Switching Water Oxidation Pathway via NiFe Dual‐Atoms on BiVO ₄ : An *O─O* Coupling Mechanism Route to Bypass Adsorbate Evolution Mechanism Limitations

Abstract

ABSTRACT Dual‐atom catalysts (DACs) with heterogeneous active sites represent an emerging frontier in photoelectrochemical (PEC) water splitting. However, the corresponding reaction mechanism on DACs is still unclear. Herein, we present a photoanode architecture comprising NiFe dual atoms (DAs) anchored on a TiO x ‐coated BiVO 4 photoanode (NiFe DAs/TiO x /BiVO 4 ), which delivers an impressive photocurrent density of 6.13 mA cm −2 at 1.23 V RHE , sustained stability exceeding 150 h, and an applied bias photon‐to‐current efficiency of 2.2%. Our investigation reveals a dual functionality of the NiFe DAs which serve as an efficient oxygen evolution cocatalyst and enhance charge separation—an aspect largely overlooked in previous studies. Through in situ spectroscopic investigations combined with density functional theory calculations, we elucidate that the NiFe DAs/TiO x /BiVO 4 enables a mechanistic shift from the conventional adsorbate evolution mechanism (AEM) observed in single atom‐modified‐TiO x /BiVO 4 to an *O─O* coupling mechanism (OCM). Specifically, this OCM pathway bypasses the formation of *OOH and produces the *O─O* bridging species, broking the *OOH/*OH scaling limitation in the AEM pathway. This work uncovers PEC water oxidation mechanism at the atomic level, establishing a foundational framework for designing high‐performance photoelectrodes through precise atomic‐scale engineering.