Facile growth of porous Fe2V4O13 films for photoelectrochemical water oxidation

Abstract

Porous n-type Fe₂V₄O₁₃ films on FTO substrates were prepared by a simplified successive ion layer adsorption and reaction method and characterized as photoelectrodes for photoelectrochemical (PEC) water oxidation. Synthesis parameters such as film thickness and annealing temperatures and durations were investigated to optimize the PEC performance. A band gap of ∼2.3 eV and a flat band potential of 0.5 V vs. RHE make Fe₂V₄O₁₃ a promising photoanode material. Water oxidation was kinetically limited at the surface of Fe₂V₄O₁₃ film as confirmed by tests in electrolyte with a hole scavenger (Na₂SO₃). Improved PEC performance was achieved by Mo and W doping because of enhanced carrier densities. The best performance was obtained by 2.5% W-doped Fe₂V₄O₁₃ films (actual 0.8% W-doped), which efficiently oxidize water to O₂via photogenerated holes as confirmed by oxygen evolution measurements. Moreover, the Fe₂V₄O₁₃ photoanode displayed very stable photocurrent under illumination. Due to the suitable band gap and valence band position, Fe₂V₄O₁₃ is a promising photoanode for solar water splitting. Co-catalyst loading and doping optimization are identified as routes to improve this material's performance further.