Standardized procedures important for improving single-component ceramic fuel cell technology

Standardized procedures important for improving single-component ceramic fuel cell technolog

Interaction of Amino Acids and Single-Wall Carbon Nanotubes

In this article, we investigated the interactions between oxidized single-wall carbon nanotubes and three amino acids. A simple and environmental benign method to realize solubility of oxidized single-wall carbon nanotubes (OSWNT) in water was described. The amino acids used in this study include l-glycine (Gly), l-lysine (Lys), and l-phenylalanine (Phe). The OSWNT became soluble in water under ambient conditions and formed a stable suspension when amino acids (AA) were adsorbed on it. The interactions between OSWNT and three AA were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). The results indicate that there is an increasing in the diameter of OSWNT after AA adsorption. The OSWNT with different diameters were separated as a result of AA adsorption. The smaller the diameter of OSWNT, the more the AA adsorption amount is. The adsorbed amount of different AA on OSWNT follows the trend: Lys > Phe > Gly. The Π–Π stacking is an important factor to realizing adsorption of Phe zwitterions on the sidewall of OSWNT; but for Gly and Lys zwitterions, polar interaction is a determinant factor to realizing adsorption on the sidewall of OSWNT. The AA zwitterions were adsorbed on the surface of OSWNT by conjunct interaction of the Π–Π stacking, polar interaction, hydrogen bond, and covalent bonding. Hydrogen bond and covalent bond, formed with oxygen containing groups, is dominant at the end of OSWNT. The catalysis property of OSWNT makes a noticeable reduction of decomposition temperature for AA adsorbed on OSWNT

Coupling Tetraalkylammonium and Ethylene Glycol Ether Side Chain To Enable Highly Soluble Anthraquinone-Based Ionic Species for Nonaqueous Redox Flow Battery

Nonaqueous redox flow batteries (NARFBs) have promise for large-scale energy storage with high energy density. Developing advanced active materials is of paramount importance to achieve high stability and energy density. Herein, we adopt the molecular engineering strategy by coupling tetraalkylammonium and an ethylene glycol ether side chain to design anthraquinone-based ionic active species. By adjusting the length of the ethylene glycol ether chain, an ionic active species 2-((9,10-dioxo-9,10-dihydroanthracen-1-yl)­amino)-N-(2-(2-methoxyethoxy)­ethyl)-(N,N-dimethylethan-1-aminium)-bis­(trifluoromethylsulfonyl)­imide (AQEG2TFSI) with high solubility and stability is obtained. Paired with a FcNTFSI cathode, the full battery provides an impressive cycling performance with discharge capacity retentions of 99.96% and 99.74% per cycle over 100 cycles with 0.1 and 0.4 M AQEG2TFSI, respectively

Reaction Kinetics of Ethylene Combustion in a Carbon Dioxide Stream over a Cu–Mn–O Hopcalite Catalyst in Low Temperature Range

The intrinsic kinetics of the catalytic combustion of a trace amount of ethylene in a CO₂ stream over a Cu–Mn–O catalyst prepared with a coprecipitation method is investigated. The experiments are carried out in a fixed-bed reactor with 0.3 g of catalyst in a low temperature range (470 to 620 K) and varying the concentration of C₂H₄ and O₂ in the feed stream. The power rate law, Langmuir–Hinshelwood (LH), Eley–Rideal (ER), and Mars–van Krevelen (MVK) models are compared. The residual error distribution of the ethylene conversion is employed to optimize the model equations. The extended MVK model containing desorption terms of the combustion products fit the data well. The pilot test with a fixed-bed reactor and a commercial feed stream is carried out, and the macro kinetic equations are obtained. Combined with the extended MVK model equations of the intrinsic kinetics, the effectiveness factor is calculated, which gives further prediction of the performance of the extruded catalyst under commercial conditions

Adsorption of l-Phenylalanine on Single-Walled Carbon Nanotubes

Single-walled carbon nanotubes (SWNTs) became soluble in water and formed a stable solution when l-phenylalanine (Phe) was adsorbed. The adsorption selectivity of Phe zwitterions for larger diameter SWNTs was confirmed by analysis of Fourier transform infrared spectra and by differential thermogravimetric analysis. Enhanced adsorption of Phe on the oxidized single-walled carbon nanotubes (OSWNT) was observed in comparison with that of the purified single-walled carbon nanotubes (PSWNT). The Phe zwitterions are thought to adsorb on the surface of OSWNT by joint interaction of the π−π stacking, hydrogen bond, and part of the covalent bond. The π−π stacking is the dominant interaction in the sidewall of OSWNT without defects. The hydrogen bond and covalent bond formed with oxygen-containing groups becomes dominant on the end of OSWNT. For the PSWNT system, π−π stacking is an important factor to realize the adsorption of Phe zwitterions on the sidewall of PSWNT. The intermolecular hydrogen bond between Phe zwitterions is also formed when Phe zwitterions are adsorbed on the PSWNT

Bond-Making and Breaking between Carbon, Nitrogen, and Oxygen in Electrocatalysis

