Perovskite BiFeO3 thin film photocathode performance with visible light activity

Abstract

Perovskite materials are now an important class of materials in the application areas of photovoltaics and photocatalysis. Inorganic perovskites such as BiFeO3 (BFO) are promising photocatalyst materials with visible light activity and inherent stability. Here we report the large area sol-gel synthesis of BFO films for solar stimulated water photo oxidation. By modifying the sol-gel synthesis process we have produced a perovskite material that has p-type behaviour and a flat band potential of ∼1.15 V (versus NHE). The photocathode produces a density of −0.004 mA cm−2 at 0 V versus NHE under AM1.5 G illumination. We further show that 0.6 μmol h−1 of O2 was produced at an external bias of −0.5 V versus Ag/AgCl. The addition of a non-percolating conducting network of Ag increases the photocurrent to −0.07 mA cm−2 at 0 V versus NHE (at 2% Ag loading) with an increase to 2.7 μmol h−1 for O2 production. We attribute the enhancement in photoelectrochemical performance to increased light absorption due light scattering by the incorporated Ag particles, improved charge transfer kinetics at the Ag/BFO interface and reduced over potential losses. We support these claims by an observed shift in flat band and onset potentials after Ag modification through UV–vis spectroscopy, Mott–Schottky plots and j–v curve analysis.