Enhancing the photoelectrochemical water splitting efficiency of ZnO P–N homojunction nanorod arrays under the piezocatalyst effect

Abstract

Due to the increasing demand for clean energy sources, hydrogen has received considerable attention due to its high energy density with only water as the combustion byproduct. Among hydrogen generation methods, photoelectrochemical (PEC) water splitting driven by solar light is a promising approach for green hydrogen production. In this study, the efficiency of ZnO-nanorod array based PEC systems is enhanced by forming a ZnO p–n homojunction via a two-step hydrothermal method with antimony (Sb) doping. The formation of the p–n homojunction facilitates the separation of photo-generated carriers due to the built-in electric field. Additionally, in the context of piezocatalysis, applying external forces during water splitting could not only modulate the Schottky barrier height and the width of the depletion region, but also cause the energy band bending towards the oxygen revolution reaction potential. Consequently, holes could more easily transport to the interface with the electrolyte, and carrier separation is further improved, suppressing the recombination rate. The synergistic effect between the built-in electric field and stress-induced Schottky barrier modulation leads to an enhancement in photocurrent. This study provides a facile method for synthesizing ZnO p–n homojunctions and contributes to the improvement of output efficiency in PEC water splitting systems.