Mechanistic Understanding of Curvature Effects on ORR/OER Activity in Single-Atom Catalysts From Atomic-Scale Perspective.

The sluggish kinetics of oxygen reduction and evolution reactions (ORR/OER) severely limit metal-air battery performance. Here, we employ first-principles calculations to systematically elucidate the role of nanotube curvature in tuning catalytic activity. By establishing the structural and electronic feasibility of boron nitride nanotubes (BNNTs) as electrocatalysts through a comprehensive analysis of cohesive energies, curvature energies, and density of states. Subsequently, we explore the catalytic performance of Cu-doped BNNTs with varying diameters, followed by an evaluation of Cu-doped BN monolayers and nanotubes for ORR/OER under strain, with consistent B-N configurations. Curvature not only enhances the catalytic activity but also circumvents the conventional scaling relationships that typically limit activity optimization. Tensile strain modulates catalytic properties by shifting the d-band center at the active site, whereas curvature exerts a more profound influence by redistributing the energy splitting among d-orbital sublevels. Notably, curvature induces a dramatic inversion of orbital energy ordering, whereby the d z 2 ${d_{{z^2}}}$ orbital shifts from the highest to the lowest energy level, and the degeneracy of the dxy and d x 2 - y 2 ${d_{{x^2} - {y^2}}}$ orbitals are lifted. These changes alter the binding modes, effectively breaking the linear relationship between intermediates. This study provides new insights into the microscopic mechanisms of curvature effects on catalytic activity.