Electrochemical CO_(2)reduction to C_(2)H_(4)can provide a sustainable route to reduce globally accelerating CO_(2)emissions and produce energy-rich chemical feedstocks.However,the poor selectivity in C_(2)H_(4)electr...Electrochemical CO_(2)reduction to C_(2)H_(4)can provide a sustainable route to reduce globally accelerating CO_(2)emissions and produce energy-rich chemical feedstocks.However,the poor selectivity in C_(2)H_(4)electrosynthesis limits its implementation in industrially interesting processes.Herein,we report a composite structured catalyst composed of Ag and Cu_(2)O with different crystal faces to achieve highly efficient reduction of CO_(2)to C_(2)H_(4).The catalyst composed of Ag and octahedral Cu_(2)O enclosed with(111)facet exhibits the best CO_(2)electroreduction performance,with the Faradaic efficiency(FE)and partial current density reaching 66.8%and 17.8 mA cm2 for C_(2)H_(4)product at-1.2 VRHE in 0.5 M KHCO_(3),respectively.Physical characterization and electrochemical test analysis indicate that the high selectivity for C_(2)H_(4)product stems from the synergistic effect of crystal faces control engineering and tandem catalysis.Specifically,Ag can provide optimal availability of CO intermediate by suppressing hydrogen evolution;subsequently,C-C coupling is promoted on the intimate surface of Cu_(2)O with facetdependent selectivity.The insights gained from this work may be beneficial for designing efficient multicomponent catalysts for improving the selectivity of electrochemical CO_(2)reduction reaction to generate C2þproducts.展开更多
FTO(Fischer-Tropsch to olefins)作为合成气制备低碳烯烃(C_(2)^(=)~C_(4)^(=))的代替路径在工业上具有重要意义。CoMnNa作为FTO反应催化剂而备受关注,但由于反应过程中CO_(2)C活性相的形成,导致CO_(2)选择性较高。引入AlO(OH)载体,制...FTO(Fischer-Tropsch to olefins)作为合成气制备低碳烯烃(C_(2)^(=)~C_(4)^(=))的代替路径在工业上具有重要意义。CoMnNa作为FTO反应催化剂而备受关注,但由于反应过程中CO_(2)C活性相的形成,导致CO_(2)选择性较高。引入AlO(OH)载体,制备了Co_(1)Mn_(1)Na/AlO(OH)催化剂,通过XRD、STEM、EDX-mapping、N_(2)吸附-脱附等温线、孔径分布曲线对催化剂进行了表征,通过H_(2)-TPR对催化剂的还原性进行了分析,并对催化剂的FTO反应性能进行了评价。结果表明,利用载体与CoMn的相互作用,降低了CoMn氧化物的还原性,有效抑制了CoMn中Co的析出及CO_(2)C的形成,减少了CoMn体系中Co和CO_(2)C活性相;在低碳烯烃选择性高达32.4%的情况下,成功将CO_(2)选择性降至10%以下。展开更多
To explain the presence and spatial distribution of NO_(3)^(−)and N-NH_(3)in the Aquifer of the Metropolitan Area of Mexico City(AMAMC),a hydrogeochemical and isotopic analysis using^(13)C DIC(as well as the stable is...To explain the presence and spatial distribution of NO_(3)^(−)and N-NH_(3)in the Aquifer of the Metropolitan Area of Mexico City(AMAMC),a hydrogeochemical and isotopic analysis using^(13)C DIC(as well as the stable isotopes^(18)O and^(2)H)in groundwater was conducted.This aquifer is located in an old closed lacustrine volcano-sedimentary basin;some wells hosted in the semi-confined zone contain high N-NH_(3)concentrations,while others present NO_(3)^(−)contents in the recharge zones(hosted in an oxidizing environment).In this study,a change in the isotopic signature(primarily in^(18)O and^(2)H)was observed from the recharge zones to the basin center in some of the wells with high NO_(3)^(−)concentrations,this behavior can be attributed to evaporation during the incorporation of recently infiltrated water.In addition,the results for^(13)C(along with ^(2) H)in wells with the highest N-NH_(3)concentrations exhibited an atypically broad range of values.Results indicated the occurrence of hydrogeochemical and/or biochemical processes in the aquifer(in an oxidizing or reducing environment),such as organic degradation,bacterial decomposition(primarily in the ancient Lake Texcoco and which acts as a natural sink for carbon,nitrogen,sulfur,and phosphorus),besides rock weathering and dissolution,which may be responsible for a very marked isotopic modification of the^(13)C(and,to a lesser extent,2 H).Methanotrophic bacterial activity and methanogenic activity may be related to N-NH_(3)removal processes by oxidation and residual water incorporation respectively,whereas the increase in the NO_(3)^(−)content in some wells is due to the recent contribution of poor-quality water due to contamination.展开更多
