Boosting CO2 Electroreduction to Multi-carbon Products via Oxygen-rich Vacancies and Ce4+−O2−−Cu+ Structure in Cu/CeO2 for Stabilizing Cu+

Cu is a promising electrocatalyst for the CO₂ reduction reaction (CO₂RR) to produce high-value C₂₊ products. Due to the fierce competition of the hydrogen evolution reaction, the slow diffusion of CO₂, and the high energy barrier of the C−C coupling reaction, it is still challenging to achieve high activity and high selectivity to produce multi-carbon products on copper-based electrocatalysts. In this work, we synthesized Cu/CeO₂ catalysts with varying amounts of Cu doping, aiming at effectively converting CO₂ into C₂₊ products through electroreduction. At a copper doping level of 9.77 wt%, the catalyst exhibited a current density of 16.8 mA cm⁻² using a standard H-type cell, achieving a C₂₊ faradaic efficiency (FE) of 78.3 %. Through additional experiments and material characterization, we confirmed that controlling the Cu loading on the surface of CeO₂ is an effective way to regulate the ratio of Cu⁺ to Cu⁰ active sites and the number of oxygen vacancies. Furthermore, the strong electron interaction between Ce⁴⁺−O²⁻−Cu⁺ structure can stabilize Cu⁺ species and enhance the overall stability of the catalyst. This strategy enhances the selectivity towards C₂₊ products and effectively suppresses the competing hydrogen evolution reaction.     

Electrosynthesis of a Defective Indium Selenide with 3D Structure on a Substrate for Tunable CO2 Electroreduction to Syngas

Syngas (CO/H₂) is a feedstock for the production of a variety of valuable chemicals and liquid fuels, and CO₂ electrochemical reduction to syngas is very promising. However, the production of syngas with high efficiency is difficult. Herein, we show that defective indium selenide synthesized by an electrosynthesis method on carbon paper (γ-In₂Se₃/CP) is an extremely efficient electrocatalyst for this reaction. CO and H₂ were the only products and the CO/H₂ ratio could be tuned in a wide range by changing the applied potential or the composition of the electrolyte. In particular, using nanoflower-like γ-In₂Se₃/CP (F-γ-In₂Se₃/CP) as the electrode, the current density could be as high as 90.1 mA cm⁻² at a CO/H₂ ratio of 1:1. In addition, the Faradaic efficiency of CO could reach 96.5 % with a current density of 55.3 mA cm⁻² at a very low overpotential of 220 mV. The outstanding electrocatalytic performance of F-γ-In₂Se₃/CP can be attributed to its defect-rich 3D structure and good contact with the CP substrate.     

Selective reduction of nitroarenes to N-arylhydroxylamines by use of Zn in a CO2–H2O system, promoted by ultrasound

The promoting effect of ultrasound on the selective reduction of nitroarenes to N-arylhydroxylamines by use of Zn in an environmentally benign CO₂–H₂O system has been demonstrated. The yield of N-phenylhydroxylamine reaches 95 % when the reaction is carried out with a Zn-to-nitrobenzene molar ratio of 2.2 under ultrasound (40 kHz) at 25 °C and normal pressure of CO₂ for 60 min. Application of ultrasound to the reaction has the advantages of higher yield of N-arylhydroxylamines, shorter reaction time, and consumption of less Zn.     

Induction Plasma Synthesis of Graphene Nano-flakes with In Situ Investigation of Ar–H2–CH4 Plasma by Optical Emission Spectroscopy

Plasma Chemistry and Plasma Processing - Synthesis process of graphene nano-flakes produced in radio-frequency inductively coupled plasma system by axially injecting CH4 into Ar–H2 plasma is...     

Asymmetric Cu−N−La Species Enabling Atomic-Level Donor-Acceptor Structure and Favored Reaction Thermodynamics for Selective CO2 Photoreduction to CH4

Photocatalytic CO₂ reduction into ideal hydrocarbon fuels, such as CH₄, is a sluggish kinetic process involving adsorption of multiple intermediates and multi-electron steps. Achieving high CH₄ activity and selectivity therefore remains a great challenge, which largely depends on the efficiency of photogenerated charge separation and transfer as well as the intermediate energy levels in CO₂ reduction. Herein, we construct La and Cu dual-atom anchored carbon nitride (LaCu/CN), with La-N₄ and Cu-N₃ coordination bonds connected by Cu−N−La bridges. The asymmetric Cu−N−La species enables the establishment of an atomic-level donor-acceptor structure, which allows the migration of electrons from La atoms to the reactive Cu atom sites. Simultaneously, intermediates during CO₂ reduction on LaCu/CN demonstrate thermodynamically more favorable process for CH₄ formation based on theoretical calculations. Eventually, LaCu/CN exhibits a high selectivity (91.6 %) for CH₄ formation with a yield of 125.8 μmol g⁻¹, over ten times of that for pristine CN. This work presents a strategy for designing multi-functional dual-atom based photocatalysts.     

