One-Pot Synthesis of Co/Co3O4/Co(OH)2/N-Doped Mesoporous Carbon for Both Oxygen Reduction Reactions and Oxygen Evolution Reactions

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are two major processes in renewable energy technologies. However, discovering high performance bifunctional electrocatalyst for OER and ORR still remains a tremendous challenge. Herein, we present effective bifunctional electrocatalysts Co/Co3O4/Co(OH)(2)/N-doped mesoporous carbon (Co-NC) via one-pot synthesis. As resulted, the best-performing Co-NC 750 consists of the highest amounts of pyridinic nitrogen and optimized ratio of three cobalt species. The strong confinement effect between Co/Co3O4/Co(OH)(2) core and N-graphitic shell of Co-NC 750 leads to excellent ORR activity and superior OER performance, along with a low reversible overvoltage of 1.02 V between ORR and OER under alkaline environment, endowing it economical and efficient for reversible oxygen electrode reactions. In addition, we discovered a potential research direction of advancing bifunctional catalysts with synergy effect by optimizing metal crystal structures and doping nitrogen to accelerate oxygen electrode reactions merely by altering its pyrolyzation temperatures.