Periodic Reporting for period 2 - NANOMXM (Nanoscale Chemical Imaging of MXene Electrochemical Storage by Operando Scanning X-ray Microscopy)
Período documentado: 2022-08-01 hasta 2024-01-31
Finding efficient ways to store and deliver electrical energy is urgently needed for the large-scale development of renewable energy sources. The use of pseudocapacitive materials, such as 2D transition metal carbides and nitrides, so-called MXenes, is an extremely promising solution to achieve electrochemical energy storage with high power and energy densities, benefiting from fast redox reactions on transition metal oxides. Such materials may allow the development of new electrical devices with reduced charging times despite keeping a high amount of stored energy. Nevertheless, local electrochemical processes occurring at the solid-liquid interface of pseudocapacitors are currently largely unexplored. The goal of this project is to image for the first time electrochemical processes occurring during pseudocapacitive electrochemical storage on MXenes at the nanoscale with operando Scanning Transmission X-ray microscopy (STXM). This will allow a better understanding of pseudocapacitive electrochemical energy storage that will enable the discovery of new 2D materials enabling ultrafast electrochemical energy storage devices.
First operando experiments performed by infrared spectroscopy have evidenced that the confinement of the electrolyte between the MXene layers may play a significant role in the superior electrochemical performances of Ti3C2Tx MXenes in acidic environment and water-in-salt electrolytes. Furthermore, first MXenes materials were images using STXM at the synchrotron BESSY II. We also developed a custom electrochemical flow cell enabling STXM characterization of MXene in aqueous environment. Change of the titanium electronic structure in Ti3C2Tx MXenes single few-layered flakes was evidenced upon cation intercalation for the first time.
Using both infrared spectroscopy and STXM, we have achieved spectroscopic identification of changes of both MXenes and the electrolyte during electrochemical cycling. These results have especially enabled to prove that the confined electrolyte within the MXene interlayer have a different structure than bulk electrolyte, which may play a significant role in pseudocapacitive energy storage. Furthermore, we have achieved major breakthroughs in operando STXM by being able to image single MXene layers directly in acidic and neutral aqueous electrolytes. I anticipate that by the end of the project, we will have unravelled how intercalated ion do interact with the MXene surface chemistry. We may also discover how defects in MXene facilitate hydrolysis and other MXene degradation mechanisms in aqueous environment.