Ni-Co oxide formation with Cu assisted method on Ni foam: Unexpected higher areal capacitance of inner layer with naturally formed nanotubes

Ni Foam substrate directly serves as the Ni source for the final Ni-Co oxide product with a Cu assisted chemical method. Especially, after shaking off top layer of Ni-Co oxide grown on Ni Foam, the sample unexpectedly exhibits a greatly enhanced areal capacitance from 4.17 to 11.44 F cm−2 (1 mA cm−2). Finer structures including oxide nanotubes are interestingly found underneath the top layer, which may account for this extraordinary phenomenon.