Electrochemical CO2 reduction (CO2RR) driven by renewable electricity is an effective way to produce high value-added fuels. Among the various products, multi-carbon products (C2+) are favored due to their high energy density. However, severe hydrogen evolution during the reaction significantly reduces the coverage of *Co intermediates, thereby reducing the chance of C-C coupling. Manipulating the electrode-electrolyte interface microenvironment is an effective way to inhibit HER activity and improve C2+ selectivity. A large number of studies have shown that the regulation of the microenvironment, especially hydrophobicity, can help to achieve this goal. However, aquifer modification always triggers a combined effect: the reduction in water availability not only inhibits the activity of HER, but also affects the process of the proton-electrical coupling step in CO2RR. Therefore, it is necessary to deeply understand and precisely regulate the hydrophobic microenvironment at the molecular level.
Recently,Xiao Chunhui, Xi'an Jiaotong UniversityThrough electrochemical in-situ vibrational spectroscopy combined with molecular dynamics simulation, the research group used a polydimethylsiloxane-modified copper catalyst (PDMS) with controllable thickness as a model catalyst to study the dynamic change of water structure at the surface interface of charged and phobic electrodes, and further improved the mechanism of inhibiting electrode activity and improving the selectivity of multi-carbon products. The results show that there is a strong hydrogen bonding interaction between the interfacial water molecules near the surface of the hydrophobic electrode, and the strength of the hydrogen bonding interaction increases with the increase of bias pressure. Strong intermolecular hydrogen bonding makes reorientation of water molecules difficult, resulting in longer distances between metal and hydrogen, inhibiting the dissociation of water molecules, and reducing the coverage of *h.
Moderate *H coverage can not only inhibit the hydrogen evolution reaction, but also promote the C-C dimerization reaction through the hydrogenation reaction of the intermediates. Thus, the selectivity of the modified Cu(111)@pdms catalyst for H2 was significantly inhibited, from 218% down to 104%；At -0The Faraday efficiency (Fe) of C2H4, CH3CH2OH and CH3COOH at 98 VRHE were respectively. 2% and 128%, in -1The current density of the C2+ moiety at 08 VRHE is as high as -135 mA cm-2, which is better than that of the unmodified Cu (111) catalyst. In addition, the Fe content of C2+ remained above 60% after continuous electrolysis for 8 h, which proved that the catalyst @pdms Cu (111) had good stability. In conclusion, this study proves that the hydrogen bond structure of interfacial water plays an important role in the CO2RR reaction, which provides a theoretical basis for precise control of reaction selectivity.
strong hydrogen-bonded interfacial water inhibiting hydrogen evolution kinetics to promote electrochemical co2 reduction to c2+. acs catalysis, 2024. doi: 10.1021/acscatal.3c05880