Tuning the coordination atoms of central metal is an effective means to improve the electrocatalytic activity of atomic catalysts.Herein,iridium(Ir) is proposed to be asymmetrically anchored by sp-N and pyridinic N of...Tuning the coordination atoms of central metal is an effective means to improve the electrocatalytic activity of atomic catalysts.Herein,iridium(Ir) is proposed to be asymmetrically anchored by sp-N and pyridinic N of hydrogen-substituted graphdiyne(HsGDY),and coordinated with OH as an Ir atomic catalyst(Ir_(1)-N-HsGDY).The electron structures,especially the d-band center of Ir atom,are optimized by these specific coordination atoms.Thus,the as-synthesized Ir_(1)-N-HsGDY exhibits excellent electrocatalytic performances for oxygen reduction and hydrogen evolution reactions in both acidic and alkaline media.Benefiting from the unique structure of HsGDY,IrN_(2)(OH)_(3) has been developed and demonstrated to act as the active site in these electrochemical reactions.All those indicate the fresh role of the sp-N in graphdiyne in producing a new anchor way and contributing to promote the electrocatalytic activity,showing a new strategy to design novel electrochemical catalysts.展开更多
Rare earth（Y, La and Nd） doped TiO2 thin films were prepared on glass slides by sol-gel method. The photocatalytic decomposition of methylene blue in aqueous solution was used as a probe reaction to evaluate their p...Rare earth（Y, La and Nd） doped TiO2 thin films were prepared on glass slides by sol-gel method. The photocatalytic decomposition of methylene blue in aqueous solution was used as a probe reaction to evaluate their photocatalytic activities. The effects of hydroxyl groups on hydrophilic and photocatalytic activities were investigated by means of techniques such as X-ray diffraction（XRD）, atomic force microscopy（AFM）, Fourier transform infrared（FTIR）, optical contact angle, UV-Visible spectroscopy and VIS spectroscopy. The results showed that an appropriate doping of rare earth could cause the TiO2 lattice distortion, inhibited phase transition from anatase to rutile, accelerated surface hydroxylation and produced more hydroxyl groups, which resulted in a denser surface and smaller grains（40–60 nm）, and a significant improvement in the hydrophilicity and photoreactivity of TiO2 thin films. The optimal content of rare earth was between 0.1 wt.% and 0.3 wt.%. Moreover, the modification mechanism of rare earth doping was also discussed.展开更多
The minerals of chevkinite group were commonly considered to be anhydrous minerals. The infrared absorption spectrum of natural nonmetamict chevkinite-（Ce） from the aegirine-alkali granite, Miannlng, Sichuan Provinc...The minerals of chevkinite group were commonly considered to be anhydrous minerals. The infrared absorption spectrum of natural nonmetamict chevkinite-（Ce） from the aegirine-alkali granite, Miannlng, Sichuan Province, China, exhibited two broad peaks in the 3600-2800 cm^-1 region owing to the OH stretching. The corresponding H20 content required for the charge balance in formula was 1.27%. The O-H. … O bond lengths maight cover from 0.2658 to 0.2794 nm by the correlated OH stretching energies. An electrostatic charge balance for chevkinite-（Ce） based on the assigned site-population from chemical data was calculated without the hydrogen contribution. The resulting empirical bond-valence sum on 06, 08, 02, 03, 05, and 04 ranged from 1.73 to 1.95 vu. The partial substitution of O by OH may occur in four atom sites： 06, 02, 04, and 05. The small differences in the bond-valence sums between the supposed donors and acceptors may mean a mixed donor/acceptor role of the involved oxygen atoms. The IR spectral features between 3394 and 3035 cm-1 consisted of various hydrous species at different structural sites and orientations. The OH groups in the chevkinlte-（Ce） appeared to be involved in local charge imbalance in the structure and to be present when the mineral crystallized hydrothermally.展开更多
The effect of exogenous hydroxyl,carboxyl groups and/or Sn^(2+) on pyrolysis reactions of poly(L-lactide)(PLLA)was investigated by thermogravimetric analysis(TGA).The activation energy(fa)of pyrolysis reactions was es...The effect of exogenous hydroxyl,carboxyl groups and/or Sn^(2+) on pyrolysis reactions of poly(L-lactide)(PLLA)was investigated by thermogravimetric analysis(TGA).The activation energy(fa)of pyrolysis reactions was estimated by the Kissinger-Akahira-Sunose method.The kinetic models were also explored by the Malek method,and the random degradation behavior was determined by comparing the plots of ln{-ln[1-(1-w)05]}versus 1/7for experimental data from TGA with model reactions.The pyrolysis reaction rate of PLLA was affected slightly by exogenous hydroxyl and carboxyl groups at lower levels of Sn with 65-70 mg·kg^(-1)but increased appreciably in the presence of extraneous Sn^(2+),-COOH/Sn^(2+),or-OH/Sn^(2+).The Ea values for the pyrolysis reactions of the PLLAs that provided lactide were different under the catalysis of Sn2+in different chemical environments because Sn^(2+) can form the new Sn-carboxylate and Sn-alkoxide with exogenous carboxyl and hydroxyl groups,which were different in steric hindrance for the formation of activated complex between Sn^(2+) and PLLA.Under the catalysis of Sn^(2+),a lactide molecule can be directly eliminated selectively at a random position of PLLA molecular chains,and the molecular chain of PLLA cannot change two PLLA fragments at the elimination site of lactide.However,it was regenerated into a new PLLA molecule with the molecular weight reduced by 144 g·mol^(-1).展开更多
