Enhanced photoelectrochemical water oxidation performance of a hematite photoanode by decorating with Au-Pt core-shell nanoparticles.

It is well known that bimetallic nanomaterials usually exhibit unique catalytic, optical, electric and magnetic properties due to the synergistic effect between different metals. In this work, we reported on a scalable method to fabricate an AuPt bimetallic core-shell nanoparticles loaded hematite (α-Fe2 O3 ) photoanode for solar-driven photoelectrochemical water oxidation. Compared to single metal-modified α-Fe2 O3 photoanodes, the AuPt bimetallic core-shell nanoparticles loaded α-Fe2 O3 photoanodes exhibited a synergistic effect for photoelectrochemical water oxidation. The photocurrent density of AuPt0.2 /α-Fe2 O3 was boosted to 0.83 mA cm-2 at 1.23 V versus a reversible hydrogen electrode in a neutral electrolyte (0.5 M Na2 SO4 aqueous solution) under 45 W xenon lamp irradiation. The incident photon-to-photocurrent efficiency value of optimum AuPt0.2 /α-Fe2 O3 was estimated to be 58%, which was significantly higher than the single metal-modified α-Fe2 O3 and pristine α-Fe2 O3 photoanodes (<10%). Electrochemical impedance spectroscopy and Mott-Schottky analysis confirmed that the Schottky junction formed by the AuPt bimetallic nanoparticles and α-Fe2 O3 led to enhanced charge separation and band bending, resulting in a negative shift of onset potential. Based on the experimental and characterized results, a possible mechanism was proposed. This work provides an important reference for the design of other bimetallic-modified photoanodes for application in energy conversion.