Single-atom dispersed Co–N–C catalyst: structure identification and performance for hydrogenative coupling of nitroarenes†
Co–N–C catalysts are promising candidates for substituting platinum in electrocatalysis and organic transformations. The heterogeneity of the Co species resulting from high-temperature pyrolysis, however, encumbers the structural identification of active sites. Herein, we report a self-supporting Co–N–C catalyst wherein cobalt is dispersed exclusively as single atoms. By using sub-Ångström-resolution HAADF-STEM in combination with XAFS and DFT calculation, the exact structure of the Co–N–C is identified to be CoN4C8-1-2O2, where the Co center atom is coordinated with four pyridinic N atoms in the graphitic layer, while two oxygen molecules are weakly adsorbed on Co atoms in perpendicular to the Co–N4 plane. This single-atom dispersed Co–N–C catalyst presents excellent performance for the chemoselective hydrogenation of nitroarenes to produce azo compounds under mild reaction conditions.