3. Results and discussion
3.1. Morphology and structure of MgCo2O4 NCAs
As shown in Fig. 1, the fabrication process of MgCo2O4 NCAs mainly involves two steps. In the first step, after the removal of potential NiO layer from the surface by acid treatment, the skeleton of the bare nickel foam is surrounded by parent ions and then light purple mesoporous MgCo-precuosor NCAs are formed by a simple surfactant-assisted hydrothermal process. In the second step, the MgCo-precuosor is thermally transformed to dark MgCo2O4 NCAs supported on the nickel foam, as can be described by the simple dehydration reaction. The inset shows the physical map of bare nickel foam (NF) and the black product MgCo2O4.