Photothermal CuS as a Hole Transfer Layer on BiVO₄ Photoanode for Efficient Solar Water Oxidation

Sluggish hole transport kinetics are one of the key limitations of bismuth vanadate (BiVO₄) photoanodes in photoelectrochemical (PEC) water splitting, severely impeding the attainment of high solar-to-hydrogen (STH) conversion efficiency. Herein, a copper sulfide (CuS) hole transfer layer (HTL) with photothermal effect is reported to markedly enhance the PEC water splitting via the synergistic action of photothermal effect and hole transfer. This is demonstrated in the BiVO₄/CuS/NiFeCoO_x photoanode, where the CuS layer establishes a transport channel for photogenerated holes, effectively inhibiting charge recombination and trapping. Additionally, the thermal effect induced by localized surface plasmon resonance (LSPR) enhances the water oxidation activity of the surface NiFeCoO_x cocatalyst and boosts the charge mobility. The optimized BiVO₄/CuS/NiFeCoO_x photoanode exhibits exceptional performance, achieving a water oxidation photocurrent density of 6.56 mA cm^-2 at 1.23 V versus reversible hydrogen electrode (V_RHE) and a STH conversion efficiency of 7.17% when connected in series with Si solar cells. Experimental analyzes and density functional theory (DFT) calculations collectively reveal the pivotal role of CuS HTL in facilitating carrier separation and transport. This work highlights the potential of interfacial engineering to facilitate charge separation and transfer, providing a new strategy for the construction of photoanodes to achieve efficient water splitting.