CH4 reforming with CO2 for syngas production over La2O3 promoted Ni catalysts supported on mesoporous nanostructured γ-Al2O3

Nanostructured γ-Al₂O₃ with high surface area and mesoporous structure was synthesized by sol-gel method and employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide. The prepared samples were characterized by XRD, N₂ adsorption-desorption, TPR, TPO, TPH, NH₃-TPD and SEM techniques. The BET analysis showed a high surface area of 204 m²·g⁻¹ and a narrow pore-size distribution centered at a diameter of 5.5 nm for catalyst support. The BET results revealed that addition of lanthanum oxide to aluminum oxide decreased the specific surface area. In addition, TPR results showed that addition of lanthanum oxide increased the reducibility of nickel catalyst. The catalytic evaluation results showed an increase in methane conversion with increasing lanthanum oxide to 3 mol% and further increase in lanthanum content decreased the catalytic activity. TPO analysis revealed that the coke deposition decreased with increasing lanthanum oxide to 3 mol%. SEM and TPH analyses confirmed the formation of whisker type carbon over the spent catalysts. Addition of steam and O₂ to dry reforming feed increased the methane conversion and led to carbon free operation in combined processes.     

Effect of Acid–Base Characteristics of In2O3-Al2O3 (ZrO2) Compositions on Their Catalytic Properties in the Oxidative Dehydrogenation of Propane to Propylene with CO2

Theoretical and Experimental Chemistry - The effect of the nature of the support and the method of preparation of indium–aluminum(zirconium) oxide compositions on their acid–base...     

In Situ Hydrothermal Synthesis of a Mononuclear Copper（Ⅱ） Complex： Cu（H2SIP-O）（bpy）（H2O） （H4SIP-O = 4-Hydroxyl-5-sulfoisophthalic Acid）

The mononuclear complex, Cu（H2SIP-O）（bpy）（H2O） （H4SIP-O = 4-hydroxyl- 5-sulfoisophthalic acid and bpy = 2,2＇-dipyridyl）, has been synthesized by the hydrothermal reaction of Cu（OH）2 with NaH2SIP and bpy at 160 ℃, and characterized by single-crystal X-ray diffraction, elemental analysis and IR spectrum. The new ligand 4-hydroxyl-5-sulfoisophthalic acid derived from 5-sulfoisophthalic acid ligand under an in situ hydrothermal condition. The crystal of the complex crystallizes in a triclinic system, space group P1, with a = 7.757（4）, b = 10.663（6）, c = 11.727（7）A, α = 94.272（4）, β = 104.067（7）, γ = 97.400（7）°, V= 927.4（9）A^3, Z = 2, C18H14N2O9SCu, Mr= 497.93, Dc= 1.783 g/cm^3,μ = 1.350 mm^-1, F（000） = 506, the final R = 0.0518 and wR = 0.1513 for 4180 observed reflections with I 〉 2σ（I）. The central Cu（II） ion is five-coordinated by two oxygen atoms from the H2SIP-O^2- ligand and two nitrogen atoms of bpy ligand in a distorted square-planar geometry as well as a water oxygen atom in the apical position to complete a distorted square-pyramidal coordination geometry. The mononuclear copper molecules are linked by hydrogen bonds between coordinated water molecules and sulfonate groups to form a one-dimensional double-chain structure. The chains are further held together through extensive π-π stacking interactions between the aromatic rings to form a three- dimensional supramolecular structure.     

Supramolecular Assemblies via Hydrogen Bonding and π-π Stacking Interactions: Crystal Structures of [Co(phen)(H2O)4]L·0.5H2O and [CO2(phen)2(H2O)2L2] with H2L = Adipic Acid

Reaction of freshly-prepared CoCO₃, phenanthroline monohydrate and adipic acid (H₂L) in CH₃OH/H₂O produced a mixture of [Co(phen)(H₂O)₄]L·0.5H₂O (1) and [CO₂(phen)₂(H₂O)₂L₂] (2). Complex 1 crystallizes in the orthorhombic space group Pbcn with cell dimensions a = 23.380(2), b = 12.347(1), c = 12.821(1) Å, and D _calc = 1.390 g/cm³ for Z = 8, and complex 2 in the triclinic space group P1; with cell dimensions a = 8.203(1), b = 9.809(1), c = 11.827(1) Å, α = 70.34(1), β = 74.81(1), γ = 71.54(1)° and D _calc = 1.592 g/cm³ for Z = 1. Complex 1 consists of [Co(phen)(H₂O)₄]²⁺ complex cations, adipate anions and crystal H₂O molecules. The Co atoms are each octahedrally coordinated by one chelating phen ligand and four water molecules with d(Co-O) = 2.041-2.097 Å and d(Co-N) = 2.144, 2.160 Å. Through hydrogen bonds, the [Co(phen)(H₂O)₄]²⁺ complex cations and adipate anions are interconnected into 2D layers, whose assembly could be ascribed to weak π-π stacking interactions between interdigitating phen ligands. Complex 2 is composed of centrosymmetric dinuclear [Co₂(phen)₂(H₂O)₂L₂) molecules, in which the Co atoms are each coordinated by two N atoms of one chelating phen ligand and four O atoms of one H₂O molecule and two adipato ligands to form distorted octahedra with d(Co-O) = 2.027-2.248 Å and d(Co-N) = 2.112, 2.162 Å. The centrosymmetric molecules are assembled via intermolecular hydrogen bonds and π-π interactions into 2D layers.     

