Perovskite oxides (ABO3) containing Nb5+ and Ta5+ at the B-site have shown promise in photocatalytic applications. These compounds, such as AgNbO3, AgTaO3, NaNbO3, and NaTaO3 can absorb light in the solar spectrum to excite electrons across the band gap, driving the splitting of water to create hydrogen (a potential fuel) and oxygen gas. These compounds exist in a remarkable variety of structural phases, exhibiting B-O octahedral rotations and polar distortions that can be tuned via temperature and epitaxial strain. In this work, we use Density Functional Theory (DFT) calculations to explore the effects of elemental composition, experimentally-achievable amounts of strain, and distortions on the structural energy landscapes, band gaps, and band-edge orbitals of these compounds. We examine how the size and shape of the unit cell, internal distortions of the structure, and presence (or absence) of d orbitals on the A-site cation dictate the crystal orbital interactions and resulting electronic structure. In doing so, we provide generalizable insights and specific synthetic routes to optimize these compounds for photocatalytic applications.

Band gap and edge engineering of perovskite niobate and tantalate photocatalysts

256th National Meeting (2018)

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