Porosity-Induced High Selectivity for CO2 Electroreduction to CO on Fe-Doped ZIF-Derived Carbon Catalysts

Metal-doped zeolitic imidazolate framework-8 (ZIF-8)-derived carbon materials are attractive for the electrocatalytic reduction of CO2 into CO. In such carbon materials, due to the fusion and aggregation of ZIF-8 precursors during the high-temperature pyrolysis process, it is desirable yet still challenging to create a high specific surface area with more active sites available for reacting with reactants. Using SiO2 as a protective coating on the ZIF-8 surface, we synthesize Fe, N-co-doped porous carbon nanoparticles (Fe-CNPs) which possess a hierarchical pore structure with a specific surface area as high as 1156.6 m2 g–1, much higher than the counterparts without a SiO2 coating (360.1 m2 g–1). Over these highly porous Fe-CNPs, the total current densities are more than 3 times higher than those of the lowly porous ones for the electrochemical CO2 reduction. More importantly, the maximum CO Faradaic efficiency for Fe-CNPs increases from ca. 75.0 to 98.8% in a concentrated KHCO3 solution (1 mol L–1). The porosity-induced high selectivity for CO production is also revealed on Ni-doped and Co-doped ZIF-derived CNPs, suggesting a new pathway for designing high-performance carbon catalysts through engineering the porosity for the electrochemical CO2 reduction.