In order to avoid the addition of polymer binders and conductive
agents, which are non-desirable for high-performance supercapacitors,
nanostructured cobalt selenide was directly grown on
nickel foam substrate by a facile hydrothermal method. From the
XRD pattern (Fig. 1a), all Bragg peaks can be indexed to hexagonal
Co0.85Se phase (JCPDS card No. 52e1008).