The room temperature synthesis of a CuO-Bi-BiOBr ternary Z-scheme photocatalyst for enhanced sunlight driven alcohol oxidation

The room temperature synthesis of an all-solid-state Z-scheme CuO-doped BiOBr (CuO-Bi-BiOBr) photocatalyst has been described. These CuO-Bi-BiOBr ternary heterojunctions exhibit efficient photocatalytic activities for selective alcohol oxidation. The structures, morphologies, and compositions of the nanostructures were well characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and atomic absorption spectroscopy (AAS). The X-ray diffraction (XRD) pattern of the as-synthesized nanostructures confirms the formation of phase-segregated CuO and BiOBr nanocrystals, whereas X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) analyses clearly indicate the formation of metallic bismuth nanoparticles (NPs). Next, the developed CuO-Bi-BiOBr ternary heterojunctions were applied as an efficient photocatalyst for the oxidation of alcohols into their corresponding aldehydes/ketones with high selectivity (>99%) and high conversion ratios (>99%). Herein, Bi metal NPs act as an electron mediator and bridge the connectivity between the two semiconductors, BiOBr and CuO, and, thus, a Z-scheme heterojunction is established. As expected, CuO-Bi-BiOBr has shown significantly superior activities compared to those of pure BiOBr. A possible mechanism for the photocatalytic oxidation process has been proposed. Radical scavenging experiments suggest that the active species, h⁺, ˙OH, e^-, and ˙O₂^-, are dominant in the alcohol oxidation process. The as-synthesized CuO-Bi-BiOBr was reused several times without any significant deterioration in the original activities and it thus possesses relatively high stability for practical applications.

Recent advances of polyoxometalate-catalyzed selective oxidation based on structural classification

The structural diversity and tenability observed in POMs has encouraged extensive investigations into their catalytic activity. Based on the structural classification of POMs, this review summarizes recent advances relating to POM-catalyzed selective oxidation and places most emphasis on dynamic developments from 2015 onwards. Work which contributes to comparing the catalytic performance of POMs with delicate structural differences (e.g. the same type of POM structure with differences of the heteroatom, addenda, protonated state or counter-ion) and in elucidating the origin/distinction of catalytic activity, as well as reasonable mechanisms, are especially highlighted.

Polyoxotungstates incorporated organophosphonate and nickel: synthesis, characterization and efficient catalysis for epoxidation of allylic alcohols

“Top-down” synthetic strategy was performed to incorporate nickel into the organophosphonate-based POTs showing superior catalysis for the epoxidation of allylic alcohols.

A silver NP-dispersed water extract of fly ash as a green and efficient medium for oxidant-free dehydrogenation of benzyl alcohols

Herein, a green, efficient, and new catalytic system for dehydrogenative oxidation of benzyl alcohols using Ag nanoparticles (NPs) dispersed in water extract of fly ash (WEFA) has been developed. Various characterization techniques were performed to authenticate the formation of Ag@WEFA. The as-prepared Ag NPs (10–20 nm) were found to be dispersed in WEFA, as indicated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) images. With Ag@WEFA, a variety of substituted benzyl alcohols were efficiently converted to carbonyl compounds in high yields. All the reactions were deliberately carried out without using any ligand or hazardous organic solvent. This catalytic system involving WEFA is a genuinely new concept. It is, therefore, expected to attract attention from researchers working in the areas of sustainable chemistry.

A new catalytic system for dehydrogenative oxidation of benzyl alcohols using Ag nanoparticles dispersed in WEFA is developed.

Silicotungstate, a Potential Electron Transporting Layer for Low-Temperature Perovskite Solar Cells

Thin films of a heteropolytungstate, lithium silicotungstate (Li₄SiW₁₂O₄₀, termed Li-ST), prepared by a solution process at low temperature, were successfully applied as electron transporting layer (ETL) of planar-type perovskite solar cells (PSCs). Dense and uniform Li-ST films were prepared on FTO glass by depositing a thin Li-ST buffer layer, followed by coating of a main Li-ST layer. The film thickness was controlled by varying the number of coating cycles, consisting of spin-coating and thermal treatment at 150 °C. In particular, by employing 60 nm-thick Li-ST layer obtained by two cycles of coating, the fabricated CH₃NH₃PbI₃ PSC device demonstrates the photovoltaic conversion efficiency (PCE) of 14.26% with J_SC of 22.16 mA cm^-2, V_OC of 0.993 mV and FF of 64.81%. The obtained PCE is significantly higher than that of the PSC employing a TiO₂ layer processed at the same temperature (PCE = 12.27%). Spectroscopic analyses by time-resolved photoluminescence and pulsed light-induced transient measurement of photocurrent indicate that the Li-ST layer collects electrons from CH₃NH₃PbI₃ more efficiently and also exhibits longer electron lifetime than the TiO₂ layer thermally treated at 150 °C. Thus, Li-ST is considered to be a promising ETL material that can be applied for the fabrication of flexible PSC devices.

Challenges in polyoxometalate-mediated aerobic oxidation catalysis: catalyst development meets reactor design

Current challenges and future directions i of polyoxometalates for selective aerobic oxidation catalysis is discussed with an emphasis on catalyst and reactor design.

New sterically encumbered arylimido hexamolybdates for organic oxidation reactions

Surface modification of the parent hexamolybdate by aryl amines results in useful catalysts for the oxidation of cyclohexene to cyclohexene epoxide and benzyl alcohol to benzaldehyde and benzoic acid.

Two polymolybdate-based complexes and their graphene composites with visible-light photo-responses

Two polymolybdate-based complexes with different band gaps show different visible-light photo-responses, and their graphene composite materials possess improved electrocatalytic activities for HER.

Efficient dye-sensitized solar cell with a pure thin film of a hybrid polyoxometalate covalently attached organic dye as a working electrode in a cobalt redox mediator system

A Keggin-type hybrid polyoxometalate is used as a pure semiconductor thin film in the working electrode of a dye-sensitized solar cell fabricated with a D35 organic dye and a cobalt redox mediator system, giving a maximum IPCE of about 91% .