Researchers Find Therate-determining Step on Common Copper Surfaces Change in Carbon Dioxide Electroreduction
A research team led by Prof. GAO Minrui from University of Science and Technology of China (USTC) of Chense Academy of Sciences (CAS) found that the rate-determining steps (RDS) on common copper (Cu) surfaces differ in carbon dioxide (CO2) electroreduction, resulting in distinct catalytic performance. The study was published in the Proceedings of the National Academy of Sciences (PNAS).
RDS in the CO2 to ethylene conversion process （Image by GAO et al.）
Electrochemically converting CO2 to ethylene (C2H4) using renewable electricity is crucial for advancing China’s carbon resource conversion and achieving the carbon peaking and carbon neutrality goals. However, insufficient Faradaic efficiency, low production rates, and complex mechanistic pathways hinder the use of green electricity for producing multi-carbon chemicals from CO2.
The researchers employed a plasma treatment strategy to form oxygen vacancies on CuO nanosheets, which modulate the density of states near the Fermi level and result in a lower work function. Density functional theory (DFT) calculations predicted that the presence of oxygen vacancies favors *CO adsorption and promotes the formation of Cu (100), whereas CuO without oxygen vacancies tends to form the energetically more stable Cu (111) facet.
Electron microscopy results showed that the plasma-treated CuO well inherited the sheet-like morphology of the original o-CuO catalyst. High-resolution transmission electron microscopy (HRTEM) and electrochemical OH- adsorption experiments confirmed that the surfaces of the two catalysts predominantly exposed Cu (100) and Cu (111) facets, respectively.
Performance evaluations of the catalysts in both flow cell and membrane electrode assembly systems showed that at 500 mA/cm-², oxide-derived Cu (100)-dominant Cu catalyst attained a C2H4 FE of 72%, significantly higher than that of the Cu (111) facet-dominant catalyst.
In situ spectroscopic studies and electrokinetic experiments indicated that the C2H4 formation pathways differed on catalysts with different dominant facets. For the Cu (100) facet-dominant catalyst, the RDS was the bonding of two *CO molecules, whereas for the Cu (111) facet-dominant catalyst, the RDS was the protonation coupling of *CO with H2O.
The study will shed lights on how to mitigate greenhouse gas emissions and how to synthesize high-value C2H4, contributing to the environmental protection.
Paper link: https://doi.org/10.1073/pnas.2400546121
(Written by LI Rui, edited by HUANG Rui, USTC News Center)
