Facile synthesis of various highly dispersive CoP nanocrystal embedded carbon matrices as efficient electrocatalysts for the hydrogen evolution reaction

Abstract

In order to promote the hydrogen evolution reaction (HER) catalytic efficiency of cobalt phosphide (CoP) and then construct efficient HER catalysts, a facile procedure has been adopted to prepare tiny CoP nanoparticle (NP) embedded carbon matrices without using any extreme conditions and harmful organic reagents or surfactants. Meanwhile, in order to explore the influence of structures of carbon matrices on preventing the free growth of CoP NPs and enhancing the HER catalytic efficiency of the CoP–carbon catalysts, imporous reduced graphene oxide (RGO), macroporous carbon (MPC), mesoporous carbon vesicles (MCVs) and ordered mesoporous carbon (OMC) were used for preparing CoP–carbon HER catalysts. SEM and TEM measurements show that size-controlled CoP NPs indeed grew more uniformly on the OMC frameworks than those on MCVs, MPC and RGO. As expected, the HER is catalyzed more efficiently on CoP–OMC accompanied by a small onset potential of −77.74 mV vs. RHE, a low Tafel slope of 56.67 mV dec⁻¹, a small over-potential value of 112.18 mV at 10 mA cm⁻², and the outstanding long-term stability. These results show that CoP–OMC inherently exhibits better HER catalytic activity than other CoP-based catalysts in acidic electrolytes. Such excellent performances are attributed to the synergistic effect of the highly catalytic sites provided by the uniformly dispersed and size-controlled CoP NPs embedded on OMC, excellent proton transport efficiency, and improved electron transport with a high electron transfer rate. Our results provide useful information that the mesoporous conductive matrices could be applied to greatly improve the HER catalytic efficiency of various HER catalytically active centers.