Ferroelectric polarization-enhanced charge separation in a vanadium-doped ZnO photoelectrochemical system

Abstract

Efficient charge separation is a key factor that determines the efficiency of photoelectrochemical (PEC) water splitting. Here, we introduce controllable vanadium dopants to the ZnO nanorod arrays (NRAs) as a photoanode. The optimal vanadium doping amount exhibited a negative shift in the flatband potential, which was favorable for charge separation, resulting in a maximum applied bias photo-to-current efficiency of 0.8%, which was 2.1 times that of the pristine ZnO photoanode. More importantly, V-doping induced ZnO ferroelectric behavior was adopted to further optimize the PEC performance through the ferroelectric polarization by external electric field poling. The negative bias poling enlarged the band bending at the electrode/electrolyte interface, which facilitated the separation of photogenerated charges and thus resulted in an increased efficiency of 1.04%. This work provides a new method for the design of ferroelectric materials as efficient photoanodes for PEC water splitting.