3D porous cellular NiCoO2/graphene network as a durable bifunctional electrocatalyst for oxygen evolution and reduction reactions

Abstract

In this work, a 3D porous cellular NiCoO2/graphene (NC-GN) network is readily synthesized using a sodium dodecyl sulfate (SDS)-templated strategy via filtration assembly of NiCoO2 precursor and partially reduced graphene oxide (rGO) nanosheets, freeze-casting, and thermal treatment processes. The 3D porous cellular NiCoO2/graphene (NC-GN) network demonstrates advantageous bifunctional electrocatalytic durability and activity toward oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), owing to its fascinating 3D morphology, the high conductivity of graphene oxide (rGO) nanosheets, and catalytic active sites of NiCoO2 binary transition oxides. In comparison with the commercial OER electrocatalyst (IrO2) and ORR electrocatalyst (Pt/C), the 3D porous cellular NiCoO2/graphene (NC-GN) network exhibits superior OER catalytic performance with a satisfactory overpotential of 436 mV vs. RHE at 10 mA cm−2. Furthermore, the 3D porous NC-GN network displays a good ORR catalytic activity with an adequate half-wave potential of 665 mV vs. RHE. The cycling stability and limiting current density of the 3D porous NC-GN network towards OER and ORR are both better than the commercial IrO2 and Pt/C catalysts. The 3D porous cellular NiCoO2/graphene (NC-GN) network shows excellent potentials toward various energy conversion applications such as metal-air batteries, fuel cells, and water splitting.