High‐Pressure CO Electroreduction at Silver Produces Ethanol and Propanol

Abstract

Reducing CO2 to long‐chain carbon products is attractive considering such products are typically more valuable than shorter ones. However, the best electrocatalyst for making such products from CO2, copper, lacks selectivity. By studying alternate C2+ producing catalysts we can increase our mechanistic understanding, which is beneficial for improving catalyst performance. Therefore, we investigate CO reduction on silver, as density functional theory (DFT) results predict it to be good at forming ethanol. To address the current disagreement between DFT and experimental results (ethanol vs. no ethanol), we investigated CO reduction at higher surface coverage (by increasing pressure) to ascertain if desorption effects can explain the discrepancy. In terms of product trends, our results agree with the DFT‐proposed acetaldehyde‐like intermediate, yielding ethanol and propanol as C2+ products—making the CO2 electrochemistry of silver very similar to that of copper at sufficiently high coverage.

The presence and role of the intermediary CO reservoir in heterogeneous electroreduction of CO 2

“…This principle is also in line with a recent finding showing that even a Ag catalyst can improve its otherwise negligible selectivity towards C2+ products given a high enough CO pressure. 58 Taken these data, a key consideration in the development of catalysts moving forward should be increasing the COint density at lower overpotentials. Accordingly, the Cu NP ensemble reaches an adequate COint density at an overpotential 100 mV lower than the foil (Fig.…”

Enhancing CO2 electroreduction to CH4 over Cu nanoparticles supported on N-doped carbon

“…[25][26][27] However, it is still challenging to achieve high selectivity for CH 4 at a high current density. [28][29][30][31][32][33] This is because the generation of CH 4 involves eight electrons and four protons, which easily bifurcates to give broad product distributions. [34][35][36] According to a previous report, 37 the coadsorption of *CO and *H played an important role in the production of CH 4 , and the selectivity of CH 4 can be enhanced by a high surface *H coverage, due to sufficient *H supply for the hydrogenation of intermediates.…”

2022 roadmap on low temperature electrochemical CO2 reduction

“…Although OC-CO dimerization and HOC-CO coupling are accepted as C-C bond formation pathways for C 2 products, it is less clear how the additional C-C bond is made for the synthesis of propanol and other C 3 compounds. Recent work suggests carbonyl coupling as the most likely pathway [35,175] but more research is needed to exclude potential alternatives. Formation of butanol and C 4+ compounds are never reported with FEs better than 1% and therefore there are not many studies about the reaction mechanism for C 4+ compounds.…”

“…Also, we believe that are fundamental opportunities in high-temperature and high-pressure experiments. Such 'new' conditions would allow us to gain more knowledge about the mechanisms as new pathways may open up or current pathways appear applicable to new catalysts, such as for example C 2+ formation on Ag at high pressure [175]. Moreover, high-pressure and high-temperature experiments can bridge towards thermocatalytic CO 2 R, and may elucidate certain mechanisms that remain elusive in electrochemical CO 2 R, such as methanol synthesis.…”