Hollow NiCoP nanocubes derived from a Prussian blue analogue self-template for high-performance supercapacitors

Transition metal phosphides (TMPs) have attracted great interest owing to the metallic properties and high specific capacities. Here, we designed hollow NiCoP nanocubes with increased specific surface area using a Ni-Co Prussian blue analogue as a self-template and NH3·H2O as an etching agent. During the synthesis, both carbonization and phosphorization are completed in one step. The obtained hollow structure alleviates the volume variation of electrode material during reversible electrochemical reaction. Meanwhile, the residual carbon distributed uniformly in NiCoP at the molecular level, resulting in a high conductivity. DFT calculations further reveal that the electrical conductivity of NiCoP is superior to those of monometallic phosphide and metal oxide. Therefore, the optimized NiCoP-4–500 displays a high specific capacity (1590 F g−1 at 1 A g−1) and outstanding cycling stability (78.2% retention after 12,000 cycles). Moreover, a prepared hybrid supercapacitor device delivers an energy density of 38.4 W h kg−1 with a power density of 799.9 W kg−1 at 1 A g−1. The results indicate that the obtained high-performance TMPs with hollow structures have an application potential for energy storage devices.