Unveiling the high activity origin of NiFe catalysts decorated Ta3N5 photoanodes for oxygen evolution reaction

Bimetallic NiFe catalysts could effectively promote the photoelectrochemical (PEC) water splitting activities of Ta3N5 photoanodes, while exploring the intrinsic activity origin is crucial for constructing highly efficient solar-energy conversion systems. Herein, we demonstrate a simple impregnation strategy for rational deposition of NiFe catalysts nanolayers on Ta3N5 nanotube photoanodes, which achieved a superior photocurrent density of 11.2 mA cm-2 at 1.23 V versus the reversible hydrogen electrode (RHE) accompanied by a low onset potential (0.3 VRHE). More importantly, systematic studies reveal that the preferred deposition of Fe catalysts nanolayers on Ta3N5 photoanode surfaces could effectively promote the charge separation and hole transfer, while the subsequent formation of Ni catalysts nanolayers could provide the catalytic active-sites for water oxidation. Accordingly, their synergistic effects significantly improve the interfacial hole transfer and surface oxygen evolution kinetics, leading to an outstanding PEC water splitting activity. This work not only clarifies the intrinsic high-activity origins of NiFe/Ta3N5 photoanodes, but also provides new insights into the rational construction of highly efficient OER catalysts for PEC water splitting.