Insight into the Effect of Cu Species and Its Origin in Pt-Based Catalysts on Reaction Pathways of Glycerol Oxidation

CuO-supported Pt–Cu nanoalloy catalysts were prepared to systematically explore the effect of metal introduction ways on the reaction path in the oxidation of glycerol, taking unsupported Pt–Cu catalysts and supported monometallic Pt catalysts as contrast. PtCu/CuO nanoalloys showed the preferable catalytic activity and high selectivity of dihydroxyacetone (DHA), while unsupported Pt–Cu sol catalysts tended to generate glyceraldehyde (GLD) and glyceric acid (GLA). This change in product distribution was due to the oxidation of the primary hydroxyl group when glycerol adsorbed on the Pt0–Cu0 site in Pt–Cu sol catalysts. However, in supported Pt–Cu alloy catalysts, owing to the contribution of Cu species in the support, the secondary hydroxyl group of glycerol preferred to adsorb on the Pt0–CuII sites with lower transition state energy for oxidation, responsible for higher DHA selectivity. This work provides a fundamental understanding on the effect of Cu species and its origin in Pt-based catalysts on the reaction pathways for glycerol oxidation

Pd Nanoparticles Loaded on CoAlCe Layered Double Oxide Nanosheets for Phenol Hydrogenation

The catalytic upgrading of phenolic derivatives is vital for the efficient utilization of biomass resources. Herein, we construct a reductive layered double oxide material (CoAlCe-LDO) with the Ce–Co interface and abundant oxygen vacancy (VO) via heat-treating layered double hydroxide (LDH) precursors. The support spontaneous in situ redox method is employed to prepare the supported catalyst using CoAlCe-LDO as a support and reductant. Interestingly, highly dispersed Pd nanoparticles prefer to distribute at the contact edge of the Ce–Co interface. Pd2+ is successfully reduced to Pd0 by the reductive Co/Ce sites. Due to the redox reaction between the support and Pd species, a strong metal–support interaction is introduced. The Pd/CoAlCe-LDO catalyst shows high activity for phenol hydrogenation under mild conditions and a low molar ratio of Pd to phenol. The kinetic study suggests that the highly dispersed Pd sites could preferably activate H2 molecules, thereby boosting the rapid phenol hydrogenation

Synthesis and Gas Sensing Performance of Dandelion-Like ZnO with Hierarchical Porous Structure

It is of great interest to develop gas-sensing materials with excellent performance in a facile and mild route. In this work, dandelion-like hollow ZnO hierarchitectures assembled with ZnO nanoparticles have been synthesized by annealing a zinc complex precursor, which was produced from zinc acetate and ammonium bicarbonate at room temperature. The nanoparticle size in the hierarchitectures enlarges from 10 to 23 nm with the annealing temperature increasing from 350 to 550 °C. The ZnO hierarchitectures have shown high sensing response (34.5), fast response (6 s) and recovery (7 s), and low optimal operating temperature (250 °C) toward 50 ppm ethanol because of large surface area and rich pore. Also, the obtained ZnO dandelion-like hierarchitectures exhibits good selectivity toward alcohols. The obtained results suggest that the dandelion-like ZnO hierarchitectures synthesized herein are a promising gas sensing material

Opening up a Radical Cross-Coupling Etherification Path by a Defect-Rich Cu/ZrO₂ Catalyst for a High-Value Transformation of HMF

In this work, a radical coupling path was opened up for the construction of C–O bonds in the reduction–etherification of 5-hydroxymethylfurfural (HMF) by designing the unpaired electron defect-rich catalyst Cu/ZrO2. A decent 2,5-bis­(isopropoxymethyl)­furan (BPMF) yield (86.3%) was obtained under the absence of H2 and external pressure. A radical quenching experiment proved that the etherification process, which is the key step for achieving BPMF, indeed belongs to a radical-related route. Subsequently, a series of in situ FTIR, radical capture experiment, and electron spin density analyses were used to elucidate the formation of key radical intermediates at the molecular level in which the O–H dissociation of 2.5-dihydroxymethylfuran and C–O dissociation of isopropanol occurred on the zirconium-vacancy-adjacent lattice oxygen atom (VZr–O–) and oxygen vacancy (VO) sites, respectively. Furthermore, we revealed the induction mechanism of the alkoxy radical intermediate at the electronic level and the electron structure cycle process of the unpaired electron VZr–O– sites via a combination of density functional theoretical calculations and isotope labeling. More importantly, the calculation result from Gaussian showed that radical intermediates do not occur in a chain reaction with unactivated molecules; thus, the optimal path of radical cross-coupling to produce BPMF was clarified. The findings reported by this article reveal the role of unpaired electron defects in opening up a radical coupling path and thus broaden the downstream production of the high-value transformation of HMF. Furthermore, this study could provide a reference for the construction of C–O bonds in other heterogeneous reaction systems

Interfacial Bifunctional Effect Promoted Non-Noble Cu/Fe<i>_y</i>MgO<i>_x</i> Catalysts for Selective Hydrogenation of Acetylene

