Synergy of Single-Atom Platinum and Oxygen Vacancy Engineering Boosts Photoelectrochemical Water Oxidation of ZnFe ₂ O ₄ Photoanodes with Surface State Reconstruction

Photoelectrochemical (PEC) water splitting performance remains fundamentally constrained by sluggish surface carrier transfer kinetics, a phenomenon closely linked to surface state (SS) electronic structures yet complicated by ambiguous and contested structure–property relationships. To address this limitation, zinc ferrite (ZnFe 2 O 4, ZFO) photoanodes functionalized with surface single-atom Pt sites were developed, synergistically assisted by oxygen vacancy engineering. At 1.23 V RHE, the optimized ZFO photoanode achieved a 35-fold enhancement in photocurrent density (0.7 mA cm –2 ) compared to unmodified ZFO (0.02 mA cm –2 ). Multimodal spectroscopy analyses identified SS reconstruction as the fundamental mechanism for PEC performance enhancement and revealed a bias-dependent mediating mechanism. In contrast to conventional detrimental SS as recombination centers, the reconfigured beneficial SS with optimized state position and density demonstrate effectively suppressed recombination and significantly improved surface carrier transfer. This work provides mechanistic insights into single-atom cocatalysts and supports photoelectrode design through atomic-scale surface state reconstruction.