Co₃O₄ Nanoparticles as Robust Water Oxidation Catalysts Towards Remarkably Enhanced Photostability of a Ta₃N₅ Photoanode

Abstract

Abstract Despite the fact that Ta 3 N 5 absorbs a major fraction of the visible spectrum, the rapid decrease of photocurrent encountered in water photoelectrolysis over time remains a serious hurdle for the practical application of Ta 3 N 5 photoelectrodes. Here, by employing a Co 3 O 4 nanoparticle water oxidation catalyst (WOC) as well as an alkaline electrolyte, the photostability of Ta 3 N 5 electrode is significantly improved. Co 3 O 4 /Ta 3 N 5 photoanode exhibits the best durability against photocorrosion to date, when compared with Co(OH) x /Ta 3 N 5 and IrO 2 /Ta 3 N 5 photoanodes. Specifically, about 75% of the initial stable photocurrent remains after 2 h irradiation at 1.2 V vs. RHE (reversible hydrogen electrode). Meanwhile, a photocurrent density of 3.1 mA cm −2 has been achieved on Co 3 O 4 /Ta 3 N 5 photoanode at 1.2 V vs. RHE with backside illumination under 1 sun AM 1.5 G simulated sunlight. The reason for the relatively high stability is discussed on the basis of electron microscopic observations and photoelectrochemical measurements, and the surface nitrogen content is monitored by X‐ray photoelectron spectroscopic analysis.