Non-noble metal-based catalysts are gradually employed for the conversion of the unsaturated carbon–carbon bond, which exhibits improved selectivity but at the expense of catalytic activity. Herein, in this work, an FeyMgOx-modified Cu interfacial structure with different Cu/Fe ratios was constructed by a structural topotactic transformation of layered double hydroxides, in which Cu-Fe0.16MgOx displayed an enhanced catalytic behavior (95% of selectivity at 100% of conversion and turnover frequency (TOF) of 0.048 s–1) in selective hydrogenation of acetylene. By virtue of X-ray absorption spectroscopy, reaction kinetic models, and the calculation based on density functional theory on analyzing the Cu-FeyMgOx interfacial structure, we demonstrated the formation of the low coordinated Cuδ−-Fe0.16δ+MgOx interfacial sites and further unraveled their dual functions. Specifically, the interfacial Cuδ− sites played a role in the activation of acetylene and hydrogen, while the formed intermediate bounded with the interfacial Cu atom and the interfacial Fe atom, respectively, which was favorable for the desorption to produce ethylene instead of over hydrogenation. This study offers a basic understanding on bifunctional interfacial catalysis for the conversion of the unsaturated carbon–carbon bond, which is of constructive significance for the rational design and preparation of supported non-noble metal materials with high efficiency

Co<b>-</b>intercalation of Acid Red 337 and a UV Absorbent into Layered Double Hydroxides: Enhancement of Photostability

Organic–inorganic hybrid pigments with enhanced thermo- and photostability have been prepared by co-intercalating C.I. Acid Red 337 (AR337) and a UV absorbent (BP-4) into the interlayer of ZnAl layered double hydroxides through a coprecipitation method. The obtained compounds were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric–differential thermogravimetric–differential thermal analysis, UV–visible spectroscopy, and the International Commission on Illumination (CIE) 1976 L*a*b* color scales. The results show the successful co-intercalation of AR337 and BP-4 into the interlayer region of layered double hydroxides (LDHs) and reveal the presence of host–guest interactions between LDH host layers and guest anions of AR337 and BP-4 and guest–guest interactions between AR337 and BP-4. The intercalation can improve the thermostability of AR337 due to the protection of LDH layers. Moreover, the co-intercalation of AR337 and BP-4 not only markedly enhances the photostability of AR337 but also significantly influences the color of the hybrid pigment

Template-free Synthesis of Large-Pore-Size Porous Magnesium Silicate Hierarchical Nanostructures for High-Efficiency Removal of Heavy Metal Ions

It remains a big challenge to develop high-efficiency and low-cost adsorption materials to remove toxic heavy metal ions in water. Here, we developed a template-free synthesis method to fabricate high surface area and large pore size magnesium silicate hierarchical nanostructures in a mixed solvent of ethanol and water and carefully investigated the corresponding adsorption behavior for Pb2+, Zn2+, and Cu2+ in aqueous solution. The results reveal that the ethanol volume fraction in the solvent plays an important role to optimize the pore structure, which directly determines the adsorption capacity and the adsorption rate for heavy metal ions. When the ethanol volume fraction is beyond 50%, the obtained magnesium silicate presents a flowerlike structure with a hierarchical pore distribution: 0.5–2, 2–30, and 30–200 nm. When the ethanol volume faction is 90%, for example, the sample exhibits a maximum adsorption capacity of 436.68, 78.86, and 52.30 mg/g for Pb2+, Zn2+, and Cu2+ ions, which has a BET surface area of 650.50 m2/g and an average pore diameter of 6.89 nm, respectively. Also, the sample presents excellent repeated adsorption performance after three elutions. The obtained materials show widely promising and practical applications in water treatment in a wide pH range from 2.8 to 5.8

Novel Carbon Paper@Magnesium Silicate Composite Porous Films: Design, Fabrication, and Adsorption Behavior for Heavy Metal Ions in Aqueous Solution

It is of great and increasing interest to explore porous adsorption films to reduce heavy metal ions in aqueous solution. Here, we for the first time fabricated carbon paper@magnesium silicate (CP@MS) composite films for the high-efficiency removal of Zn²⁺ and Cu²⁺ by a solid-phase transformation from hydromagnesite-coated CP (CP@MCH) precursor film in a hydrothermal route and detailedly examined adsorption process for Zn²⁺ and Cu²⁺ as well as the adsorption mechanism. The suitable initial pH range is beyond 4.0 for the adsorption of the CP@MS to remove Zn²⁺ under the investigated conditions, and the adsorption capacity is mainly up to the pore size of the porous film. The composite film exhibits excellent adsorption capacity for both of Zn²⁺ and Cu²⁺ with the corresponding maximum adsorption quantity of 198.0 mg g^–1 for Zn²⁺ and 113.5 mg g^–1 for Cu²⁺, which are advantageous over most of those reported in the literature. Furthermore, the adsorption behavior of the CP@MS film follows the pseudo-second-order kinetic model and the Langmuir adsorption equation for Zn²⁺ with the cation-exchange mechanism. Particularly, the CP@MS film shows promising practical applications for the removal of heavy metal ions in water by an adsorption–filtration system

Facile Synthesis and Acetone Sensing Performance of Hierarchical SnO₂ Hollow Microspheres with Controllable Size and Shell Thickness

A facile method to prepare SnO₂ hollow microspheres has been developed by using SiO₂ microspheres as template and Na₂SnO₃ as tin resource. The obtained SnO₂ hollow microspheres were characterized by X-ray diffraction, scanning electron microscopy, high resolution and transmission electron microscopy, and Brunauer–Emmett–Teller analysis, and their sensing performance was also investigated. It was found that the diameter of SnO₂ hollow microspheres can be easily controlled in the range of 200–700 nm, and the shell thickness can be tuned from 7.65 to 30.33 nm. The sensing tests showed that SnO₂ hollow microspheres not only have high sensing response and excellent selectivity to acetone, but also exhibit low operating temperature and rapid response and recovery due to the small crystal size and thin shell structure of the hollow microspheres, which facilitate the adsorption, diffusion, and reaction of gases on the surface of SnO₂ nanoparticles. Therefore, the SnO₂ hollow microsphere is a promising material for the preparation of high-performance gas sensors