Electrochemically-induced highly reactive PdO^(*) interface on modulated mesoporous MOF-derived Co_(3)O_(4) support for selective ethanol electro-oxidation

Herein,Pd nanoparticles loaded Co_(3)O_(4)catalysts(Pd@Co_(3)O_(4))are constructed from zeolitic imidazolate framework-67(ZIF-67)for the ethanol oxidation reaction(EOR).It is demonstrated for the first time that the electrochemical conversion of Co_(3)O_(4)support would result in the charge distribution alignment at the Pd/Co_(3)O_(4)interface and induce the formation of highly reactive Pd-O species(PdO^(*)),which can further catalyze the consequent reactions of the intermediates of the ethanol oxidation.The catalyst,Pd@Co_(3)O_(4)-450,obtained under the optimized conditions exhibits excellent EOR performance with a high mass activity of 590 mA mg-1,prominent operational stability,and extraordinary capability for the electro-oxidation of acetaldehyde intermediates.Importantly,the detailed mechanism investigation reveals that Pd@Co_(3)O_(4)-450 could be benefit to the C-C bond cleavage to promote the desirable C1 pathway for the ethanol oxidation reaction.The present strategy based on the metal-support interaction of the catalyst might provide valuable inspiration for the design of high-performing catalysts for the ethanol oxidation reaction.

Self-Decoration of PtNi Alloy Nanoparticles on Multiwalled Carbon Nanotubes for Highly Efficient Methanol Electro-Oxidation

A simple one-pot method was developed to prepare Pt Ni alloy nanoparticles,which can be self-decorated on multiwalled carbon nanotubes in [BMIm][BF4] ionic liquid.The nanohybrids are targeting stable nanocatalysts for fuel cell applications.The sizes of the supported Pt Ni nanoparticles are uniform and as small as 1–2 nm.Pt-to-Ni ratio was controllable by simply selecting a Pt Ni alloy target.The alloy nanoparticles with Pt-to-Ni ratio of 1:1 show high catalytic activity and stability for methanol electro-oxidation.The performance is much higher compared with those of both Pt-only nanoparticles and commercial Pt/C catalyst.The electronic structure characterization on the Pt Ni nanoparticles demonstrates that the electrons are transferred from Ni to Pt,which can suppress the CO poisoning effect.

Carbon nanotubes-Nafion composites as Pt-Ru catalyst support for methanol electro-oxidation in acid media

Carbon nanotubes-Nafion （CNTs-Nation） composites were prepared by impregnated CNTs with Nation in ethanol solution and characterized by FT-IR. Pt-Ru catalysts supported on CNTs-Nafion composites were synthesized by microwave-assisted polyol process. The physical and electrochemical properties of the catalysts were characterized by X-ray diffraction （XRD）, transmission electron microscope （TEM）, CO stripping voltammetry, cyclic voltammetry （CV） and chronoamperometry （CA）. The results showed that the Nation incorporation in CNTs-Nation composites did not significantly alter the oxygen-containing groups on the CNTs surface. The Pt-Ru catalyst supported on CNTs-Nafion composites with 2 wt% Naton showed good dispersion and the best CO oxidation and methanol electro-oxidation activities.

Solvent effects on Pt-Ru/C catalyst for methanol electro-oxidation

Alloying degree, particle size and the level of dispersion are the key structural parameters of Pt-Ru/C catalyst in fuel cells. Solvent（s） used in the preparation process can affect the particle size and alloying degree of the object substance, which lead to a great positive impact on its properties. In this work, three types of solvents and their mixtures were used in preparation of the Pt-Ru/C catalysts by chemical reduction of metal precursors with sodium borohydride at room temperature. The structure of the catalysts was characterized by X-ray diffraction （XRD） and Transmission electron microscopy （TEM）. The catalytic activity and stability for methanol electro-oxidation were studied by Cyclic Voltammetry （CV） and Chronoamperometry （CA）. Pt-Ru/C catalyst prepared in H2O or binary solvents of H2O and isopropanol had large particle size and low alloying degree leading to low catalytic activity and less stability in methanol electro-oxidation. When tetrahydrofuran was added to the above solvent systems, Pt-Ru/C catalyst prepared had smaller particle size and higher alloying degree which resulted in better catalytic activity, lower onset and peak potentials, compared with the above catalysts. Moreover, the catalyst prepared in ternary solvents of isopropanol, water and tetrahydrofuran had the smallest particle size, and the high alloying degree and the dispersion kept unchanged. Therefore, this kind of catalyst showed the highest catalytic activity and good stability for methanol electro-oxidation.