Reduced graphene oxide is the precursor to produce graphene in a large scale;however,to date,there has been no consensus on the electronic structure of reduced graphene oxide.In this study,we carried out an ab initio ...Reduced graphene oxide is the precursor to produce graphene in a large scale;however,to date,there has been no consensus on the electronic structure of reduced graphene oxide.In this study,we carried out an ab initio molecular dynamics simulation to investigate the adsorption process of hydroxyl groups on graphene surface.During the adsorption process,the OH group needs to firstly pass through a physical adsorption complex with the OH above the bridge site of two carbon atoms,next to surmount a transition state,then to be adsorbed at the atop site of a carbon atom.With a 5×5 graphene surface,up to 6 hydroxyl groups can be adsorbed on the graphene surface,indicating the concentration coverage of the hydroxyl groups on graphene surface is about 12%.The simulation results show that the negative adsorption energy increases linearly as the number of adsorbed hydroxyl groups increases,and the band gap also increases linearly with the number of adsorbed hydroxyl groups.展开更多
New electron donors with hydroxyl groups were synthesized and characterized spectroscopically. Their redox potentials were determined with cyclic voltammetry, and the comparison with BEDT-TTF [Bis(ethylenedithio)tetra...New electron donors with hydroxyl groups were synthesized and characterized spectroscopically. Their redox potentials were determined with cyclic voltammetry, and the comparison with BEDT-TTF [Bis(ethylenedithio)tetrathiafulvalene] in this aspect was made. These results indicated that the new electron donors had similar electron-donating capabilities as BEDT-TTF.展开更多
Solar-driven CO_(2)conversion and pollutant removal with an S-scheme heterojunction provides promising approach to alleviate energy shortage and environmental crisis,yet the comprehensive regulation of the charge sepa...Solar-driven CO_(2)conversion and pollutant removal with an S-scheme heterojunction provides promising approach to alleviate energy shortage and environmental crisis,yet the comprehensive regulation of the charge separation and the activation sites of reactant molecules remains challenging.Herein,a dual-active groups regulated S-scheme heterojunction for hydroxy-regulated BiOBr modified amino-functionalized g-C_(3)N_(4)(labeled as HBOB/ACN)was designed by spatially separated dual sites with hydroxyl group(OH)and amino group(NH_(2))toward simultaneously photocatalytic CO_(2)reduction and ciprofloxacin(CIP)oxidation.The optimized HBOB/ACN delivers around 2.74-fold CO yield rate and 1.61-times CIP removal rate in comparison to BiOBr/g-C_(3)N_(4)(BOB/CN)without surface groups,which chiefly ascribed the synergistic effect of OH and NH_(2)group.A series of experiments and theoretical calculation unveiled that the OH and NH_(2)group trapped holes and electrons to participate in CIP oxidation and CO_(2)reduction,respectively.Besides,dual-functional coupled reaction system realized the complete utilization of carriers.This work affords deep insights for dual-group modified S-scheme heterojunctions with redox active sites toward dual-functional coupled reaction system for environment purification and solar fuel production.展开更多
The side-chain alkylation of toluene with methanol over alkali-cation-containing zeolite Y is an important reaction for industrial production of styrene,but the exact mechanism of this reaction is still unclear.The mo...The side-chain alkylation of toluene with methanol over alkali-cation-containing zeolite Y is an important reaction for industrial production of styrene,but the exact mechanism of this reaction is still unclear.The most accepted opinion is that the Lewis acid-base sites in zeolite Y activate the transformation from methanol to formaldehyde,the side-chain alkylation of toluene with formaldehyde,and the formation of 2-phenylethanol and styrene afterwards.In this study,we investigate the roles of various types of hydroxyl groups that could possibly exist in zeolite Na-Y during this reaction,including the Br6nsted acid sites and the terminal Al-OH and Si-OH groups,respectively.Through density functional theory （DFT） calculations,we find that the Brtnsted acid sites in Na-Y may catalyze the ring alkylation of toluene and be responsible for the formation of xylene,a side product discovered in experiments.More importantly,we find,for the first time,a new reaction pathway from 2-phenylethanol to styrene over various types of hydroxyl groups in Na-Y,which is kinetically more favorable than the conventional pathway.According to our calculation results,the most possible mechanism for this styrene production process may involve reactions over both the Lewis acid-base sites and the hydroxyl groups in Na-Y.展开更多
Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity a...Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity and selectivity of rare-earth compounds along with no residual impact on polymer product's performance,highly efficient catalytic reduction systems containing sodium borohydride(NaBH_(4))and rare-earth chloride(RECl_(3))were specifically designed for a telechelic carboxyl-terminated liquid fluoroeslastomer,aiming to facilitate the conversion of chainend carboxyl groups into hydroxyl groups and improvement in end-group reactivity.To achieve this,lanthanum chloride(LaCl_(3)),cerium chloride(CeCl_(3)),and neodymium chloride(NdCl_(3))were used separately to form catalytic reduction systems with NaBH_(4).The effects of solvent dosage,reaction temperature,reaction time length,and reductant dosage on carboxylic conversion were investigated,and the molecular chain structure,molecular weight,and functional group content of the raw materials and the products were analyzed and characterized by means of infrared spectroscopy(FTIR),proton nuclear magnetic resonance(^(1)H-NMR),fluorine-19 nuclear magnetic resonance(^(19)F-NMR),gel permeation chromatography(GPC),and chemical titration.Moreover,the catalytic activity and selectivity of the rare-earth chlorides,as well as the corresponding underlying interactions were discussed.Results indicated that the rare-earth-containing catalytic reduction systems studied in this work could efficiently convert the chain-end carboxyl groups into highly active hydroxyl groups,with a highest conversion up to 87.0%and differing catalytic reduction activities ranked as NaBH_(4)/CeCl_(3)>NaBH_(4)/LaCl_(3)>NaBH_(4)/NdCl_(3).Compared with the conventional lithium aluminum hydride(LiAIH_(4))reduction system,the NaBH_(4)/RECl_(3)systems provide multiple advantages such as mild reaction conditions,high conversion ratio with good selectivity,and environmental innocuity,and are potentially applicable as new reduction-catalysis combinations for the synthesis and functionalization of polymer materials.展开更多
