Alkaline-stable nickel manganese oxides with ideal band gap for solar fuel photoanodes. Issue 36 (19th April 2018) - Suram, Santosh K.
Abstract : Combinatorial photoelectrochemistry combined with first principles calculations demonstrate that NiMnO3 and its mixture with Ni6 MnO8 are photoanodes with phenomenal absorptivity and band alignment to the oxygen evolution reaction. Abstract : Combinatorial (photo)electrochemical studies of the (Ni–Mn)O x system reveal a range of promising materials for oxygen evolution photoanodes. X-ray diffraction, quantum efficiency, and optical spectroscopy mapping reveal stable photoactivity of NiMnO3 in alkaline conditions with photocurrent onset commensurate with its 1.9 eV direct band gap. The photoactivity increases upon mixture with 10–60% Ni6 MnO8 providing an example of enhanced charge separation via heterojunction formation in mixed-phase thin film photoelectrodes. Density functional theory-based hybrid functional calculations of the band edge energies in this oxide reveal that a somewhat smaller than typical fraction of exact exchange is required to explain the favorable valence band alignment for water oxidation.