Adsorption Of Ethanol Research Articles

Intermetallic Pd3Pb nanobranches with low-coordinated surface atoms for highly efficient ethanol oxidation reaction

Pd based bimetallic nanocrystals (NCs) with low-coordinated surface atoms endow a tremendous ability to modify electronic properties and have the synergistic effect to improve electrocatalytic performance. Among various bimetallic NCs with different compositions, intermetallic Pd-Pb NCs can improve the poisoning tolerance of surface active sites during electrocatalytic reactions. In addition, Pb can provide abundant oxygen-containing species (OHads) and has the ability to cleavage the C–C bond during electrocatalysis that can hinder the production of COads intermediate species, thereby improving ethanol oxidation reaction (EOR) performance. Herein, we report a wet-chemical method for synthesizing highly uniform Pd3Pb nanobranches (NBs). The growth process of Pd3Pb NBs was controlled using ascorbic acid as a reductant, oleylamine as a solvent, 1-octadecene as a surfactant, and ammonium bromide as a shape-directing agent. Their unique NB morphology makes them suitable as electrocatalysts, attributed to the effective adsorption of ethanol and (OH)ads and enhanced removal capability of intermediates adsorbed on the active site of Pd3Pb NBs due to the intermetallic Pd–Pb composition and high density of low-coordinated surface atoms in Pd3Pb branches that can enhance EOR in alkaline media. The prepared Pd3Pb NBs exhibited significantly higher mass activity than Pd3Pb nanocubes and commercial Pd/C catalysts.

AP-XPS Study of Ethanol Adsorption on Rutile TiO2(110)

The photoactivity of rutile TiO2(110) renders its surfaces of particular interest for the study of surface reactions. In particular, rutile TiO2(110) surfaces are active for hydrogen production, both via the water splitting process and via ethanol degradation under ultraviolet illumination. The selective photocatalytic dehydrogenation of rutile TiO2(110) is not fully understood yet, and an important question in this context is how ethanol adsorbs onto the rutile TiO2(110) surface under ambient conditions. Here, we present the first in situ experimental study on the absorption of ethanol on rutile TiO2(110) at room temperature and near-ambient conditions. The surface sensitivity of synchrotron-based ambient pressure X-ray photoelectron spectroscopy allows for an in-depth analysis of the surface species (molecular ethanol and ethoxies) and their coverage as well as an estimation of the energy difference between the two species. Through modeling of the O 1s core level and comparison to experimental results we show that both molecular and dissociative adsorption of ethanol occurs. The difference in adsorption energy range calculated from modeling of the O 1s core level was 0.018–0.033 eV, with dissociative adsorption the most energetically favorable. The difference in adsorption energy is almost an order of magnitude lower than previous estimations from theoretical calculations. In addition, we show that at room temperature a multilayer is formed with increasing pressure of ethanol.

Highly strained gold (Au)-palladium (Pd) core-shell nanobipyramids with extraordinary high activity and durability towards ethanol electrooxidation

Direct ethanol fuel cells (DEFCs) have emerged as promising power sources for mobile electronics due to their eco-friendly advantages over analogous devices fed with hydrogen. However, the ethanol oxidation reaction (EOR), the anode reaction of DEFCs, suffers from slower oxidation kinetics compared to the existing H2-fuel cells. Herein, we report a strategy based on maximum strain in Au@Pd core-shell nanobipyramid (NBP) structure where strain induced electronic effect enhances surface adsorption of ethanol towards boosted EOR. The novelty of construction of the present core-shell nanoparticle (NP) lies not only in showing up maximum tensile strain due to the lattice mismatch between the core (Au) and shell (Pd) atoms but also in introducing an additional amount of strain manifested by the 5-fold twins and stacking faults type defects, caused by the presence of an optimally size selected bipyramid shape Au core. Finally, we have discovered that such highly strained Au@Pd core-shell NBPs with the thinnest possible Pd shell exhibit extraordinary high electrocatalytic effect up to highest level of mass activity of 15.26 A mgPd−1 in the EOR under alkaline conditions which is superior to that of any Pd-based catalysts reported so far and commercial Pd/C catalysts.

