Phosphorus-induced electronic coupling between Fe single atoms and Fe2O3 nanoparticles on biomass-derived carbon for efficient oxygen reduction.

Developing non-noble metal catalysts with both high activity and stability for the oxygen reduction reaction (ORR) remains a major challenge. Herein, we report a phosphorus-induced electronic coupling strategy to construct a dual-active-site catalyst composed of Fe single atoms and Fe2O3 nanoparticles anchored on a hierarchically porous carbon matrix derived from sugarcane bagasse biochar (Fe-P-C-Fe2O3/SBB). Phosphorus doping modulates the local coordination environment and facilitates the formation of Fe-P-O bonds, which bridge Fe single atoms and Fe2O3 nanoparticles, enabling interfacial charge redistribution. This electronic coupling optimizes the Fe d-band center, balances the adsorption strength of oxygen intermediates, and promotes a four-electron ORR pathway. As a result, the Fe-P-C-Fe2O3/SBB catalyst delivers a half-wave potential of 0.80 V (vs. RHE) and a Tafel slope of 75.6 mV dec-1, rivaling commercial Pt/C. Notably, the achieved ORR performance is comparable to or surpasses that of many recently reported non-noble metal catalysts, highlighting its strong potential for practical applications in fuel cells and metal-air batteries. Moreover, the catalyst exhibits remarkable durability and methanol tolerance. This work not only provides an atomically and electronically coupled Fe-based catalytic system but also offers a general strategy for designing sustainable biomass-derived dual-active-site catalysts through heteroatom-induced electronic coupling.