Ternary Rare Earth Sulfide CaCe2S4: Synthesis and Characterization of Stability, Structure, and Photoelectrochemical Properties in Aqueous Media

Publication date: Available online 7 March 2018 Source:Journal of Solid State Chemistry Author(s): Paola Sotelo, Melissa Orr, Miguel Tayar Galante, Mohammad Kabir Hossain, Farinaz Firouzan, Abbas Vali, Jun Li, Mas Subramanian, Claudia Longo, Krishnan Rajeshwar, Robin T. Macaluso 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 ~2.1eV, 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 −0.33V (vs. Ag/AgCl/KCl 4M) 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. Graphical abstract
Source: Journal of Solid State Chemistry - Category: Chemistry Source Type: research