Pyrrole Nitrogen Coordination Activates Intrinsically Catalytically Inert Mo for Oxygen Reduction Reaction

Electronic structure modulation is a promising approach to enhance the properties of intrinsically inert metals in an electrocatalytic oxygen reduction reaction. Herein, a molybdenum (Mo) single atom (Mo SAs) catalyst with pyrrole-rich nitrogen/oxygen double coordination has been designed and synthesized (defined as Mo SAs/N-C). The pyrrole-nitrogen (Pyrr-N) coordination was shown to effectively regulate the metal-centered electronic structure of Mo. This coordination strategy enables Mo SAs/N-C to exhibit superior catalytic activity and enhanced 4e^- transfer selectivity. The electrochemical performance evaluations revealed that Mo SAs/N-C exhibit exceptional durability (with only a 2.0 mV half-wave potential decay after 5000 cycles) and resistance to methanol toxicity, outperforming commercial Pt/C (20%). Notably, as an air-cathode catalyst for zinc-air batteries, Mo SAs/N-C achieved a peak power density of 242 mW cm^-2. Combining experimental results with density functional theory calculations, it was found that Pyrr-N effectively modulates the adsorption of OOH* intermediates on Mo atoms, promoting the 4e^- transfer pathway and significantly enhancing the performance of the ORR. This study provides valuable insights into the role of Pyrr-N coordination in improving the performance of single-atom catalysts.