Facile Construction of Metal Phosphides (MP, M = Co, Ni, Fe, and Cu) Wrapped in Three-Dimensional N,P-Codoped Carbon Skeleton toward Highly Efficient Hydrogen Evolution Catalysis and Lithium-Ion Storage.

Transition metal phosphides (TMPs) have been demonstrated for prospective applications in electrocatalytic reaction and energy conversion owing to their specialties of catalytic activity and superhigh theoretical capacity. Herein, a facile and robust strategy for confining phosphides in a three-dimensional N,P-codoped carbon skeleton was achieved through a simple evaporation method. After calcination treatment, metal phosphide nanoparticles (MP, M = Co, Ni, Fe, and Cu) were successfully encapsulated in an interconnected N,P-codoped carbon network, which not only endowed high electrical conductivity and electrochemical stability but also provided more active sites and ion diffusion channels. As-prepared CoP@N,P-C exhibited satisfactory hydrogen evolution reaction activity, displaying lower overpotential of 140 and 197 mV at 10.0 mA cm-2 in 0.5 M H2SO4 and 1.0 M KOH, respectively. Moreover, CoP@N,P-C also delivered satisfactory lithium-ion storage properties. A higher specific capacity of 604.9 mAh g-1 was retained after 1000 cycles at 0.5 A g-1, one of the best reported performances of CoP-based anode materials. This work highlights a facile pathway to encapsulate metal phosphides in a conductive carbon skeleton, which is suitable for scaled-up production of bifunctional composites for efficient energy storage and conversion.