WSe2 Thin-Film Photocathodes for Photoelectrochemical Hydrogen Evolution.

Hydrogen produced from solar energy has the potential to replace petroleum in the future. To this respect, there is a need in the abandoned and efficient materials that can continuously split water molecules using solar energy. In this report, an ammonium thiomolybdate (ATM: (NH4)2Mo3S13) is evaluated as a p-type semiconductor film photocathode for hydrogen evolution reaction. The ATM thin films are prepared by spin-coating on fluorine-doped tin oxide substrates, and their structural, morphological, optical, photoelectrical, and photoelectrochemical (PEC) properties are studied. Transient surface photovoltage (TSPV) spectroscopy and spectroscopic ellipsometry indicate the band gap Eg = 1.9 eV for the ATM thin films. Furthermore, the photovoltage of the ATM thin films measured by TSPV is correlated to the photocurrents measured by the PEC characterization that can be used to evaluate the material potential for hydrogen generation. The films exhibit a low photocurrent density of 46 μA cm-2 at 0 VRHE. However, its combination with WSe2 thin-film photocathodes results in a significant increase in photocurrent density up to 4.6 mA cm-2 at 0 VRHE (100 times). The reason for such a strong charge carrier transfer effect for ATM/WSe2 heterojunction photocathodes is studied by TSPV spectroscopy that allows a comprehensive evaluation of potential photovoltaic materials toward PEC hydrogen production. Furthermore, the photovoltage generated by a WSe2 thin film is 30 times lower than that of its single crystal, which indicates that the quality of WSe2 thin films should be improved for faster PEC hydrogen evolution.

High-performance bulk heterojunction-based photocathode with facile architecture for photoelectrochemical water splitting

Organic semiconductors are promising candidates as photoactive layers for photoelectrodes used in photoelectrochemical (PEC) cells due to their excellent light absorption and efficient charge transport properties with the help of interfacial materials. However, the use of multilayers will make the charge transfer mechanism more complicated and decrease the PEC performance of the photoelectrode caused by the increased contact resistance. In this work, a PM6:Y6 bulk heterojunction (BHJ)-based photocathode is fabricated for efficient PEC hydrogen evolution reaction (HER) in an acidic aqueous solution. With RuO2 as an interfacial modification layer, the photocathode with a simple structure (fluorine-doped tin oxide (FTO)/PM6:Y6/RuO2) generates a maximum photocurrent density up to −15 mA/cm2 at 0 V vs. reference hydrogen electrode (RHE), outperforming all previously reported BHJ-based photocathodes in terms of PEC performance. The highest ratiometric power-saved efficiency of 3.7% is achieved at 0.4 V vs. RHE.

A Ni(II) Metal-Organic Framework with Mixed Carboxylate and Bipyridine Ligands for Ultrafast and Selective Sensing of Explosives and Photoelectrochemical Hydrogen Evolution.

We report a Ni-MOF (nickel metal-organic framework), Ni-SIP-BPY, synthesized by using two linkers 5-sulfoisophthalic acid (SIP) and 4,4'-bipyridine (BPY) simultaneously. It displays an orthorhombic crystal system with the Ama2 space group: a = 31.425 Å, b = 19.524 Å, c = 11.2074 Å, α = 90°, β = 90°, γ = 90°, and two different types of nickel(II) centers. Interestingly, Ni-SIP-BPY exhibits excellent sensitivity (limit of detection, 87 ppb) and selectivity toward the 2,4,6-trinitrophenol (TNP)-like mutagenic environmental toxin in the pool of its other congeners via "turn-off" fluorescence response by the synergism of resonance energy transfer, photoinduced electron transfer, intermolecular charge transfer, π-π interactions, and competitive absorption processes. Experimental studies along with corroborated theoretical experimentation, vide density functional theory studies, shed light on determining the plausible mechanistic pathway in selective TNP detection, which is highly beneficial in the context of homeland security perspective. Along with the sensing of nitroaromatic explosives, the moderately low band gap and the p-type semiconducting behavior of Ni-SIP-BPY make it suitable as a photoanode material for visible-light-driven water splitting. Highly active surface functionalities and sufficient conduction band minima effectively reduce the water and result in a seven times higher photocurrent density under visible-light illumination.

