Cobalt-Embedded N-Doped Carbon Arrays Derived In Situ as Trifunctional Catalyst Toward Hydrogen and Oxygen Evolution, and Oxygen Reduction

The carbons containing metals coordinated with nitrogen are emerging as the most promising catalysts toward various heterogeneous catalyses. In this paper, such a carbon catalyst is prepared through a chemical vapor deposition (CVD)-supported precursor pyrolysis. Compared with the direct pyrolysis of polypyrrole@cobalt salt precursor, the incorporation of dicyanodiamide as the CVD source facilitates the diversification and hierarchization of carbon morphology, the reduction of Co particle size, and the increase of the proportion of interfacial Co-N-C and pyridinic-N. The catalyst is composed of in-situ-grown multiple-morphology carbons (MMCs) with metallic Co particles embedded, where the MMCs are a combination of nano-particles, -rods, and -wires, all comprised by small N-doped carbon nanoflakes. Owing to the combined modulation on morphology configurations and defect states, the Co/MMCs catalyst demonstrates excellent activities toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). A half-wave potential of 0.84 V and low overpotentials of 86 and 180 mV at 10 mA cm(-2) current density for HER and OER are achieved, respectively. Additionally, the catalyst also demonstrates favorable prospects for large-scale applications in overall water splitting and Zn-air battery.