Theoretical Investigation of Cu-Au Alloy for Carbon Dioxide Electroreduction: Cu/Au Ratio Determining C1/C2 Selectivity

Mechanism of surface oxygen-containing species promoted electrocatalytic CO2 reduction

Oxygen-containing species have been demonstrated to play a key role in facilitating electrocatalytic CO2 reduction (CO2RR), particularly in enhancing the selectivity towards multi-carbon (C2+) products. However, the underlying promotion mechanism is still under debate, which greatly limits the rational optimization of the catalytic performance of CO2RR. Herein, taking CO2 and O2 co-electrolysis over Cu as the prototype, we successfully clarified how O2 boosts CO2RR from a new perspective by employing comprehensive theoretical simulations. Our results demonstrated that O2 in feed gas can be rapidly reduced into *OH, leading to the partial oxidation of Cu surface under reduction conditions. Surface *OH accelerates the formation of quasi-specifically adsorbed K+ due to the electrostatic interaction between *OH and K+ ions, which significantly increases the concentration of K+ near the Cu surface. These quasi-specifically adsorbed K+ ions can not only lower the C-C coupling barriers but also promote the hydrogenation of CO2 to improve the CO yield rate, which are responsible for the remarkably enhanced efficiency of C2+ products. During the whole process, O2 co-electrolysis plays an indispensable role in stabilizing surface *OH. This mechanism can be also adopted to understand the effect of high pH of electrolyte and residual O in oxide-derived Cu (OD-Cu) on the catalytic efficiency towards C2+ products. Therefore, our work provides new insights into strategies for improving C2+ products on the Cu-based catalysts, i.e., maintaining partial oxidation of surface under reduction conditions.

Theoretical Insights into Enhancing Catalytic Performance of Al-Cu Alloy for CO2 Electroreduction toward Ethene Production

The understanding of the reaction mechanism of CO2 electroreduction (CO2RR) is essential for the precise design of catalysts for specific products with high selectivity. In this work, combined with the computational hydrogen electrode model and kinetic energy barrier calculations, CO2RR pathways on Cu(100) and Al1Cu3(100) are intensively investigated. The free energy barrier of the rate-determining step of ethylene formation is reduced from 1.08 eV for *CCOH formation on Cu(100) to 0.51 eV for *CH2OCHOH formation on Al1Cu3(100) and enhances the catalytic activity. The reaction free energy of *CO-*CO coupling is remarkably reduced from 0.86 eV on Cu(100) to -0.43 eV on Al1Cu3(100) and the coupling barrier is reduced from 0.97 to 0.37 eV, suppressing the production of gas phase CO and enhancing the production of C2 products. Furthermore, the selectivity toward C-O breaking of *CH2CHOH on Cu(100) and *CH2CH2OH on Al1Cu3(100) ensures high selectivity toward ethene rather than ethanol.

Research Progress of Copper-Based Bimetallic Electrocatalytic Reduction of CO2

Fossil fuels are still the main source of energy in today’s society, so emissions of CO2 are inevitable, but when the CO2 level in the atmosphere is too high, many environmental problems will arise, such as the greenhouse effect, among others. Electrocatalytic reduction of CO2 is one of the most important methods that one can use to reduce the amount of CO2 in the atmosphere. This paper reviews bimetallic catalysts prepared on the basis of copper materials, such as Ag, Au, Zn and Ni. The effects of different ratios of metal atoms in the bimetallic catalysts on the selectivity of CO2RR were investigated and the effects of bimetallic catalysts on the CO2RR of different ligands were also analysed. Finally, this paper points out that the real reaction of CO2RR still needs to be studied and analysed, and the effect of the specific reaction environment on selectivity has not been thoroughly studied. This article also describes some of the problems encountered so far.