Purification and ultra-high-performance liquid chromatography tandem mass spectrometry analysis of phenolics extracted from male walnut flowers

ABSTRACT In this study, phenolics extracted from male walnut flowers were purified and analyzed by ultra-high-performance liquid chromatography tandem mass spectrometry. After ultrasonic extraction of male walnut flowers with 60% ethanol, AB-8, D3520, NKA-9, D101, and NKA macroporous adsorption resins were compared for purification. The AB-8 macroporous resin gave the best adsorption and desorption performance for 0.7 mg gallic acid equivalents/mL samples (pH 3.0) loaded at a flow rate of 1 mL/min. Elution was carried out with 50% ethanol without pH adjustment. The purity of the phenolics in the eluate (72.5%) was 3.1 times that in the original extract. Analysis by ultra-high-performance liquid chromatography tandem mass spectrometry identified 16 compounds, including phenolic acids, flavonoids, and coumarins in the purified phenolics. The most abundant compounds were chlorogenic acid, kaempferol, and methoxycoumarin. Two compounds were got in male walnut flowers for the first time, and those need yet to be proved by further experiments.

The influence of water and ethanol adsorption on the optical blinking in InGaN quantum wells

We studied the adsorption of liquids over the surface of InGaN quantum well based wide band-gap devices and found that the immersion in certain liquids has noticeable effects on the optical blinking phenomena. We used two samples with different indium concentrations, emitting on the green and blue range, and immersed them while under direct illumination with 365 nm ultraviolet light. We found that especially water and ethanol provoked evident optical variations compared to observation in air. While blinking spots can be observed irrespective of the In concentration, their contrast and luminosity increased for samples with the emission in the 510 nm range, rather than for those in the 460 nm. Based on these results, we put forward the hypothesis that the presence of liquids induces the formation of radiative centers, possibly complexes related to intrinsic defects binding with adsorbed impurities, such hydrogen or oxygen.

Ethanol Electro-oxidation Reaction Selectivity on Platinum in Aqueous Media

Ethanol fuel cells require selective catalysts for complete oxidation of the fuel, which involves C–C bond cleavage. From experiments on well-defined surfaces and calculations, the mechanism controlling the ethanol electro-oxidation selectivity on platinum in aqueous media as a model system is elucidated. Adsorbed OH favors ethanol adsorption and conversion into adsorbed ethoxy, which favorably evolves to adsorbed COCH3. On Pt(111), adsorbed OH is also readily incorporated into adsorbed COCH3 to yield acetic acid. A higher barrier for this latter step on Pt(100) enables the COCH3 dehydrogenation to adsorbed COCH2, favoring C–C bond cleavage. As adsorbed OH plays an essential role as a reactant in this process, its adsorption properties have a decisive impact on this reaction. Furthermore, the adsorbed OH diffusion rate on the surface, which depends on the adsorbate/media/surface interaction at the interface, modulates the availability of this key reactant. These results highlight that the search for selective electrocatalysts requires holistic consideration of reactants, adsorbates, media, and substrate.

A Molecular Dynamics Model for Biomedical Sensor Evaluation: Nanoscale Numerical Simulation of an Aluminum-Based Biosensor.

