XMCD analysis for spin polarization effect in cobalt-doped molybdenum disulfide

The control of the electron spin state of catalysts to accelerate electrocatalytic activity is a topic of major current interest. In particular, magnetic fields can be used as a simple method to manipulate the spin state and determine its role in the catalyst performance. In recent previous works, we have demonstrated this strategy to be highly effective in accelerating the sulfur redox reactions and improving the performance of lithium- and sodium-sulfur batteries, obtaining unprecedented capacities, rate performance, and stabilities. We have recently developed an optimized Co-based single metal catalyst showing exceptional activity in promoting the Li-S redox reaction thus enabling high-performance Li-S batteries. We propose here to follow the spin state of each element through XMCD at the Co L2,3 , S K-edge, and Mo L3-edge, both in fluorescence and TEY mode. Differences in the absorption of left-handed and right-handed polarized X-rays by the Co L2,3 and S K edges in Co-MoS2 will be used to identify the spin polarization degree. We will elucidate the effect of a magnetic field on the electronic structure of Co-MoS2 by comparing the degree of spin polarization of three different Co-doped MoS2 (0 doping MoS2, 10 at.% Co doping MoS2 and 20 at.% Co doping MoS2) and the number of electron transfer charges from Co 3d orbital to S 2p orbital. We expect that the XMCD spectra of the Co L2,3 -edge and S K-edges, and the Mo L3-edge will provide insight into the extent to which changes in the spin state of ferromagnetic catalysts affect electron-orbit coupling, and the degree to which outer-shell electron transitions interact. This data will be combined with that obtained at MSPD and CLAESS to gain insight into the role of electron spin in the Li-S electrochemical reaction and the overall Li-S battery performance.