A strong influence of nitrogen gas on the content of surface hydroxyl groups of TiO2 films by atomic layer deposition（ALD） was investigated by X-ray photoelectron spectroscopy（XPS）, contact angle measuring system,...A strong influence of nitrogen gas on the content of surface hydroxyl groups of TiO2 films by atomic layer deposition（ALD） was investigated by X-ray photoelectron spectroscopy（XPS）, contact angle measuring system, and UV–Vis spectrophotometer. XPS spectra of O 1s indicate that the content of surface hydroxyl groups is varied when using N2 as carrier gas. The results of water contact angles and optical reflection spectra show that the content variation of surface hydroxyl groups influences the wetting properties and optical reflectivity of TiO2 films. A surface reaction model is suggested to explain the ALD reaction process using N2 as carrier gas.展开更多
YiO2 nanorods have been prepared on ITO substrates by dc reactive magnetron sputtering technique. The hydroxyl groups have been introduced on the nanorods surface. The structure and the optical properties of these nan...YiO2 nanorods have been prepared on ITO substrates by dc reactive magnetron sputtering technique. The hydroxyl groups have been introduced on the nanorods surface. The structure and the optical properties of these nanorods have been studied. The dye-sensitized solar cells （DSSCs） have been assembled using these TiO2 nanorods as photoelectrode. And the effect of the hydroxyl groups on the properties of the photoelectric conversion of the DSSCs has been studied.展开更多
The hydroxyl group of carbocyclic nucleosides was inversed when the compounds were treated with Me3SiCl, KCN and a catalytic mount of NaI in DMF/CH3CN.
Formaldehyde(HCHO)is a significant indoor pollutant found in various sources and poses potential health risks to humans.Noble metal catalysts show efficient and stable catalytic activity for ambient-temperature HCHO o...Formaldehyde(HCHO)is a significant indoor pollutant found in various sources and poses potential health risks to humans.Noble metal catalysts show efficient and stable catalytic activity for ambient-temperature HCHO oxidation,yet suffer from low metal utilization.Efforts focus on designing catalysts with enhanced intrinsic activity and reduced noble metal loading.In this study,we developed a simple pretreatment method using ammonia solution on SiO_(2)carrier to enhance the activity of the Pd/SiO_(2)catalyst for HCHO oxidation.After the carrier was pretreated with an ammonia solution,a significant promoting effect was observed on the Pd/SiO_(2)(NH_(3)·H_(2)O)-R catalyst.It achieved almost complete oxidation of 150 ppmV of HCHO at 25℃,much better than the Pd/SiO_(2)-R(5%HCHO conversion rate).Multiple characterization results indicated that the ammonia solution pretreatment of the SiO_(2)carrier increased the surface defects,facilitating the anchoring of Pd nanoparticles and increasing their dispersion.The increase dispersion of Pd resulted in the generation of additional oxygen vacancies on the catalyst surfaces.The increased in oxygen vacancies on the catalyst was beneficial for enhancing the catalyst's ability to activate H_(2)O to form surface hydroxyl groups,thereby accelerating the catalytic oxidation process of HCHO.The reaction mechanism of HCHO on the Pd/SiO_(2)(NH_(3)·H_(2)O)-R catalyst mainly follows an efficient pathway:firstly,the HCHO being oxidized by surface active hydroxyl groups to formate;subsequently,the formate being oxidized by hydroxyl groups to H_(2)O and CO_(2).This study provides a promising strategy for designing high-performance noble metal catalysts for HCHO catalytic oxidation.展开更多
Selective oxidation of glycerol provides a feasible route towards the sustainable synthesis of high value-added chemicals.Herein,the hydroxyapatite(HAP)supported palladium(Pd)species were fabricated by impregnation an...Selective oxidation of glycerol provides a feasible route towards the sustainable synthesis of high value-added chemicals.Herein,the hydroxyapatite(HAP)supported palladium(Pd)species were fabricated by impregnation and subsequent calcination.The as-obtained heterogeneous Pd catalyst afforded not only excellent selectivity to glyceric acid(GLA)up to 90%with 59%conversion of glycerol but also good recyclability by using molecular oxygen as an oxidant under mild conditions.The characterization of catalysts indicated that both the surface basicity and Pd sites on the catalyst played a crucial role in promoting glycerol oxidation.Notably,it demonstrated that the presence of the vicinal hydroxyl group of glycerol molecule can assist the oxidation reaction via forming a coordination between the vicinal hydroxyl group and Ca^(2+) sites on HAP-derived catalysts.In this catalytic process,the secondary hydroxyl of glycerol kept untouched and the primary hydroxyl of glycerol was converted into carboxyl group,while the Pd species acted as active centers for cooperatively promoting the subsequent oxidation to generate GLA.Additionally,this catalytic system can be extended widely for the oxidative conversion of other vicinal diols into the corresponding a-hydroxycarboxylic acids selectively.Isotope labeling experiment using H_(2)^(18)O confirmed that H_(2)O not only acted as solvent but also was involved in the catalytic cycles.On the basis of the results,a possible reaction mechanism has been proposed.The HAP-supported Pd catalytic system has been shown to serve as an effective approach for the upgrading of bio-derived vicinal diols to high value-added chemicals.展开更多
