Natural sulvanite Cu3MX4 (M = Nb, Ta; X = S, Se): Promising visible-light photocatalysts for water splitting

Abstract

The identification of natural mineral photocatalysts with excellent visible-light absorption, suitable band edge positions, and large carrier mobility is significant for water-splitting applications. Herein, by applying density functional theory simulation, the natural sulvanite Cu3MX4 (M = Nb, Ta; X = S, Se) compounds are proposed as efficient photocatalysts for visible-light water splitting. Calculation of the phonon dispersions and elastic constants of the Cu3MX4 (M = Nb, Ta; X = S, Se) compounds reveal that they are dynamically stable. In addition, their electronic structures indicate that these compounds are indirect semiconductors with band gaps in the desired range of 2–3 eV, and the position of the band-edge energy perfectly straddles the water oxidation and reduction potentials. Partial density charge analysis reveals that the electrons are mainly located near the Nb/TaS/Se bond, whereas the holes occupy the CuS/Se bonds. Furthermore, the effective mass, deformation potential parameters, and carrier mobility were quantitatively investigated to evaluate the photocatalytic dynamics. A small average effective mass and effective separation of photogenerated carriers in space was observed. Our calculations provide guidance for experimental synthesis and will expand the scope of these natural minerals for visible-light-driven water splitting with excellent performance.