High-valent bimetal Ni2P/Co2P heterostructures induced by Mo doping as an advanced electrode for hybrid supercapacitors

Abstract

The development of advanced electrode materials with fast reaction kinetics and optimized morphology is key to achieving high-performance hybrid supercapacitors with high energy density and outstanding cycling performance. Herein, an ingenious strategy is developed to prepare M doped Ni2P/Co2P (M = Cu, Zn, Mo) bimetallic phosphide electrode materials with heterostructure. For the Mo-doped Ni2P/Co2P, the unique morphology of hollow nanocubes consisting of ultrathin nanosheets facilitates the availability of more electrochemical active sites and relieves the deformational effects. In addition, the formation of heterogeneous structures modulates the electronic structure and the causes redistribution of interfacial charges, while the introduction of Mo cation can promote the formation of more high-valent Ni/Co sites, which synergistically accelerate reaction kinetics. Consequently, the Mo-Ni2P/Co2P hollow nanocubes with heterogeneous interfaces exhibit an optimal specific capacitance of 2300 F g−1 at 1 A g−1. In addition, when combined with activated carbon (AC) as a hybrid supercapacitor (HSC), the Mo-Ni2P/Co2P //AC device displays an energy density of 35.56 Wh kg−1 at a splendid power density of 800.0 W kg−1 and a remarkable cycling performance (the capacitance retention of 84.83% after 15,000 cycles). This study reveals that the introduction of Mo cation induces the formation of high-valence Ni/Co, providing a meaningful reference for the construction of high-performance metal phosphides with unique morphology and massive phase boundaries.