Switching Co/N/C Catalysts for Heterogeneous Catalysis and Electrocatalysis by Controllable Pyrolysis of Cobalt Porphyrin.

Identifying the optimal synthetic and structural parameters in preparing pyrolyzed metal/nitrogen/carbon (M/N/C) materials is crucial for developing effective catalysts for many important catalytic processes. Here we report a group of mesoporous Co/N/C catalysts ranging from polymerized cobalt porphyrin to Co/N-doped carbons, which are prepared by pyrolysis of cobalt porphyrin using silica nanoparticles as templates at different temperatures, for boosting both heterogeneous catalysis and electrocatalysis. It is revealed that the polymerized cobalt porphyrin prepared at low temperature (500°C) is a polymer-like network with exclusive single-atom Co-N sites, and that the high-temperature-pyrolysis (>600°C) produces an electrically conductive Co/N-doped carbon, accompanied by part degradation of Co-N centers. We identify that the polymerized cobalt porphyrin with undecomposed Co-N centers is optimal for heterogeneous catalytic oxidation of ethylbenzene, whereas the electrically conductive Co/N-doped carbon is ideal for eletrocatalytic oxygen reduction. Our results provide new insights for rationally optimizing M/N/C catalysts for different reactions.