Design Superior Alkaline Hydrogen Evolution Electrocatalyst by Engineering Dual Active Sites for Water Dissociation and Hydrogen Desorption

Abstract

In alkaline media, the water-dissociation-related Volmer process always suppresses the hydrogen formation/ desorption process, which makes it challenging to develop non-noble-metal alkaline electrocatalysts with excellent catalytic activity. Here, we proposed a two-pronged strategy to simultaneously promote the kinetic process of both water dissociation and hydrogen desorption with the Co-doped WO 2 /amorphous Co x W hybrid electrocatalyst. Impressively, the optimized hybrid exhibits an outstanding hydrogen evolution reaction (HER) activity with the quite small Tafel slope of 19.77 mV dec −1 and ultralow overpotential of just 25 mV to reach a current density of 10 mA cm −2 in alkaline media. Both experiments and density functional theory calculations reveal that the top-level HER performance can be attributed to the cooperation of two different active components, in which the water molecule can easily be activated on the amorphous Co x W with low energy barrier (ΔG w = 0.46 eV), while hydrogen atoms can rapidly desorb from the Co-doped WO 2 with an optimal Gibbs free energy of hydrogen adsorption (ΔG H* = −0.06 eV). Also, the density functional theory calculation further confirms that the H* tends to combine with another H* via Tafel step rather than Heyrovsky step. The findings provide unique insights for the development of the state-of-the-art non-noble-metal HER electrocatalyst with a Pt-like kinetic behavior in alkaline media.

Ultralow Pt Catalyst Loading Prepared by the Electroreduction of a Supramolecular Assembly for the Hydrogen Evolution Reaction

“…We obtained exchange current density 38 by the combination of the simplified Butler−Volmer equation and eq 2 (2) where R is the ideal gas constant, α is the transfer coefficient, F is the Faraday constant, n is the number of electrons transferred, j 0 is the exchange current density, and j is the kinetic current density. The Tafel slope 39 was obtained from the polarization curve using the Tafel equation3 (3) where η is overpotential, a is the intercept, b is the Tafel slope, and j is the current density.…”

In Situ Integrated Co3W−WN Hybrid Nanostructure as an Efficient Bifunctional Electrocatalyst by Accelerating Water Dissociation and Enhancing Oxygen Evolution

“…As shown in Figure 3a and 3b, after removing the Co 3 W alloys, the overpotential at current density of 10 mA cm −2 and Tafel slope of it increase to 90 mV and 114.43 mV dec −1 , respectively, which means Co 3 W alloys play an important role in accelerating the HER kinetic process. Density functional theory (DFT) calculation in previous report has shown that cobalt tungsten alloy has a water dissociation energy barrier of 0.46 eV, closing to 0.44 eV of Pt (110), which could effectively accelerate the water dissociation process of HER in alkaline solution [33] . As widely accepted, Tafel slopes of 120, 40 and 30 mV dec −1 are corresponding to the Volmer, Heyrovsky and Tafel determining rate steps, respectively [34] .…”

Designing Self-Supported Electrocatalysts for Electrochemical Water Splitting: Surface/Interface Engineering toward Enhanced Electrocatalytic Performance

“…The catalytic activity thereby can be remarkably promoted by effectively integrating the multiple advantages of each component. 33 A novel Ni(OH) 2 /MoS 2 hybrid was developed as active electrocatalysts for HER catalysis in an alkaline solution. 171 The Ni(OH) 2 /MoS 2 electrocatalyst exhibited enhanced electrocatalytic activity with an onset overpotential of 20 mV, and a Tafel slope of 60 mV dec −1 .…”

“…This phenomenon is perceived as synergistic effect. , For example, different components exhibit specific activity for different elementary steps of reactions. The catalytic activity thereby can be remarkably promoted by effectively integrating the multiple advantages of each component …”

“…Schematic illustration of interface/surface engineering strategies with various effective approaches for high-performance HER/OER electrocatalysts. [Reprinted with permission from refs (Copyright 2018, Elsevier), (Copyright 2017, American Chemical Society, Washington, DC), (Copyright 2013, American Chemical Society, Washington, DC), (Copyright 2020, American Chemical Society, Washington, DC), (Copyright 2020, The Royal Society of Chemistry, London), (Copyright 2019, American Chemical Society, Washington, DC), (Copyright 2018, American Chemical Society, Washington, DC), (Copyright 2020, Wiley–VCH, Weinheim, Germany), (Copyright 2019, American Chemical Society, Washington, DC), (Copyright 2015, American Chemical Society, Washington, DC), (Copyright 2015, American Chemical Society, Washington, DC), (Copyright 2020, Elsevier), (Copyright 2019, Wiley–VCH, Weinheim, Germany), (Copyright 2019, American Chemical Society, Washington, DC), and (Copyright 2019, Cell Press). ]…”