Spherical polystyrene‐supported ammonium salts containing different linking chains between the support and ammonium groups were prepared as efficient and easily reusable heterogeneous catalysts for the cycloadditions...Spherical polystyrene‐supported ammonium salts containing different linking chains between the support and ammonium groups were prepared as efficient and easily reusable heterogeneous catalysts for the cycloadditions of CO2and epoxides.The effects of the length of the linking chains and a hydroxyl group pendent on the linking chain on the catalytic performance of ionic liquid immobilized catalysts and their mechanisms were studied through experiments and density functional theory calculations.It was found that,compared with a short linking chain,a long chain can make the halogen anion more negative and provide a larger contact area of the catalysts with the reactants,thus enhancing the reaction kinetics.The hydroxyl group can stretch the C-O bonds of the epoxides,promoting the reaction thermodynamics.As a result,for the cycloaddition of propylene oxide,the yield of propylene carbonate is much higher for the catalyst with a long linking chain(yield:91.4%)compared with the yield for that with a short chain(yield:70.9%),and is further increased in the presence of pendent hydroxyl groups(yield:98.5%).The catalyst also shows a high catalytic activity even at mild temperature and good reusability(yield:≥96%for10cycles),and the selectivity is always above99%.展开更多
The paper explores the evolution of thermal behavior of the material by studying the variations in thermal diffusivity using the single beam thermal lens(TL) technique. For this purpose, the decomposition of Cu(OH)_(2...The paper explores the evolution of thermal behavior of the material by studying the variations in thermal diffusivity using the single beam thermal lens(TL) technique. For this purpose, the decomposition of Cu(OH)_(2) into CuO is studied in a time range up to 120 h, by subjecting the sample to morphological, structural, and spectroscopic characterizations. The time evolution of thermal diffusivity can be divided into three regions for demonstrating the dynamics of the reaction. When the reaction is complete, the thermal diffusivity is also found to be saturated. In addition to the morphological modifications,from rods to flakes, the variations in the amount of hydroxyl group are attributed to be responsible for the enhancement of base fluid's thermal diffusivity by 165%. Thus the study unveils the role of hydroxyl groups in the thermal behavior of CuO.展开更多
Compound 2 with 14β-hydroxyl group was successfully converted into its epimerized α-counterpart via oxidation - reduction.The elimination product (6) was auto-oxidized to epoxide 8,even in the solid state
Quaternary phosphonium salts （QPS） with reactive groups used as antibacterial agents are promising which could be covalently linked to inert polymer surfaces by in situ polymerization. In this work, two kinds of qua...Quaternary phosphonium salts （QPS） with reactive groups used as antibacterial agents are promising which could be covalently linked to inert polymer surfaces by in situ polymerization. In this work, two kinds of quaternary phosphonium salts with hydroxyl groups were synthesized successfully. Characterization of these two quaternary phosphonium salts was performed by the Fourier transform infrared spectroscopy （FT-IR） and nuclear magnetic resonance （NMR） spectrometry. The thermal stability and antibacterial activity of antibacterial agents were also investigated by using thermo-gravimetric analysis, differential scanning calorimetry （TG-DSC） and agar diffusion method. The test results showed that these two QPS exhibited good thermal stability and excellent antibacterial activity against both bacteria： Staphylococcus aureus and Escherichia coll.展开更多
The oxyhydroxides boehmite,goethite,and manganite were synthesized,and their structure,texture,and morphology features were determined by different analytical techniques.Content of surface hydroxyl groups and zero poi...The oxyhydroxides boehmite,goethite,and manganite were synthesized,and their structure,texture,and morphology features were determined by different analytical techniques.Content of surface hydroxyl groups and zero point of charge(pH_(zpc))were measured by potentiometry,and the surface fractal dimension(D_(f))values were obtained through adsorption-desorption N_(2) iso-therms and the Pfeifer and Cole method.The synthesized materials resulted crystalline,mesoporous,pure,and thermally stable,exhibiting high surface areas,between 188 and 413 m^(2)/g.The pH_(zpc) values were 9.2,12.4,and 2.2 and surface hydroxyl group contents were for 1.16,1.7,and 0.855 meq OH-/g,for boehmite,goethite,and manganite,respectively.Surface fractal dimensions were 1.5,1.7,and 1.4 for boehmite,goethite and manganite,respectively,de-noting relatively smooth surfaces.Surface hydroxyl group content linearly correlated with D_(f) values.Characterization of these oxyhydroxides is valuable for several physicochemical adsorption processes of contaminants present in aqueous media.展开更多
Producing hydrogen peroxide(H_(2)O_(2))through visible-light-driven photocatalytic oxygen reduction in pure water is crucial for sustainable ecological applications but poses significant challenges.It include the rapi...Producing hydrogen peroxide(H_(2)O_(2))through visible-light-driven photocatalytic oxygen reduction in pure water is crucial for sustainable ecological applications but poses significant challenges.It include the rapid recombination of electron-hole pairs and a scarcity of effective catalytic sites,which traditionally limit the process efficiency.To address these issues,we have developed a novel catalyst,designated as KCNOH,which consists of a three-dimensional(3D)porous g-C_(3)N_(4)framework doped with potassium(K^(+))and modified with surface hydroxyl groups(–OH).This design significantly enhances H_(2)O_(2)yield,achieving 91.36μmol g^(-1)h^(-1)(cut 420 nm)-a yield approximately 36 times higher than conventional bulk g-C_(3)N_(4)(2.57μmol g^(-1)h^(-1)).The introduction of a 3D porous structure provides an abundance of active-sites.The dual-dipole mechanism,facilitated by K^(+) ions and hydroxyl groups,plays a pivotal role by efficiently transporting photogenerated electrons and consuming holes,respectively.Through density functional theory(DFT)calculations,the changes in the band structure of the catalyst caused by the doping of K^(+) and the grafting of–OH were elucidated.In addition,the transition state affinity of oxygen induced by the–OH was also studied to reveal the synergistic catalytic mechanism.This mechanism markedly reduces carrier recombination and accelerates charge migration,underscoring its importance in catalyst design.Our findings not only improve the understanding of charge dynamics but also open novel perspectives for the design of highly-efficient composite materials,which is crucial for energy and environmental applications.展开更多