Ru effect on the catalytic performance of Pd@Ru/C catalysts for methanol electro-oxidation

Pd@Ru bimetallic nanoparticles deposited on carbon black electro-catalysts have been fabricated by microwave-assisted polyol reduction method and investigated for methanol electro-oxidation （MEO）. The structure and electro-catalytic properties of the as-prepared catalysts were characterized by XRD, SEM, TEM and cyclic voltammetry （CV） techniques. The results showed that the introduction of Ru element （2-10 wt%） into Pd 20 wt%/C （hereafter, denoted as Pd/C） produced a series of core-shell structured binary catalysts. Pd@Ru 5 wt%/C （hereafter, denoted as Pd@Rus/C） catalyst displayed the highest catalytic activity towards MEO. And the mass activity of Pd@Ru5/C electrode catalyst at E = -0.038 V （vs. Hg/HgO） was 1.42 times higher than that of Pd/C electrode catalyst. In addition, the relationship between the catalytic stability for MEO on Pd@Ru/C catalysts and the value of dbp/dfp （the ratio of MEO peak current density in the negative scan and positive scan） were also investigated. The result demonstrated that Pd@Rus/C offering the smallest value of Jbp/Jfp displayed the best stable catalytic performance.

Carbon Nanotubes Supported Pt-Ru-Ni as Methanol Electro-Oxidation Catalyst for Direct Methanol Fuel Cells

Carbon nanotubes （CNTs） supported Pt-Ru and Pt-Ru-Ni catalysts were prepared by chemical reduction of metal precursors with sodium borohydride at room temperature. The crystallographic properties and composition of the catalysts were characterized by X-ray diffraction （XRD） and energy dispersive X-ray （EDX） analysis, and the catalytic activity and stability for methanol electro-oxidation were measured by electrochemical impedance spectroscopy （EIS）, linear sweep voltammetries （LSV）, and chronoamperometry （CA）. The results show that the catalysts exhibit face-centered cubic （fcc） structure. The particle size of Pt-Ru-Ni/CNTs catalyst is about 4.8 nm. The catalytic activity and stability of the Pt-Ru-Ni/CNTs catalyst are higher than those of Pt-Ru/CNTs catalyst.

OH regulator of highly dispersed Ru sites on host Pd nanocrystals for selective ethanol electro-oxidation

The ethanol oxidation reaction(EOR)is crucial in direct alcohol fuel cells and chemical production.However,the electro-oxidation of ethanol molecules to produce acetaldehyde and carbon monoxide can poison the active sites of nanocatalysts,resulting in reduced performance and posing challenges in achieving high activity and selectivity for ethanol oxidation.In this study,we employed a dynamic seed-mediated method to precisely modify highly dispersed Ru sites onto well-defined Pd nanocrystals.The oxyphilic Ru sites serve as"OH valves",regulating water dissociation,while the surrounding Pd atomic arrangements control electronic states for the oxidation dehydrogenation of carbonaceous intermediates.Specifically,Ru0.040@Pd nanocubes(Ru:Pd=0.04 at.%),featuring(100)facets in Ru-Pd4 configurations,demonstrate an outstanding mass activity of 6.53 A·mgPd^(-1) in EOR under alkaline conditions,which is 6.05 times higher than that of the commercial Pd/C catalyst(1.08 A·mgPd-1).Through in-situ experiments and theoretical investigations,we elucidate that the hydrophilic Ru atoms significantly promote the dynamic evolution of H_(2)O dissociation into OHads species,while the electron redistribution from Ru to adjacent Pd concurrently adjusts the selective oxidation of C_(2) intermediates.This host-guest interaction accelerates the subsequent oxidation of carbonaceous intermediates(CH_(3)CO_(ads))to acetate,while preventing the formation of toxic*CHx and*CO species,which constitutes the rate-determining step.

