Transition Metal Doped BiVO4 Photoanodes: A Mechanistic Study

Abstract

BiVO4 has emerged as one of the most promising materials to fabricate efficient photoanodes for photoelectrochemical (PEC) solar water splitting. BiVO4 is an n-type semiconductor, with a 2.4 eV bandgap and a theoretical solar to hydrogen (STH) efficiency of 9.2% with a maximum photocurrent of 7.5 mA cm2 under AM 1.5 G illumination, low overpotential and favourable band-edge positions towards the Oxygen Evolution Reaction (OER).1 However, BiVO4 also presents poor electron transport, high surface recombination and slow water oxidation kinetics. Hence, enormous efforts have been made in the past few years to mitigate these drawbacks through different approaches such as nanostructuring,2 doping,3 heterostructuring,4 and the use of efficient co-catalysts.5 The present study proposes a transition metal doping (Ni, Fe and Co) of BiVO4 photoelectrodes that boosts their water oxidation performance. The origin of this enhanced performance towards Oxygen Evolution Reaction (OER) was studied by a combination of a suite of structural, chemical, and mechanistic advanced characterization techniques including X-Ray Photocurrent Spectroscopy, Electrochemical Impedance Spectroscopy and Transient Absorption Spectroscopy, among others.[1] J. Li and N. Wu, Catal. Sci. Technol., 2015, 5, 1360–1384.[2] S. P. Berglund, D. W. Flaherty, N. T. Hahn, A. J. Bard and C. B. Mullins, J. Phys. Chem. C, 2011, 115, 3794–3802.[3] S. K. Pilli, T. E. Furtak, L. D. Brown, T. G. Deutsch, J. A. Turner and A. M. Herring, Energy Environ. Sci., 2011, 4, 5028–5034.[4] J. Su, L. Guo, N. Bao and C. A. Grimes, Nano Lett., 2011, 11, 1928–1933.[5] D. K. Lee and K.-S. Choi, Nat. Energy, 2018, 3, 53–60.