Alkylamine‐Functionalized Carbon Supports to Enhance the Silver Nanoparticles Electrocatalytic Reduction of CO2 to CO

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Alkylamine-Functionalized Carbon Supports to Enhance the Silver Nanoparticles Electrocatalytic Reduction of CO2 to CO

Hydrophobicity and selectivity: The contact angle images (left) show the possibility to tune the hydrophobicity of carbon by changing the chain length of alkylamine functional groups. The CO2RR selectivity (right), produced by Ag nanoparticles (background) on carbon materials, was influenced by the functionalization: not only H2 formation was suppressed, but also CO production was enhanced, with an optimum around 6 carbon atoms.


Abstract

Silver electrocatalysts enable the conversion of CO2 to CO, thereby facilitating the transition to a carbon neutral society. To lower the cost of the expensive metal, silver nanostructures are often supported on carbon. This substrate offers great electrical conductivity, but it enhances the selectivity towards the competing hydrogen evolution reaction. In this work, carbon supports were functionalized with linear alkylamines of different chain lengths, to understand its effect on electrochemical performance. Alkylamines interact with the carbon surface and confer hydrophobic properties to the carbon support as well as making the local environment less acidic. These properties led not only to a suppression of the hydrogen evolution, but also to a remarkable enhancement in CO production. Despite the low silver weight loading (0.0016 mgAg cm−2), hexylamine-functionalized carbon-based catalysts achieved a CO to H2 ratio of 2.0, while the same material without the alkylamine functionalization only reached a ratio of 0.3, at −1.3 V vs RHE. This demonstrates the potential of hydrophobic functionalization for enhancing the CO selectivity of carbon-supported catalysts.

Lattice Tuning of Copper Single‐Crystal Surface for Electrochemical Carbon Monoxide Coupling Reaction: A Density Functional Theory Simulation

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Lattice Tuning of Copper Single-Crystal Surface for Electrochemical Carbon Monoxide Coupling Reaction: A Density Functional Theory Simulation

The relationship between strain and reaction selectivity of CO reduction reaction on the deformation of Cu(111) and Cu(100) electrode surface have been studied by using the density functional theory calculation, *CHO and CO coupling is the favorable pathway on expanded Cu(111) surface, two *CO coupling is the favorable pathway on contracted copper surface.


Abstract

CO is a key intermediate of electrocatalytic CO2 reduction reaction, which determines the product species. Understanding the effect of metal electrode structure on the adsorption ability and reaction activity of CO is helpful for the design of high selective catalysts. Herein, the DFT calculations are used to investigate the relationship between lattice structure and reaction mechanism of CO, with copper electrode of various lattice constants used as catalysts. By analyzing the adsorption and reaction energies of CO at different lattice constants of Cu(111) and Cu(100) surfaces, we found that the CO adsorption ability is proportional to the increase in lattice, and *CO dimerization to *COCO is the main reaction pathway on Cu(100) surface. Furthermore, the forecasted possible reaction mechanism and products suggest that the coupling of *CO and *CHO to *COCHO and then to C2 products is the preferred pathway on Cu(111) surface for the lattice contraction. Alternatively, reduction of *CO to C1 products through *CHO intermediate is more beneficial for the normal and expanded lattice of Cu(111). This work offers an example of the geometrical influence factor on the CO adsorption ability and reaction activity, and helps to understanding the fundamental role of lattice expansion and contraction in catalysis.

Nanofiller‐Based Novel Hybrid Composite Membranes for High‐Capacity Lithium‐Sulfur Batteries

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Nanofiller-Based Novel Hybrid Composite Membranes for High-Capacity Lithium-Sulfur Batteries

Al2O3 reinforced Nafion/Aquivion hybrid composite membranes were prepared for Li−S battery applications. Forming a hybrid composite membrane with nano-Al2O3 increased the electrochemical capacity. 868 mAhg−1 discharge capacity and 63.8 % capacity retention were obtained at the end of 300 cycles. The properties of the Nafion/Aquivion composite membrane have been improved by utilizing nanomaterial reinforcement.


