High-Performance Silver-Doped Porous CuBi2O4 Photocathode Integrated with NiO Hole-Selective Layer for Improved Photoelectrochemical Water Splitting

Abstract

CuBi2O4(CBO) has received considerable attention owing to its ideal optical bandgap and positive photocurrent onset potential. However, CBO photocathodes exhibit poor charge carrier separation and transfer across the conducting substrate interface. Herein, a systematic incorporation of Ag+-cations into nanosized porous CBO network (ACBO) using a simple pulsed-electrodeposition method. In ACBO photocathode, the Ag+-ions replace the Bi3+-ions, thereby building an increased hole concentration, which further signifies the photogenerated electron-hole separation. Additionally, introducing a low-cost NiO hole-selective layer between ACBO and the conducting substrate enables a back-interface-aided hole-extraction and electron blocking, resulting in an improved charge transfer across the back interface. Compared with an unmodified CBO, the NiO/ACBO photocathode exhibits a three-fold enhanced photocurrent performance. This enhances the photocurrent originating from the incorporation of a substantial amount of Ag+-ions into the CBO structure, leading to an increased acceptor density as well as the formation of an appropriate hole-selective layer across the back-contact. The absorption percentage, time-resolved photoluminescence, and photoelectrochemical impedance spectroscopy measurements unveil the potential light harvesting, charge separation, and transfer characteristics of the NACBO photoelectrode, respectively. Through this systematic study, an efficient and simple strategy is determined for developing ternary metal oxide-based photocathode/photoanode systems for sustainable energy applications.