Vertical CoP Nanoarray Wrapped by N,P-Doped Carbon for Hydrogen Evolution Reaction in Both Acidic and Alkaline Conditions

Hydrogen evolution reaction (HER) is a key reaction in water splitting, and developing efficient and robust non-noble electrocatalysts for HER is still a great challenge for large-scale hydrogen production. Herein, a vertically aligned core-shell structure grown on Ti foil with CoP nanoarray as a core and N,P-doped carbon (NPC) as a shell (CoP/NPC/TF) is first reported as an efficient electrocatalyst for HER. Results indicate that CoP/NPC/TF only demands the overpotentials of 91 and 80 mV to drive the current density of 10 mA cm(-2) in acidic and alkaline solutions. The electrochemical measurements and theoretical calculations show that the synergy of CoP nanorod core and porous NPC shell enhances HER performance significantly, because the introduction of porous NPC shell not only offers more active sites but also improves the electrical conductivity and durability of the sample in acidic and alkaline solutions. Density functional theory calculation further reveals that all the C atoms between N and P atoms in CoP/NPC are the most efficient active sites, which greatly improve the HER performance. The identification of active species in this work provides an effective strategy to design and synthesize the low-cost, high-efficient, and robust CoP-based electrocatalysts.