Khagesh Kumar1,Alireza Ahmadiparidari1,Amin Salehi-Khojin1,Jordi Cabana1
University of Illinois at Chicago1
Khagesh Kumar1,Alireza Ahmadiparidari1,Amin Salehi-Khojin1,Jordi Cabana1
University of Illinois at Chicago1
Electrocatalytic reactions offer alternative routes for the conversion and storage of energy. For instance, the electrocatalytic reduction of carbon dioxide could lead to energy-rich syngas, methanol, or even hydrocarbons. Layered transition metal dichalcogenide nanomaterials, such as MoS<sub>2,</sub> WSe<sub>2</sub>, have emerged as electrocatalysts towards CO<sub>2</sub> reduction with high efficiency and low overpotentials [1]. However, the underlying chemical and electronic states defining the catalytic activity have not yet been completely defined. These key states can be probed for both metals and ligands in selected MX<sub>2</sub> (M=W, Mo, W; X=S, Se) using synchrotron-based X-ray absorption spectroscopy (XAS). Metal <i>d</i>-states are said to be the active states for catalysis and studying ligand K- pre-edge gives insight into active metal <i>d</i> states as pre-edge reflects a transition to metal-ligand hybridized orbitals [2]. <i>In-situ/operando</i> XAS characterization technique offers an opportunity to probe changes in the electronic and chemical states during active conditions.<br/>In recent work, we performed <i>in-situ/Operando</i> HERFD-XAS measurements at Se K-edge for MSe<sub>2</sub> (M= W, Mo) nanosheets. HERFD gives more spectral resolution than conventional partial fluorescence yield measurement, which helps track small electronic and chemical structures changes [3]. Measurements at Se K-edge showed changes at the pre-edge and edge, indicating changes in the number of available occupied states and Z<sub>eff</sub>. Given the vast compositional space of metal and ligand for MX<sub>2</sub>, the knowledge of how <i>d</i>-state activity will serve to pave the way to a better study of metal and chalcogenide combinations to improve the electrocatalytic performance.<br/><br/><br/><b>References</b><br/>[1] Science, <b>2016</b>, 353, 467–470<br/>[2] Nano Energy, <b>2020</b>, 71, 104601<br/>[3] Journal of the American Chemical Society, <b>2019</b>, 141, 13676–13688