基金supported by the National Natural Science Foundation of China(22172090,21790051)the National Key Research and Development Project of China(2022YFA1204500,2022YFA1204501)+2 种基金the Natural Science Foundation of Shan-dong Province(ZR2021MB015)the Open Funds of the State Key Laboratory of Electroanalytical Chemistry(SKLEAC202202)the Young Scholars Program of Shandong University。
文摘Tuning the coordination atoms of central metal is an effective means to improve the electrocatalytic activity of atomic catalysts.Herein,iridium(Ir) is proposed to be asymmetrically anchored by sp-N and pyridinic N of hydrogen-substituted graphdiyne(HsGDY),and coordinated with OH as an Ir atomic catalyst(Ir_(1)-N-HsGDY).The electron structures,especially the d-band center of Ir atom,are optimized by these specific coordination atoms.Thus,the as-synthesized Ir_(1)-N-HsGDY exhibits excellent electrocatalytic performances for oxygen reduction and hydrogen evolution reactions in both acidic and alkaline media.Benefiting from the unique structure of HsGDY,IrN_(2)(OH)_(3) has been developed and demonstrated to act as the active site in these electrochemical reactions.All those indicate the fresh role of the sp-N in graphdiyne in producing a new anchor way and contributing to promote the electrocatalytic activity,showing a new strategy to design novel electrochemical catalysts.
基金Project supported by the National Natural Science Foundation of China(51162022,21201098)Jiangxi Provincial Education Department(GJJ14126)
文摘Rare earth（Y, La and Nd） doped TiO2 thin films were prepared on glass slides by sol-gel method. The photocatalytic decomposition of methylene blue in aqueous solution was used as a probe reaction to evaluate their photocatalytic activities. The effects of hydroxyl groups on hydrophilic and photocatalytic activities were investigated by means of techniques such as X-ray diffraction（XRD）, atomic force microscopy（AFM）, Fourier transform infrared（FTIR）, optical contact angle, UV-Visible spectroscopy and VIS spectroscopy. The results showed that an appropriate doping of rare earth could cause the TiO2 lattice distortion, inhibited phase transition from anatase to rutile, accelerated surface hydroxylation and produced more hydroxyl groups, which resulted in a denser surface and smaller grains（40–60 nm）, and a significant improvement in the hydrophilicity and photoreactivity of TiO2 thin films. The optimal content of rare earth was between 0.1 wt.% and 0.3 wt.%. Moreover, the modification mechanism of rare earth doping was also discussed.
基金the National Natural Science Foundation of China (40572029)
文摘The minerals of chevkinite group were commonly considered to be anhydrous minerals. The infrared absorption spectrum of natural nonmetamict chevkinite-（Ce） from the aegirine-alkali granite, Miannlng, Sichuan Province, China, exhibited two broad peaks in the 3600-2800 cm^-1 region owing to the OH stretching. The corresponding H20 content required for the charge balance in formula was 1.27%. The O-H. … O bond lengths maight cover from 0.2658 to 0.2794 nm by the correlated OH stretching energies. An electrostatic charge balance for chevkinite-（Ce） based on the assigned site-population from chemical data was calculated without the hydrogen contribution. The resulting empirical bond-valence sum on 06, 08, 02, 03, 05, and 04 ranged from 1.73 to 1.95 vu. The partial substitution of O by OH may occur in four atom sites： 06, 02, 04, and 05. The small differences in the bond-valence sums between the supposed donors and acceptors may mean a mixed donor/acceptor role of the involved oxygen atoms. The IR spectral features between 3394 and 3035 cm-1 consisted of various hydrous species at different structural sites and orientations. The OH groups in the chevkinlte-（Ce） appeared to be involved in local charge imbalance in the structure and to be present when the mineral crystallized hydrothermally.
基金the National Key Research and Development Program of China(No.2016YFB0302500)the National Natural Science Foundation of China(Nos.51873209,51873210,51773194 and 51973219)Jilin Scientific and Technological Development Program,China(No.20200403022SF).
文摘The effect of exogenous hydroxyl,carboxyl groups and/or Sn^(2+) on pyrolysis reactions of poly(L-lactide)(PLLA)was investigated by thermogravimetric analysis(TGA).The activation energy(fa)of pyrolysis reactions was estimated by the Kissinger-Akahira-Sunose method.The kinetic models were also explored by the Malek method,and the random degradation behavior was determined by comparing the plots of ln{-ln[1-(1-w)05]}versus 1/7for experimental data from TGA with model reactions.The pyrolysis reaction rate of PLLA was affected slightly by exogenous hydroxyl and carboxyl groups at lower levels of Sn with 65-70 mg·kg^(-1)but increased appreciably in the presence of extraneous Sn^(2+),-COOH/Sn^(2+),or-OH/Sn^(2+).The Ea values for the pyrolysis reactions of the PLLAs that provided lactide were different under the catalysis of Sn2+in different chemical environments because Sn^(2+) can form the new Sn-carboxylate and Sn-alkoxide with exogenous carboxyl and hydroxyl groups,which were different in steric hindrance for the formation of activated complex between Sn^(2+) and PLLA.Under the catalysis of Sn^(2+),a lactide molecule can be directly eliminated selectively at a random position of PLLA molecular chains,and the molecular chain of PLLA cannot change two PLLA fragments at the elimination site of lactide.However,it was regenerated into a new PLLA molecule with the molecular weight reduced by 144 g·mol^(-1).
