Elucidating the Discharge\nBehavior of Aqueous Zinc\nSulfur Batteries in the Presence of Molybdenum(IV) Chalcogenide Catalyst:\nThe Criticality of Interfacial Electrochemistry

The aqueous zinc–sulfur battery holds promise\nfor significant\ncapacity and energy density with low cost and safe operation based\non environmentally benign materials. However, it suffers from the\nsluggish kinetics of the conversion reaction. Here, we highlight the\nefficacy of molybdenum(IV) sulfide (MoS<sub>2</sub>) to reduce the\noverpotential of S-ZnS conversion in aqueous electrolytes and study\nthe discharge products formed at the solid–solid and solid–liquid\ninterfaces using experimental and theoretical approaches. Specifically,\nthe MoS<sub>2</sub>-catalyzed electrochemical conversion reaction\nis characterized via <i>ex situ</i> X-ray diffraction (XRD),\ntransmission electron microscopy (TEM) with energy dispersive spectroscopy\n(EDS), Raman spectroscopy, synchrotron-based Mo <i>K</i>-edge X-ray absorption spectroscopy (XAS), and <i>in situ</i> synchrotron-based X-ray computed tomography (XCT). Additionally, <i>operando</i> synchrotron-based S <i>K</i>-edge XAS\nand X-ray fluorescence (XRF) maps are collected to determine the spatial\nevolution of sulfur-based species at the electrode–electrolyte\ninterface. Coupling the <i>operando</i> S <i>K</i>-edge XAS data with the simulated spectra and fitting the data suggested\na possible ZnS<sub>2</sub> intermediate phase.