Photoelectrochemical properties of BiMnO3 thin films and nanostructures

We report and compare the properties of BiMnO3 (BMO) nanostructures and thin films as photoanodes in photoelectrochemical solar cells. BMO films are grown on Niobium doped SrTiO3 crystalline substrates using pulse laser deposition. Nanoscale patterns of BMO are obtained by depositing through nanostencils, namely shadow masks with nanometer-scale circular apertures. We demonstrate that BMO nanostructures exhibit superior photoelectrochemical properties, compared to BMO thin films when used as photoelectrodes in cells for hydrogen production. A photocurrent density of ∼0.9 mA cm−2 at 0.8 V vs Ag/AgCl (1.38 V vs RHE) under 1 Sun is recorded for BMO nanostructures. On the other hand, BMO films exhibit a photocurrent density of ∼40 μA cm−2 at 0.4 V vs Ag/AgCl (0.98 V vs RHE) under 2 Sun which is four times higher than that recorded under 1 Sun illumination (∼10 μA cm−2 at 0.4 V vs Ag/AgCl). Mott-Schottky analysis evidences n-type characteristics for both BMO thin films and nanostructures. According to band alignment with respect to the redox potential of water, we conclude that both types of photoelectrodes are suitable for oxygen evolution reaction.