The base-free aerobic oxidation of 5-hydroxymethylfurfural(HMF) to 2,5-furandicarboxylic acid(FDCA)in water is recognized as an important and sustainable upgrading process for cellulosic carbohydrates.However,selectiv...The base-free aerobic oxidation of 5-hydroxymethylfurfural(HMF) to 2,5-furandicarboxylic acid(FDCA)in water is recognized as an important and sustainable upgrading process for cellulosic carbohydrates.However,selectivity control still remains a challenge.Here,we disclose that the unique synergy in magnetic Ni_(x)Co_(1)O_(y)(x=1,3 and 5) bimetallic oxides can induce reactive oxygen defects and simultaneously stabilize small-sized metallic Au nanoparticles in the Au/Ni_(x)Co_(1)O_(y)catalysts.Such catalytic features render effective adsorption and activation of O_(2),OH and C=O groups,realizing selective oxidation of HMF to FDCA.On a series of magnetic Au/Ni_(x)Co_(1)O_(y)catalysts with almost identical Au loadings(ca.0.5 wt%) and particle sizes(ca.2.7 nm),the variable Ni/Co molar ratios give rise to the tunable electron density of Au sites and synergistic effect between NiO and CoO_(y).The initial conversion rates of HMF and its derived intermediates(i.e., DFF,HMFCA and FFCA) show a volcano-like dependence on the number of oxygen defects(i.e.,O_(2)^(-)and O^(-)) and electron-rich Au0sites.The optimum Au/Ni3Co1Oycatalyst exhibits a highest productivity of FDCA(12.5 mmol_(FDCA)mol_(Au)^(-1)h^(-1)) among all the Au catalysts in the literature and achieves> 99% yield of FDCA at 120℃ and 10 bar of O_(2).In addition,this catalyst can be easily recovered by a magnet and show superior stability and reusability during six consecutive cycling tests.This work may shed a light on Au catalysis for the base-free oxidation of biomass compounds by smartly using the synergy in bimetallic oxide carriers.展开更多
Selective oxidation of saturated C(sp^(3))-H bonds in hydrocarbon to target chemicals under mild conditions remains a signifi-cant but challenging task because of the chemical inertness and high dissociation energy of...Selective oxidation of saturated C(sp^(3))-H bonds in hydrocarbon to target chemicals under mild conditions remains a signifi-cant but challenging task because of the chemical inertness and high dissociation energy of C(sp^(3))-H bonds.Semiconductor photocatalysis can induce the generation of holes and oxidative radicals,off ering an alternative way toward selective oxidation of hydrocarbons under ambient conditions.Herein,we constructed N-doped TiO_(2) nanotubes(N-TNTs)that exhibited remark-able activity and selectivity for toluene oxidation under visible light,delivering the conversion of toluene and selectivity of benzaldehyde of 32% and>99%,respectively.Further mechanistic studies demonstrated that the incorporation of nitrogen induced the generation of N-doping level above the O 2p valance band,directly contributing to the visible-light response of TiO_(2).Furthermore,hydroxyl radicals generated by photogenerated holes at the orbit of O 2p were found to be unselective for the oxidation of toluene,aff ording both benzaldehyde and benzoic acid.The incorporation of nitrogen was able to inhibit the generation of hydroxyl radicals,terminating the formation of benzoic acid.展开更多
A nematode Caenorhabditis elegans(C. elegans) is a filter feeder, which draws a suspension of bacteria and separates bacteria from the solvent by using pharyngeal pumping motions and specific mouth parts. This mechani...A nematode Caenorhabditis elegans(C. elegans) is a filter feeder, which draws a suspension of bacteria and separates bacteria from the solvent by using pharyngeal pumping motions and specific mouth parts. This mechanism has not been fully understood. We investigated the mechanism of filtering of bacteria in the pharynx of C. elegans by visualization by fluorescent particles and dyed E. coli. We succeeded in quantifying the selectivity of bacteria-sized particles by C. elegans. The most accumulated particles were those of 0.5 μm in diameter. The quantity of accumulated particles of 0.2 μm or 1.0 μm in diameter was about one third of that of particles of 0.5μm in diameter. The least accumulated particles were those of 0.05 μm in diameter. These results suggest that the pharyngeal structures of C. elegans would be suitable for eating bacteria because the size of bacteria ingested by C. elegans worms is about 0.5 μm in diameter. We also succeeded in visualizing pharyngeal structures and pumping motions and flow in the pharynx. We found that there were phase differences in the motions among procorpus, metacorpus and isthmus. This result suggests filtering would occur at the two tips of procorpus and isthmus by the phase differences. We found that bacteria-sized particles and bacteria were flowed and trapped in the channels, which existed along the central lumen from tip of procorpus to isthmus. From our results, we proposed the novel mechanism of filtering of bacteria through the channels for flowing and trapping. In future, this selective filtering mechanism of C. elegans would be applied to development of microfluidic filtration devices for medical and biological equipment.展开更多
基金This work was supported by the University of Science and Technology Beijing.DG acknowledges the financial support from 111 Project(no.B170003)Foshan Science and Technology Innovation Project(no.2018IT100363).