Metallic nanostructured-based biosensors provide label-free, multiplexed, and real-time detections of chemical and biological targets. Aluminum-based biosensors are favored in this category, due to their enhanced stability and profitability. Despite the recent advances in nanotechnology and the significant improvement in development of these biosensors, some deficiencies restrict their utilization. Hence a detailed insight into their behavior in different conditions would be crucial, which can be achieved with nanoscale numerical simulation. With this aim, an Aluminum-based biosensor is chosen to be analyzed with the help of all-atom molecular dynamics model (AA-MD), using large-scale atomic/molecular massively parallel simulator (LAMMPS). The surface properties and adsorption process through different flow conditions and various concentration of the target, are investigated in this study. In the future work, the results of this study will be used for developing a predictive model for surface properties of the biosensor. Clinical Relevance- The role of biosensors in clinical applications and early diagnosis is evident. This work provides a model for predicting the binding behavior of the target molecules on the biosensor surface in different conditions. Results demonstrate an increase in the adsorption of ethanol on the biosensor surface of 7% up to 80% with changing the velocity from 0.001 m/s to 1 m/s Although for cases with higher concentration this trend becomes complicated necessitating the implementation of machine learning models in the future works.

Unzipping MWCNTs for controlled edge- and heteroatom-defects in revealing their roles in gas-phase oxidative dehydrogenation of ethanol to acetaldehyde

Bioethanol is a promising candidate for acetaldehyde production. In this study, we controllably unzipped multi-walled carbon nanotubes into open-edged nanotube/nanoribbon hybrids via a nano-cutting strategy for metal-free oxidative dehydrogenation of ethanol to acetaldehyde and unravelled the catalytic role of edge defects in the reaction. The edge-rich structure of the 1D-nanotube/2D-nanoribbon hybrid can accelerate the catalytic reaction more efficiently than pristine carbon sample. Moreover, edges can further accommodate nitrogen defects to preferentially form edge-doped nitrogen. Through engineering the concentration and speciation of defects, the structure-performance relationship between the defective structure and ethanol conversion rate is intensively investigated. Theoretical calculations unveil that the nitrogen doped at edge sites other than in basal planes can effectively facilitate O2 dissociation and formation of oxygen-containing active centers. Temperature-programmed ethanol desorption and kinetic measurements further supplement the catalytic interplay of edge and nitrogen defects on ethanol adsorption and reaction kinetics. The synergistic edge and nitrogen defects of the engineered hybrid produced a steady ethanol conversion of 47.9% and acetaldehyde selectivity of 90.2% at the gas hourly space velocity of 48,000 mL gcat-1h−1 on stream of 48 h. This work offers more insights to intrinsic properties and mechanism of enriched defective structures for development of effective carbocatalysts in catalytic applications.

Thermodynamic analysis of cooling cycles based on statistical physics modeling of ethanol adsorption isotherms

Thermodynamic analysis of two different adsorption cooling cycles was presented; the first cycle is based on an isobaric adsorption process and the second one projects an isothermal adsorption instead of an isobaric adsorption. These cooling cycles are carried out by employing the grand canonical ensemble of the statistical physics formalism. This investigation is done for two different adsorbate/adsorbent pairs i.e. Ethanol/Waste Palm Trunk (WPT-AC) and Ethanol/Mangrove wood (M-AC). The corresponding adsorption isotherms have been fitted by statistical physics models to give a description of the adsorption process through interpretations of the evolution of the involved physico-chemical parameters, specific for this process. The results showed that the ethanol molecules have been mainly adsorbed with a multimolecular process and non-parallel to the adsorbent surface involving an aggregation process before molecules adsorption. Their adsorption energies are varying from 1.40 to 3.64 kJ/mol for WPT-AC and from 3.2 to 3.81 kJ/mol for the M-AC. These values reflected a physisorption process. The calculated internal energy values suggested the exothermicity and the spontaneity of the ethanol adsorption process. The investigation aims providing a methodology of calculation of the COP for an adsorption cooling cycle by using the statistical physics treatment. The entropy and the enthalpy functions are calculated and used to perform the thermodynamic evaluation and to calculate the coefficient of performance (COP). This parameter was found to be in the interval [0.12–0.69] for ethanol/WPT-AC and [0.11-0.6] for ethanol/M-AC for the first cycle and for the second cycle [0.15-0.81] and [0.15-0.74] respectively.