Heterogeneous nanocomposites consisting of Pt_(3)Co alloy particles and CoP_(2) nanorods towards high-efficiency methanol electro-oxidation

Heterogeneous nanocomposites comprising chemically distinct constituents are particularly promising in electrocatalysis.We herein report a synthetic strategy that combines the reduction of Pt and Co ionic precursors at an appropriate ratio with the subsequent phosphating at an elevated temperature for forming heterogeneous nanocomposites consisting of quasi-spherical Pt_(3)Co alloy domains and rod-like CoP_(2) domains for high-efficiency methanol electrooxidation.The strong electronic coupling between Pt_(3)Co and CoP_(2) domains in the nanocomposites render the electron density around Pt atoms to decrease,which is favorable for reducing the adsorption of poisoning CO-like intermediates on the catalyst surfaces.Accordingly,the as-prepared heterogeneous Pt_(3)Co–CoP_(2) nanocomposites show good performance for methanol electrooxidation both in acidic and alkaline media.In specific,at a Pt loading of only 6.4%on a common carbon substrate,the mass-based activity of Pt_(3)Co–CoP_(2) nanocomposites in an acidic medium is about 2 and 1.5 times as high as that of commercial Pt/C catalyst(20%mass loading)and home-made Pt_(3)Co alloy nanoparticles(8.0%mass loading),while in the alkaline medium,these values are 3 and 2,respectively.

High stability three-dimensional porous PtSn nano-catalyst for ethanol electro-oxidation reaction

In addition to the theoretical research,direct ethanol fuel cells have great potential in practical applications.The performance of direct ethanol fuel cells largely depends on the electrocatalysts.Ptbased electrocatalysts have been promising candidates for advancing direct ethanol fuel cells for its high catalytic activity and great durability.Here,a PtSn catalyst with unique three-dimensional porous nanostructure has been designed and synthesized via a two-step liquid phase reduction reaction.Sn formed a self-supporting framework in PtSn alloy particles(~3.5 nm).In ethanol electro-oxidation reaction,the PtSn catalyst exhibited high mass activity and excellent recycling time compared with that of Pt/C.After the morphology characterization before and after potential cycling,the PtSn alloy-based nano-catalyst showed good stability.The PtSn catalysts effectively avoid structural instability due to the external carriers,and prolong the leaching time of Sn.In addition,the introduction of a certain amount of Sn can also solve the poisoning phenomenon of active sites on Pt surface.The design strategy of porous alloy nano-catalyst sheds light on its applications in direct ethanol fuel cells.

Preparation of PtSn_2–SnO_2/C nanocatalyst and its high performance for methanol electro-oxidation

PtSn2-SnO2/C nanocatalyst was prepared by co-reduction of Pt and Sn precursor at ca,15℃.The formation of PtSn2-SnO2 nanoparticle was determined by XRD,TEM and XPS characterization.This PtSn2-SnO2/C nanocatalyst exhibits stronger resistance to CO poisoning and effectively improves methanol electro-catalytic effect,up to 3 times than the commercial Pt/C catalyst.

Preparation and application of ZnO doped Pt-CeO2 nanofibers as electrocatalyst for methanol electro-oxidation

ZnO doped Pt/CeO2 nanocomposites were prepared by electrospinning and reduction impregnation.Xray diffraction（XRD）,transmission electron microscopy（TEM）,energy disperse spectroscopy（EDS） and X-ray photoelectron spectroscopy（XPS） were employed to characterize the nanocomposites.It is observed that ZnO and CeO2 form the hexagonal wurtzite phase and cubic fluorite phase in the nanocomposite,respectively,whilst Pt nanoparticles（NPs） with the number-averaged size of ca.3.1 nm are uniformly distributed on the surface of nanofibers.The mass fraction of Pt NPs in the nanocomposites is about 10 wt%.The doping of ZnO is effective to promote reactive oxygen species,surface reaction sites and the interaction between Pt and oxides.The catalytic performance of nanocomposites was evaluated by the methanol electro-oxidation.indexed with the catalytic activity,stability of catalyst.As a result,it is found that the nanocomposite exhibits much higher activity and stability for methanol oxidation than the undoped Pt/CeO2 catalyst.

