Co-SrCO3/N-doped carbon: a highly efficient hybrid electrocatalyst for the oxygen reduction reaction and Zn-air batteries

Zn-air battery is a promising energy conversion and storage technique because of its high specific energy density; however, the sluggish oxygen reduction reaction (ORR) in the cathode decreases its efficiency, thus hindering its practical application. Therefore, highly efficient electrocatalysts are required for ORR and Zn-air batteries. Herein, Co-SrCO3/N-doped carbon (NC) hybrid electrocatalysts were developed through the pyrolysis of a bimetal precursor (Co, Sr). The hybrid electrocatalysts with core-shell configuration include the outer NC shells and the inner inorganic nanoparticles (SrCO3 with surface SrO and metallic Co). The outer NC shells had direct contributions to the ORR processes, whereas the inner inorganic nanoparticles had indirect contributions, both of which were investigated in detail, especially the important roles of SrCO3 with surface SrO. Together with high surface content of doped N, high charge transfer efficiency, high BET surface area, and greater surface SrO of SrCO3, the optimized CoSrCO3/ NC-600 possesses high ORR activity, high selectivity of the apparent 4e(-) pathway, and excellent durability. The Zn-air battery with Co-SrCO3/NC-600 also shows high battery performance. This study provides a new protocol for developing highly efficient electrocatalysts for the ORR and Zn-air batteries, through using alkaline earth metal based materials.