学 术 报 告
Revealing Carbon Dioxide Adsorption and Activation on Metal Catalysts by Ambient Pressure X-ray Photoelectron Spectroscopy
Dr. Ye Yifan
Lawrence Berkeley National Laboratory
Converting carbon dioxide (CO2) into liquid fuels and synthesis gas is a national priority. But there is no experimental information on the initial atomic level events for CO2 reduction on the metal catalysts to provide the basis for developing improved catalysts. In order to provide this experimental information, we used ambient pressure X-ray photoelectron spectroscopy (APXPS) to examine the processes as metal catalyst surfaces exposed to CO2 both alone and in the presence of H2O at 298K, the results of which we correlated with quantum mechanics density to provide definitive interpretations.
We first investigated the interaction between CO2 (+H2O) with the Ag surface. On Ag we found very different gas adsorption and activation process compared to that on Cu. We found that physisorbed(l-) and chemisorbed (b-) CO2 are not stable on pure Ag surface, but rather gaseous CO2 reacts with absorbed O on Ag surface to form a chemisorbed surface species (O=CO2δ−). Adding H2O and CO2 then leads to up to four water attaching on (O=CO2δ−) and two water attaching onto b-CO2 on the surface. We then also monitored the interaction between CO2 (+H2O) with the bimetallic AgCu surface and found a totally different adsorption and activation process compared to those on both Ag and Cu. We discovered how the chemistry and population of adsorbed species depends on the thermodynamics and surface kinetics of AgCu surface alloy. In particular, we find that adsorption of CO2 and surface O induce subsurface Cu to migrate to the surface, modifying the stability and activation of CO2 related chemisorbed species. Each metal surface modifies both the chemical speciation and the respective adsorption energies, thus providing a new basis for tuning CO2 adsorption behavior to facilitate selective product formations.
Yifan Ye got his bachelor degree of physical chemistry from University of Science and Technology of China at 2011. Then he got his PhD degree of Nuclear technology and science from University of Science and Technology of China at 2016 under the supervision of Prof. Junfa Zhu. During pursing for PhD degree, he visited Advanced Light Source, Lawrence Berkeley National Lab as a visit student from 2013 to 2016. After graduating, he continued his researches at Lawrence Berkeley National Lab as a joint postdoc in Advanced Light Source and Joint Center for Artificial Photosynthesis.
He has a particular interest in studying the solid/gas, solid/liquid, and solid/solid interfaces of energy storage and conversion materials such as fuel cells, electrolyzers, catalysts, and batteries using in-situ soft and hard X-ray absorption/emission spectroscopy, and soft and tender Ambient Pressure X-ray Photoelectron Spectroscopy. Now, he has published more than 40 papers on peer-review journals, including Science, Nature Communication, JACS, etc.