Single‐Nanometer Spinel with Precise Cation Distribution for Enhanced Oxygen Reduction

Designing spinel nanocrystals (NCs) with tailored structural composition and cation distribution is crucial for superior catalytic performance but remarkably challenging due to their intricate nature. Here, an aggregation growth restricted hot‐injection method is presented by meticulously investigating the fundamental nucleation and aggregation‐driven growth kinetics governing spinel NC formation to address this challenge. Through controlled collision probability of nuclei during growth, this approach enables the synthesis of spinel NCs with unprecedented, single nanometer (1.2 nm). Single‐nanometer CoMn2O4 spinel via this method exhibits a highly tailored structure with a maximized population of highly active octahedral Mn atoms, thereby optimizing oxygen intermediate adsorption during oxygen reduction reaction (ORR). Consequently, it exhibits a remarkable half‐wave potential of 0.88 V in ORR and leads to a superior power density (170.9 mW cm−2) in zinc–air battery, outperforming commercial Pt/C and most reported spinel oxides, revealing a clear structure–property relationship. This structure design strategy is readily adaptable for the precise synthesis and engineering of various spinel structures, opening new avenues for developing advanced electrocatalysts and energy storage materials. This work unveils an aggregation‐driven mechanism for synthesizing spinel oxides via hot injection that enables single‐nanometer (1.2 nm) spinel. The resulting single‐nanometer CoMn2O4 exhibits precise cation distribution with maximal octahedral Mn occupancy to form highly active catalytic centers, leading to superior electrocatalytic activity. This advancement offers a novel way for specifically engineering spinel structures and elucidating crucial structure–property relationships.