Tailoring d-band center over electron traversing effect of NiM@C-CoP (M=Zn, Mo, Ni, Co) for high-performance electrocatalysis hydrogen evolution

Abstract

Attaining a highly efficient and inexpensive electrocatalyst is significant for the hydrogen evolution reaction (HER) but still challenging nowadays. The transition-metal phosphides (TMPs) catalysts with platinum-like electronic structures are a potential candidate for the HER, but those are prone to be strongly bound with hydrogen intermediates (H*), resulting in sluggish HER kinetics. Herein we report a unique hybrid structure of CoP anchored on graphene nanoscrolls@carbon nano tubes (CNTs) scaffold (NiM@C-CoP) encapsulating various NiM (M=Zn, Mo, Ni, Co) bimetal nanoalloy via chemical vapor deposition (CVD) growth of CNT on graphene nanoscrolls followed by the impregnation of cobalt precursors and phosphorization for efficiently electrocatalytic hydrogen evolution. CoP nanoparticles mainly scattered at the tip of CNT branches which exhibited the analogical ``Three-layer core-shell'' structures. Experiments and density functional theory(DFT) calculations consistently disclose that the encapsulated various NiMs can offer different numbers of electrons to weaken the interactions of outmost CoP with H* and push the downshift of the d-band center to different degrees as well as stabilize the outmost CoP nanoparticles to gain catalytic stability via the electron traversing effect. The electrocatalytic HER activity can be maximumly enhanced with low overpotentials of 78 mV (alkaline) and 89 mV (acidic) at a current density of 10 mA/cm2 and sustained at least 24 h especially for NiZn@C-CoP catalyst. This novel system is distinct from conventional three-layer heterostructure, providing a specially thought of d-band center control engineering strategy for the design of heterogeneous catalysts and expanding to other electrocatalysts, energy storage, sensing, and other applications.