Ternary rare earth sulfide CaCe2S4: Synthesis and characterization of stability, structure, and photoelectrochemical properties in aqueous media

A red-orange rare earth ternary chalcogenide, CaCe2S4, was prepared in powder form by solid-state synthesis. The structural details of this compound were determined by powder X-ray diffraction. The optical band gap of CaCe2S4 was determined by diffuse reflectance spectroscopy (DRS) to be ~ 2.1 eV, c...

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Bibliographic Details
Published in:Journal of solid state chemistry 2018-06, Vol.262 (C), p.149-155
Main Authors: Sotelo, Paola, Orr, Melissa, Galante, Miguel Tayar, Hossain, Mohammad Kabir, Firouzan, Farinaz, Vali, Abbas, Li, Jun, Subramanian, Mas, Longo, Claudia, Rajeshwar, Krishnan, Macaluso, Robin T.
Format: Article
Language:English
Subjects:
CaCe2S4
Chalcogenides
Hydrogen
Semiconductor
Solar fuels
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Summary:A red-orange rare earth ternary chalcogenide, CaCe2S4, was prepared in powder form by solid-state synthesis. The structural details of this compound were determined by powder X-ray diffraction. The optical band gap of CaCe2S4 was determined by diffuse reflectance spectroscopy (DRS) to be ~ 2.1 eV, consistent with the observed red-orange color. Quantitative colorimetry measurements also support the observed color and band gap of CaCe2S4. Both direct and indirect optical transitions were gleaned from Tauc analyses of the DRS data. Photoelectrochemistry experiments on CaCe2S4 films showed n-type semiconductor behavior. Analyses of these data via the Butler-Gärtner model afforded a flat-band potential of − 0.33 V (vs. Ag/AgCl/KCl 4 M) in ~ pH 9 aqueous sulfite electrolyte. The potential and limitations of this material for solar water splitting and photocatalytic environmental remediation (e.g., dye photodegradation) are finally presented against the backdrop of its photoelectrochemical stability and surface hole transfer kinetics in aqueous electrolytes. Valence band edge and conduction band edge locations for n-CaCe2S4 [Display omitted] •CaCe2S4 was synthesized without flowing H2S or CS2 gas.•The ternary chalcogenide synthesized was shown to be an n-type semiconductor.•Thermal stability was established to be superior to the binary counterpart, Ce2S3.•Capabilities of CaCe2S4 for solar photoelectrochemical water splitting are presented.
ISSN:0022-4596
1095-726X
DOI:10.1016/j.jssc.2018.02.014