Electronic synergy between CoP/NiCoP heterostructure and Co, Ni single atoms for efficient hydrogen evolution and overall water splitting

Transition metal phosphides (TMPs) are considered as potential electrocatalysts for hydrogen evolution (HER) and overall water splitting (OWS), but their excessively strong adsorption property toward H* limits the reaction kinetics. Herein, we design a bifunctional electrocatalyst (CoP/NiCoP/Co-Ni-N-C) supported by CoP/NiCoP heterostructure and Co, Ni single atoms, which was prepared via facile one-pot pyrolysis process. The interfacial electronic synergy between the high-electropositive Co-N-C, Ni-N-C and the electron-rich CoP/NiCoP heterostructure balanced the hydrogen binding strength, resulting in fast kinetics and high intrinsic activity. Besides, the g-C3N4 was applied as a self-sacrificial template to construct the N doped hierarchical porous carbon carrier, which provided abundant mass transfer pathways and enhanced the charge transfer efficiency. Additionally, the fluid catalytic cracking (FCC) slurry was intelligently applied as extra carbon source, which not only limited the size of CoP/NiCoP nanoparticles, but also increased the loading of Co and Ni single atoms. Benefit from those advantages, the optimized CoP/NiCoP/Co-Ni-N-C exhibited low overpotentials of 40 mV at 10 mA cm-2 toward HER in 1 M KOH. Meanwhile, the two-electrode system only need 1.54 V to achieve the current density of 10 mA cm-2. This work provided a kind of potential electrocatalyst for efficient water splitting and a method for lowcost catalyst design.