Operando Raman Spectroscopy Reveals Mechanism for Converting Carbon Dioxide to Ethanol on Ag Nanowires

Recently, researchers from the School of Chemistry at Zhejiang University and the College of Chemistry and Chemical Engineering at Xiamen University used operando Raman spectroscopy to investigate the conversion of carbon dioxide (CO₂) to ethanol on Ag nanowires (NWs) (1). The study, published in Science China Chemistry, found that partially oxidized Ag NWs demonstrated high ethanol selectivity for CO₂ electroreduction (1).

To understand the significance of the study, it is important to first understand what operando Raman spectroscopy is. Operando Raman spectroscopy is a technique that combines Raman spectroscopy with other analytical tools to study chemical reactions as they occur in real time under a set of operating conditions. This technique helps identify reaction intermediates and monitors catalyst performance (1).

To conduct the experiment, the researchers used an Xplora Raman spectrometer with a 50x microscope objective and a 638-nm excitation wavelength from a He–Ne laser (1). The analysis revealed that proper adsorption energy of CO on the partially oxidized Ag NWs was noticeable in correlating the high ethanol selectivity for CO₂ electroreduction with the partially oxidized active center (1).

Ag catalysts are known to exhibit high selectivity for CO₂ electroreduction to CO at low overpotentials with depressed hydrogen evolution, which is promising for ethanol production by tuning the adsorption energy of CO (1). This study provides new insights to design efficient catalysts and investigate mechanisms to improve selectivity (1).

Interestingly, the study found that high ethanol Faradaic efficiency (FE) was obtained on partially oxidized Ag NWs for CO₂ electroreduction, and operando EC-SERS combined with density functional theory (DFT) calculation explained the mechanisms behind the high ethanol selectivity (1). The ethanol FE reached as high as 85% on partially oxidized Ag NWs at −0.95 V (1).

High coverage of CO greatly facilitated ethanol formation on partially oxidized Ag NWs during CO₂ electroreduction (1). DFT calculation results showed that the adsorption energy of CO on the partially oxidized Ag NWs was higher than that on Cu (1). The reaction free energy of CO coupling with *CHO to *COCHO intermediate on partially oxidized Ag NWs was smaller than that on Cu surface, explaining the high ethanol selectivity (1).

DFT is a computational method used to study the electronic properties and behavior of molecules and materials. It allows for the calculation of properties such as energy, structure, and electronic density (1). DFT is based on the idea that the total energy of a system can be expressed as a functional of the electron density, making it a powerful tool in the field of theoretical chemistry and materials science (1).

The study shows that partially oxidized Ag NWs can provide high ethanol selectivity for CO₂ electroreduction (1). The findings provide new clues for designing Ag-based catalysts to improve ethanol selectivity and mechanism studies (1).

Reference

(1) Science China Press, Using Operando Raman spectroscopy to Investigate Converting Carbon Dioxide to Ethanol on Ag Nanowires. https://phys.org/news/2023-03-operando-raman-spectroscopy-carbon-dioxide.html (accessed 2023-04-05).