Grain Boundary—A Route to Enhance Electrocatalytic Activity for Hydrogen Evolution Reaction

Abstract

The electrocatalytic hydrogen evolution reaction (HER) of a given metal catalyst is intrinsically related to its electronic structure, which is difficult to alter for further improvement. Recently, it was discovered that the density of grain boundaries (GBs) is mechanistically of great importance for catalytic activity, implying that GBs are quantitatively correlated with the active sites in the HER. Here, by modeling the atomistic structure of GBs on a Au(110) surface, we find that HER performance is greatly enhanced by Au GBs, suggesting the feasibility of the HER mediated by GBs. The promoted HER performance is due to an increase in the capability of binding adsorbed hydrogen on the sites around GBs. A Au catalyst with a dominantly exposed (110) plane is synthesized, where considerable GBs exist for experimental verification. It is found that HER activity is inherently correlated with the density of the GBs in Au NPs. The improvement in HER activity can be elucidated from the geometrical and electronic points of view; the broken local spatial symmetry near a GB causes a decrease in the coordination numbers of the surface sites and the shift up of the d–band center, thereby reducing the limiting potential for each proton−electron transfer step. Our finding represents a promising means to further improve the HER activity of a catalyst.

Grain Boundary-Rich Tungsten Carbide Nanoparticle Films Exhibit High Intrinsic Activity Toward Hydrogen Evolution

“…These TOFs were orders of magnitude higher than previously reported TOFs for tungsten carbides reported in the literature (Table ). This can be attributed to the high density of grain boundaries in the WC films. − The disordered atomic arrangement at the grain boundaries causes symmetry breaking, altering of the electronic structure, and an increase in the d z 2 orbital energy level of W. ,, In hydrogen evolution, the adsorption strength of H atoms on the W surface (σ bond between H 1s and W d z 2 ) determines the electrocatalytic activity based on Sabatier’s principle. The WC samples with a high density of GBs and more efficient active sites (optimized Δ G H* ) led to the high intrinsic activity (based on TOF).…”

“…This can be attributed to the high density of grain boundaries in the WC films. 43−46 The disordered atomic arrangement at the grain boundaries causes symmetry breaking, altering of the electronic structure, and an increase in the d z 2 orbital energy level of W. 43,47,48 In hydrogen evolution, the adsorption strength of H atoms on the W surface (σ bond between H 1s and W d z…”

Hydrogen Evolution Reaction on Ultra-Smooth Sputtered Nanocrystalline Ni Thin Films in Alkaline Media—From Intrinsic Activity to the Effects of Surface Oxidation

“…The TEM bright-field image shows a contrast sensitive to the grain orientations and therefore reveals that the synthesized Ni thin films are nanocrystalline with an estimated mean grain size of ~9 nm. This small grain size and, therefore, high density of grain boundaries (GBs) has already been found to potentially have a positive influence on the catalytic activity towards HER [ 36 , 37 ]. It was shown in a combined DFT and experimental study by Jiang et al that the GBs efficiently affect the activity of Au catalysts.…”

“…It was shown in a combined DFT and experimental study by Jiang et al that the GBs efficiently affect the activity of Au catalysts. As a consequence, it is concluded that a high density of GBs can be traced to an increased ability to adsorb hydrogen and stabilize H* during the reaction steps [ 37 ]. The accompanying selected area electron diffraction (SAED) pattern and the corresponding profile obtained by azimuthal integration [ 38 ] confirm the polycrystalline fcc structure of the sputter-deposited film ( Figure 1 a).…”

Low-Carbon Water Treatment and Energy Recovery

“…found that HER activity is inherently correlated with the density of the GBs in Au NPs, where active sites bind H 2 more strongly [3]. Their finding holds promise for enhancing the catalyst's HER performance.…”