Identification of an efficient adsorbent for ethanol sensing at room temperature using quartz crystal microbalance

Zeolite coated quartz crystal microbalance (QCM) is proposed as an efficient sensor for the detection of ethanol at room temperature. In this work, three zeolites DaY, ZSM-5, and BEA were investigated in order to determine the most efficient adsorbent for ethanol sensing at room temperature. The sensing performances were found to be mostly influenced by the acid site density and the zeolite's pore size. The BEA coated QCM sensor exhibited the best performances with a high relative frequency shift from 9.0 × 10−7 to 2 × 10−6 for 10 ppm of ethanol. Furthermore, this sensor exhibited fast response and recovery times which makes it a suitable material for the monitoring of ethanol in the air. In addition, the ethanol diffusion order was evaluated using Fickian diffusion law and was found to be the highest for the zeolite BEA. A sensing mechanism was also proposed for the adsorption and desorption of ethanol into zeolites based on unstable protonated dimers, water and diethyle ether resides for the energy-efficient ethanol sensor.

Low Temperature Multilayer Adsorption of Methanol and Ethanol on Platinum.

Adsorption of methanol and ethanol on the clean Pt (111) surface was studied at temperatures between 80 and 130 K using polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS). It was shown that adsorption of methanol at 80 K leads to the formation of amorphous solid methanol, and fast crystallization of the amorphous phase occurs upon warming at 100 K. Vapor deposition of methanol at 100 K directly leads to the formation of well-crystallized layers of solid methanol. According to PM-IRRAS, these crystalline layers consist of chains of hydrogen-bonded methanol molecules lying in a plane oriented close to the normal to the platinum surface. Adsorbed methanol is removed completely from platinum after heating to 120 K. Vapor deposition of ethanol at 80 K also leads to the formation of amorphous solid ethanol. However, subsequent warming does not lead to ordering of the adsorption layers, and at 130 K, ethanol is also completely desorbed.

Mechanistic Investigation and Free Energies of the Reactive Adsorption of Ethanol at the Alumina/Water Interface

Mechanistic Investigation and Free Energies of the Reactive Adsorption of Ethanol at the Alumina/Water Interface

Electrochemical reforming of ethanol with acetate Co-Production on nickel cobalt selenide nanoparticles

The energy efficiency of water electrolysis is limited by the sluggish reaction kinetics of the anodic oxygen evolution reaction (OER). To overcome this limitation, OER can be replaced by a less demanding oxidation reaction, which in the ideal scenario could be even used to generate additional valuable chemicals. Herein, we focus on the electrochemical reforming of ethanol in alkaline media to generate hydrogen at a Pt cathode and acetate as a co-product at a Ni1-xCoxSe2 anode. We first detail the solution synthesis of a series of Ni1-xCoxSe2 electrocatalysts. By adjusting the Ni/Co ratio, the electrocatalytic activity and selectivity for the production of acetate from ethanol are optimized. Best performances are obtained at low substitutions of Ni by Co in the cubic NiSe2 phase. Density function theory reveals that the Co substitution can effectively enhance the ethanol adsorption and decrease the energy barrier for its first step dehydrogenation during its conversion to acetate. However, we experimentally observe that too large amounts of Co decrease the ethanol-to-acetate Faradaic efficiency from values above 90% to just 50 %. At the optimized composition, the Ni0.75Co0.25Se2 electrode delivers a stable chronoamperometry current density of up to 45 mA cm−2, corresponding to 1.2 Ag−1, in a 1 M KOH + 1 M ethanol solution, with a high ethanol-to-acetate Faradaic efficiency of 82.2% at a relatively low potential, 1.50 V vs. RHE, and with an acetate production rate of 0.34 mmol cm−2h−1.

