Xingchen Fu,Hui Chang,Zhichao Shang,Pingle Liu,Jikai Liu,He'an Luo
Cuprous oxide (Cu 2 O) has been envisioned as a promising photocathode material for photoelectrochemical (PEC) water reduction due to its abundance, scalability and nontoxicity. Herein, a three-dimensional (3D) Cu 2 O nanorods (NRs) photocathode is prepared by in-situ growing Cu 2 O NRs on a copper foam substrate. The bare 3D Cu 2 O NRs photocathode exhibits a high photocurrent density of −4.02 mA cm −2 at 0 V versus the reversible hydrogen electrode (RHE) under AM 1.5 G simulated sunlight. The oxygen vacancies enriched Ti 3 C 2 T X flakes are obtained by reducing Ti 3 C 2 T X with H 2 /Ar gas (denoted as H:Ti 3 C 2 T X ). The H:Ti 3 C 2 T X /Cu 2 O, Ti 3 C 2 T X /Cu 2 O as well as Au/Cu 2 O composite photocathodes are fabricated through a facile dip-coating method. The H:Ti 3 C 2 T X /Cu 2 O and Ti 3 C 2 T X /Cu 2 O yield a photocurrent density of −5.41 and −4.45 mA cm −2 respectively, which is higher than the bare Cu 2 O and Au/Cu 2 O (−4.31 mA cm −2 ). The results suggest that the Ti 3 C 2 T X is more effective than noble metal Au for improving the PEC performance of Cu 2 O photocathode. The superior performance of H:Ti 3 C 2 T X /Cu 2 O is attributed to enriched oxygen vacancies in the H:Ti 3 C 2 T X which can enhance the conductivity, light-harvesting efficiency and charge-transfer ability of fabricated photocathode. A PEC tandem cell with H:Ti 3 C 2 T X /Cu 2 O as the photocathode and BiVO 4 as the photoanode is designed for unassisted solar water splitting. Due to the high porosity and optical transmittance of the 3D copper foam substrate, we illuminate the cell from the H:Ti 3 C 2 T X /Cu 2 O side rather than from the BiVO 4 side in usual fashion. The present configuration exhibits a 1.6 times higher solar-to-hydrogen (STH) conversion efficiency of 0.55% than the conventional design with a STH conversion efficiency of 0.34%. The enhanced STH conversion efficiency in our configuration is due to the higher light-harvesting efficiency.
Dynamics and morphology play a crucial role in the field of photocatalytic hydrogen production. Regulating the transfer of photogenerated charges is an effective way to improve the catalytic activity. In this paper, 1T-WS2 is introduced into a p–n heterostructure, ZnCdS/NiV-LDH, as a metalloid electron pump to transfer photogenerated electrons from semiconductors with larger work functions to metalloid materials with smaller work functions, effectively to attract photogenerated electrons, and promote charge rearrangement at the p–n heterostructure interface, so as to achieve the best utilization efficiency of photogenerated charges. Second, adjusting the morphology to increase the light absorption area of the catalyst is also a way to improve the photocatalytic activity. Two different nanosheet structures dispersed heavily stacked ZnCdS, increasing the light absorption area of the system. The optimal catalyst ratio achieves a hydrogen evolution rate of 22.37 mmol g−1 h−1, achieving 7.98% AQE and 2.12% STH conversion efficiency at 450 nm. The potential mechanism was demonstrated through in situ XPS. This study provides new insights into adding “electron pumps” to heterostructures to enhance photocatalytic activity.
Hydrogen production from solar water splitting, especially via photovoltaic-electrocatalysis, has been regarded as a promising approach for the conversion of abundant but intermittent solar energy into storable chemical fuels. Despite much progress, conventional combined photoelectrochemical devices usually suffer from severe instability issues, which largely inhibit them for practical applications and may also lead to the uncertain efficiency value for true overall water splitting. Here, we report an unassisted solar water splitting device with concurrent high efficiency and stability, which is constructed by spatial coupling of tandem III-V-based GaInP/GaAs/Ge light absorber and robust earth-abundant Ni foil-based MoNi 4 /MoO 2 bifunctional electrocatalysts . Remarkably, apart from the outstanding hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance, bifunctional MoNi 4 /MoO 2 electrocatalysts also largely avoid electrode contamination issues, while the robust Ni substrate protects III-Vs from conventional corrosion problems . Consequently, this integrated photovoltaic-electrolysis system device exhibits a high solar-to-hydrogen (STH) conversion efficiency of 17.6 % in alkaline electrolytes with long-term stability of up to 845 h. Further construction into a wireless unassisted monolithic device could lead to an artificial leaf with an STH efficiency of 4.28 %, holding great promise in future solar fuel production with concurrent high efficiency, good stability as well as low cost.
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