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

Amorphous cocatalysts effectively enhance the photoelectrochemical (PEC) water oxidation performance of BiVO 4 (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/cm 2 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/cm 2 and 2.20%, respectively. This work provides insights into the development of PEC systems for water oxidation.