CoP Embedded in Hierarchical N-Doped Carbon Nanotube Frameworks as Efficient Catalysts for the Hydrogen Evolution Reaction

Highly efficient, nonprecious and stable electrocatalysts for the hydrogen evolution reaction (HER) are absolutely crucial for renewable energy conversion, yet the design of such catalysts remains to be a long and arduous task. Herein, cobalt phosphide (CoP) nanoparticles (NPs) embedded in hierarchical N-doped carbon nanotube frameworks (CoP-HNCs) have been synthesized by controlled phosphidation of cobalt NPs embedded in hierarchical N-doped carbon nanotube frameworks (Co-HNCs). The Co-HNCs were prepared by direct carbonization of Co-based zeolitic imidazolate networks (ZIF-67). Benefitting from multiple structural and compositional features, such as a multitude of catalytically active sites, a high degree of graphitization, and a thin carbon layer enclosing the NPs, CoP-HNCs serve as a superior electrocatalyst towards the hydrogen evolution reaction. The synthesized CoP-HNCs delivered a low overpotential at a current density of 10 mA cm(-2) (eta(10)) of 79 mV and 96 mV with small Tafel slope value of 45.6 m Vdec(-1) and 49.5 m Vdec(-1) in acidic and alkaline conditions, respectively. In addition, the catalyst showed long-time durability under both acidic and alkaline electrolyte conditions, further demonstrating their potential to replace Pt-based precious catalysts.