A ternary-structured NiCo-LDH/Ni/BiVO4 photoanode with enhanced charge dynamics for photoelectrochemical water splitting

Solar-driven photoelectrochemical (PEC) water splitting is one of the promising technologies to produce green hydrogen as the carbon-free energy carrier. However, the ideal photoanode material BiVO₄ still suffers from sluggish carrier dynamic problem. Here, NiCo-LDH/Ni/BiVO₄ (NC/N/BVO) composite photoanode with a three-layer structure was successfully fabricated by introducing Ni layer followed by NiCo-LDH on BiVO₄ by magnetron sputtering and electrochemical deposition, respectively. The optimized structure of NC/N/BVO exhibited a photocurrent of 4.15 mA cm⁻² (1.23 V_REH) in neutral solution, which was 2.8 times of pristine BiVO₄. Besides, the photocurrent can be well maintained at 98 % for NC/N/BVO in 1h reaction, which dramatically decreases to 60 % for BiVO₄. In this composite photoanode, NiCo-LDH as excellent water oxidation catalyst can effectively enhance the kinetic process of water oxidation on the surface, while the introduction of Ni layer can not only promote the following deposition of NiCo-LDH being a finer nanostructure with high surface area, but also increase the charge conduction efficiency and promote the charge transfer process between NiCo-LDH and BiVO₄ substrate. The appropriate deposition sequence of Ni and NiCo-LDH layers ultimately highly improved the charge injection efficiency of NC/N/BVO resulting in a high performance of PEC water splitting.