Regulation of biochar interfaces by loading an Fe,N-carbon layer for the oxygen reduction reaction in acid electrolytes

Oxygen reduction catalyst (Fe/Fe 3 N/C) with Fe/Fe 3 N encapsulated carbon active sites were synthesized by coated Fe , N layer onto cellulose-derived carbon through the coordination of iron (Fe 3+ ) and formamide solution with cellulose and subsequent carbonization to enhance electrical conductivity of biochar surfaces as cathode in fuel cells. Fe/Fe 3 N/C catalyst exhibited a half-wave potential of 0.74 V vs . reversible hydrogen electrode in 0.5  M H 2 SO 4 with excellent stability over 100 h. Electrochemical impedance spectroscopy tests showed that the charge transfer resistance was only 1.671 Ω using this novel method, indicating that the cellulose-derived carbon in the core significantly enhanced the electron transport efficiency. Quantum mechanical calculations confirmed strong coordination interaction between the carbonyl groups in formamide and the hydroxyl groups in cellulose with Fe to form Fe/Fe 3 N structure by carbonization. This study provides an effective renewable material solution for Proton exchange membrane fuel cells.