[M(μ-O2C-C6H4-CO2)(NH3)2] (M = Cu,Cd; O2C-C6H4-CO2 = benzene-1, 4-dicarboxylate,terephthalate): 1D Coordination Polymers with Strong Inter-Chain Hydrogen Bonding

Compounds [M(μ-O₂C-C₆H₄-CO₂)(NH₃)₂] crystallize as straight- (M = Cu) and kinked-chain (M = Cd) coordination polymers through the bridging action of the bis-mono (Cu) and bis-bidentate (Cd) benzene-1, 4-dicarboxylate (terephthalate) ligand. N-H···O hydrogen bonding connects the chains to a three-dimensional supramolecular network. Thermogravimetry shows the compounds to be stable up to 255 °C (M = Cu) and 70 °C (M = Cd) where decomposition starts with the loss of one ammin ligand. [Cd(μ-O₂C-C₆H₄-CO₂)(NH₃)₂] exhibits a luminescence with λ_{em, max} = 392 nm (λ_ex = 240 nm) on the same order of magnitude as Na₂(O₂C-C₆H₄-CO₂).     

Dinuclear copper(II) complexes with ferromagnetic and antiferromagnetic interactions mediated by a bridging oxalato group: structures and magnetic properties of [Cu2L4(μ-C2O4)](PF6)2(H2O)2 and [Cu2L2(μ-C2O4)(NO3)2((CH3)2NCOH)2] (L = di-2-pyridylamine)

Two dinuclear Cu^II complexes of formula [Cu₂(dpyam)₄(μ-C₂O₄)](PF₆)₂(H₂O)₂ (1) and [Cu₂(dpyam)₂(μ-C₂O₄)(NO₃)₂(DMF)₂] (2) (dpyam=di-2-pyridylamine) have been synthesized and their spectroscopic and magnetic properties characterized. Complex (1) crystallizes in the non-centrosymmetric monoclinic space group Pc, while (2) crystallizes in the non-centrosymmetric triclinic space group P1. Compound (1) involves the compressed octahedral Cu^II environment, whereas (2) exhibits an elongated octahedral Cu^II geometry. Both complexes contain six-coordinate metal centers bridged by planar bis-didentate oxalate group. The geometry, spectroscopic properties and the effective magnetic moment of (1) are very close to those of the recently published [Cu₂(dpyam)₄ (μ-C₂O₄)](ClO₄)₂(H₂O)₃ and [Cu₂(dpyam)₄(μ-C₂O₄)](BF₄)₂(H₂O)₃. Thus (1) is expected to exhibit a very weak ferromagnetic interaction between the Cu^II centers which is confirmed by EPR spectrum. Those of (2) are comparable to those of the recently published [Cu₂(dpyam)₂(μ-C₂O₄)(NO₃)₂(DMSO)₂]. Therefore a strong antiferomagnetic interaction is expected. The effective magnetic moment at room temperature of (1) was measured to be 2.55 BM/dimer, which agrees with the spin only value of Cu^II, 2.45BM calculated for two uncoupled spin=1/2 centers. In (2) the room temperature effective magnetic moment of 2.16 BM/dimer indicates the partial spin paring by antiferromagnetic coupling. This is confirmed by the e.p.r. spectrum and is explained as a result of the magnetic interaction between the coplanar ${\rm d}_{x^2-y^2}$ orbitals on the two copper atoms.     

