Atomically Dispersed Iron on Functionalized Boron Nitride Nanosheets for Efficient Oxygen Reduction in Proton Exchange Membrane Fuel Cells

Abstract

Iron single-atom (Fe-SA) catalysts are promising alternatives to platinum for proton-exchange membrane fuel cells (PEMFCs), but their high performance often lacks long-term stability during operation. Designing a unique Fe coordination environment beyond the traditional Fe–N4 structure in Fe–N–C catalysts could overcome current stability limitations of Pt-free catalysts, though this remains unexplored. Herein, iron single-atom catalysts embedded in carbon mesopores and integrated with hydroxylated boron nitride nanosheets (OH-BN/C/Fe-SA) exhibit enhanced oxygen reduction reaction (ORR) activity. The distinctive Fe coordination in OH-BN/C/Fe-SA markedly enhances 4e– ORR activity and selectivity, reducing H2O2 production to below 1% compared to the Fe-SA catalyst. The OH-BN/C/Fe-SA catalyst shows high cyclic stability, with less than 5 mV drop in half-wave potential (E1/2) after long cycles, making it the most stable Pt-free catalyst reported for PEMFCs. The 2D coordination structure effectively prevents demetalation of the OH-BN/C/Fe-SA catalyst, ensuring long-term stability and improved PEMFC durability. Our study lays the foundation for next-generation Pt-free catalysts for PEMFCs.