Iron-containing sulfur/nitrogen co-doped porous carbons via composite salt modification to promote the oxygen reduction catalysis

Abstract

Carbon materials with high micropore volume and great specific surface area (SSA) are developed as catalysts for oxygen reduction reaction. Sodium lignosulfonate was used as the primary starting material for effectively doping of iron and nitrogen using ferric chloride hexahydrate and melamine, capitalizing on its robust coordination characteristics. The influences of the magnesium oxide template and composite salt etching on the pore structure and catalytic performance are comprehensively investigated. Modulation of MgO template and composite salt during high-temperature pyrolysis produces the catalyst (Fe-NS-PC) with a hierarchical porous structure and a 1699 m² g⁻¹ of specific surface area. It promotes the exposure of active sites, and mobility of reactants and products during oxygen reduction process. Thus, the Fe-NS-PC catalyst possess an oxygen reduction reaction (ORR) activity (E_1/2 = 0.865 V vs. RHE) in alkaline medium, being similar to the Pt/C catalyst. In zinc-air battery (ZAB) testing, the specific energy density is reduced by 6% after ∼120 h of uninterrupted discharge when the negative zinc foil is substituted, demonstrating the exceptional stability. This work presents a practical guide for the subsequent modification of carbon materials using template and composite salts modification.