Preparation of ultrahigh surface area carbon microspheres under solvent-free hypersaline environment for zinc-air batteries with high power density

It is of great significance to develop efficient non-noble metal electrocatalysts for oxygen reduction reaction (ORR). Herein, the starch-based carbon microspheres (CMS) electrocatalyst with ultrahigh specific surface area (SSA) of 2799 m(2) g(-)(1) is prepared by solvent-free method under hypersaline environment that composed of ZnCl2 and FeCl(3)middotH(2)O. The formed carbon microspheres with hierarchical porous structure are beneficial to the adequate exposure of active sites and the free transportation of electrolyte. Importantly, the hypersaline environment favors not only the high yield of carbon material, but also the creation of abundant carbon defects with the presence of ZnFe2O4 coated on carbon microspheres, thus promoting the oxygen adsorption and desorption. The assembled zinc-air battery based on CMS2-800 exhibits prominent cycle stability, high open circuit voltage (1.43 V) and big power density (183.5 mW cm(-)(2)), superior to the battery constructed with commercialized Pt/C + RuO2. This work provides an efficient strategy to prepare electrocatalysts with starch as the starting material for high-performance zinc-air battery.