Roe-shaped Ni3(PO4)2/RGO/Co3(PO4)2 (NRC) nanocomposite grown in situ on Co foam for superior supercapacitors

A roe-shaped ternary nanocomposite, Ni3(PO4)2/RGO/Co3(PO4)2 (NRC), was grown in situ on cobalt foam (CoF). The synthesis and loading of NRC on the CoF was completed through a one-step hydrothermal process by immersing the CoF in an aqueous solution of GO and Ni2+ in the presence of H2PO4−, in which the CoF served as the support, reductant and Co source. Three interfaces of Co3(PO4)2/CoF, RGO/Co3(PO4)2, and Ni3(PO4)2/RGO with strong interactions were constructed based on an in situ conversion reaction of Co to Co3(PO4)2, a redox reaction between GO and the CoF, and the electrostatic attraction force of Ni2+ and GO, respectively. The as-synthesized NRC@CoF had a hierarchically porous structure, and directly acted as a supercapacitor electrode and delivered excellent electrochemical performances: a specific capacitance of 10 237.5 mF cm−2 (1137.5 F g−1) at 5 mA cm−2 (0.56 A g−1) with a capacity retention of 117.8% after 14 000 cycles. Furthermore, NRC@CoF-based asymmetric supercapacitors (ASCs) exhibited a specific capacitance of 4845.9 mF cm−2 (115.4 F g−1) at 5 mA cm−2 (0.12 A g−1), and a high energy density of 44.82 W h kg−1 at a power density of 428.6 W kg−1, as well as good cyclic stability (91.9% after 18 000 cycles).