Enhancing the Photoelectrochemical Hydrogen Evolution Reaction through Nanoscrolling of Two-Dimensional Material Heterojunctions.

The clean production of hydrogen from water using sunlight has emerged as a sustainable alternative toward large-scale energy generation and storage. However, designing photoactive semiconductors that are suitable for both light harvesting and water splitting is a pivotal challenge. Atomically thin transition metal dichalcogenides (TMD) are considered as promising photocatalysts because of their wide range of available electronic properties and compositional variability. However, trade-offs between carrier transport efficiency, light absorption, and electrochemical reactivity have limited their prospects. We here combine two approaches that synergistically enhance the efficiency of photocarrier generation and electrocatalytic efficiency of two-dimensional (2D) TMDs. The arrangement of monolayer WS2 and MoS2 into a heterojunction and subsequent nanostructuring into a nanoscroll (NS) yields significant modifications of fundamental properties from its constituents. Spectroscopic characterization and ab initio simulation demonstrate the beneficial effects of straining and wall interactions on the band structure of such a heterojunction-NS that enhance the electrochemical reaction rate by an order of magnitude compared to planar heterojunctions. Phototrapping in this NS further increases the light-matter interaction and yields superior photocatalytic performance compared to previously reported 2D material catalysts and is comparable to noble-metal catalyst systems in the photoelectrochemical hydrogen evolution reaction (PEC-HER) process. Our approach highlights the potential of morphologically varied TMD-based catalysts for PEC-HER.

Bi2S3 entrenched BiVO4/WO3 multidimensional triadic photoanode for enhanced photoelectrochemical hydrogen evolution applications

The catalytic reactivity and photoactivity of WO 3 and BiVO 4 oxide semiconductors have general obstacles as electrodes in emergent photo-electrochemical (PEC) hydrogen evolution applications. The present work comprises the integration of photocatalyst with wide visible photon absorption material which is vital for hydrogen evolution in photo-electrocatalytic water splitting. Herein, the 1D WO 3 NWs have been integrated with stable water oxidation photocatalysts of BiVO 4 and Bi 2 S 3 as a photoanode (Bi 2 S 3 /BiVO 4 /WO 3 ) for photoelectrochemical hydrogen evolution reactions. The morphological variations in the Bi 2 S 3 /BiVO 4 /WO 3 heterostructure manifest catalytic activity and rapid charge transfer characteristics owing to band alignment and a wide range of visible photon absorption. The optimized Bi 2 S 3 /BiVO 4 /WO 3 multidimensional photoanode accomplishes a superior photocurrent density of 1.52 mA/cm 2 , a seven-fold higher than pristine WO 3 photoanode counterpart (0.2 mA/cm 2 ) at 1 V vs. RHE. A prodigious lowest onset potential of −0.01 V vs. RHE) has been achieved which enables very high solar to hydrogen conversion. The photoelectrode with entangled morphology such as nanosheets, nanocrystals and nanorods expanded their surface to volume ratio having enhanced catalytic performance. The hybrid photoanodes have demonstrated the lowest charge transfer resistance of 360 Ohm/cm 2 with a 7-fold rise in hydrogen evolution performance. The resultant triadic Bi 2 S 3 /BiVO 4 /WO 3 heterostructure appeared to be an emerging stable photo-electro catalyst for hydrogen evolution applications. • A multidimensional Bi 2 S 3 /BiVO 4 /WO 3 is prepared by hydrothermal and SILAR method. • The hetero-structure upholds photo-excitation and enhances carriers' kinetics. • The open triadic structure improves the hydrogen evolution. • A type II band alignment in Bi 2 S 3 /BiVO 4 /WO 3 hetero-structure is proposed.

Metal-Thiolate Framework for Electrochemical and Photoelectrochemical Hydrogen Generation.

