In Situ Growth of Lead-Free Cs2CuBr4 Perovskite Quantum Dots in KIT-6 Mesoporous Molecular Sieve for CO2 Adsorption, Activation, and Reduction

Highly efficient and 100 % selectivity of CO generation via CO2 Photoreduction over a novel CsBr@CuBr2 Heterojunction

To address the global challenge posed by excessive carbon dioxide emissions, our research pioneers the transformation of CO2 into valuable hydrocarbon fuels. Central to this approach is the innovation of photocatalysts, engineered to exhibit exceptional photoresponse characteristics. In this research, the CsBr@CuBr2 photocatalyst was innovatively synthesized through a straightforward and effective one-pot method. The catalyst displayed remarkable efficacy, achieving a CO2 photoreduction rate of 201.47 μmol g-1 within just 4 h. The incorporation of CsBr into CuBr2 effectively captures excited-state electrons, thereby significantly enhancing charge separation efficiency. Utilizing in situ DRIFTS and DFT theoretical analysis, the experiment reveals the complex process of CO2 photoreduction to CO. The results of this experiment provide breakthrough insights for the systematic design of metal bromide heterostructures, which possess robust CO2 adsorption/activation potential and notable stability.

Synthesis, crystal and electronic structures, linear and nonlinear optical properties, and photocurrent response of oxyhalides CeHaVIO4 (Ha = Cl, Br; VI = Mo, W)

Four heteroanionic oxyhalides, CeClMoO4, CeBrMoO4, CeClWO4, and CeBrWO4, have been studied as multifunctional materials, which show a combination of good second harmonic generation (SHG) response and photocurrent signals. Millimeter-sized CeHaVIO4 (Ha = Cl, Br; VI = Mo, W) crystals were grown by halide salt flux. The crystal structure of CeHaVIO4 crystals was accurately determined by single-crystal X-ray diffraction. CeClMoO4, CeBrMoO4, and CeBrWO4 are isostructural to each other, and crystallize in the acentric LaBrMoO4 structure type. CeClWO4 crystallizes in a new structure type with unit cell parameters of a = 19.6059(2) Å, b = 5.89450(10) Å, c = 7.80090(10) Å, and β = 101.4746(8)°. The bandgaps of CeHaVIO4 fall into the range of 2.8(1)-3.1(1) eV, which are much smaller than those of isotypic LaHaVIO4 (Ha = Cl, Br; VI = Mo, W) in the range of 3.9(1)-4.3(1) eV. The narrowing of bandgaps in CeHaVIO4 originates from the presence of partially filled 4f orbitals of cerium atoms, which was confirmed by density functional theory (DFT) calculations. The moderate bandgaps make CeHaVIO4 suitable for infrared nonlinear optical (IR NLO) applications. CeBrMoO4 and CeBrWO4 exhibit moderate SHG responses of 0.58× AGS and 0.46× AGS, respectively, and are both type-I phase-matching materials. Moderate SHG response, easy growth of crystals, high ambient stability, and type-I phase-matching behavior make CeBrMoO4 and CeBrWO4 great materials for IR NLO applications. CeHaVIO4 films also exhibited good photocurrent response upon light radiation. This work demonstrates the rich structural chemistry of the REHaVIO4 (RE = Y, La-Lu; Ha = Cl, Br; VI = Mo, W) family and the potential presence of more multifunctional materials.

Regulating Oxygen Vacancies and Fermi Level of Mesoporous CeO2-x for Intensified Built-In Electric Field and Boosted Charge Separation of Cs3 Bi2 Br9 /CeO2-x S-Scheme Heterojunction

Regulating the built-in electric field (BEF) in the heterojunction is is a great challenge in developing high-efficiency photocatalysts. Herein, by tailoring the content of oxygen vacancies in the constituent reduction semiconductor (mesoporous CeO2-x ), a precise Fermi level (EF ) regulation of CeO2-x is realized, yielding an amplified EF gap and intensified BEF in the Cs3 Bi2 Br9 perovskite quantum dots/CeO2-x S-scheme heterojunction. Such an enhanced BEF offers a strong driving force for directional electron transfer, boosting charge separation in the S-scheme heterojunction. As a result, the optimized Cs3 Bi2 Br9 /CeO2-x heterojunction delivers a remarkable CO2 conversion efficiency, with an impressive CO production rate of 80.26 µmol g-1  h-1 and a high selectivity of 97.6%. The S-scheme charge transfer mode is corroborated comprehensively by density functional theory (DFT) calculations, in situ X-ray photoelectron spectroscopy (XPS), and photo-irradiated Kelvin probe force microscopy (KPFM). Moreover, diffuse reflectance infrared Fourier transform spectra (DRIFTS) and theoretical calculations are conducted cooperatively to reveal the CO2 photoreduction pathway.

Encapsulation of CsPb2Br5 in TiO2 Microcrystals to Enhance Environmental Stability

All-inorganic lead halide perovskite has emerged as an attractive semiconducting material due to its unique optoelectronic properties. However, its poor environmental stability restricts its broad application. Here, a simple method for the fabrication of CsPb2Br5/TiO2 is investigated. The introduction of p-aminobenzoic acid, which has two functional groups, is critical for the capping of amorphous TiO2 on CsPb2Br5. After calcination at 300 °C, amorphous TiO2 crystallizes into the anatase phase. The CsPb2Br5/TiO2 NCs show high long-term stability in water and enhanced stability against ultraviolet radiation and heat treatment, owing to the chemical stability of TiO2. More importantly, photo-electrochemical characterizations indicate that the formation of TiO2 shells can increase the charge separation efficiency. Hence, CsPb2Br5/TiO2 exhibits improved photoelectric activity owing to the electrical conductivity of the TiO2 in water. This study provides a new route for the fabrication of optoelectronic devices and photocatalysts based on perovskite NCs in the aqueous phase. Furthermore, the present results demonstrate that CsPb2Br5/TiO2 NCs has considerable potential to be used as a photoelectric material in optical sensing and monitoring.