基金supported by the National Natural Science Foundation of China(No.11774206)Taishan Scholarship Fund from Shandong Province。
文摘Reduced graphene oxide is the precursor to produce graphene in a large scale;however,to date,there has been no consensus on the electronic structure of reduced graphene oxide.In this study,we carried out an ab initio molecular dynamics simulation to investigate the adsorption process of hydroxyl groups on graphene surface.During the adsorption process,the OH group needs to firstly pass through a physical adsorption complex with the OH above the bridge site of two carbon atoms,next to surmount a transition state,then to be adsorbed at the atop site of a carbon atom.With a 5×5 graphene surface,up to 6 hydroxyl groups can be adsorbed on the graphene surface,indicating the concentration coverage of the hydroxyl groups on graphene surface is about 12%.The simulation results show that the negative adsorption energy increases linearly as the number of adsorbed hydroxyl groups increases,and the band gap also increases linearly with the number of adsorbed hydroxyl groups.
基金the Chinese Academy of Sciences(KJ951-A1-501-03)
文摘New electron donors with hydroxyl groups were synthesized and characterized spectroscopically. Their redox potentials were determined with cyclic voltammetry, and the comparison with BEDT-TTF [Bis(ethylenedithio)tetrathiafulvalene] in this aspect was made. These results indicated that the new electron donors had similar electron-donating capabilities as BEDT-TTF.
文摘Solar-driven CO_(2)conversion and pollutant removal with an S-scheme heterojunction provides promising approach to alleviate energy shortage and environmental crisis,yet the comprehensive regulation of the charge separation and the activation sites of reactant molecules remains challenging.Herein,a dual-active groups regulated S-scheme heterojunction for hydroxy-regulated BiOBr modified amino-functionalized g-C_(3)N_(4)(labeled as HBOB/ACN)was designed by spatially separated dual sites with hydroxyl group(OH)and amino group(NH_(2))toward simultaneously photocatalytic CO_(2)reduction and ciprofloxacin(CIP)oxidation.The optimized HBOB/ACN delivers around 2.74-fold CO yield rate and 1.61-times CIP removal rate in comparison to BiOBr/g-C_(3)N_(4)(BOB/CN)without surface groups,which chiefly ascribed the synergistic effect of OH and NH_(2)group.A series of experiments and theoretical calculation unveiled that the OH and NH_(2)group trapped holes and electrons to participate in CIP oxidation and CO_(2)reduction,respectively.Besides,dual-functional coupled reaction system realized the complete utilization of carriers.This work affords deep insights for dual-group modified S-scheme heterojunctions with redox active sites toward dual-functional coupled reaction system for environment purification and solar fuel production.
文摘The side-chain alkylation of toluene with methanol over alkali-cation-containing zeolite Y is an important reaction for industrial production of styrene,but the exact mechanism of this reaction is still unclear.The most accepted opinion is that the Lewis acid-base sites in zeolite Y activate the transformation from methanol to formaldehyde,the side-chain alkylation of toluene with formaldehyde,and the formation of 2-phenylethanol and styrene afterwards.In this study,we investigate the roles of various types of hydroxyl groups that could possibly exist in zeolite Na-Y during this reaction,including the Br6nsted acid sites and the terminal Al-OH and Si-OH groups,respectively.Through density functional theory （DFT） calculations,we find that the Brtnsted acid sites in Na-Y may catalyze the ring alkylation of toluene and be responsible for the formation of xylene,a side product discovered in experiments.More importantly,we find,for the first time,a new reaction pathway from 2-phenylethanol to styrene over various types of hydroxyl groups in Na-Y,which is kinetically more favorable than the conventional pathway.According to our calculation results,the most possible mechanism for this styrene production process may involve reactions over both the Lewis acid-base sites and the hydroxyl groups in Na-Y.
文摘Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity and selectivity of rare-earth compounds along with no residual impact on polymer product's performance,highly efficient catalytic reduction systems containing sodium borohydride(NaBH_(4))and rare-earth chloride(RECl_(3))were specifically designed for a telechelic carboxyl-terminated liquid fluoroeslastomer,aiming to facilitate the conversion of chainend carboxyl groups into hydroxyl groups and improvement in end-group reactivity.To achieve this,lanthanum chloride(LaCl_(3)),cerium chloride(CeCl_(3)),and neodymium chloride(NdCl_(3))were used separately to form catalytic reduction systems with NaBH_(4).The effects of solvent dosage,reaction temperature,reaction time length,and reductant dosage on carboxylic conversion were investigated,and the molecular chain structure,molecular weight,and functional group content of the raw materials and the products were analyzed and characterized by means of infrared spectroscopy(FTIR),proton nuclear magnetic resonance(^(1)H-NMR),fluorine-19 nuclear magnetic resonance(^(19)F-NMR),gel permeation chromatography(GPC),and chemical titration.Moreover,the catalytic activity and selectivity of the rare-earth chlorides,as well as the corresponding underlying interactions were discussed.Results indicated that the rare-earth-containing catalytic reduction systems studied in this work could efficiently convert the chain-end carboxyl groups into highly active hydroxyl groups,with a highest conversion up to 87.0%and differing catalytic reduction activities ranked as NaBH_(4)/CeCl_(3)>NaBH_(4)/LaCl_(3)>NaBH_(4)/NdCl_(3).Compared with the conventional lithium aluminum hydride(LiAIH_(4))reduction system,the NaBH_(4)/RECl_(3)systems provide multiple advantages such as mild reaction conditions,high conversion ratio with good selectivity,and environmental innocuity,and are potentially applicable as new reduction-catalysis combinations for the synthesis and functionalization of polymer materials.
