Interfacial assembly of binary atomic metal-N_x sites for high-performance energy devices

Anion-exchange membrane fuel cells and Zn-air batteries based on non-Pt group metal catalysts typically suffer from sluggish cathodic oxygen reduction. Designing advanced catalyst architectures to improve the catalyst's oxygen reduction activity and boosting the accessible site density by increasing metal loading and site utilization are potential ways to achieve high device performances. Herein, we report an interfacial assembly strategy to achieve binary single-atomic Fe/Co-N_x with high mass loadings through constructing a nanocage structure and concentrating high-density accessible binary single-atomic Fe/Co-N_x sites in a porous shell. The prepared FeCo-NCH features metal loading with a single-atomic distribution as high as 7.9 wt% and an accessible site density of around 7.6 × 10¹⁹ sites g^-1, surpassing most reported M-N_x catalysts. In anion exchange membrane fuel cells and zinc-air batteries, the FeCo-NCH material delivers peak power densities of 569.0 or 414.5 mW cm^-2, 3.4 or 2.8 times higher than control devices assembled with FeCo-NC. These results suggest that the present strategy for promoting catalytic site utilization offers new possibilities for exploring efficient low-cost electrocatalysts to boost the performance of various energy devices.