Phosphorus-induced Electronic Coupling between Fe Single Atoms and Fe₂O₃ Nanoparticles on Biomass-Derived Carbon for Efficient Oxygen Reduction

Abstract

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. 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.