Nitrogen-doped graphite supported cobalt nanoparticles as excellent ORR/OER/HER trifunctional electrocatalysts

Non precious metal catalysts (NMCs) are considered to have great potential for applications in oxygen reduction reaction (ORR) and water splitting reaction (OER and HER). Compared with traditional precious metal catalysts, NMCs have the characteristics of low cost, better catalytic performance, wider applicability, and better durability. This article reports a facile method for preparing layered Co-N-C catalysts by simple ball milling and pyrolysis of a mixture of graphite, ammonium carbonate, melamine and cobalt phthalocyanine. The synthesized nanoCo@bmGr and nanoCo@bmGr-EG samples exhibit excellent performance in ORR, OER and HER. For ORR in alkaline electrolyte, the nanoCo@bmGr and nanoCo@bmGr-EG present very close Tafel slopes to Pt/C catalyst. For OER under alkaline condition, the nanoCo@bmGr and nanoCo@bmGr-EG exhibit smaller Tafel slopes than IrO 2 catalyst, and at a current density of 10 mA∙cm −2 , their potential difference with IrO 2 is only 50 and 70 mV respectively. For the chronopotentiometric tests of OER at current densities of 20 and 30 mA∙cm −2 , the two samples show lower potentials than IrO 2 . In HER testing, nanoCo@bmGr and nanoCo@bmGr-EG display very similar onset potentials and Tafel slopes to Pt/C. This work provides a simple approach for preparing catalysts with good catalytic activity for ORR/OER/HER.