The coupling of renewable energies to produce hydrogen by electrolysis of water is an effective way to develop new energy uses and solve the energy crisis. It is important to fully understand the mechanism of the cathodic hydrogen evolution reaction (HER). Compared to the fast kinetics under acidic conditions, the kinetics under alkaline conditions are two orders of magnitude slower, indicating that the reaction mechanism becomes more complicated than under acidic conditions. Therefore, a thorough descriptor-based understanding of the HER mechanism under alkaline conditions is of practical importance to improve HER activity.
Researchers from Chongqing University stated that “water molecules act as solvents in catalyzing HER in acid, while water molecules play a dual role in catalyzing HER in alkaline, i.e. i.e. reagent and solvent”. Based on their research and knowledge in the field of HER, the researchers focused on the contribution of water molecules to HER, summarized the development of the HER activity descriptor over the past decade and provided their understanding of how water molecules affect kinetics. and the dynamics of ELLE. For example, the commonly used activity descriptor, hydrogen bonding energy, can refer to alkaline HER activity after being corrected by water adsorption energy. The dissociation of water involved the bonding of hydroxide and OH– and cation adsorption have been recognized as descriptors of HER. Additionally, interfacial water is highlighted as a crucial factor affecting pH-dependent HER activity, and it can be deliberately enriched and redirected to dramatically improve HER kinetics.
The review article was recently published in SCIENCE CHINA Chemistry. The work is led by the head of the materials chemistry and new energy chemical engineering group, Zidong Wei. Chao Cheng and Mingming Deng are the first authors. The group has spent years researching the underlying mechanism of electrocatalysis, designing new high-performance electrocatalysts, thereby improving the conversion efficiency between matter and energy in the field of new energies, including water electrolysis, fuel cells, etc. Al.
Water molecule as reactant in HER
The researchers said, “Water molecules are the few molecules that can penetrate the depth of the electrode/electrolyte interface due to a strong interaction between the charged electrode and the water dipole.” And “In neutral and alkaline solutions, water acts as a reagent to provide the source of hydrogen evolution. The continuous HER will be suppressed if water is weakly adsorbed on the catalyst surface and is not supplied as timely.”
The role of interfacial water in the catalysis of HER
“Interfacial water configuration and dynamic process are of great importance in determining the HER performance of catalysts,” Zidong Wei said. And he further pointed out that “Based on our previous studies, we concluded that the electric field at the electrode/solution interface can regulate interfacial water activation enrichment, reorientation, and dissociation, thus promoting the coupling of the elementary steps of HER and the improvement of its reaction dynamics in the high polarization region, and this coupling mechanism is also universal.
See the article:
The contribution of water molecules to the hydrogen evolution reaction
https://doi.org/10.1007/s11426-022-1371-x
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Science China Chemistry
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