Heterostructures for Electrochemical Hydrogen Evolution Reaction: A Review

Abstract

Developing sustainable and renewable energy sources along with efficient energy storage and conversion technologies is vital to address environmental and energy challenges. Electrochemical water splitting coupling with gridscale renewable energy harvesting technologies is becoming one of the most promising approaches. Besides, hydrogen with the highest mass-energy density of any fuel is regarded as the ultimate clean energy carrier. The realization of practical water splitting depends heavily on the development of low-cost, highly active, and durable catalysts for hydrogen evolution reactions (HERs) and oxygen evolution reactions (OERs). Recently, heterostructured catalysts, which are generally composed of electrochemical active materials and various functional additives, have demonstrated extraordinary electrocatalytic performance toward HER and OER, and particularly a number of precious-metalfree heterostructures delivered comparable activity with precious-metal-based catalysts. Herein, an overview is presented of recent research progress on heterostructured HER catalysts. It starts with summarizing the fundamentals of HER and approaches for evaluating HER activity. Then, the design and synthesis of heterostructures, electrochemical performance, and the related mechanisms for performance enhancement are discussed. Finally, the future opportunities and challenges are highlighted for the development of heterostructured HER catalysts from the points of view of both fundamental understandings and practical applications.

Construction of CoP/NiCoP Nanotadpoles Heterojunction Interface for Wide pH Hydrogen Evolution Electrocatalysis and Supercapacitor

“…X-ray absorption near-edge structure (XANES) of Ni K-edge (Figure 3a) and Co K-edge ( Figure 3b) suggest that the valence of Ni in CoP/NiCoP NTs is higher than that of Ni foil, but lower than that of NiCoP and NiO, and the valence of Co in CoP/NiCoP NTs is higher than that of CoP and NiCoP, but lower than that of CoO and Co 3 O 4 . [16] We also employed Fourier-transformed (FT) k 3 -weighted extended X-ray absorption fine structure (EXAFS) spectroscopy, with R-space of Ni foil, NiO, Ni 2 P, Co Adv. [16] We also employed Fourier-transformed (FT) k 3 -weighted extended X-ray absorption fine structure (EXAFS) spectroscopy, with R-space of Ni foil, NiO, Ni 2 P, Co Adv.…”

“…It was found that water dissociation is the key step, and even may determine the overall reaction rate for HER process in alkaline. [35][36][37] However, it is uneconomical and environmental unfriendly to conduct water electrolysis in either extremely acidic or alkaline solutions, [16] and we went on to explore whether this catalyst is also effective under other pH conditions. [34] With the cooperation between Ni and Co, the heterostructured catalyst displays an improved catalytic activity.…”

“…This is due to the upshift of d-band center of H* capture sites from the Fermi level after elimination of terminal P atoms (Figure 7b). [16,43] So the H 2 O adsorption energy (∆E H2O ) was further calculated. Bader charge analysis results reveal that the average valence charge of surface P atoms in NiCoP decreases from −0.32 to −0.33 after the introduction of Co atoms (the negative Bader charge corresponds to electronic accumulation), in agreement with XPS results above.…”

“…[16] However, there is still a lack of effective fabrication strategy to design heterostructures possessing particular morphology or facet for improving the accessibility of active interfaces. [16] However, there is still a lack of effective fabrication strategy to design heterostructures possessing particular morphology or facet for improving the accessibility of active interfaces.…”

Reversing Interfacial Catalysis of Ambipolar WSe2 Single Crystal

“…[11] Therefore, the Volmer reaction is the key step in HER and it is strongly dependent on the electron transfer, the density of active sites, and the Gibbs free energy of adsorbed atomic hydrogen. [11] Therefore, the Volmer reaction is the key step in HER and it is strongly dependent on the electron transfer, the density of active sites, and the Gibbs free energy of adsorbed atomic hydrogen.…”