Nanoparticles of NiO and CoO simultaneously dispersed on a mesoporous carbonaceous support as bifunctional electrocatalysts for ORR and OER reactions and Zn-air battery performance.

This work aims to study the effect of different atmospheres and temperatures in the synthesis of a bifunctional electrocatalyst for ORR and OER reactions in the cathode of a Zn-air battery, using a carbonaceous support for dispersing Ni and Co species. At 300oC, NiCo2O4 with a size of 4.93nm under O2 and 150.14nm using air, were obtained. These materials exhibited low specific surface area and pore volume and failed to show bifunctional activity. Instead, the simultaneous dispersion of NiO and CoO nanoparticles, with a size of 2.55nm was achieved at 300oC under N2 (NiCo/MC-N300), leading to a surface enrichment in Co2+ and Ni2+ species, while Ni and Co nanoparticles, 12.81nm, were obtained at 700oC under N2 (NiCo/MC-N700). These catalysts exhibited high specific surface area and pore volume, and bifunctional electrochemical activity; as well as high specific-capacity in a home-made Zn-air battery.