Mn-N-C with High-Density Atomically Dispersed Mn Active Sites for the Oxygen Reduction Reaction.

The utilization of transition metal-based catalysts as alternatives presents an attractive solution for enhancing the sluggish oxygen reduction reaction (ORR) and reducing costly platinum-based electrocatalysts in hydrogen fuel cells. Manganese-based nitrogen-carbon (Mn-N-C) is anticipated to exhibit durability due to its weaker Fenton reaction propensity. However, a key obstacle lies in boosting intrinsic electrocatalytic activity and increasing the density of Mn active sites, crucial for practical integration into fuel cell operations. Herein, a three-step method is developed to synthesize atomically dispersed Mn-N-C materials with a rich mesoporous structure as highly effective ORR catalysts. The high Mn loading (3.42 wt%) promotes the generation of Duo-MnN active sites, demonstrating outstanding performance and durability for fuel cells. Specifically, the exceptional performance of proton exchange membrane fuel cells (PEMFC) reaches 649 mW cm and anion exchange membrane fuel cells (AEMFC) achieves 770 mW cm. Notably, the durability of the Mn-N-C catalyst in PEMFC is reported for the first time, showing only 18.4% decay after 30 000 square-wave cycles. This work provides a unique perspective and a systematic design strategy for building feasible nonprecious metal catalysts with a high active site density, addressing the challenges of inefficiency and performance limitations across various electrocatalytic applications.