First-principles study of electronic structure and photocatalytic properties of MnNiO3 as an alkaline oxygen-evolution photocatalyst

Abstract

We present a first-principles study of MnNiO₃, a promising oxygen-evolution photocatalyst. Using density functional theory with the PBE + U functional and the screened hybrid functional of Heyd, Scuseria, and Ernzerhof (HSE), we compute and analyze the ground-state geometry and electronic structure. We find that MnNiO₃ is a ferrimagnetic semiconductor with an indirect band gap, consistent with experimental observations. We also predict that MnNiO₃ has promising band edge positions relative to the vacuum, with potential to straddle the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) redox potentials in aqueous solution. A detailed analysis of the band structure and density of states provides a clear explanation for why MnNiO₃ has appropriate electronic properties for OER. Furthermore, comprehensive calculations of its Pourbaix diagram suggest that MnNiO₃ is stable in alkaline solution at potentials relevant for oxygen evolution.