Metal–organic framework-derived nano-CoS-enhanced photoelectrochemical water splitting performance of the BiVO4 photoanode†

The utilization of metal–organic frameworks (MOFs) as oxygen evolution reaction (OER) co-catalysts for BiVO₄-based photoelectrochemical (PEC) water splitting is limited by their intrinsic low conductivity and low availability of accessible catalytic metal sites. In this work, we transformed the cobalt-based imidazole-based ZIF-67 catalyst into a MOF-derived CoS cocatalyst through a two-step vulcanization process to construct a novel M-CoS/BiVO₄ photoanode. The resulting M-CoS/BiVO₄ photoanode demonstrated a photocurrent density of 5.22 mA cm⁻² at 1.23 V versus the reversible hydrogen electrode under AM 1.5G light irradiation. Both the experimental results and theoretical calculations indicated that the built-in electric fields of the CoS/BiVO₄ heterojunction effectively suppressed charge recombination in the bulk system. Furthermore, the MOF-derived CoS provided active sites with larger specific surface areas and increased the electronic conductivity, which effectively enhanced the charge separation and water oxidation kinetics, promoting the PEC water splitting performance. These findings indicate the potential of this new method in designing highly efficient photoanodes from MOFs.