CoFe Layered Double Hydroxide Supported on Fe-Doped BiVO₄ Nanoparticles as Photoanode for Photoelectrochemical Water Splitting

The application of BiVO 4 in photoelectrochemical water splitting for efficient clean hydrogen energy production encounters challenges arising from the sluggish kinetics of water oxidation. Motivated by the synergistic interplay of metal sites and ligands on the catalyst surface, we utilized the photoelectric deposition technique to introduce amorphous nanothin layers of cobalt–iron double hydroxide (referred to as CoFe-LDH) onto the Fe-doped BiVO 4 surface. Fe dopants lead to a size reduction of BiVO 4 nanoparticles while enlarging the specific surface area and pore volume, thus increasing the reaction sites, which is favorable for photoelectrochemical water splitting. The unique dual-layered structure of CoFe-LDH not only enhances the mobility of charge carriers but also addresses surface defects through passivation. Additionally, it optimizes the exposure of active sites on the surface and expedites the flow of charge carriers, effectively mitigating recombination. The CoFe/Fe-BiVO 4 photoanode demonstrates outstanding photocatalytic performance, achieving a substantial photocurrent of 2.56 mA cm –2 (at 1.23 V vs RHE) and an impressive incident photon current conversion efficiency (IPCE) of 52.1% at 400 nm, which is approximately a 270% increment in photocurrent and a remarkable 2.2-fold improvement in IPCE compared to those of the unmodified sample. In addition, the charge surface transport efficiency increases from 16.8% to 62.5% at 1.23 V vs RHE after modification of the cobalt–iron hydroxide bilayer. This study not only emphasizes the promising results of employing binary polymetallic co-catalysts but also provides a strategic pathway to improve semiconductor-based photoelectrodes in various photoelectrochemical applications.