Strain-Modulated Tuning of Rashba Signature and Catalytic Activity on Oxynitride Surface: Facet Matters

Tantalum-based oxynitride perovskite SrTaO₂N distinguishes itself as a rare semiconducting material, exhibiting remarkable stability in aqueous environments and a narrow band gap, rendering it a highly active catalyst for the hydrogen evolution reaction (HER). In this study, we employ first-principles density functional theory (DFT) calculations to provide mechanistic insights into the electrochemical HER occurring on the low-indexed (001) and (110) surfaces. The computed adsorption free energy of hydrogen adsorption (ΔG_H) for these facets indicates their favorable catalytic activity toward HER. Additionally, a detailed analysis of the system's electronic structure reveals the elemental contribution to both the valence and conduction band edges. The influence of the biaxial strain on enhancing the selectivity of the oxynitride system for hydrogen evolution is also thoroughly examined. Finally, the strain-modulated HER activity is elucidated through changes in the charge profile, providing a deeper understanding of the strain-induced effects on surface charge contribution and catalytic performance.