Shape-Controlled Synthesis of Co₂P Nanostructures and Their Application in Supercapacitors

Co₂P nanostructures with rod-like and flower-like morphologies have been synthesized by controlling the decomposition process of Co(acac)₃ in oleylamine system with triphenylphosphine as phosphorus source. Investigations indicate that the final morphologies of the products are determined by their peculiar phosphating processes. Electrochemical measurements manifest that the Co₂P nanostructures exhibit excellent morphology-dependent supercapacitor properties. Compared with that of 284 F g^-1 at a current density of 1 A g^-1 for Co₂P nanorods, the capacitance for Co₂P nanoflowers reaches 416 F g^-1 at the same current density. Furthermore, an optimized asymmetric supercapacitor by using Co₂P nanoflowers as anode and graphene as cathode is fabricated. It can deliver a high energy density of 8.8 Wh kg^-1 (at a high power density of 6 kW kg^-1) and good cycling stability with over 97% specific capacitance remained after 6000 cycles, which makes the Co₂P nanostructures potential applications in energy storage/conversion systems. This study paves the way to explore a new class of cobalt phosphide-based materials for supercapacitor applications.