Hydrogen production by methanol steam reforming on a cordierite monolith reactor coated with Cu–Ni/LaZnAlO<Subscript>4</Subscript> and Cu–Ni/γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The performance of Cu–Ni/LaZnAlO₄ and Cu–Ni/γ-Al₂O₃ catalysts in the methanol reforming process in a monolith reactor in the temperature range of 200–350 °C, feed flow rate of WHSV = 20.8 h^?1 and atmospheric pressure has been investigated. In order to perform a more thorough investigation, surface area, morphology and crystalline structure of the synthetic catalysts have been studied using BET, FE-SEM, TPR, FT-IR, TEM, TGA and XRD analyses. The results have shown that Cu–Ni/LaZnAlO₄ catalyst synthesized by combustion reaction method under ultrasound irradiation has a very high efficiency and catalytic activity, low reduction temperature, high mechanical resistance and large pore sizes. The latter causes a higher percentage of active metal impregnation and better distribution on the support, greater resistance against sintering and maintenance of catalyst inertness at temperatures over 1000 °C, in comparison with conventional catalysts such as Cu–Ni/γ-Al₂O₃. This make its substitution for currently used catalysts affordable.     

Brushite (Ca,M)HPO4, 2H2O doping with bioactive ions (M = Mg2+, Sr2+, Zn2+, Cu2+, and Ag+): a new path to functional biomaterials?

Dicalcium phosphate dihydrate, DCPD (CaHPO₄·2H₂O), brushite, is an important calcium phosphate compound encountered in mineralized tissues and used in medicine, especially in bone cement formulations. However, the use of DCPD as direct implantable biomaterial has not received dedicated attention. In addition, the possibility to dope DCPD with biologically active ions to modulate its performances was not systematically explored. We have investigated in depth the doping of DCPD with Mg²⁺, Sr²⁺, Zn²⁺, Cu²⁺, and Ag⁺ ions. Clear modifications in terms of chemical composition, particle size, pore distribution, crystal morphology, and affinity for water were pointed out. Then, the samples were cultured with human adipose-derived stem cells to explore cytotoxicity and proliferation. Various behaviors were noticed dependent on the incorporated metal ions. Such DCPD compounds associated with bioactive metal ions, and particularly Ag⁺ and Zn²⁺, appear promising as a new family of reactive materials for use, as such or in combination, in bone-related applications.     

Formation of the unusual cluster Cu4(μ4-OH)(μ-(CF3)2pz)4(μ-OOCPh)2(μ-OH)2(OH2)(Et3NH)[O(CH2Ph)2]2 in the thermolysis of a copper μ-aqua complex with bridging pyrazolate and acetate ligands in dibenzyl ether in the presence of atmospheric oxygen

A room-temperature reaction of cupric acetate dihydrate with 3,5-bis(trifluoromethyl)pyrazole ((CF₃)₂pzH) in chloroform in the presence of triethylamine gave a complex of the formula [Cu₂(??-(CF₃)₂pz)₂(??-OH₂)(OC(Me)OHNEt₃)(OH₂)(HCCl₃)(OOCMe)(??-OOCMe)]₂ (2). Heating of this complex at 180°C in dibenzyl ether (DBE) in air yielded the tetranuclear pyrazolate-benzoate cluster Cu₄(??₄-OH)(??-(CF₃)₂pz)₄(??-OOCPh)₂(??-OH)₂(OH₂)(Et₃NH)[O(CH₂Ph)₂]₂. It was suggested that such complexes can be intermediates in the liquid-phase oxidation of DBE with atmospheric oxygen in the presence of copper complexes containing pyrazolate bridges.     

Dinuclear Ruthenium(II) Carbonyl Complexes Doubly Bridged by a Bromine Atom and a C5H3N-2-C(O)CH2-6-CH2 (Q) Group. Crystal Structures of Ru2(μ-Br)(μ-Q)Br(CO)4(PPh3)(MeOH) and Ru2(μ-Br)(μ-Q)Br(CO)3(PPh3)2

The oxidative addition reaction of 2,6-bis(bromomethyl)pyridine to Ru₃(CO)₁₂ gave scarcely soluble {Ru₂Br₂(-Q)(CO)₄} _n , 1, [Q=C₅H₃N-2-C(O)CH₂-6-CH₂] or a mixture of 1 and the mononuclear complex RuBr(Q)(CO)₃, 2, [Q=C₅H₃N-2-C(O)CH₂-6-CH₂Br] according to the reactant's mole ratio. Further reactions of 1 with some N- and P-donor ligands (L) afforded readily soluble dinuclear complexes, Ru₂(-Br)(-Q)Br(CO) _n (L) _m [n=4, m=1, L=PPh₃ 3a, or py 3b; n=3, m=2, L=PPh₃ 5a, or PPh₂(o-tolyl) 5b]. In this paper, the characterization of these products by the elemental analyses and the spectroscopic methods are described. The X-ray crystal structures of Ru₂(-Br) (-Q)Br(CO)₄(PPh₃)(MeOH), 4, which was obtained by crystallization of 3a from MeOH, and of 5a · (2CHCl ₃ ) are also described. Each of the metal atoms in 4 has a distorted octahedral coordination, while in 5a · (2CHCl ₃ ) one metal atom takes a distorted octahedral geometry and the other pseudooctahedral, which is completed by presenting a Ru ··· Br secondary bonding interaction.