Hydrogen has evolved as the cleanest and most sustainable fuel, produced directly from naturally abundant water resources. Generation of hydrogen by electrochemical or photoelectrochemical splitting of water has been conceived as the most effective method for hydrogen production. Herein, a robust solid metal-thiolate framework (MTF-1) was obtained by hydrothermal crystallization of the reaction mixture consisting of 1,3,5-triazine-2,4,6-trithioltrisodium salt and CuII under mild synthesis conditions. The material was thoroughly characterized and explored as efficient catalyst for electrochemical and photoelectrochemical hydrogen evolution reaction (HER) via water splitting reactions. MTF-1 showed onset potential 0.045 VRHE and overpotential η(@10 mA cm-2 ) at 0.096 VRHE . The electrochemical surface area of MTF-1 was found to be 509 m2 g-1 . The photo current density at pH 5.0 was found to be 0.487 mA cm-2 at 0.6 VRHE . The feasibility of the reaction pathway was correlated from the density function theory study, which suggested the complete downhill energetics indicating spontaneous electrochemical hydrogen generation in the acidic medium.

Subwavelength Densely Packed Disordered Semiconductor Metasurface Units for Photoelectrochemical Hydrogen Generation

For most semiconductors, especially the visible-light-absorbing ones, the carrier diffusion length is significantly shorter than the light penetration depth, limiting their photoactivities. This limitation could be mitigated through the use of subwavelength semiconductor-based metasurfaces and metamaterials. In this paper, a large-scale compatible metasurface photocathode, made of densely packed disordered p-type chromium oxide (CrOX), is developed to be utilized in photoelectrochemical (PEC) hydrogen generation. For this purpose, first, tightly packed random Cr nanorods are fabricated using an oblique angle deposition technique. Afterward, an annealing step is applied to the sample to transform these metallic units into a semiconducting p-type CrOX-based metasurface. Based on the experimental characterization results and numerical simulations, the proposed design can provide strong light–matter interactions in an ultra-broadband-wavelength range, mainly due to its multidimensional random geometry and ultrasmall gap sizes. Finally, to substantiate the activity of the CrOX nanorods, a core–crown geometry is developed where the NiOX capping layer catalyzes the hydrogen evolution reaction (HER). The proposed heterostructure metasurface absorber can impose photocurrent values as large as 50 μA cm–2 with a photocurrent spectral response extended up to 500 nm. Moreover, the electrode shows outstanding operation under light irradiation for 9 hours. This work demonstrates a simple, scalable design strategy to fabricate low-cost and stable photocathodes for PEC hydrogen evolution.

Band Structure Engineering and Defect Passivation of Cu x Ag1-x InS2/ZnS Quantum Dots to Enhance Photoelectrochemical Hydrogen Evolution.

The AgInS2 colloidal quantum dot (CQD) is a promising photoanode material with a relatively wide band gap for photoelectrochemical (PEC) solar-driven hydrogen (H2) evolution. However, the unsuitable energy band structure still forms undesired energy barriers and leads to serious charge carrier recombination with low solar to hydrogen conversion efficiency. Here, we propose to use the ZnS shell for defect passivation and Cu ion doping for band structure engineering to design and synthesize a series of CuxAg1–xInS2/ZnS CQDs. ZnS shell-assisted defect passivation suppresses charge carrier recombination because of the formation of the core/shell heterojunction interface, enhancing the performance of PEC devices with better charge separation and stability. More importantly, the tunable Cu doping concentration in AgInS2 CQDs leads to the shift of the quantum dot band alignment, which greatly promotes the interfacial charge separation and transfer. As a result, CuxAg1–xInS2/ZnS CQD photoanodes for PEC cells exhibit an enhanced photocurrent of 5.8 mA cm–2 at 0.8 V versus the RHE, showing excellent photoelectrocatalytic activity for H2 production with greater chemical-/photostability.

