Exploiting XPS for the identification of sulfides and polysulfides

Abstract

The identification of surface sulfide and polysulfide species based on the curve fitting of S2p photoelectron\ud spectra and, for the first time, of X-ray excited S KLL Auger spectra has been performed. The different sulfur\ud chemical states present on the surface (sulfide S2, central S and terminal S in polysulfide chains) could be\ud unambiguously assigned in the chemical state plot. Sulfur atoms in the central or terminal position,\ud respectively, are found on a line with slope ca. 3 irrespective of the cation indicating similar initial state\ud effects. On the other hand, for a given polysulfide, e.g. K2Sn, sulfur atoms both in central or terminal\ud positions are found on the same line with slope 1 indicating similar final state effects. This behavior can\ud be rationalized with the fact that the negative charge in polysulfide chains is located mainly on sulfur\ud atoms in the terminal position; indeed, sulfur present as central S shows a binding energy shift of 0.6\ud eV with respect to elemental sulfur (S8), and sulfur in terminal S a shift of 2.4 eV. An application of this\ud approach tested on commercial alkali polysulfides is provided for the curve fitting of SKLL signals and\ud sulfur speciation of three different sulfide minerals enargite (Cu3AsS4), chalcopyrite (CuFeS2) and\ud arsenopyrite (FeAsS). Also for the surface of mineral sulfides, terminal S atoms and central S atoms in the\ud polysulfide chains can successfully be identified

Alkali Metals Doping for High‐Performance Planar Heterojunction Sb2S3 Solar Cells

“…The binding energy of Li 1s, Na 1s, K 2p 3/2 , Rb 3d 5/2 , and Cs 3d 5/2 peaks are observed at 54.8, 1071.5, 292.8, 109.7 and 724.3 eV, respectively. These peak positions match well with the data reported for alkali metals sulfides, indicating again alkali metals coordinating with sulfur in the Sb 2 S 3 films. The Sb 3d XPS spectra of alkali‐metal‐doped and pristine Sb 2 S 3 films are illustrated in Figure b, the peak positions and shape of alkali‐metal‐doped and pristine samples are almost unchanged.…”

“…For alkali‐metals‐doped films, a weak double peak is detected in each of the doped Sb 2 S 3 films. After fitting the S 2p XPS curves, the binding energies of these weak S 2p 3/2 peaks are estimated as 163.28, 163.32, 163.51, 163.52, and 163.55 eV for Li, Na, K, Rb and Cs‐doped films, respectively, which are typical binding energies of the corresponding alkali‐S bond in alkali sulfide compounds . Furthermore, Figure S3 (Supporting Information) exhibits magnified XPS spectra of Li 1s, Na 1s, K 2p, Rb 3d, and Cs 3d of alkali‐metals‐doped Sb 2 S 3 films.…”

Photovoltaic materials: Cu2ZnSnS4 (CZTS) nanocrystals synthesized via industrially scalable, green, one‐step mechanochemical process

“…The presence of polysulfide species is not detected. The presence of surface sulfate species SO 4 2− is apparent in the sample prepared from elements with the broad peak appearing at approximately 168 eV …”

Unique aqueous Li-ion/sulfur chemistry with high energy density and reversibility

“…S4, only the spectra in the range of 158−166 eV were selected to fit the S2p of S 8 , S 0 , S 1− , and S 2− (Fig. 2B) (28,29). At SOC = 0%, only S 8 (164.4 eV) was observed, whereas polysulfide species S x 2− (8 ≥ x ≥ 2) appeared during lithiation, which were fitted with S 0 at 164.0 eV and S −1 at 162.2 eV, respectively.…”