Durable CuxO/mesoporous TiO2 photocatalyst for stable and efficient hydrogen evolution

Heterogeneous structures containing highly dispersed semiconductor nanoparticles on a photoactive support are effective for the photocatalytic hydrogen evolution reaction (HER). In this work, the interlayer ion-exchange and space confining nature of layered titanate nanosheets was used to embed copper ions in titanates, which were then transitioned to mesoporous Cu_xO/TiO₂ with highly dispersed Cu_xO nanostructures. Both experimental and density functional theory (DFT) studies demonstrated that the fine-decoration of Cu_xO nanostructures and the reducible valence of the copper species enabled stable superior photocatalytic activity. The HER efficiency was enhanced to 12.45 mmol g^-1 h^-1 for the mesoporous Cu_xO/TiO₂ composites in comparison to an efficiency of 0.38 mmol g^-1 h^-1 for the non-modified TiO₂. Steady HER performances over 10 h, cyclic HER measurement over 60 h, and testing of the composite kept under ambient conditions for over one year, demonstrated excellent stability of the composite against photochemical and wet-chemical erosion.

New Dual-Functional and Reusable Bimetallic Y2ZnO4 Nanocatalyst for Organic Transformation under Microwave/Green Conditions

A novel bimetallic and reusable Y₂ZnO₄ nanocatalyst was synthesized by a simple coprecipitation method. The prepared nanocatalyst exhibited dual catalytic activity and was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The average crystallite and grain sizes were found to be 17 ± 1 and 10 ± 2 nm, respectively. On the one hand, the catalytic activity of the nanocatalyst was studied for the Knoevenagel condensation reaction of aromatic aldehydes with active methylene compounds, such as ethyl cyanoacetate and malononitrile, under microwave irradiation and solvent-free conditions. On the other hand, the nanoparticles also showed faster photocatalytic activity against methyl orange (MO) compared to other dyes. The nanocatalyst was easily recoverable by a simple filtration method and was recycled without any significant loss of catalytic activity. The advantages of this nanocatalyst were a simple workup procedure, high reaction yields, solvent-free conditions, reusability, and a short reaction time under green reaction conditions.

Unravelling the structure sensitivity of CuO/SiO2 catalysts in the NO + CO reaction

CuO/SiO₂ catalysts with vast difference in copper dispersion were prepared by impregnation and ammonia-evaporation methods and used for exploring the structure sensitivity of CuO/SiO₂ catalysts in the NO + CO reaction.

Simultaneous catalytic reduction of SO2 and NO from flue gas using H2S as a reductant at low temperatures

High-efficiency simultaneous removal of NO and SO₂ in flue gas can be realized by catalytic reduction with H₂S on CeO₂–AT catalyst in the low temperature range of 240 to 280 °C.

Ethynylation of Formaldehyde over CuO/SiO2 Catalysts Modified by Mg Species: Effects of the Existential States of Mg Species

The highly effective catalytic synthesis of 1,4-butynediol (BD) from the Reppe process is a fascinating technology in modern chemical industry. In this work, we reported the effects of the existential states of Mg species in the CuO/silica-magnesia catalysts for the ethynylation of formaldehyde in a simulative slurry reactor. The physichemical properties of the supports and the corresponding catalysts were extensively characterized by various techniques. The experimental results indicated that the introduced Mg species in the form of MgO particles, MgO microcrystals, or Si-O-Mg structures effectively resulted in an abundance of medium-strong basic sites, which can synergize with the active Cu⁺ species, facilitate the activation of acetylene, and improve the ethynylation activity. For the CuO/MgO-SiO₂ catalyst, the existence of Si-O-Mg structures strengthened the Cu–support interaction, which were beneficial to improving the dispersion and the valence stability of the active Cu⁺ species. The highly dispersed Cu⁺ species, its stable valence state, and the abundant medium-strong basic sites enhanced the synergistic effect significantly, leading to the superior activity and stability of CuO/MgO-SiO₂. The insights into the role of the existential states of Mg species and the revelation of the synergistic effect between active Cu⁺ species and basic sites can provide theoretic guidance for future rational design of catalysts for the ethynylation reation.

