Mixed metal/metal oxides interfaces on lignin-derived defect-rich partially graphitized carbon catalysts for improved OER studies

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Carbon structures with dual metallic sites enable synergistic electronic coupling and strong metal-support interactions, making them promising alternatives to noble metal electrocatalysts for the energy-intensive oxygen evolution reaction (OER). Herein, Fe and Mn-containing carbon electrocatalysts (Fe–C, Mn–C, and FeMn–C) were synthesized via a direct carbonization of lignin feedstock, yielding defect-rich, partially graphitized frameworks and uniformly distributed metal/metal oxide species. The FeMn–C system exhibited enhanced interfacial electronic coupling arising from π−π∗ interactions within the defective carbon matrix and mixed oxidation states of Mn and Fe sites embedded in the carbon support. Electrochemical OER studies in 1 M KOH showed that FeMn–C/CP delivered superior OER performance with a low overpotential of 251 mV at 10 mA cm −2 and a Tafel slope of 60 mV dec −1 , outperforming Fe–C/CP (328 mV, 91 mV dec −1 ) and Mn–C/CP (419 mV, 157 mV dec −1 ). The enhanced performance is attributed to synergy and strong metal-support interactions, as reflected by the reduced charge-transfer resistance (2.33 Ω), improved stability over 500 cycles with ∼58 mV increases in overpotential at 10 mA cm −2 . The pH (12-14) and temperature-dependent (30-60 °C) studies highlighted a favorable reaction rate and electron transfer kinetics in the FeMn–C/CP catalyst. The presence of dual-metal sites on carbon matrices thus offers an effective approach for designing high-performance OER electrocatalysts.