A mechanism for Li-S battery operation with a composite electrode and an adsorption additive obtained by using operando UV/Vis spectroscopy and X-ray absorption spectroscopy confirms the role of the adsorption additive and reflects the conversion mechanism of sulfur into Li 2 S. Operando UV/Vis spectroscopy shows a reversible appearance of the long-chain polysulfides in the separator in the fifth cycle, whereas the appearance of mid-and short-chain polysulfides suggests a polysulfide shuttle mechanism. By using a non-sulfur-containing electrolyte, a high-precision analysis of sulfur K-edge XANES and EXAFS spectra is possible. The XANES analysis shows that polysulfides reach the maximum concentration at the end of the high-voltage plateau, and the low-voltage plateau is characteristic of the polysulfides/Li 2 S equilibrium. The relative amount of Li 2 S increases linearly until the end of discharge and reaches a relative amount of 75 %. This is confirmed by sulfur K-edge EXAFS analysis. Additionally, a quantitative analysis of EXAFS spectra measured during discharge evidences a decrease of the average S-S coordination number. This can be interpreted as a decrease of the chain length of polysulfides. EXAFS analysis showed that there are no specific interactions of the polysulfide species with the matrix or with other species in the electrolyte.

Wet hydrogen peroxide catalytic oxidation (WHPCO) is one of the most important industrially applicable advanced oxidation processes (AOPs) for the decomposition of organic pollutants in water. It is demonstrated that manganese functionalized silicate nanoparticles with interparticle porosity act as a superior Fenton‐type nanocatalyst in WHPCO as they can decompose 80% of a test organic compound in 30 minutes at neutral pH and room temperature. By using X‐ray absorption spectroscopic techniques it is also shown that the superior activity of the nanocatalyst can be attributed uniquely to framework manganese, which decomposes H2O2 to reactive hydroxyls and, unlike manganese in Mn3O4 or Mn2O3 nanoparticles, does not promote the simultaneous decomposition of hydrogen peroxide. The presented material thus introduces a new family of Fenton nanocatalysts, which are environmentally friendly, cost‐effective, and possess superior efficiency for the decomposition of H2O2 to reactive hydroxyls (AOP), which in turn readily decompose organic pollutants dissolved in water.

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