The present work,in which cellulose isolated from formic acid fractionation(FAC)is decorated with polyetherimide(PEI)to attain highly efficient cellulose-derived PdAgbimetallic catalyst(PdAg-PEI-FAC),has been investig...The present work,in which cellulose isolated from formic acid fractionation(FAC)is decorated with polyetherimide(PEI)to attain highly efficient cellulose-derived PdAgbimetallic catalyst(PdAg-PEI-FAC),has been investigated,and the catalyst properties are characterized by XRD,XPS,BET,ICP-AES and HAADF-STEM.The as-obtained Pd_(3.75)Ag_(3.75)-PEI-FAC exhibits excellent catalytic performance for H_(2)evolution from a sodium formate-free formic acid(FA)aqueous medium at ambient temperature and the turnover frequency(TOF)reaches a high value of 2875 h^(-1)which is superior to most of the previously reported Pd-based heterogeneous catalysts supported on a carbon matrix in the literature.The remarkable catalytic activities of PdAg-PEI-FAC result from high dispersion Pd and synergistic effects between the PdAg bimetallic system.Furthermore,the amide(-NH)group in PEI coated on cellulose acting as a proton scavenger efficiently improves the catalytic property of catalyst.In addition,the critical factors affecting H;release,such as FA concentration,reaction temperature,PdAg compositions and support matrix type,are also evaluated.Based on the experimental results,the probable three-step mechanism of H_(2)evolution from FA over Pd_(3.75)Ag_(3.75)-PEI-FAC is proposed.In the end,the activation energy(Ea)of Pd_(3.75)Ag_(3.75)-PEI-FAC catalyst is calculated to 53.97 kJ mol^(-1),and this catalyst shows unique robustness and satisfactory re-usability with no loss of catalytic activity after five recycles.The findings in this work provide a novel routine from lignocellulose fractionation towards cellulose-derived catalyst for H_(2)evolution.展开更多
The synthesis of 5-substituted 1H-tetrazoles in n,n-dimethylformamide（DMF） with b-cyclodextrin（β-CD） as catalyst can get an excellent yield in short reaction time.The interaction of β-CD with p-chlorobenzonitril...The synthesis of 5-substituted 1H-tetrazoles in n,n-dimethylformamide（DMF） with b-cyclodextrin（β-CD） as catalyst can get an excellent yield in short reaction time.The interaction of β-CD with p-chlorobenzonitrile plays an important role in this process.This paper studies the complex of β-CD with p-chlorobenzonitrile using density functional theory（DFT） method.The minimum energy structure is investigated in water,DMF and DMSO.Hydrogen bonds are researched on the basis of natural bonding orbital（NBO） analysis.The relative position between p-chlorobenzonitrile and β-CD in DMF is confirmed by 1H nuclear magnetic resonance（1H NMR）.The data from 13 C and 15 N spectra indicate that more positive charges focus on the carbon atom of cyanogroup（C11） and more negative charges concentrate on the nitrogen atom of cyanogroup（N12） upon complexation.The results from frontier molecular orbitals and Mulliken charge reveal that β-CD catalyst improves the reactivity and electrophilicity of p-chlorobenzonitrile.Meanwhile,the functional group of p-chlorobenzonitrile is easier to be attacked by azide ions in the presence of β-CD as catalyst.展开更多
Single-atom catalysts have high catalytic activity due to their unique quantum size effects and optimal atom utilization.Herein,visi-ble-light-responsive photocatalysts were designed by coupling CdS with graphene quan...Single-atom catalysts have high catalytic activity due to their unique quantum size effects and optimal atom utilization.Herein,visi-ble-light-responsive photocatalysts were designed by coupling CdS with graphene quantum dots(GQDs)and platinum single atoms(PtSAs).GQDs and PtSAs were successively loaded on ultrathin CdS nanosheets through freeze-drying and in-situ photocatalytic reduction.The synergistic effect between PtSAs and GQDs results in superior photocatalytic activity with a hydrogen production rate of 13488μmol h^(-1)g^(-1)as well as the maximum apparent quantum efficiency(AQE)of 35.5%in lactic acid aqueous solution,which is 62 times higher than that of pristine CdS(213μmol g^(-1)h^(-1)).The energy conversion efficiency is ca.13.05%.As a photosensitizer and an electron reservoir,GQDs can not only extend the light response of CdS to the visible-light region(400-800 nm),but also promotes the separation of photoinduced electron-hole pairs.Meanwhile,PtSAs,with unique electronic and geometric features,can provide more efficient proton reduction sites.This finding provides an effective strategy to remarkably improve the photocatalytic H_(2) production performance.展开更多