Methanol electro-oxidation to formate on iron-substituted lanthanum cobaltite perovskite oxides

Electrochemically producing formate by oxidizing methanol is a promising way to add value to methanol.Noble metal-based electrocatalysts,which have been extensively studied for the methanol oxidation reaction,can catalyze the complete oxidation of methanol to carbon dioxide,but not the mild oxidation to formate.As a result,exploring efficient and earth-abundant electrocatalysts for formate production from methanol is of interest.Herein,we present the electro-oxidation of methanol to formate,catalyzed by iron-substituted lanthanum cobaltite(LaCo_(1-x)Fe_(x)O_(3)).The Fe/Co ratio in the oxides greatly influences the activity and selectivity.This effect is attributed to the higher affinity of Fe and Co to the two reactants:CH3OH and OH,respectively.Because a balance between these affinities is favored,LaCo_(0.5)Fe_(0.5)O_(3) shows the highest formate production rate,at 24.5 mmol h^(-1) g_(oxide)^(-1),and a relatively high Faradaic efficiency of 44.4%in a series of(LaCo_(1-x)Fe_(x)O_(3))samples(x=0.00,0.25,0.50,0.75,1.00)at 1.6 V versus a reversible hydrogen electrode.

Restructuring of 4H Phase Au Nanowires and its Catalytic Behavior toward CO Electro-oxidation

Au nanowires in 4H crystalline phase(4H Au NWs)are synthesized by colloid solution methods.The crys-talline phase and surface structure as well as its performance toward electrochemical oxidation of CO be-fore and after removing adsorbed oleylamine molecules(OAs)intro-duced from its synthesis are evaluat-ed by high-resolution transmission electron microscopy(HR-TEM),X-ray diffraction(XRD),underpoten-tial deposition of Pb(Pb-upd)and cyclic voltammetry.Different methods,i.e.acetic acid cleaning,electrochemical oxidation cleaning,and diethylamine replacement,have been tried to remove the adsorbed OAs.For all methods,upon the removal of the adsorbed OAs,the morphology of 4H gold nanoparticles is found to gradually change from nanowires to large dumbbell-shaped nanoparticles,accompanying with a transition from the 4H phase to the face-centered cubic phase.On the other hand,the Pb-upd results show that the sample sur-faces have almost the same facet composition before and after removal of the adsorbed OAs.After electrochemical cleaning with continuous potential scans up to 1.3 V,CO electro-oxida-tion activity of the 4H Au sample is significantly improved.The CO electro-oxidation activi-ty is compared with results on the three basel Au single crystalline surfaces reported in the lit-erature,possible origins for its enhancement are discussed.

Roles of hydroxyl and oxygen vacancy of CeO_(2)·xH_(2)O in Pd-catalyzed ethanol electro-oxidation

In the field of noble metal-catalyzed alcohol electro-oxidation reaction(AOR),huge attention is paid on the composition,size,facet,and structure of the metals,while the support engineering should also be emphasized.CeO_(2)has been widely used as a unique support in AOR,primarily due to its abundant oxygen vacancies(O_(v)).Herein,we report CeO_(2)·xH_(2)O nanoparticles with both massive hydroxyl groups(OH)and O_(v)remarkably enhance the catalytic activity and stability of Pd toward ethanol oxidation reaction(EOR).The CO striping experiments and density functional theory(DFT)calculations suggest that OH and O_(v)on CeO_(2)·xH_(2)O surface bring about a large downshift of Pd d-band center and a significant weakening of CO absorption on Pd.Moreover,OH and O_(v)also play synergic roles in the removal of toxic intermediates.Consequently,the important roles of OH and O_(v)of CeO_(2)·xH_(2)O are confirmed in Pd-catalyzed EOR.The facile CeO_(2)·xH_(2)O-enhanced strategy can contribute to the catalyst design for other energy conversion reactions.