Abstract

Herein, Al2O3 nanofiller-reinforced lithiated Nafion:Aquivion hybrid composite ion-exchange membranes have been produced by mixing lithiated Nafion and Aquivion ionomers. After the electrochemical tests, the Li-Naf : Li-Aqu/1 : 2 compound, which offers the best electrochemical performance, was selected. Lithiated hybrid composite membranes were obtained by reinforcing Al2O3 nanofillers at different rates to this composition. The ion exchange capacity, polysulfide transition and solvent uptake of the obtained membranes were investigated and the structural characterizations were applied by tensile test, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and membrane morphology was examined with Field Emission Scanning Electron Microscopy (FESEM). For performing the electrochemical tests, CR2032 half cells were designed. Electrochemical characterizations of the produced membranes were carried out by Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), and galvanostatic charge-discharge tests. The best electrochemical performance was achieved with 868 mAhg−1 discharge capacity and 63.8 % capacity retention when Li-Naf : Li-Aqu/1 : 2 composition was reinforced with 1 % Al2O3 nanofiller. As a result, lithiated hybrid composite ion exchange membranes could prevent the shuttle effect of polysulfides while enabling the passing of Li ions for high-performance Li−S batteries.

Recent advances in catalytic carbonylation reactions in alternative reaction media

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Comprehensive Summary

Since the discovery of the hydroformylation (oxo-synthesis or Roelen reaction) and the Reppe-reaction, the transition metal-catalyzed carbonylation reactions, providing versatile, facile, and even atom-economic methods for the selective incorporation of C=O functionality to various skeletons, have gained tremendous importance in synthetic organic chemistry from laboratories to industrial applications. The carbonylation of carbon-carbon multiple bonds, aromatic halides, triflates etc. in the presence of various nucleophiles has led the way to produce aldehydes, carboxylic acids, esters, amides, etc. in the fine chemical industry. However, these protocols usually proceed in conventional, fossil-based, and usually toxic reaction environments. Thus, several attempts have been directed to develop efficient carbonylation methods in alternative, less harmful, non-fossil-based and even in renewable reaction media. In this review, we overview the recent applications of alternative solvents such as water, biomass-based alcohols, γ-valerolactone (GVL), 2-methyltetrahydrofuran (2Me-THF), ionic liquids (ILs), deep eutectic solvents (DES), and alkyl levulinates, limonene, α-pinene, and dimethyl carbonate as well as fluorous media to improve efficiency, safety and environmentally benign nature of carbonylation protocols.

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The Effects of Heteroatom Doping and Physicochemical Character on Electrochemical Properties of Graphene Sheets

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Graphene attracted great interest in the electrochemical applications due to its stability and extremely high surface-area-to-mass ratio. Wet chemical and electrochemical synthesis allows affordable and single to multilayer graphenes with functional groups that contribute to surface accessibility, and electrolyte diffusion. These materials also have faradaic and pseudocapacitive reaction sites which enhance the electrochemical performance while altering their capacitive nature based on reaction type and density of these sites. Therefore heteroatom doping of graphene has been studied widely, and various outcomes, some of which have been controversial, were reported. In this study, we investigated the doping modification with multiple samples and also conduct a detailed physicochemical characterization. Oxidation-reduction and electrochemical exfoliation methods utilized to synthesize; pristine, nitrogen-doped, and phosphorus-doped reduced graphene oxide as well as the phosphorus-doped and pristine electrochemically exfoliated graphene materials. Samples have been characterized in terms of doping level, particle size, number of layers, defect density, and exfoliation homogeneity. Electrochemical measurements showed that surface wrinkling property among similarly large rGO particles (~9x) and small particle size (~2x) of graphenes are effective in determination of specific capacitance (Cspecific) and capacitive characteristic of samples while heteroatom doping doesn’t produce any significant change on these properties.

Pinacol Cross‐Coupling Promoted by an Aluminyl Anion

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A simple sequential addition protocol for the reductive coupling of ketones and aldehydes by a potassium aluminyl grants access to unsymmetrical pinacolate derivatives. Isolation of an aluminium ketyl complex presents evidence for the accessibility of radical species. Product release from the aluminium centre was achieved using an iodosilane, forming the disilylated 1,2-diol and a neutral aluminium iodide, thereby demonstrating the steps required to generate a closed synthetic cycle for pinacol (cross) coupling at an aluminyl anion.

Reductive Coupling of a Diazoalkane Derivative Promoted by a Potassium Aluminyl and Elimination of Dinitrogen to Generate a Reactive Aluminium Ketimide

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The reaction of 9-diazo-9H-fluorene (fluN2) with the potassium aluminyl K[Al(NON)] ([NON]2– = [O(SiMe2NDipp)2]2–, Dipp = 2,6-iPr2C6H3) affords K[Al(NON)(κN1,N3-{(fluN2)2})] (1). Structural analysis shows a near planar 1,4-di(9H-fluoren-9ylidene)tetraazadiide ligand that chelates to the aluminium. The thermally induced elimination of dinitrogen from 1 affords the neutral aluminium ketimide complex, Al(NON)(N=flu)(THF) (2) and the 1,2di(9H-fluoren-9-yl)diazene dianion as the potassium salt, [K2(THF)3][fluN=Nflu] (3). The reaction of 2 with N,N'diisopropylcarbodiimide (iPrN=C=NiPr) affords the aluminium guanidinate complex, Al(NON){N(iPr)C(N=CMe2)N(CHflu)} (4), showing a rare example of reactivity at a metal ketimide ligand. Density functional theory (DFT) calculations have been used to examine the bonding in the newly formed [(fluN2)2]2– ligand in 1 and the ketimide bonding in 2. The mechanism leading to the formation of 4 has also been studied using this technique.

