Strain effect on photocatalytic oxygen evolution activity in Sr<sub>3</sub>NF<sub>3</sub> mixed anion perovskite using first-principles density functional theory (DFT).

Abstract

This work presents a first-principles investigation of the mixed-anion perovskite Sr₃NF₃, evaluating its photocatalytic potential under biaxial strain. Stability analysis confirms its structural, dynamic and mechanical robustness. Sr₃NF₃ exhibits a direct bandgap of 2.06 eV (HSE06), tunable from 1.77 eV under +6% tensile strain to 2.16 eV under -6% compressive strain. Electron density difference plots reveal strong internal charge separation attributed to the mixed-anion framework. Optical results show that Sr₃NF₃ exhibits high absorption in both visible and UV regions, with compressive strain enhancing absorption (∼1.35 × 10⁵ cm^-1) and the static dielectric constant (<i>ε</i> = 4.11), improving carrier separation. While unsuitable for hydrogen evolution, Sr₃NF₃ shows strong intrinsic oxidation driving force for oxygen evolution, exhibiting an overpotential of 1.51 eV at -6% strain. Low carrier effective masses further suggest fast charge transport. These findings identify Sr₃NF₃ as a promising, strain-tunable mixed-anion perovskite with favorable intrinsic electronic properties for oxygen evolution, and suitable as an OER-oriented component in advanced photocatalytic architectures.