Laser-assisted synthesis of Au aerogel with high-index facets for ethanol oxidation

Gold (Au) can be used as an ideal metal electrocatalyst for ethanol and glucose oxidation reactions due to its high performance-to-cost ratio. In this paper, the Au aerogel with high-index facets was synthesized by using the laser ablation in liquid technology, which can improve the electrocatalytic activity of Au. The as-prepared Au aerogel showed excellent mass activity and specific activity toward ethanol oxidation reaction, which are 4.6 times and 2.1 times higher than Au/C, respectively. The 3D porous nature and rich defect of the Au aerogel provide more active sites. In addition, the high-index facets with under-coordinated atoms enhance the adsorption of ethanol and glucose molecules, thus improving the intrinsic catalytic activity of Au aerogel. The effect of high-index facets has also been investigated by density functional theory calculations. Furthermore, the Au aerogels also show good electrocatalytic activity and stability toward glucose oxidation reaction. These results are conducive to promote the practical application of Au in electrocatalysis.

Ethanol adsorption on Ni doped Mo2C(001): a theoretical study

Ethanol adsorption on Ni doped Mo2C(001): a theoretical study

Defect-rich BN-supported Cu with superior dispersion for ethanol conversion to aldehyde and hydrogen

Copper-based heterogeneous catalysts commonly exhibit uncontrolled growth of copper species under reaction conditions because of the low Hüttig temperature (surface mobility of atoms) and Tamman temperature (bulk mobility) for copper at just 134 and 405 °C, respectively. Herein, we report the use of defect-enriched hexagonal boron nitride nanosheets (BNSs) as a support to anchor the Cu species, which resulted in superior dispersion of the Cu species. The obtained Cu/BNS catalyst was highly stable for ethanol dehydrogenation, with a high selectivity of 98% for producing acetaldehyde and an exceptionally high acetaldehyde productivity of 7.33 gAcH gcat–1 h–1 under a weight hourly space velocity of 9.6 gEtOH gcat–1 h–1. The overall performance of our designed catalyst far exceeded that of most reported heterogeneous catalysts in terms of the stability of the Cu species and the yield of acetaldehyde in this reaction. The hydroxyl groups at the defect edges of BNS were responsible for the stabilization of the copper species, and the metal-support interaction was reinforced through charge transfer, as evidenced by coupling atomic resolution images with probe molecule infrared spectroscopy and X-ray photoelectron spectroscopy. A designed in situ diffuse reflectance infrared Fourier transform spectroscopy study of ethanol/acetaldehyde adsorption further revealed that Cu/BNS favored ethanol adsorption while suppressing acetaldehyde adsorption and further side reactions. This study demonstrates a new method for designing highly dispersed Cu-based catalysts with high durability.

Photoluminescence-based sensing of ethanol gas with ultrafine WO3 nanorods.

Ultrafine one-dimensional WO3 nanorods (NRs) with diameters of 10-200 nm have been fabricated using a hydrothermal synthesis method. The optical performance of the WO3 NRs strongly depends on their various defects as well as their crystal quality. Upon exposure to trace quantities of ethanol gas, the photoluminescence (PL) spectra of these nanorod samples under ultraviolet illumination showed a large variation in intensity. WO3-NR-based ethanol gas sensing via PL spectra variation demonstrated a 100 ppm sensitivity detection limit and a wide linear detection range of 200-2000 ppm at 100°C. This outstanding optical ethanol sensing performance can be ascribed to the very large surface area to volume ratio of this material, which increases the density of active sites for ethanol adsorption and reaction with adsorbed oxygen species.

Selective Photocatalytic Activation of Ethanol C-H and O-H Bonds over Multi-Au@SiO2/TiO2: Role of Catalyst Surface Structure and Reaction Kinetics.

