Abstract
Hydrogen has been considered as the cleanest renewable energy and the ideal alternative to fossil fuels. Electrocatalytic Hydrogen Evolution Reaction (HER) via water splitting also plays an indispensable role in high-efficiency energy con- version. Compared with the well-investigated acidic HER, the relatively slow kinetics and unclear mechanism of HER in alkaline environments largely make the design of electrocatalysts a trial-and-error process, retarding the scalable development of efficient, sustainable hydrogen production. Furthermore, two-dimensional transition metal dichalcogenides (2D TMDs) have been demonstrated to be promising acidic/ alkaline HER catalysts in water electrolysis due to their outstanding atom-level thickness and surface-based properties.
Highlights
In the 21st century, in order to reduce the reliance on less cleaning and non-renewable energy such as fossil fuels, hydrogen has been gradually widely developed as an ideal, eco- friendly source due to its high energy density and nontoxicity[1][2]
Its performance depends primarily on the catalytic reactivity of anode electrode materials as electrocatalysts[4][5]. It is of great impor- tance to explore further two questions: How do electrolyte solutions affect the Hydrogen Evolution Reaction (HER) activity and kinetics? What is the relationship between the electrocatalyst nanostructures and electroca- talytic performance?
hydrogen binding energy (HBE) is reckoned to be correlated with HER kinetics, as change of hydrogen underpotential adsorption/desorption (Hupd) peak positions is related to H2 production rates
Summary
In the 21st century, in order to reduce the reliance on less cleaning and non-renewable energy such as fossil fuels, hydrogen has been gradually widely developed as an ideal, eco- friendly source due to its high energy density and nontoxicity[1][2]. The outline of 2D TMDs is highlighted to signify the structure-, surface- and morphology-related roles for connections with key activity descriptors of alkaline hydrogen generation More importantly, this systematic knowledge is extended to a broader level, which entails the design rules of practically well-defined electrocatalysts by discussing the correlations between the nanostructures of TMDs and the contributions of active sites. Besides the demonstration of a strikingly weakened HER activity in alkali, the increasing pH up to pH=4 presents a pure diffusion limiting current different from the typical polarisation profile, revealing the characteristic change of metallic surfacespecific electrode potential This discovery signifies the key influential factors of HER. When the electrolyte solutions become neutral or alkaline, the polarisation processes behind the current-potential curves of different electrocatalysts are clearly free from the change of pH values, indicating that currents is intimately related to pH-independent transformation from water to hydrogen molecules[19][20]
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