Construction of Co/N-doped porous rose-like structure for efficient oxygen reduction reaction catalyst and Zn-air battery

Highlights: • This work provides a simple and efficient approach to synthesize Pod-Co catalyst. • Co@NCs-900 exhibits a rose-like hierarchical porous structure with high SSA. • Co@NCs-900 shows an excellent electrochemical performance towards ORR and has a half-wave potential of 0.83 V. • The Co-N_x active sites can increase the catalytic activity for ORR. • Zn-air battery based on Co@NCs-900 displays long-term stability of 1116 h, which can drive a LED. Reasonable design of nanostructures is the key to efficient electro-catalytic reactions. Herein, a facile and efficient approach is used to successfully construct Co/N-doped carbon composites (Co@NCs-T). The resultant Co@NCs-900 exhibits a rose-like hierarchical porous structure with high specific surface area (SSA), which can greatly expose a large number of active sites. The embedded cobalt nanoparticles contribute to the improvement of oxygen adsorption capacity and the enhancement for corrosion resistance performance of the metal active centers. The Co-N_x active sites resulted from the combination of Co and N species can increase the ORR catalytic activity. The Co@NCs-900 performs a four-electron reaction process and exhibits a good catalytic activity with a half-wave potential of 0.83 V and limiting current density of 5.93 mA cm⁻² in alkaline medium. The excellent ORR electro-catalytic activities of Co@NCs-900 benefits from the synergetic effect between pyridinic-N, graphitic-N and Co-N_x. The Zn-air battery assembled by Co@NCs-900 exhibits open circuit voltages of 1.441 V and a maximum power density of 57.63 mW cm⁻². Meanwhile, it shows outstanding reversibility and ultra-long-life span (1116 h, 3045 cycles). In this work, the catalyst with a rose-like structure is successfully synthesized, and the mechanism of Co-N_x active sites in the ORR is investigated.