Interface engineering induced electrocatalytic behavior in core-shelled CNTs@NiP₂/NbP heterostructure for highly efficient overall water splitting

Earth-abundant and efficient bifunctional electrocatalysts for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) are crucial for electrochemical water splitting to produce green hydrogen fuel. In this work, core–shell heterostructure catalyst by NiP₂/NiP nanosheets shelled carbon nanotubes supported on three-dimensional framework were prepared by new effective approach. Benefiting from the unique morphological feature of carbon nanotubes architecture, the synergy of inner carbon nanotubes and outer NiP₂/NiP nanosheets, and the good couple interactions at interface between NiP₂ and NbP phases, this electrocatalyst showed low overpotential of 137.0 and 248.2 mV for HER and OER at a current density of 20 mA cm⁻², respectively. These overpotentials were one of the smallest values of noble-metal-free electrocatalyst for HER and OER in alkaline electrolyte. Moreover, when the advanced catalyst was assembled in two-electrode configuration for full water electrolysis, a very low cell voltage of 1.51 V was required to achieve 10 mA cm⁻² current density and a higher current density of 100 mA cm⁻² was reached at a cell voltage of only 2.32 V.