N doped carbon dots modified needle-like NiCo2O4 supported on graphene as efficient dual-functional electrocatalyst for oxygen reduction and evolution reactions

On account of the inexpensive and environmental, the transition metal oxides have been broadly used as catalysts in electrochemical energy storage and conversion technologies. However, many transition metal oxides possess lower catalytic activity as catalysts in dual-functional oxygen reduction (ORR) and evolution reactions (OER). Within this work, we have devised and fabricated an N doped carbon dots (CDs) modified needle-like NiCo2O4 supported on graphene (NiCo2O4-G-NCDs) composite as promising dual-functional catalyst in both ORR and OER. Needle-like NiCo2O4-G-NCDs composites were fabricated by one-pot solvothermal method and displayed significantly enhanced electrocatalytic performances in both ORR and OER (0.82 V vs. RHE of half-wave potentials for ORR, smaller Tafel slopes (63.94 mV dec(-1)) and lower OER overpotential (308 mV vs. RHE at 10 mA cm(-2)) than that of NiCo2O4-G and NiCo2O4-G-CDs). The resulting NiCo2O4-G-NCDs composite shows comparable dualfunctionality to the PVC and RuO2 for ORR and OER in alkaline condition. The enhanced electrocatalytic performances of NiCo2O4-G-NCDs composite should ascribe to the synergy between N-doped CDs and NiCo2O4. Our study affords a feasible strategy for the development of multifunctional electrocatalyst in metal-air batteries.