| Summary: | In this study, a hematite photoanode with a CoFe-ADH co-catalyst loaded on the surface was successfully prepared through hydrothermal treatment, annealing, and electrodeposition. We investigated the influence of the deposition time and Co/Fe molar ratio for CoFe-ADH on the performance of α-Fe<sub>2</sub>O<sub>3</sub> in photoelectrochemical (PEC) water oxidation. With an optimized condition of CoFe-ADH, the prepared CoFe-ADH/α-Fe<sub>2</sub>O<sub>3</sub> photoanode exhibited a high photocurrent density of 1.58 mA/cm<sup>2</sup> at 1.23 V<sub>RHE</sub>, which is about 2.5 times as high as that of α-Fe<sub>2</sub>O<sub>3</sub>. A series of characterization results and detailed mechanism studies reveal that surface modification of hematite by introducing CoFe-ADH can boost the surface charge transfer efficiency, which can be attributed to the good optical transparency, the amorphous structure of CoFe-ADH, and the synergism of Co and Fe in CoFe-ADH. The good optical transparency contributes to decreasing the loss of light absorption by the photoanodes; the amorphous structure could prevent the formation of grain boundaries and provide more active catalytic sites for PEC water oxidation; and the synergism of Co and Fe in CoFe-ADH enhances photogenerated carriers effective separation and the hole’s injection. This work provides valuable insights into the influence of bimetallic co-catalysts on the PEC performance of photoanodes, offering guidance for photoanodes to achieve excellent performance.
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