High-performance bulky crystalline copper bismuthate photocathode for enhanced solar water splitting

Abstract

Copper bismuthate (CuBi2O4, CBO) has attracted attention as a promising photocathode material for photoelectrochemical (PEC) water-splitting because of its small bandgap (1.6–1.8 eV), high internal photovoltage, and moderate stability in aqueous media. Herein, we report a novel solution synthesis method to fabricate bulky crystalline CBO photocathodes via an evaporation decomposition controlled process. The CBO photocathode synthesized under optimal conditions exhibited a uniform, dense film with intimate substrate contact and large-grains, allowing an enhanced charge transport and photocurrent stability in comparison to porous CBO counterparts. Consequently, the dense CBO achieved a photocurrent density of − 1.16 mA/cm2 at 0.4 V versus the reversible hydrogen electrode (RHE) without a scavenger addition under simulated sunlight irradiation (AM 1.5 G, 100 mW/cm2). Significantly, the coupling of the CBO with a cupric oxide (CuO) underlayer and a Pt electrocatalyst increased the photocurrent density further to − 2.8 and − 3.5 mA/cm2 at 0.4 V versus RHE, respectively, which is the highest value to date among all reported CBO based photocathodes.