Metal vacancies in semiconductor oxides enhance hole mobility for efficient photoelectrochemical water splitting

Abstract

Achieving efficient carrier separation in transition metal oxide semiconductors is crucial for their applications in optoelectronic and catalytic devices. However, the significant disparity in mobility between holes and electrons heavily limits device performance. In this study, we develop a general strategy for enhancing hole mobility via reducing its effective mass through metal vacancy (VM) management. The introduction of VM yields remarkable improvements in hole mobility: 430% for WO3, 350% for TiO2, and 270% for Bi2O3. To illustrate the significance of this finding, we applied the VM concept to photoelectrochemical water splitting, where efficient carrier separation is highly coveted. In particular, VM-WO3 achieves a 4.4 times enhancement in photo-to-current efficiency, yielding a performance of 4.8 mA cm-2 for both small and large scale photoelectrodes with exceptional stability for over 120 h.