Oxygen Vacancy: How Will Poling History Affect Its Role in Photoelectrocatalysis.

Oxygen vacancy (V O ) has been recognized to possess an effect to promote the charge separation and transfer (CST) in various n-type semiconductor based photoelectrodes. But how external stimulus will change this V O effect has not been investigated. In this work, external polarization is applied to investigate the effect of V O on the CST process of a typical ferroelectric BiFeO 3 photoelectrode. It is found that negative poling treatment can significantly boost V O effect, while positive poling treatment will deteriorate the CST capability in BiFeO 3 photoelectrodes. This poling history determined V O effect is rooted in the V O induced defect dipoles, wherein their alignment produces a depolarization electric field to modulate the CST driving force. This finding highlights the significance of poling history in functionalizing the V O in a photoelectrode.