BiVO4 photoelectrodes for unbiased solar water splitting devices enabled by electrodepositing of Cu2O simultaneously as photoanode and photocathode

Abstract

In this work, BiVO₄ films are firstly synthesized, followed by electrodepositing of Cu₂O to construct BiVO₄/Cu₂O heterojunction electrodes for photoelectrochemical water splitting. By regulating the electrodeposition potential, it is possible to control that Cu₂O is deposited on the surface or inside of BiVO₄, which enables them n-type or p-type semiconductivity behavior for oxygen and hydrogen evolution reactions, respectively. Due to the built-in electric field of p-n heterojunction and the Co-Pi co-catalyst layer, the anodic photocurrent density of optimized BiVO₄/Cu₂O/Co-Pi photoanode reaches 1.97 mA cm⁻² at 1.23 V vs. RHE. In the meantime, the deposition of Cu₂O inside BiVO₄ has reversed the arrangement of the BiVO₄/Cu₂O heterogeneous structure. The cathodic photocurrent density of the fabricated BiVO₄/Cu₂O-C photocathode shows − 2.9 mA cm⁻². Furthermore, the unbiased solar tandem cell is fabricated using BiVO₄/Cu₂O-C photocathode and BiVO₄/Cu₂O/Co-Pi photoanode, which exhibits 0.1 mA cm⁻² in the photoelectrochemical cell without applying any external voltage.