Guillaume Goubert
Guillaume Goubert is a professor in the Chemistry Department of the Université du Québec à Montréal (UQAM) since 2020. Prior to that, he was a senior scientist at the Swiss Federal Institute of Technology (Eidgenössische Technische Hochschule, ETH), in Zurich, with the group of professor Renato Zenobi. Pr. Goubert obtained his PhD degree at Université Laval and carried out postdoctoral studies at the Northwestern University in Illinois, United States. He is also a member of the Center of research on nanomaterials and energy (NanoQAM).
Structure and activity of MXene single flakes - following electrocatalysts in situ
The success of new energy storage solutions depends on finding and optimizing materials and electrochemical interfaces. We need to find electroactive materials that are effective at accelerating reactions or at storing large amount of charge at their surface while containing only widely available elements.
MXenes are 2D transition metal carbides, common examples include Ti3C2 , Mo2C and Nb2C. The surface chemistry of MXenes is rich and the presence of surface terminations (-O, -OH, -F…) on metal sites has a strong effect on their electrochemical properties. MXenes are considered for different applications, including supercapacitors and electrocatalysts, where the surface properties of MXene flakes are of great importance for successful application of the material.
Nanoscale methods are key to understanding the properties of single flakes of 2D materials such as MXenes, in particular the presence of defect or active sites. We focus our work on the study of single flakes of Ti3C2 at the nanoscale with tip enhanced Raman spectroscopy (TERS). TERS will allow us to interrogate the distribution of terminations on the surface of MXenes and establish the presence of zones with special composition, such as defects or edge sites.
We have synthesized Ti3C2 using different etching conditions, harsh with concentrated HF or milder with lower concentration of acid. It is known that harsher etching conditions lead to less active catalyst for the HER.
Although TERS can reveal the nanoscale structure, it does not measure the local activity of the catalyst. We also use scanning electrochemical cell microscopy (SECCM) to study single flakes of Ti3C2 . Our results show variations in activity on different flakes. We also observe two different types of response in the oxidation signal of flakes (at -0.3V and - 0.1 V vs Ag/AgCl), in agreement with the macroscopic response of delaminated Ti3C2 measured in supercapacitor experiments. These redox events are usually assigned to a Ti- O + H+ + e- → Ti-OH reaction. Our single flake measurements using SECCM show different flakes present different redox behavior.
Combined, our single flake measurements using TERS and SECCM provide advanced knowledge of MXene, its structure and its activity for catalysis.