Development of electrode materials with faster charge kinetics and high electrical conductivity are a major challenge to achieve high-performance supercapacitor. In this work, a novel bimetallic nickel cobalt phosphide hollow nanospheres of different Ni/Co molar ratios were synthesized via one-pot thermal decomposition method. Uniform presence of both Ni and Co species was confirmed by energy dispersive spectroscopy (EDS). In particular, a sample with the Ni: Co molar ratio of 1:9 exhibits the most optimized performance, i.e., high specific capacitance of 160 Fg−1 at 0.8 Ag−1, which might be attributed to the strong synergistic effect between Ni and Co species and rich surface electroactive sites in the sample. Besides, the sample also showed low charge transfer resistance (Rct), which in turn gives high electrical conductivity in comparison with other nickel cobalt phosphide (NiCoP) samples. The hollow nanospheres were incorporated into carbon nanofibers to form a free-standing carbon composite that exhibits excellent capacitance retention of 88.5% even after 5000 charge/discharge cycles. The strategy outlined here presents a facile synthesis technique of nickel-cobalt phosphide hollow nanostructures, a promising electrode material which can be explored for a wide variety of electrochemical energy storage applications. © 2019 Elsevier Ltd