Electro-oxidation of mixed reactants of ethanol and formate on Pd/C in alkaline fuel cells

Direct ethanol fuel cells have attracted attention as an alternative energy technology due to several advantages such as high theoretical energy density and abundant supply of ethanol.In spite of the advantages,commercialization of direct ethanol fuel cells is hampered by the relatively low performance caused by its slow oxidation kinetics and difficulty of complete oxidation.In this study,formate,which has relatively faster oxidation kinetics,was mixed with ethanol to compensate the latter’s sluggish kinetics.Effects of p H,concentration,scan rate,and temperature on the mixed reactants oxidation on Pd were investigated by electrochemical experiments such as potential sweep and potentiostatic methods.Furthermore,the potential of the mixed reactants as fuel was evaluated by single cell experiments.As a result,we demonstrate that mixing formate with ethanol results in enhanced power performance in a single cell system.

Albizzia chinensis(Osbeck)Merr extract YS ameliorates ethanol-induced acute gastric ulcer injury in rats by regulating NRF2 signaling pathway

Background:Around the world,there is a high incidence of gastric ulcers.YS,an extract from the Chinese herb Albizzia chinensis(Osbeck)Merr,has potential therapeutic applications for gastrointestinal diseases.Here we elucidated the protective effect and underlying mechanism of action of YS on gastric ulcer in rats injured by ethanol.Methods:The ethanol-i nduced gastric ulcer rat model was used to assess the protective effect of YS.A pathological examination of gastric tissue was performed by H&E staining.GES-1 cells damaged by hydrogen peroxide were used to simulate oxidative damage in gastric mucosal epithelial cells.Endogenous NRF2 was knocked down using small interfering RNA.Immunoprecipitation was used to detect ubiquitination of NRF2.Co-i mmunoprecipitation was used to detect the NRF2-Keap1 interaction.Results:YS(10 and 30 mg/kg,i.g.)significantly reduced the ulcer index,decreased MDA level,and increased SOD and GSH levels in gastric tissues damaged by ethanol.YS promoted NRF2 translocation from cytoplasm to nucleus and enhanced the NQO1 and HO-1 expression levels in injured rat gastric tissue.In addition,YS regulated NQO1 and HO-1 via NRF2 in H_(2)O_(2)-i nduced oxidative injured GES-1 cells.Further studies on the underlying mechanism indicated that YS reduced the interaction between NRF2 and Keap1 and decreased ubiquitylation of NRF2,thereby increasing its stability and expression of downstream factors.NRF2 knockdown abolished the effect of YS on MDA and SOD in GES-1 cells treated with H_(2)O_(2).Conclusion:YS reduced the NRF2-Keap1 interaction,promoting NRF2 translocation into the nucleus,which increasing the transcription and translation of NQO1 and HO-1 and improved the antioxidant capacity of rat stomach.

Validation of a Method for Characterization of Ethanol in Water by HS-GC-FID to Serve the Traceability of Halal Measurements

The determination of the ethanol content in food products is of fundamental importance for HALAL certification. In this work, an analytical method for the determination of ethanol in water by headspace gas chromatography with flame ionization detector (HS-GC-FID) has been developed and validated for the use in characterization of ethanol reference materials. The validation study was carried out in the linear calibration range 100 - 1500 mg/kg using the NIST SRM 2900, nominal 95.6%. The studied performance characteristics of the method were the limit of detection, LOD, the limit of quantification LOQ, selectivity, linearity, precision, recovery and bias. The validation results showed that the method is selective, precise, accurate and free from any significant bias. The LOD and LOQ were 1.27 and 3.86 mg/kg respectively and the estimated expanded uncertainty was 2% indicating that the method is fit for the purpose of certification of ethanol in water reference materials.

