(Invited) Electrocatalysis of CO2 Reduction. from Fundamental Understanding to Catalyst Design and Preparation

Abstract

Electrocatalytic reduction of CO2 is of significance in environment for reducing greenhouse gas level, in carbon recycling and sustainable energy storage when CO2 is reduced into hydrocarbon fuels and other chemicals. The big challenge in electrocatalysis of CO2 reduction consists in the high energy barrier to activate the O=C=O band and the broad distribution of products. Therefore, the key issue is design and preparation of electrocatalysts with high catalytic activity and selectivity. In recent years, we have conducted investigations of electrocatalysis of CO2 reduction in the following three aspects: (1) Using Pt single crystal planes (Pt(hkl)) as model catalysts to gain knowledge about the surface structure-catalytic functionality of CO2 reduction. In situ FTIR spectroscopy determined that the main CO2 reduction product on Pt(hkl) electrodes is CO, while the kinetics of the CO2 reduction depends on the surface atomic arrangements. It has revealed that the catalytic active centers for CO2 reduction consist of few atoms (5-6) of low coordination number (steps, kinks) in stereo structure; (2) Investigation of electrocatalytic reduction of CO2 on a series Cu-based electrodes, including Cu tetrahexahedral nanocrystals bounded by {530} high-index facets prepared through electrochemically shape-controlled synthesis, polycrystalline Cu and oxide-derived Cu electrodes decorated with Zn, Ni and Au. The CO2 reduction products were determined by using mainly NMR. It has found that the decoration of Ni on oxide-derived Cu exhibited the highest catalytic activity for CO2 reduction, evidenced by significant increase in Faraday efficiency for yielding formic acid, ethanol, and n-propanol. At -1.5 V, the Faraday efficiency are respectively 30%, 1.6% and 2.7% for formic acid, ethanol and n-propanol on Ni decorated oxide-derived Cu, while the values are 8.3%, 1.2%, and 1.6% on Zn modified surface, 20.5%, 0.2%, and 0% on Au modified surface, and 20.9%, 0.8%, and 1.0% on the bare oxide-derived Cu surface. The promotion may mainly come from the stronger adsorption of intermediate CO* on Ni decorated surface than on Cu, which facilitates further the reduction of CO* with optimized hydrogen adsorption on Ni; (3) DFT calculations of electrocatalytic reduction of CO2 through the development of methods for accurately modelling the electrochemical interface by using a liquid water/solid interface model with a number of explicit water molecules combining with ab initio molecular dynamics simulations. In this study, Cu(100) was used as model catalyst, the results revealed different intermediates and pathways involved in CO2 reduction and provided a detail description of the reaction mechanism and kinetics. Acknowledgements: The study was supported by NSFC (21573183, 21229301, 21321062).