A new polymeric nanocomposite photocatalyst A15-CdS with large spherical beads (0.70-0.80 mm in diameter) was fabricated for efficient Rhodamine B (RhB) photodegradation with facile separation during cyclic runs,and p...A new polymeric nanocomposite photocatalyst A15-CdS with large spherical beads (0.70-0.80 mm in diameter) was fabricated for efficient Rhodamine B (RhB) photodegradation with facile separation during cyclic runs,and photocorrosion,a congenital drawback of CdS,was successfully inhibited for A15-CdS.The nanocomposite catalyst was obtained by impregnating CdS nanoparticles within porous polymeric cation exchanger A15 through a facile inner-surface deposition.CdS nanoparticles (<20 nm) immobilized in A15 were deliberately distributed within an outside ring-like region of 40-50 m in depth,which is dominant for photoreaction because visible light is not expected to permeate through the inner region of nontransparent A15.As expected,efficient RhB photodegradation by A15-CdS was achieved under visible light irradiation,and large-size A15-CdS beads are expected to result in their facile separation from solution for repeated use.More significantly,negligible photocorrosion for the hybrid catalyst A15-CdS was demonstrated by the constant photodegradation efficiency and negligible CdS loss during five-cycle runs.The results indicated that nano-CdS immobilization within A15 would greatly improve the applicability of CdS nanoparticles in practical environmental remediation.展开更多
基金supported by the National Natural Science Foundation of China(No.20906034)the Key Academic Program of the 3rd Phase"211 Project" of South China Agricultural University(No.2009B010100001)China Postdoctoral Science Foundation(No.20080430820)
基金financially funded by the National Natural Science Foundation of China(NSFC,21476016,21776009)Fundamental Research Funds for the Central Universitiesthe special project for the construction of innovative province in Hunan Province of China(2019NK2031-3)
文摘The present work,in which cellulose isolated from formic acid fractionation(FAC)is decorated with polyetherimide(PEI)to attain highly efficient cellulose-derived PdAgbimetallic catalyst(PdAg-PEI-FAC),has been investigated,and the catalyst properties are characterized by XRD,XPS,BET,ICP-AES and HAADF-STEM.The as-obtained Pd_(3.75)Ag_(3.75)-PEI-FAC exhibits excellent catalytic performance for H_(2)evolution from a sodium formate-free formic acid(FA)aqueous medium at ambient temperature and the turnover frequency(TOF)reaches a high value of 2875 h^(-1)which is superior to most of the previously reported Pd-based heterogeneous catalysts supported on a carbon matrix in the literature.The remarkable catalytic activities of PdAg-PEI-FAC result from high dispersion Pd and synergistic effects between the PdAg bimetallic system.Furthermore,the amide(-NH)group in PEI coated on cellulose acting as a proton scavenger efficiently improves the catalytic property of catalyst.In addition,the critical factors affecting H;release,such as FA concentration,reaction temperature,PdAg compositions and support matrix type,are also evaluated.Based on the experimental results,the probable three-step mechanism of H_(2)evolution from FA over Pd_(3.75)Ag_(3.75)-PEI-FAC is proposed.In the end,the activation energy(Ea)of Pd_(3.75)Ag_(3.75)-PEI-FAC catalyst is calculated to 53.97 kJ mol^(-1),and this catalyst shows unique robustness and satisfactory re-usability with no loss of catalytic activity after five recycles.The findings in this work provide a novel routine from lignocellulose fractionation towards cellulose-derived catalyst for H_(2)evolution.