Rational modulation of electronic structure in PtAuCuNi alloys boosts efficient electrocatalytic ethanol oxidation assisted with energy-saving hydrogen evolution

Compared to conventional electrocatalytic water splitting,electrocatalytic ethanol oxidation reaction(EOR)along with hydrogen production is considered a more energy-efficient strategy.Herein,we prepared a type of novel quaternary alloy catalyst(PtAuCuNi@NF)that exhibits excellent activity for EOR(0.215 V at 10 mA cm^(-2))and hydrogen evolution reaction(HER)(7 mV at 10 mA cm^(-2)).Experimental results demonstrated that both Cu and Ni modulated the electronic environment around Pt and Au.The electron-rich active center facilitates the rapid adsorption and dissociation of reactants and intermediates for both EOR and HER.Impressively,in the ethanol-assisted overall water splitting(E-OWS),a current density of 10 mA cm^(-2)was achieved at 0.28 V.Moreover,an advanced acid-base self-powered system(A-Bsps)that can achieve a self-powered voltage of 0.59 V was assembled.Accordingly,the self-driven hydrogen production with zero external power supply was realized by integrating A-Bsps with the E-OWS equipment.The interesting results can provide a feasible strategy for designing and developing advanced nanoalloy-based materials for clean energy integration and use in various fields.

Antibacterial,antioxidant and antiproliferation activities of essential oils and ethanolic extracts from Chinese mugwort(Artemisia vulgaris L.)leaf in Shanxi

Background:Artemisia vulgaris,a medicinal aromatic plant,is widely used as a food item,tonic pharmaceutical,and cosmetic industry additive owing to its antibacterial,antihypertensive,hepatoprotective,antioxidant,and antispasmodic properties.But the effect of different geographic locations on the chemical composition and bioactivities of its extracts is unclear.Methods:Biological activities of essential oils and ethanol extracts of three varieties of Artemisia vulgaris leaves,which are grown in Shanxi province China,were studied.Results:Gas chromatography-mass spectrometry analysis revealed that the main components of essential oils were terpenes and ketones.Essential oils and ethanol extract of Artemisia vulgaris leaves possessed good antioxidant activities,and their half maximal inhibitory concentrations determined using 1,1-diphenyl-2-picrylhydrazyl and 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate)assays were 57.0 and 22.9μg/mL,respectively.The essential oils also exhibited remarkable antibacterial activity against three foodborne pathogenic bacterial strains.The ethanol extract presented a high anticancer activity against the MGC-803 human gastric cancer cell line.Conclusion:These biological activities were well correlated with the composition of the extract and EOs,which in turn is affected by the genetic composition of Artemisia vulgaris and geographic location and diverse climatic condition under which it is grown.These findings demonstrate the remarkable potential of Artemisia vulgaris as a valuable source of antioxidant,antibacterial,and anticancer agents.

Ethanol steam reforming over Ni/ZSM-5 nanosheet for hydrogen production

Compared to reforming reactions using hydrocarbons,ethanol steam reforming(ESR)is a sustainable alternative for hydrogen(H_(2))production since ethanol can be produced sustainably using biomass.This work explores the catalyst design strategies for preparing the Ni supported on ZSM-5 zeolite catalysts to promote ESR.Specifically,two-dimensional ZSM-5 nanosheet and conventional ZSM-5 crystal were used as the catalyst carriers and two synthesis strategies,i.e.,in situ encapsulation and wet impregnation method,were employed to prepare the catalysts.Based on the comparative characterization of the catalysts and comparative catalytic assessments,it was found that the combination of the in situ encapsulation synthesis and the ZSM-5 nanosheet carrier was the effective strategy to develop catalysts for promoting H_(2) production via ESR due to the improved mass transfer(through the 2-D structure of ZSM-5 nanosheet)and formation of confined small Ni nanoparticles(resulted via the in situ encapsulation synthesis).In addition,the resulting ZSM-5 nanosheet supported Ni catalyst also showed high Ni dispersion and high accessibility to Ni sites by the reactants,being able to improve the activity and stability of catalysts and suppress metal sintering and coking during ESR at high reaction temperatures.Thus,the Ni supported on ZSM-5 nanosheet catalyst prepared by encapsulation showed the stable performance with~88% ethanol conversion and~65% H_(2) yield achieved during a 48-h longevity test at 550-C.