Tuning the bifunctional properties of an α-Fe2O3/Fe2TiO5/Pt heterojunction photoelectrode for light-induced water oxidation and oxygen reduction activity

Abstract

Bifunctional photoelectrodes for the water oxidation reaction (WOR) and oxygen reduction reaction (ORR) have paramount importance in solar-powered rechargeable metal–air batteries. Herein, we strategically fabricate a photoactive core–shell bifunctional electrocatalyst for cathode materials in solar-powered rechargeable zinc–air batteries (SRZBs) with a type-II heterojunction band alignment, comprising an n-type α-Fe₂O₃ nanorod core and a thin pseudobrookite phase Fe₂TiO₅ shell. Pt nanoparticles (NPs) are precisely embedded on the Fe₂TiO₅ shell via the atomic layer deposition technique to induce bifunctional WOR and ORR properties of the α-Fe₂O₃/Fe₂TiO₅ heterojunction photoelectrode. The WOR and ORR properties are optimized by precisely controlling the Fe₂TiO₅ shell thickness and decorating Pt NPs on the Fe₂TiO₅ surface of the heterojunction photoelectrode. Finally, the α-Fe₂O₃/Fe₂TiO₅/Pt heterojunction photoelectrode is applied as a cathode in SRZBs, exhibiting excellent charging/discharging performance with a voltage gap of only 0.3 V under 1 sun illumination, and the SRZB maintains good cycling stability for over 50 h at 0.1 mA cm⁻² in 1 M potassium hydroxide electrolyte. This research paves the way to fabricate bifunctional photoelectrodes with efficient WOR and ORR properties for SRZB applications.