Iron carbide anchored on N-doped hierarchically porous carbon core/shell architecture for highly efficient OER water splitting

Metal-nitrogen-carbon complexes are emerging as efficient electrocatalysts for the oxygen evolution reaction (OER) owing to the excellent activity, stability, natural abundance, and cost-effectiveness of these complexes. This study introduces an innovative approach to synthesizing an N-doped porous graphitic carbon with a Fe3C core-shell structure (N-PGC@Fe3C) using biomass-derived carbon. Characterized by a large specific surface area of 3169 m2/g and hierarchical mesoporosity, the synthesized N-PGC@Fe3C catalysts demonstrate superior OER activity, achieving low overpotentials of 143.8 and 312.2 mV at current densities of 20 and 50 mA/cm2, respectively, in a 1 M KOH electrolyte. Notably, the N-PGC@Fe3C-3 exhibits outstanding cycle performance after 2000 cycles. Density functional theory calculations confirm that the core-shell-structured N-PGC@Fe3C provides the primary active site for the OER. The observed efficiency is attributed to the synergistic action of the Fe–N–C active sites, ultrafine Fe3C encapsulation, and the hierarchical porous nanosheet structure that facilitates mass diffusion and increases the exposure of active sites. Furthermore, when employed as an anode during overall water splitting, N-PGC@Fe3C achieves a cell voltage of 1.49 V at a current density of 10 mA/cm2 under alkaline conditions. This study can facilitate the development of high-performance Fe–N–C-based catalysts and clarify the underlying OER mechanisms, thereby advancing the field of electrocatalytic water splitting and energy storage systems.