Unveiling the critical role of strain-induced local structure changes in Co-N₄ single-atom catalysts for enhanced...

The rational design of cost-effective bifunctional catalysts for the oxygen reduction and oxygen evolution reactions remains a key bottleneck in advancing sustainable energy technologies. Using comprehensive density functional theory (DFT) calculations, we systematically elucidate how strain-induced structural perturbations govern the intrinsic activity of single-atom catalysts (SACs). Our results reveal that although the local coordination environment (e.g., pyridinic N vs. pyrrolic N) plays a primary role in determining activity, maximal bifunctional performance is achieved through precise control of metal-nitrogen ligand distances via applied directional strain. Free-energy landscape analysis identifies the formation of the OOH* intermediate as the common rate-determining step for both oxygen reduction and evolution, yielding an exceptionally low theoretical overpotential under optimal strain. Electronic-structure decomposition further shows that the strain-induced shift of the metal d-orbital center fine-tunes the adsorption of oxygen intermediates relative to the Fermi level. This work establishes a quantitative, atomistic correlation linking strain, electronic structure, and catalytic turnover, providing a powerful strain-based descriptor for the rational design of non-precious-metal electrocatalysts.