Synthesis of Fe3C@C core-shell catalysts with controlled shell composition for robust oxygen evolution reaction

Highlights: • Fe₃C encapsulated in graphene-like layers were prepared via carbonation process. • The role of the Fe₃C core and carbon shell were investigated for OER. • Fe₃C@C-N exhibited a remarkable OER stability under alkaline conditions. • The shell provides sites for OH⁻ adsorption leading to an enhanced OER activity. In this study, iron carbide (Fe₃C) particles were encapsulated in graphitic carbon shells by a facile carbonation process. These core-shell carbides, in which iron carbide is encapsulated in graphene-like layer (Fe₃C@C) and nitrogen doped graphene-like layer (Fe₃C@C–N) were investigated as oxygen evolution reaction (OER) catalysts to investigate the effect of the carbon shell on catalyst activity and stability. Due to the protective effect of the graphitic carbon shells, the performance of Fe₃C@C and Fe₃C@C–N were considerably better than the bare Fe₃C nanoparticles. The OER activity of Fe₃C@C–N is comparable with that of carbon-supported ruthenium oxide (RuO₂/C), and this core-shell carbide has a remarkable stability and high turnover frequency under alkaline conditions. To elucidate the real active sites of these core-shell carbides, the role of the Fe₃C core, Fe–N_x active sites, and effect of nitrogen doping in the shell were investigated in detail.