The rise of Nb-, Ta-, and Bi-based oxides/chalcogenides for photocatalytic applications

Niobates, tantalates, and bismuthates have recently attracted attention as compounds to be used in photonics and energy-harvesting applications as substitutes for the relatively unstable lead-halide perovskites. Having the photocatalytic reaction for H₂ production and CO₂ conversion in mind, we perform first-principles materials design to determine the potential for electrochemistry of certain Nb-, Ta-, and Bi-based oxides/chalcogenides: NaMO_(3−x)Q_x (M = Nb, Ta and Q = S, Se), and ABiX₂ and ABiX₃ (A = Na, K and X = O, S). The analysis of the effective masses, alongside the determination of the actual electronic dimensionality, reveals that several compounds exhibit reduced electronic dimensionality despite possessing a higher structural dimensionality. The electrochemical performances of all compounds are then investigated by computing the band-edge alignment with respect to various redox levels, against the relevant photocatalysis reactions in aqueous media at different pH's. Our work highlights the effect of chalcogen incorporation in the electrochemical performance of this class of materials, and proposes some of the Bi-based chalcogenides, namely KBiO₂ and KBiS₂, as efficient photocatalysts over a wide range of pH conditions.