The chemical bond diversity and flexible reactivity of biomass-derived ethanol make it a vital feedstock for the production of value-added chemicals but result in low conversion selectivity. Herein, composite catalysts comprising SiO2-coated single- or multiparticle Au cores hybridized with TiO2 nanoparticles (mono- or multi-Au@SiO2/TiO2, respectively) were fabricated via electrostatic self-assembly. The C-H and O-H bonds of ethanol were selectively activated (by SiO2 and TiO2, respectively) under irradiation to form CH3CH•(OH) or CH3CH2O• radicals, respectively. The formation and depletion kinetics of these radicals was analyzed by electron spin resonance to reveal marked differences between mono- and multi-Au@SiO2/TiO2. Consequently, the selectivity of these catalysts for 1,1-diethoxyethane after 6 h irradiation was determined as 81 and 99%, respectively, which was attributed to the more pronounced effect of localized surface plasmon resonance for multi-Au@SiO2/TiO2. Notably, only acetaldehyde was formed on a Au/TiO2 catalyst without a SiO2 shell. Fourier transform infrared (FTIR) spectroscopy indicated that the C-H adsorption of ethanol was enhanced in the case of multi-Au@SiO2/TiO2, while NH3 temperature-programmed desorption and pyridine adsorption FTIR spectroscopy revealed that multi-Au@SiO2/TiO2 exhibited enhanced surface acidity. Collectively, the results of experimental and theoretical analyses indicated that the adsorption of acetaldehyde on multi-Au@SiO2/TiO2 was stronger than that on Au/TiO2, which resulted in the oxidative coupling of ethanol to afford 1,1-diethoxyethane on the former and the dehydrogenation of ethanol to acetaldehyde on the latter.

Adsorption of Volatile Organic Compounds Onto Biomass-Derived Activated Carbons: Experimental Measurement and Comparison

Abstract Volatile organic compounds (VOCs) are a class of hazardous gaseous materials emitted from certain solids or liquids. They are thought to possess serious short- or long-term adverse effects on human health. Nowadays, an energy-efficient and cost-effective volatile organic compound removal system is of absolute necessity due to its adverse effects. In this regard, solar or waste heat-driven adsorption-based technologies can provide an energy-efficient system; however, most of the time, their utilization is limited by the high cost of the adsorbent materials. Right now, only one commercial high-grade activated carbon named Maxsorb III is known to have high capturing capacities. The purchasing cost of this adsorbent is very high, and it is derived from a non-renewable source. Therefore, this study is intended for the quest for low-priced biomass-derived activated carbons for an energy-efficient and cost-effective VOCs removal system. Two biomass-derived activated carbons synthesized from mangrove wood and waste palm trunk precursors are chosen, and four types of VOCs (ethanol, dichloromethane, acetone, and ethyl acetate) adsorption onto them are measured experimentally using the inverse gas chromatography technique. The zero uptake adsorption enthalpy and specific entropy of the adsorption are theoretically computed for all the adsorbent/adsorbate pairs. After that, these data are compared with the obtained data for Maxsorb III to assess the performance of the biomass-derived activated carbons. Results show that, for all the VOCs, the cost-effective mangrove-based activated carbon can be an excellent alternative to the high-priced Maxsorb III when employed as an adsorbent material for VOCs removal.

Thermal kinetics on adsorption heat transformation based on activated biocarbon and ethanol as working pairs

Cooling systems and refrigerators based on adsorption heat transformation processes (AHT) are a green alternative to compression cooling systems. Considering the increasing demand for human comfort, there is a crucial need for next-generation energy-efficient technologies, where the modeling and understanding of all parameters is a milestone. The viability and performance of the technology rely on the selected pair adsorbent/working fluid, but further from their pure thermodynamic performance, processing, and its derivates kinetic factors are depicted high relevant. In this work, ethanol adsorption kinetics on classic commercial adsorbents (activated carbon, AC) are predicted and further determined. The adsorptive phenomenon was investigated by means of computational simulation based on implemented Linear Driving Force (LDF) and the results were compared with experimental adsorption isotherms modeled by using Dubinin-Astakhov equation. The specific cooling effect (SCE) was studied by temperature monitoring during ethanol vapor adsorption experiments in a transient regime.