Transition metal nitrides (TMNs) have recently attracted increasing attention as a robust alternative to platinum electrocatalysts in alkaline oxygen reduction reaction (ORR). However, the fundamental understanding of the catalytic nature of the TMNs remains elusive, impeding the further catalyst design and optimization. Here, using ZrN as a model catalyst, we demonstrate that the unexpected catalytic activity of TMNs originates from the self-adaptive behavior of surface-reconstructed oxynitride monolayers under ORR conditions. Our first-principles calculations reveal that oxygen adsorption triggers a square-to-hexagonal symmetry transition on the ZrN surface, stabilizing a hexagonal ZrNO monolayer. At quarter-hydroxyl coverage, this reconstruction generates semi-elliptical cavities that confine the highly active Zr sites. Crucially, the flexible Zr–N–Zr linkages connecting these Zr sites and the underlying ZrN substrate undergo dynamic bond-length variations during ORR, which precisely regulate oxygen intermediate adsorption and significantly enhance catalytic activity. Experimental characterization aligns well with these theoretical predictions. The as-designed ZrNO monolayer catalyst delivers a 0.882 V half-wave potential for ORR and enables zinc–air batteries with 240 mW·cm⁻² peak power density—metrics that exceed state-of-the-art Pt/C. This study provides atomic-level insights into the nature of TMNs’ catalytic monolayers, paving the way for stable and active catalyst engineering in next-generation energy technologies.

Enzyme-like metal atomic site catalysts are promising alternatives of platinum group metals for oxygen reduction reaction (ORR) in fuel cell application. The local coordination structure at metal atomic sites plays a dominant role in optimizing the adsorption/desorption of oxygen intermediates to enhance ORR, but there is still a significant challenge in achieving. Herein, we report a type of stable and dynamically adjustable mono-oxygen-bridged asymmetric dual-atomic metal catalyst, in which the active Fe-oxo-Co motif demonstrates platinium-like ORR activity with a half-wave potential of 0.92 V vs. RHE in alkaline condition and a maximum power density of 228 mW·cm⁻² in Zn-air batteries. Theoretical calculations reveal that the Fe-oxo ligands can act as electron regulators for neighboring Co sites, which optimize and promote the d-orbitals of Co metal shift towards lower energy levels, thereby weakening the adsorption of oxygen species, facilitating the progress of the ORR. More interestingly, the Fe–oxo–Co bond will dynamically change its strength to adaptively facilitate the intermediate steps during the ORR process. The design strategy towards enzyme-like adaptive behavior of active Fe-oxo-Co motifs brings significant hope for achieveing high performance fuel cell cathode materials.