Porous nanosheet composite with multi-type active centers as an efficient and stable oxygen electrocatalyst in alkaline and acid conditions

The reversible oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are proton-coupled/decoupled four-electron reactions requiring multi-type active centers for catalysis. Herein, porous nanosheets codoped with a carbon-encapsulated FeNi alloy, metal-N species, and N defects (FeNi-N/PCN) were synthesized through a facile and environmentally friendly molten NaCl template method. The obtained FeNi-N/PCN achieved impressive performances as an oxygen electrocatalyst for the ORR and OER in alkaline ( E 1/2 of 0.88 V RHE , E j =10 of 1.57 V RHE ) and acidic electrolytes ( E 1/2 of 0.78 V RHE , E j =10 of 1.76 V RHE ). Furthermore, this FeNi-N/PCN catalyst achieved an impressive power density of 224 mW cm −2 and a specific capacity of 691 mA h g −1 in a Zn-air battery, which are 1.34- and 1.20-fold higher than that of the Pt and RuO 2 catalysts, respectively. These outstanding performances are due to the layered carbon nanosheet with multi-type active sites, including a carbon-encapsulated FeNi alloy, N defects, and metal-N sites (M-N x ).