A Prato Tour on Carbon Nanotubes: Raman Insights

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The functionalisation of carbon nanotubes has been instrumental in broadening its application field, allowing especially its use in biological studies. Although numerous covalent and non-covalent functionalisation methods have been described, the characterisation of the final materials has always been an added challenge. Among the various techniques available, Raman spectroscopy is one of the most widely used to determine the covalent functionalisation of these species. However, Raman spectroscopy is not a quantitative technique, and no studies are reported comparing its performance when the same number of functional groups are added but using completely different reactions. In this work, we have experimentally and theoretically studied the functionalisation of carbon nanotubes using two of the most commonly used reactions: 1,3-dipolar cycloaddition of azomethylene ylides and diazonium-based radical addition. The number of groups introduced onto the tubes by these reactions has been determined by different characterisation techniques. The results of this study support the idea that data obtained by Raman spectra are only helpful for comparing functionalisations produced using the same type of reaction. However, they should be carefully analysed when comparing functionalisations produced using different reaction types.

Interface Regulation via Electric Double Layer for Rechargeable Batteries

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Interface Regulation via Electric Double Layer for Rechargeable Batteries

Interface, especially the electrochemically formed solid electrolyte interphase (SEI), is significantly important for cycling stability, reaction kinetics and safety of rechargeable batteries. In order to construct ideal SEI, the fundamental understanding of the SEI and EDL at the molecular level and interfacial chemistry is required. However, as far as we know, there is no review to demonstrate the theme specially. Herein, the recent substantial progress for EDL and its impact on the formation of SEI in rechargeable batteries are reviewed and discussed.


Abstract

Interphases, especially the electrochemically formed solid electrolyte interphase (SEI), are significantly important for cycling stability, reaction kinetics and safety of rechargeable batteries. The structure and composition of the electric double layer (EDL) greatly affect the formation of the SEI and the performance of electrodes. However, as far as we know, there is no review discussing the theme specifically. Herein, the recent substantial progress for EDL and its impact on the formation of SEI in rechargeable batteries are reviewed and discussed. Firstly, the specific adsorption of electrolyte components on electrodes’ surface and the ionic solvation structure are introduced. Furthermore, various methods for controlling EDL in different electrode systems are described. Finally, the potential future advancements of the SEI through the manipulation of EDL are discussed, aiming to enhance the electrochemical performance of rechargeable batteries.

Interfacial Electron Regulation and Composition Evolution of NiFe/MoC Heteronanowire Arrays for Highly Stable Alkaline Seawater Oxidation

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Interfacial Electron Regulation and Composition Evolution of NiFe/MoC Heteronanowire Arrays for Highly Stable Alkaline Seawater Oxidation

The nanowire arrays composed of RuNi alloy nanoparticles and MoC are fabricated. The fabricated nanowire arrays exhibit an overpotential of 366 mV at a current density of 500 mA cm−2 with robust stability over 1000 h in the seawater, among the best OER catalysts reported to date.


Abstract

In alkaline seawater electrolysis, the oxygen evolution reaction (OER) is greatly suppressed by the occurrence of electrode corrosion due to the formation of hypochlorite. Herein, a catalyst consisting of MoC nanowires modified with NiFe alloy nanoparticles (NiFe/MoC) on nickel foam (NF) is prepared. The optimized catalyst can deliver a large current density of 500 mA cm−2 at a very low overpotential of 366 mV in alkaline seawater, respectively, outperforming commercial IrO2. Remarkably, an electrolyzer assembled with NiFe/MoC/NF as the anode and NiMoN/NF as the cathode only requires 1.77 V to drive a current density of 500 mA cm−2 for alkaline seawater electrolysis, as well as excellent stability. Theory calculation indicates that the initial activity of NiFe/MoC is attributed to increased electrical conductivity and decreased energy barrier for OER due to the introduction of Fe. We find that the change of the catalyst in the composition occurred after the stability test; however, the reconstructed catalyst has an energy barrier close to that of the pristine one, which is responsible for its excellent long-term stability. Our findings provide an efficient way to construct high-performance OER catalysts for alkaline seawater splitting.