基金financially supported by the National Science and Technology Major Project (No. 2009ZX02037-003)the China Postdoctoral Science Foundation (No. 2011M500996)
文摘A strong influence of nitrogen gas on the content of surface hydroxyl groups of TiO2 films by atomic layer deposition（ALD） was investigated by X-ray photoelectron spectroscopy（XPS）, contact angle measuring system, and UV–Vis spectrophotometer. XPS spectra of O 1s indicate that the content of surface hydroxyl groups is varied when using N2 as carrier gas. The results of water contact angles and optical reflection spectra show that the content variation of surface hydroxyl groups influences the wetting properties and optical reflectivity of TiO2 films. A surface reaction model is suggested to explain the ALD reaction process using N2 as carrier gas.
文摘YiO2 nanorods have been prepared on ITO substrates by dc reactive magnetron sputtering technique. The hydroxyl groups have been introduced on the nanorods surface. The structure and the optical properties of these nanorods have been studied. The dye-sensitized solar cells （DSSCs） have been assembled using these TiO2 nanorods as photoelectrode. And the effect of the hydroxyl groups on the properties of the photoelectric conversion of the DSSCs has been studied.
文摘The hydroxyl group of carbocyclic nucleosides was inversed when the compounds were treated with Me3SiCl, KCN and a catalytic mount of NaI in DMF/CH3CN.
基金supported by the Sanming University(No.23YG05)the Science Foundation of Fujian Province(No.2023J011027).
文摘Formaldehyde(HCHO)is a significant indoor pollutant found in various sources and poses potential health risks to humans.Noble metal catalysts show efficient and stable catalytic activity for ambient-temperature HCHO oxidation,yet suffer from low metal utilization.Efforts focus on designing catalysts with enhanced intrinsic activity and reduced noble metal loading.In this study,we developed a simple pretreatment method using ammonia solution on SiO_(2)carrier to enhance the activity of the Pd/SiO_(2)catalyst for HCHO oxidation.After the carrier was pretreated with an ammonia solution,a significant promoting effect was observed on the Pd/SiO_(2)(NH_(3)·H_(2)O)-R catalyst.It achieved almost complete oxidation of 150 ppmV of HCHO at 25℃,much better than the Pd/SiO_(2)-R(5%HCHO conversion rate).Multiple characterization results indicated that the ammonia solution pretreatment of the SiO_(2)carrier increased the surface defects,facilitating the anchoring of Pd nanoparticles and increasing their dispersion.The increase dispersion of Pd resulted in the generation of additional oxygen vacancies on the catalyst surfaces.The increased in oxygen vacancies on the catalyst was beneficial for enhancing the catalyst's ability to activate H_(2)O to form surface hydroxyl groups,thereby accelerating the catalytic oxidation process of HCHO.The reaction mechanism of HCHO on the Pd/SiO_(2)(NH_(3)·H_(2)O)-R catalyst mainly follows an efficient pathway:firstly,the HCHO being oxidized by surface active hydroxyl groups to formate;subsequently,the formate being oxidized by hydroxyl groups to H_(2)O and CO_(2).This study provides a promising strategy for designing high-performance noble metal catalysts for HCHO catalytic oxidation.
基金support from the National Natural Science Foundation of China(21773061,21978095)Innovation Program of Shanghai Municipal Education Commission(15ZZ031)the Fundamental Research Funds for the Central Universities。
文摘Selective oxidation of glycerol provides a feasible route towards the sustainable synthesis of high value-added chemicals.Herein,the hydroxyapatite(HAP)supported palladium(Pd)species were fabricated by impregnation and subsequent calcination.The as-obtained heterogeneous Pd catalyst afforded not only excellent selectivity to glyceric acid(GLA)up to 90%with 59%conversion of glycerol but also good recyclability by using molecular oxygen as an oxidant under mild conditions.The characterization of catalysts indicated that both the surface basicity and Pd sites on the catalyst played a crucial role in promoting glycerol oxidation.Notably,it demonstrated that the presence of the vicinal hydroxyl group of glycerol molecule can assist the oxidation reaction via forming a coordination between the vicinal hydroxyl group and Ca^(2+) sites on HAP-derived catalysts.In this catalytic process,the secondary hydroxyl of glycerol kept untouched and the primary hydroxyl of glycerol was converted into carboxyl group,while the Pd species acted as active centers for cooperatively promoting the subsequent oxidation to generate GLA.Additionally,this catalytic system can be extended widely for the oxidative conversion of other vicinal diols into the corresponding a-hydroxycarboxylic acids selectively.Isotope labeling experiment using H_(2)^(18)O confirmed that H_(2)O not only acted as solvent but also was involved in the catalytic cycles.On the basis of the results,a possible reaction mechanism has been proposed.The HAP-supported Pd catalytic system has been shown to serve as an effective approach for the upgrading of bio-derived vicinal diols to high value-added chemicals.
