Electronic Structure Modulation of AlN₄ Single-Atom Catalyst for Oxygen Reduction Reaction

Mechanistic origins of oxygen reduction reaction (ORR) in p-block metal-based single-atom catalysts (SACs) remain underexplored. Aluminium (Al) typically hinders catalytic activity due to strong binding with oxygenated intermediates, limiting its effectiveness for ORR. However, tailoring electronic structure and coordination environment around Al atoms can optimize the p-band center that may enhance catalytic activity. In this study, we disclose the high intrinsic activity of AlN₄ active sites embedded into carbon nanostructures for robust ORR performance. Comprehensive analysis of surface and bulk electronic structures combined with theoretical calculations, uncovers the origins of activity. Compared to macrocyclic aluminium phthalocyanine, the atomically dispersed AlN₄ sites exhibit a unique electronic structure, contributing to their superior activity, selectivity, and durability comparable to state-of-the-art Pt/C. Atomically dispersed aluminium single-atom on N_x-C matrix (Al-N₄-C) also employed as the cathode material in zinc-air battery and delivers stable performance over 36 h of continuous discharge-charge cycling. Density functional theory (DFT) calculations and Bader charge analysis highlight the delocalization of charge density distribution and localcoordination environment of active sites are key to enhancing 4e^- transfer ORR activity. These findings offer critical insights into engineering main-group metal-based catalysts by tuning p-band center paving the way for their application in diverse fields.