Regulation of Cu Species in CuO/SiO2 and Its Structural Evolution in Ethynylation Reaction

A Cu-based nano-catalyst has been widely used in the ethynylation of formaldehyde; however, the effects of the presence of Cu on the reaction have not yet been reported. CuO/SiO₂ catalysts with different Cu species were prepared by impregnation (IM), deposition-precipitation (DP), and ammonia evaporation (AE). The structural evolution of the Cu species in different states of the ethynylation reaction and the structure-activity relationship between the existence state of the Cu species and the catalytic properties of the ethynylation reaction were studied. The results show that the Cu species in the CuO/SiO₂ (IM), prepared using the impregnation method, are in the form of bulk CuO, with large particles and no interactions with the support. The bulk CuO species are transformed into Cu⁺ with a low exposure surface at the beginning of the reaction, which is easily lost. Thus, this approach shows the lowest initial activity and poor cycle stability. A high dispersion of CuO and copper phyllosilicate exists in CuO/SiO₂ (DP). The former makes the catalyst have the best initial activity, while the latter slows release, maintaining the stability of the catalyst. There is mainly copper phyllosilicate in CuO/SiO₂ (AE), which is slowly transformed into a highly dispersed and stable Cu⁺ center in the in situ reaction. Although the initial activity of the catalyst is not optimal, it has the optimal service stability.

Synthesis of highly active rGO-supported mono and bi-metallic nanocomposites as catalysts for chemoselective hydrogenation of α,β-unsaturated ketone to alcohol

Schematic of the complete mechanism for chemoselective hydrogenation process of α,β-unsaturated ketone to alcohol through the newly developed rGO-supported mono (Au/rGO and Pd/rGO) and bi-metallic (Cu–Au/rGO and Cu–Pd/rGO) nanocomposite catalysts.

Hydrogenation of dimethyl malonate to 1,3-propanediol catalyzed by a Cu/SiO2 catalyst: the reaction network and the effect of Cu+/Cu0 on selectivity

1,3-Propanediol was synthesized via the hydrogenation of dimethyl malonate over a Cu/SiO₂ catalyst. The reaction network and active sites were revealed for the first time.

Silica-supported NiO nanocomposites prepared via a sol–gel technique and their excellent catalytic performance for one-pot multicomponent synthesis of benzodiazepine derivatives under microwave irradiation

Heterogeneous and versatile NiO–SiO₂ NCs were synthesized by a sol–gel technique and used as a catalyst for the one-pot multicomponent synthesis of benzodiazepines.

Fabrication of Highly Stable and Efficient PtCu Alloy Nanoparticles on Highly Porous Carbon for Direct Methanol Fuel Cells

Boosting the durability of Pt nanoparticles by controlling the composition and morphology is extremely important for fuel cells commercialization. We deposit the Pt-Cu alloy nanoparticles over high surface area carbon in different metallic molar ratios and optimize the conditions to achieve desired material. The novel bimetallic electro-catalyst {Pt-Cu/PC-950 (15:15%)} offers exceptional electrocatalytic activity when tested for both oxygen reduction reaction and methanol oxidation reactions. A high mass activity of 0.043 mA/μgPt (based on Pt mass) is recorded for ORR. An outstanding longevity of this electro-catalyst is noticed when compared to 20 wt % Pt loaded either on PC-950 or commercial carbon. The high surface area carbon support offers enhanced activity and prevents the nanoparticles from agglomeration, migration, and dissolution as evident by TEM analysis.

Hard-template synthesis of three-dimensional mesoporous Cu–Ce based catalysts with tunable architectures and their application in the CO catalytic oxidation

In this paper, 3D Cu–Ce-Ox catalysts with different pores were synthesized by controlling the calcination temperaturre. The CeCu20-600 showed the highest catalytic activity, where CO can be fully oxidized at 55 °C and expressed good stability.

A simple and convenient approach for preparing core–shell-like silica@nickel species nanoparticles: highly efficient and stable catalyst for the dehydrogenation of 1,2-cyclohexanediol to catechol

A simple and convenient approach for the preparation of core–shell-like silica@nickel species nanoparticles.

Highly dispersed Cu(ii), Co(ii) and Ni(ii) catalysts covalently immobilized on imine-modified silica for cyclohexane oxidation with hydrogen peroxide

This paper describes the synthesis of Cu(ii), Co(ii) and Ni(ii) catalysts immobilized on imine-functionalized silica gel through a 3-aminopropyltriethoxysilane linker.

Organic–inorganic hybrid catalysts containing new Schiff base for environment friendly cyclohexane oxidation

Organic and inorganic entities have been hybridized using 3-aminopropyltriethoxysilane (APTES) linker for the synthesis of three novel organic–inorganic hybrid catalysts [Cu(ii), Co(ii) and Ni(ii)].