基金supported by the National Natural Science Foundation of China(21406031,21476044,U1663223)the Changjiang Scholars Program(T2012049)+3 种基金the State Key Laboratory of Fine Chemicals(KF1507)Dalian High-Level Talent Support Program(2015R056)Education Department of the Liaoning Province of China(LT2015007)Fundamental Research Funds for the Central Universities(DUT16TD19)~~
文摘Spherical polystyrene‐supported ammonium salts containing different linking chains between the support and ammonium groups were prepared as efficient and easily reusable heterogeneous catalysts for the cycloadditions of CO2and epoxides.The effects of the length of the linking chains and a hydroxyl group pendent on the linking chain on the catalytic performance of ionic liquid immobilized catalysts and their mechanisms were studied through experiments and density functional theory calculations.It was found that,compared with a short linking chain,a long chain can make the halogen anion more negative and provide a larger contact area of the catalysts with the reactants,thus enhancing the reaction kinetics.The hydroxyl group can stretch the C-O bonds of the epoxides,promoting the reaction thermodynamics.As a result,for the cycloaddition of propylene oxide,the yield of propylene carbonate is much higher for the catalyst with a long linking chain(yield:91.4%)compared with the yield for that with a short chain(yield:70.9%),and is further increased in the presence of pendent hydroxyl groups(yield:98.5%).The catalyst also shows a high catalytic activity even at mild temperature and good reusability(yield:≥96%for10cycles),and the selectivity is always above99%.
文摘The paper explores the evolution of thermal behavior of the material by studying the variations in thermal diffusivity using the single beam thermal lens(TL) technique. For this purpose, the decomposition of Cu(OH)_(2) into CuO is studied in a time range up to 120 h, by subjecting the sample to morphological, structural, and spectroscopic characterizations. The time evolution of thermal diffusivity can be divided into three regions for demonstrating the dynamics of the reaction. When the reaction is complete, the thermal diffusivity is also found to be saturated. In addition to the morphological modifications,from rods to flakes, the variations in the amount of hydroxyl group are attributed to be responsible for the enhancement of base fluid's thermal diffusivity by 165%. Thus the study unveils the role of hydroxyl groups in the thermal behavior of CuO.
文摘Compound 2 with 14β-hydroxyl group was successfully converted into its epimerized α-counterpart via oxidation - reduction.The elimination product (6) was auto-oxidized to epoxide 8,even in the solid state
文摘Quaternary phosphonium salts （QPS） with reactive groups used as antibacterial agents are promising which could be covalently linked to inert polymer surfaces by in situ polymerization. In this work, two kinds of quaternary phosphonium salts with hydroxyl groups were synthesized successfully. Characterization of these two quaternary phosphonium salts was performed by the Fourier transform infrared spectroscopy （FT-IR） and nuclear magnetic resonance （NMR） spectrometry. The thermal stability and antibacterial activity of antibacterial agents were also investigated by using thermo-gravimetric analysis, differential scanning calorimetry （TG-DSC） and agar diffusion method. The test results showed that these two QPS exhibited good thermal stability and excellent antibacterial activity against both bacteria： Staphylococcus aureus and Escherichia coll.
文摘The oxyhydroxides boehmite,goethite,and manganite were synthesized,and their structure,texture,and morphology features were determined by different analytical techniques.Content of surface hydroxyl groups and zero point of charge(pH_(zpc))were measured by potentiometry,and the surface fractal dimension(D_(f))values were obtained through adsorption-desorption N_(2) iso-therms and the Pfeifer and Cole method.The synthesized materials resulted crystalline,mesoporous,pure,and thermally stable,exhibiting high surface areas,between 188 and 413 m^(2)/g.The pH_(zpc) values were 9.2,12.4,and 2.2 and surface hydroxyl group contents were for 1.16,1.7,and 0.855 meq OH-/g,for boehmite,goethite,and manganite,respectively.Surface fractal dimensions were 1.5,1.7,and 1.4 for boehmite,goethite and manganite,respectively,de-noting relatively smooth surfaces.Surface hydroxyl group content linearly correlated with D_(f) values.Characterization of these oxyhydroxides is valuable for several physicochemical adsorption processes of contaminants present in aqueous media.
基金supported by the National Key Research and Development Program of China(No.2021YFB4000405)National Natural Science Foundation of China(52270115,52236003,and 22109178)Science Foundation of China University of Petroleum Beijing(Nos.2462023YJRC032 and 2462023YJRC022).
文摘Producing hydrogen peroxide(H_(2)O_(2))through visible-light-driven photocatalytic oxygen reduction in pure water is crucial for sustainable ecological applications but poses significant challenges.It include the rapid recombination of electron-hole pairs and a scarcity of effective catalytic sites,which traditionally limit the process efficiency.To address these issues,we have developed a novel catalyst,designated as KCNOH,which consists of a three-dimensional(3D)porous g-C_(3)N_(4)framework doped with potassium(K^(+))and modified with surface hydroxyl groups(–OH).This design significantly enhances H_(2)O_(2)yield,achieving 91.36μmol g^(-1)h^(-1)(cut 420 nm)-a yield approximately 36 times higher than conventional bulk g-C_(3)N_(4)(2.57μmol g^(-1)h^(-1)).The introduction of a 3D porous structure provides an abundance of active-sites.The dual-dipole mechanism,facilitated by K^(+) ions and hydroxyl groups,plays a pivotal role by efficiently transporting photogenerated electrons and consuming holes,respectively.Through density functional theory(DFT)calculations,the changes in the band structure of the catalyst caused by the doping of K^(+) and the grafting of–OH were elucidated.In addition,the transition state affinity of oxygen induced by the–OH was also studied to reveal the synergistic catalytic mechanism.This mechanism markedly reduces carrier recombination and accelerates charge migration,underscoring its importance in catalyst design.Our findings not only improve the understanding of charge dynamics but also open novel perspectives for the design of highly-efficient composite materials,which is crucial for energy and environmental applications.
