Hydrogel-Modulated Microporous/Mesoporous Engineering on FeCo-DAC toward Efficient Oxygen Reduction

Single-atom (SA) Fe–N–C catalysts are considered as promising electrocatalysts for the oxygen reduction reaction (ORR). However, due to the drawbacks of the microporous structure and very strong binding with O intermediates, Fe–Nx active sites may not always display satisfactory catalytic performance. Therefore, simultaneously engineering hierarchical pores and introducing the second metal atom are promising strategies to break the bottleneck of SA Fe performance. Herein, an economical and environmentally friendly method is used to prepare an Fe–Co dual-atom catalyst (DAC) with a microporous/mesoporous coupled structure (HP/FeCo-NC-2). HP/FeCo-NC-2 effectively enhances the mass transfer process and the ORR activity of Fe–N–C. The atomic dispersion of the as-synthesized catalyst was confirmed by synchrotron X-ray absorption spectroscopy. The Brunauer–Emmett–Teller test was used to assess the number of catalyst-mesoporous structures, and HP/FeCo-NC-2 has a more mesoporous structure than HP/FeCo-NC-1. More mesopores allow faster electrolyte access to the active sites inside the catalyst, facilitating the rate of mass transfer during the reaction. Consequently, the structural advantages and interactions between Fe and Co endow HP/FeCo-NC-2 with ORR performance superior to those of HP/FeCo-NC-1 and HP/Fe-NC-2 in 0.1 M KOH.