Nitrogen doped NiFe layered double hydroxide/reduced graphene oxide mesoporous nanosphere as an effective bifunctional electrocatalyst for oxygen reduction and evolution reactions

It is a crucial and challengeable task to develop non-precious metal catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in energy storage and conversion systems. Herein, a facile and cost-effective strategy was employed to prepare the mesoporous nitrogen doped NiFe layered double hydroxide/reduced graphene oxide (NiFe-LDH/NrGO) nanospheres via an one-pot solvothermal reaction by using GO, protonated g-C3N4 nanosheets (p-CNNS), mixed metal salts and alkali as precursors in presence of surfactant. The doping of p-CNNS resulted in the superior ORR activity compared to pristine NiFe-LDH and NiFe-LDH/rGO. The ORR results demonstrated that the NiFe-LDH/NrGO hybrid involved a perfect 4e mechanism with better durability and methanol tolerance ability than commercial 20% Pt/C catalyst in 0.1 M KOH. NiFe-LDH/NrGO also displayed the excellent OER activity with a close onset over potential to NiFe-LDH/rGO, but a more negative overpotential and a higher current density at eta > 300 mV in the same alkaline medium. Overall, the outstanding catalytic performance toward both ORR and OER suggested that the NiFe-LDH/NrGO composite can be a new non-precious metal bifunctional catalyst in the related renewable energy fields. (C) 2017 Elsevier B.V. All rights reserved.