A changeable critical state for a switchable photocurrent direction via the photo-electrochemical photocurrent polarity switching effect in BiFeO3 nanoparticulate films

Abstract

The photoelectrochemical photocurrent switching (PEPS) effect to change the photocurrent direction from cathodic to anodic via external bias is an important phenomenon. Specifically, tuning the critical state or the potential corresponding to a switchable photocurrent direction through easily controllable parameters is crucial for developing efficient photo-electrocatalyst systems. Although the PEPS effect has been reported in quite a few recently published studies, the changeable critical state has not yet been demonstrated. In this study, for the first time, we present a photoelectrochemical (PEC) system based on bismuth ferrite (BiFeO₃) nanoparticulate films that demonstrates a changeable critical state controlled via the composition of an electrolyte medium. In particular, the ionic strength (tuned via addition of inert salt) and the concentration of dissolved oxygen in an electrolyte medium are noted to dictate the potential corresponding to the critical state. Importantly, we demonstrate that this potential can be predicted using the Nernst equation by considering electrolyte energy level rearrangement and the kinetic theory of semiconductor electrodes. This study enhances the understanding of carrier transport in PEC activities and enables precise control over the reversal of the photocurrent direction that may pave the way for developing sophisticated multifunctional photoelectric devices and efficient photo-electrocatalyst systems.