High performance BiFeO ferroelectric nanostructured photocathodes.

Ferroelectric materials may be used as effective photoelectrocatalysts for water splitting due to enhanced charge carrier separation driven by their spontaneous polarization induced internal electric field. Compared to other ferroelectric materials, BiFeO exhibits a high catalytic efficiency due to its comparatively smaller bandgap, which enables light absorption from a large part of the solar spectrum and its higher bulk ferroelectric polarization. Here, we compare the photoelectrochemical properties of three different BiFeO morphologies, namely, nanofibers, nanowebs, and thin films synthesized via electrospinning, directly on fluorine-doped tin oxide (FTO) coated glass substrates. A significant photocathodic current in the range from -86.2 to -56.5 μA cm at -0.4 V bias (vs Ag/AgCl) has been recorded for all three morphologies in 0.1M NaSO aqueous solution (pH = 6.8). Among these morphologies, BiFeO nanofibers exhibit higher efficiency because of their larger surface area and improved charge separation resulting from rapid diffusion of photoinduced charge carriers along the axis of the nanofiber. In the case of BiFeO nanofibers, we obtained the highest photocurrent density of -86.2 µA/cm at -0.4 V bias (vs Ag/AgCl electrode) and an onset potential of 0.22 V. We also observed that the onset potential of the photocathodic current can be increased by applying a positive polarization voltage, which leads to favorable bending of band edges at the electrode/electrolyte interface resulting in increased charge carrier separation.