Asymmetric Ni–O–Co Active Sites Induce Spin‐State Transitions to Break Performance Trade‐Offs in Urea Electrolysis

Abstract

ABSTRACT Urea‐assisted water electrolysis represents a sustainable paradigm for concurrent hydrogen production and wastewater remediation; however, its efficiency is fundamentally limited by the Sabatier trade‐off between urea activation and CO 2 product desorption. Here, we report an asymmetric electronic structure engineering strategy to overcome this bottleneck by incorporating atomically dispersed Ni into Co 3 O 4 cubic hollow nanoboxes. The construction of asymmetric Ni–O–Co sites triggers a critical spin‐state transition of octahedral Co 3+ from low‐spin to intermediate‐spin through lattice distortion and polarization. This electronic reconfiguration effectively strengthens urea binding while simultaneously weakening the adsorption of poisonous *CO 2 intermediates. Synergized by a superhydrophilic and superaerophobic surface that facilitates rapid bubble release, the Ni SAC ‐Co 3 O 4 catalyst achieves an exceptionally low potential of 1.32 V for urea oxidation. In a full‐cell configuration, the system delivers a current density of 10 mA·cm −2 at only 1.34 V, doubling the hydrogen output compared to traditional water splitting while achieving a 96.7% urea degradation efficiency. Life cycle assessment further validates the environmental superiority of this system. Our work provides a versatile design principle for tailoring spin states in asymmetric architectures to break linear scaling relationships in complex multi‐electron electrocatalysis.