Samarium vanadate affixed sulfur self doped g-C3N4 heterojunction; photocatalytic, photoelectrocatalytic hydrogen evolution and dye degradation

The Thermal polycondensation method was used to make sulfur self-doped graphitic-carbon nitride (SCN) sheets that were anchored with samarium vanadate (SmV). The decorating of SmV nanoparticles on sheets of SCN is confirmed by X-ray diffraction, spectroscopic, and microscopic characterizations. When compared to the bandgap of pure SmV (2.16 eV) and SCN (2.44 eV), SmV decorating decreased the bandgap of SCN to 1.89 eV. The lowered bandgap in SmV/SCN and the formation of type II heterostructure resulted in improved performance in photoelectrochemical and photochemical hydrogen evolution and photocatalytic degradation experiments. The amount of hydrogen evolution was high in SmV/SCN which was found to be 22,618 μmol g −1 of H 2 in 4 h under photochemical conditions. The obtained onset potential at 10 mA cm 2 is −190 mV under photoelectrochemical studies. The SmV/SCN was able to absorb visible light and degraded Methyl orange (MO). The reaction conditions were thoroughly optimized, found pH 8, 10 mg L −1 initial concentration of dye and 25 mg of SmV/SCN as an optimum condition under visible light. The degradation efficiency was up to 90% in just 80 min. Scavenger investigations were used to identify the active species (OH . and . O 2 − ) and indicate which were then confirmed by electron spin resonance spectroscopic (ESR) experiments. The mechanism of photocatalysis has been well explored. The obtained results show that the SmV/SCN nanocomposite is capable of serving a choice of material for energy and environmental applications. • SmVO 4 decorated on S doped g-C 3 N 4 sheets. • Decrease in the bandgap of g-C 3 N 4 upon decoration of SmVO 4 (1.89 eV). • Enhanced H 2 evolution both in photoelectrochemical and photochemical. • Visible light driven degradation of Methyl orange (90%). • Detailed mechanism of photocatalysis based on heterostructure of Type-II.

2D-Heterostructure assisted activation of MoS2 basal plane for enhanced photoelectrochemical hydrogen evolution reaction

As a potential catalyst of hydrogen evolution reaction (HER), molybdenum disulfide (MoS2) is known to have active sites at the edges, whereas its basal plane is inert. Thus activation of basal plane of MoS2 is essential to intensify the HER catalytic activity. Among various strategies, activation of MoS2 basal plane includes defects engineering via sulfur vacancies and hetero-atom doping. However, for optimal activation, requirements of defect concentration become impractically high, which increases defect-induced high charge carrier recombination loss in photoelectrochemical (PEC) HER. Herein, we report basal plane activation of MoS2 by heterostructuring with two-dimensional (2D) MoSe2 for enhanced photoelectrochemical HER. MoS2/MoSe2 heterostructure grown on silicon nanowire (SiNW) array shows 1.2 times higher photocurrent density and 1.36 times higher incident photon-to-current efficiency (IPCE) than pristine MoS2 grown on SiNW array along with 4.44 times higher H2 evolution rate compared to pristine SiNW photocathode. Density functional theory calculations of heterostructure reveal that charge transfer from the MoSe2 layer to the basal plane of MoS2 increases overall electron density resulting in its increased affinity towards proton reduction, which supports the experimental findings. These findings will boost the strategy for basal plane activation by 2D heterostructuring for efficient photoelectrochemical HER.

Cu2 O/CeO2 Photo-electrochemical Water Splitting: A Nanocomposite with an Efficient Interfacial Transmission Path under the Co-action of a p-n Heterojunction and Micro-mesocrystals.

Cu2 O is an ideal p-type material for photo-electrochemical (PEC) hydrogen evolution, although serious electron-hole recombination and photocorrosion restrict its further improvement for PEC activity. In this work, CeO2 nanoparticles (NPs) self-assemble on the surface of Cu2 O octahedra, thus successfully forming a Cu2 O/CeO2 structure in which p-n heterojunctions and micro-mesocrystals (m-MCs) work together. The optimum Cu2 O/CeO2 composite, without the use of any cocatalyst, exhibits a fivefold higher photocurrent density (4.63 mA cm-2 at 0 V vs. the reversible hydrogen electrode) than that of Cu2 O octahedra, which is better than most Cu2 O-based photocathodes without cocatalyst and even comparable with advanced Cu2 O-based photocathodes. The hydrogen production of the optimal Cu2 O/CeO2 (Faradaic efficiency of ∼100 %) is 17.5 times higher than that of pure Cu2 O octahedra, and the photocurrent shows almost no decay under the 12 h stability test. The delicately designed Cu2 O/CeO2 structure in this work provides reference and inspiration for the design of cathodes materials.