In-MOF-derived ultrathin heteroatom-doped carbon nanosheets for improving oxygen reduction

Abstract

For electrocatalysis, the development of highly active and low-cost stable electrocatalysts, which would be directly applied in cathodes for fuel cells that are regarded as the most promising candidates for clean energy conversion in the quest for alternatives to conventional fossil fuel technology, remains a massive challenge. In this context, oxygen reduction reaction (ORR) is a critical process under intense research for the direct conversion of chemical energy into electricity. Herein, a facile synthetic method is proposed for the preparation of hierarchically porous 2-dimensional nanosheets consisting of Fe₄C and FeCo nanoparticles incorporated in N/S-doped carbon materials at 900 °C, denoted as InFeCo@CNS900. This composite can be conveniently prepared by directly calcining the crystalline indium–organic framework of InOF-24, which is impregnated with the ferric thiocyanate and cobalt ammonium complexes under Ar atmosphere, in which Fe₄C and FeCo nanoparticles were in situ formed and embedded into the well-developed carbon materials, which display the hierarchically porous nanosheets with microporous and mesoporous structures. Due to the synergistic effects between different active substances, high specific surface area, suitable graphitization degree, and rich active sites, the as-obtained InFeCo@CNS900 electrocatalyst exhibits an excellent ORR activity, which shows a lower Tafel slope of 59.5 mV dec⁻¹, higher diffusion limit current of 5.15 mA cm⁻², and better stability than the commercial 20 wt% Pt/C catalyst. This study provides a facile approach for the design and synthesis of highly efficient non-noble metal-doped carbon materials with a unique 2-dimensional morphology, which are potentially applied in energy science and technology.