Controlled synthesis of NiCo2O4@Ni-MOF on Ni foam as efficient electrocatalyst for urea oxidation reaction and oxygen evolution reaction

Abstract

Heterostructured materials with special interfaces and features give a unique character for much electrocatalytic process. In this work, the introduction of exogenous modifier Ni-MOF improved the reaction kinetics and morphology of the NiCo2O4@Ni-MOF/NF catalyst. As-obtained NiCo2O4@Ni-MOF/NF has excellent oxygen evolution reaction (OER) performance and urea oxidation reaction (UOR) performance. The catalyst need overpotential of 340 mV at a current density of 100 mA cm−2 for OER and a potential of 1.31 V at the same current density for UOR. The Tafel slopes of NiCo2O4@Ni-MOF/NF is 38.34 and 15.33 mV dec−1 for OER and UOR respectively, which is more superior than 78.58 and 66.73 mV dec−1 of NiCo2O4/NF. The nanosheets microstructure is beneficial to the adsorption and transport of electrolyte and the presence of a large number of mesoporous channels can also accelerate gas release, and then improves activity of the catalyst. Density functional theory calculation demonstrate that NiCo2O4 plays a role in absorbing water, while the existence of in situ generated NiOOH can promote the electron transfer efficiency. It is synergies of NiCo2O4 and in situ generated NiOOH that enhance the decomposition of water on the surface of the NiCo2O4@Ni-MOF/NF. This investigation provides a new strategy for the application of spinel oxide and MOF materials.