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Aliovalently Al ³⁺ doped strontium titanate enables overall water splitting in type 1 baggie particle suspension reactors in direct sunlight.

This study focuses on a solid solution series, Ca(La_1–xCe_x)₂S₄ (0 ≤ x ≤ 1), where the f electron density is absent in CaLa₂S₄ and is progressively increased until it is maximized in CaCe₂S₄. Correspondingly, these samples, synthesized by a sealed ampule method, showed progressive variations in color ranging from gray for CaLa₂S₄ to orange-red for CaCe₂S₄. The crystal structural nuances of both the end members and three solid solutions with $$x$$ = 0.25, 0.50, and 0.75 were established with the complementary use of synchrotron X-ray diffraction and neutron scattering. Interestingly, these data were consistent with a two-phase composition centered aroundmore » each nominal solid solution stoichiometry. Optical characterization via diffuse reflectance spectroscopy and Tauc analyses showed a shrinking of the energy band gap (from the UV to vis range) when Ce was progressively introduced into the host CaLa₂S₄ structure. Overall, these data were in concert with electronic band structure calculations, using density functional theory, which showed the progressive formation of an intermediate f band when Ce was introduced intro the structure. Photoelectrochemical measurements in an aqueous redox electrolyte, as well as surface photovoltage and Kelvin probe measurements, revealed all samples to be n-type semiconductors. The valence and conduction band edge positions of the end members and the three solid solutions could be mapped, on both the redox and vacuum reference energy scales, by combining these measurements with the optical data.« less

Aliovalently Al³⁺doped strontium titanate enables overall water splitting in type 1 baggie particle suspension reactors in direct sunlight.

A quaternary oxide, CuSnW₂O₈ (CTTO), has been predicted by density functional theory (DFT) to be a suitable material for sustainable photovoltaic applications. CTTO possesses band gaps of 1.25 eV (indirect) and 1.37 eV (direct), which were evaluated using the hybrid functional (HSE06) as a post-DFT method. The hole mobility of CTTO was higher than that of silicon. Further, optical absorption calculations demonstrate that CTTO is a better absorber of sunlight than Cu₂ZnSnS₄ and CuIn_xGa_1–xSe₂ (x = 0.5). In addition, CTTO exhibits rigorous thermodynamic stability comparable to WO₃, as investigated by different thermodynamic approaches such as bonding cohesion, fragmentation tendency, andmore » chemical potential analysis. Chemical potential analysis further revealed that CTTO can be synthesized at flexible experimental growth conditions, although the co-existence of at least one secondary phase is likely. Lastly, like other Cu-based compounds, the formation of Cu vacancies is highly probable, even at Cu-rich growth condition, which could introduce p-type activity in CTTO.« less