基金supported by the National Natural Science Foundation of China(51672089)the Science and Technology Planning Project of Guangdong Province(2015B020215011)the State Key Laboratory of Advanced Technology for Material Synthesis and Processing(Wuhan University of Technology)(2015-KF-7)~~
基金supported by the Scientific Research Fund of Hunan Provincial Education Department(No.12A132)
文摘The synthesis of 5-substituted 1H-tetrazoles in n,n-dimethylformamide（DMF） with b-cyclodextrin（β-CD） as catalyst can get an excellent yield in short reaction time.The interaction of β-CD with p-chlorobenzonitrile plays an important role in this process.This paper studies the complex of β-CD with p-chlorobenzonitrile using density functional theory（DFT） method.The minimum energy structure is investigated in water,DMF and DMSO.Hydrogen bonds are researched on the basis of natural bonding orbital（NBO） analysis.The relative position between p-chlorobenzonitrile and β-CD in DMF is confirmed by 1H nuclear magnetic resonance（1H NMR）.The data from 13 C and 15 N spectra indicate that more positive charges focus on the carbon atom of cyanogroup（C11） and more negative charges concentrate on the nitrogen atom of cyanogroup（N12） upon complexation.The results from frontier molecular orbitals and Mulliken charge reveal that β-CD catalyst improves the reactivity and electrophilicity of p-chlorobenzonitrile.Meanwhile,the functional group of p-chlorobenzonitrile is easier to be attacked by azide ions in the presence of β-CD as catalyst.
基金supported by the National Key Research and Development Program of China(2018YFB1502001)National Natural Science Foundation of China(NSFC)(Nos.51872220,51961135303,51932007,U1905215,21871217 and 52073223)Deanship of Scientific Research(DSR)at King Abdulaziz University,Jeddah(No.RG-72-130-42)。
文摘Single-atom catalysts have high catalytic activity due to their unique quantum size effects and optimal atom utilization.Herein,visi-ble-light-responsive photocatalysts were designed by coupling CdS with graphene quantum dots(GQDs)and platinum single atoms(PtSAs).GQDs and PtSAs were successively loaded on ultrathin CdS nanosheets through freeze-drying and in-situ photocatalytic reduction.The synergistic effect between PtSAs and GQDs results in superior photocatalytic activity with a hydrogen production rate of 13488μmol h^(-1)g^(-1)as well as the maximum apparent quantum efficiency(AQE)of 35.5%in lactic acid aqueous solution,which is 62 times higher than that of pristine CdS(213μmol g^(-1)h^(-1)).The energy conversion efficiency is ca.13.05%.As a photosensitizer and an electron reservoir,GQDs can not only extend the light response of CdS to the visible-light region(400-800 nm),but also promotes the separation of photoinduced electron-hole pairs.Meanwhile,PtSAs,with unique electronic and geometric features,can provide more efficient proton reduction sites.This finding provides an effective strategy to remarkably improve the photocatalytic H_(2) production performance.
基金support from the National Natural Science Foundation of China (51008151 & 51078179)Jiangsu Natural Science Foundation (BK2009253)+1 种基金the Ministry of Education of China (200802840034)the National High Technology Research and Development Program of China (2009AA06A418)
文摘A new polymeric nanocomposite photocatalyst A15-CdS with large spherical beads (0.70-0.80 mm in diameter) was fabricated for efficient Rhodamine B (RhB) photodegradation with facile separation during cyclic runs,and photocorrosion,a congenital drawback of CdS,was successfully inhibited for A15-CdS.The nanocomposite catalyst was obtained by impregnating CdS nanoparticles within porous polymeric cation exchanger A15 through a facile inner-surface deposition.CdS nanoparticles (<20 nm) immobilized in A15 were deliberately distributed within an outside ring-like region of 40-50 m in depth,which is dominant for photoreaction because visible light is not expected to permeate through the inner region of nontransparent A15.As expected,efficient RhB photodegradation by A15-CdS was achieved under visible light irradiation,and large-size A15-CdS beads are expected to result in their facile separation from solution for repeated use.More significantly,negligible photocorrosion for the hybrid catalyst A15-CdS was demonstrated by the constant photodegradation efficiency and negligible CdS loss during five-cycle runs.The results indicated that nano-CdS immobilization within A15 would greatly improve the applicability of CdS nanoparticles in practical environmental remediation.
