Ru–O Hybridization Strengthens Spatial Charge Separation for Enhanced Photoelectrochemical Water Oxidation

Amorphous cocatalysts effectively enhance the photoelectrochemical (PEC) water oxidation performance of BiVO4 (BVO). Nonetheless, their ability to extract photogenerated holes still suffers from limited efficiency and directionality. Here, we deliberately fabricate Ru single atoms immobilized on amorphous NiFeAl layered double hydroxide (NiFeAl-a) cocatalysts as a hole transport mediator and systematically elucidate the underlying promotion mechanism. Our investigations reveal that the formation of Ru−O hybridization states near the Fermi level augments the energy difference between BVO and NiFeAl-a. This modulation increases the band bending at their heterointerface, thereby facilitating hole extraction and suppressing the backflow of photogenerated electrons. These synergistic effects promote spatial charge separation. As a result, BVO/NiFeAl-a/Ru achieves a photocurrent density of 6.78 mA/cm2 at 1.23 V versus the reversible hydrogen electrode (vs RHE) and a half-cell applied bias photon-to-current efficiency of 2.63% at 0.61 V vs RHE. These values are higher than those of BVO/NiFeAl-a, which are 5.77 mA/cm2 and 2.20%, respectively. This work provides insights into the development of PEC systems for water oxidation.