Many catalytic reactions involving small molecules, which are key transformations in sustainable energy and chemistry, involve the making or breaking of a bond between carbon, nitrogen and oxygen. It has been observed that such heterogeneously (electro)­catalyzed reactions often exhibit remarkable and unusual structure sensitivity, in the sense that they take place preferentially on catalyst surfaces with a long-ranged two-dimensional (100) atomic structure. Steps and defects in this two-dimensional structure <i>lower</i> the catalytic activity. Such structure sensitivity must be due to the existence of a special active site on these two-dimensional (100) terraces. Employing detailed density functional theory calculations, we report here the identification of this special active site for a variety of catalytic reactions. The calculations also illustrate how this specific site breaks the well-known rule that under-coordinated surface atoms bind adsorbates stronger, thereby providing the atomic-level explanation for the lack of reactivity of steps and defects for the reactions under consideration. The breakdown of such rule results in significant deviations from commonly observed energetic scaling relations between chemisorbates. Thus, this work provides new design rules for the development of thermodynamically efficient catalysts for an important class of bond-making and bond-breaking reactions

Solvent- and Base-Free Oxidation of 5‑Hydroxymethylfurfural over a PdO/AlPO₄‑5 Catalyst under Mild Conditions

A solvent-free method was proposed to upgrade the biomass-derived compound 5-hydroxymethylfurfural (HMF). The oxidation of HMF to produce 2,5-furandicarboxylic acid (FDCA) has been examined in the presence of O2 without the addition of solvent and base. Different from the conversion of the aldehyde group on HMF as the initial oxidation step in H2O solvent, the hydroxyl group on HMF was first oxidized and FDCA was finally generated without the addition of solvent. The role of O2 is to replenish the consumption of active oxygen species on the catalyst surface. The oxidation of HMF to FDCA proceeded due to the solvent-free effect. A 83.6% FDCA selectivity at 38.8% HMF conversion was measured with a PdO/AlPO4-5 catalyst at 80 °C for 5 h and the reaction mechanism was proposed

Amorphous Nickel Oxides Supported on Carbon Nanosheets as High-Performance Catalysts for Electrochemical Synthesis of Hydrogen Peroxide

The development of high-performance yet cost-effective catalysts for electrochemical synthesis of H2O2 is a great challenge. Here, the amorphous nickel oxide NiOx supported on carbon nanosheets was prepared by the photochemical metal organic deposition method. The evolution of the crystalline structure, microstructure, and 2-electron oxygen reduction reaction (2e-ORR) activity in 0.1 M KOH was systematically investigated. The results reveal that the amorphous NiOx is highly efficient and selective toward 2e-ORR with an onset potential of 0.76 V versus reversible hydrogen electrode (RHE), 91% selectivity, and an electron transfer number of ∼2.2 over a wide potential range of 0.15–0.60 V versus RHE, which is outstanding among the metal oxide-based catalysts for 2e-ORR. Such a performance is closely associated with the mesoporous structure of the carbon nanosheets. Furthermore, the appropriate bonding strength of Ni–OH derived from the amorphous nature is crucial for the high selectivity. The theoretical calculation reveals that the *OOH intermediate prefers to adsorb on the amorphous NiOx-C by the end-on mode, facilitating the 2e-ORR process. The present amorphous NiOx loaded on carbon nanosheets can be promising electrocatalysts for synthesizing H2O2 after the stability issues are well addressed

Acid-Treated RuO₂/Co₃O₄ Nanostructures for Acidic Oxygen Evolution Reaction Electrocatalysis

RuO2 is widely used as an acidic electrocatalyst to achieve high catalytic activity, but the severe leaching and scarcity of the Ru element restrict application on a large scale. Strategies such as designing nanostructures and adjusting metals’ electronic properties to regulate the adsorption of reaction intermediates can be used for the design and preparation of catalysts. Herein, we designed an acid-treated RuO2/Co3O4 nanostructure electrocatalyst with low Ru content and an intimate heterogeneous interface to disrupt the trade-off relationship between stability and activity. The resulting acid-treated RuO2/Co3O4 displayed an overpotential of 152 mV in a 0.5 M H2SO4 electrolyte, greatly exceeding that of commercial RuO2 (221 mV). Despite continuous operation for 150 h, it still exhibited good stability with a degradation rate of 0.67 mV·h–1. Multiple characterization analyses revealed that an electron transfer occurs from Ruoct to Cooct(III) sites through the mutual O atoms in acid-treated RuO2/Co3O4, which is further strengthened by the presence of oxygen vacancies. The oxygen vacancy and heterogeneous interface synergistically regulate electronic dispersion, optimize the adsorption of the oxygen intermediates (*OOH), and improve the reaction kinetics of the oxygen evolution reaction (OER). This work brings to light the significance of oxygen vacancies for modulating the electronic structure of RuO2 nanoparticles and enhancing stability on Co3O4 support, thus highlighting the use of nanostructure and interfacial engineering to achieve better acidic OER catalyst design

Solvent-Enhanced Coupling of Sterically Hindered Reagents and Aryl Chlorides using Functionalized Ionic Liquids

A highly efficient and poison-resistant system for the Suzuki reaction based on hydroxyl-functionalized ionic liquids has been established. The ionic liquid plays a critical role in catalyst/substrate activation directly facilitating “ligand-free” coupling reactions