Hybrid functional study on optical properties of Sr2M2O7−xNx(M = Nb, Ta) photocatalysts with perovskite-slab structures

•The electronic and optical properties are calculated with the HSE06 functional.•Sr2Nb2O7 and Sr2Ta2O7 have a good optical performance under the UV region.•N-doping can extend the absorption edge to the visible region.•Enhancing in doping ratio can increase the absorption effect in the UV–VIS region.

sWe present the electronic, dielectric, and optical properties of layered perovskite pure and N-doped Sr2M2O7 (M = Nb and Ta) based on density functional theory with the HSE06 approximation. The band gaps for pure Sr2M2O7 (M = Nb and Ta) are consistent with the experimental data. Optical properties are obtained and compared with the experimental results. Pure Sr2Nb2O7 and Sr2Ta2O7 have broad applications in photocatalysis in the ultra-violet region. In contrast with Sr2Ta2O7, the absorption ability of Sr2Nb2O7 is slightly stronger. The N doping in Sr2Nb2O7 shifts the light absorption boundary into the visible region. The optical absorption effect of Sr2Nb2O5N2 is better than Sr2Nb2O6.5N0.5 in the visible region. The N doping in Sr2Ta2O7 reduces the band gap and produces visible light absorptions. Sr2Ta2O5N2 shows higher absorption effect in the visible light region than Sr2Ta2O6.5N0.5.

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