文摘Electrochemical CO_(2)reduction to C_(2)H_(4)can provide a sustainable route to reduce globally accelerating CO_(2)emissions and produce energy-rich chemical feedstocks.However,the poor selectivity in C_(2)H_(4)electrosynthesis limits its implementation in industrially interesting processes.Herein,we report a composite structured catalyst composed of Ag and Cu_(2)O with different crystal faces to achieve highly efficient reduction of CO_(2)to C_(2)H_(4).The catalyst composed of Ag and octahedral Cu_(2)O enclosed with(111)facet exhibits the best CO_(2)electroreduction performance,with the Faradaic efficiency(FE)and partial current density reaching 66.8%and 17.8 mA cm2 for C_(2)H_(4)product at-1.2 VRHE in 0.5 M KHCO_(3),respectively.Physical characterization and electrochemical test analysis indicate that the high selectivity for C_(2)H_(4)product stems from the synergistic effect of crystal faces control engineering and tandem catalysis.Specifically,Ag can provide optimal availability of CO intermediate by suppressing hydrogen evolution;subsequently,C-C coupling is promoted on the intimate surface of Cu_(2)O with facetdependent selectivity.The insights gained from this work may be beneficial for designing efficient multicomponent catalysts for improving the selectivity of electrochemical CO_(2)reduction reaction to generate C2þproducts.
文摘FTO(Fischer-Tropsch to olefins)作为合成气制备低碳烯烃(C_(2)^(=)~C_(4)^(=))的代替路径在工业上具有重要意义。CoMnNa作为FTO反应催化剂而备受关注,但由于反应过程中CO_(2)C活性相的形成,导致CO_(2)选择性较高。引入AlO(OH)载体,制备了Co_(1)Mn_(1)Na/AlO(OH)催化剂,通过XRD、STEM、EDX-mapping、N_(2)吸附-脱附等温线、孔径分布曲线对催化剂进行了表征,通过H_(2)-TPR对催化剂的还原性进行了分析,并对催化剂的FTO反应性能进行了评价。结果表明,利用载体与CoMn的相互作用,降低了CoMn氧化物的还原性,有效抑制了CoMn中Co的析出及CO_(2)C的形成,减少了CoMn体系中Co和CO_(2)C活性相;在低碳烯烃选择性高达32.4%的情况下,成功将CO_(2)选择性降至10%以下。
基金support granted to carry out the research,and for the funding,Dr.Graciela Herrera Zamarron,responsible for the project with Contract number 0266-1O-ED-F-DGAT-UNAM-2-19-1928.
文摘To explain the presence and spatial distribution of NO_(3)^(−)and N-NH_(3)in the Aquifer of the Metropolitan Area of Mexico City(AMAMC),a hydrogeochemical and isotopic analysis using^(13)C DIC(as well as the stable isotopes^(18)O and^(2)H)in groundwater was conducted.This aquifer is located in an old closed lacustrine volcano-sedimentary basin;some wells hosted in the semi-confined zone contain high N-NH_(3)concentrations,while others present NO_(3)^(−)contents in the recharge zones(hosted in an oxidizing environment).In this study,a change in the isotopic signature(primarily in^(18)O and^(2)H)was observed from the recharge zones to the basin center in some of the wells with high NO_(3)^(−)concentrations,this behavior can be attributed to evaporation during the incorporation of recently infiltrated water.In addition,the results for^(13)C(along with ^(2) H)in wells with the highest N-NH_(3)concentrations exhibited an atypically broad range of values.Results indicated the occurrence of hydrogeochemical and/or biochemical processes in the aquifer(in an oxidizing or reducing environment),such as organic degradation,bacterial decomposition(primarily in the ancient Lake Texcoco and which acts as a natural sink for carbon,nitrogen,sulfur,and phosphorus),besides rock weathering and dissolution,which may be responsible for a very marked isotopic modification of the^(13)C(and,to a lesser extent,2 H).Methanotrophic bacterial activity and methanogenic activity may be related to N-NH_(3)removal processes by oxidation and residual water incorporation respectively,whereas the increase in the NO_(3)^(−)content in some wells is due to the recent contribution of poor-quality water due to contamination.
基金supported by the National Natural Science Foundation of China(22272149,22062025,21763031)the Yunnan Fundamental Research Projects(202001AW070012,202101AT070171)+3 种基金the Yunnan University’s Research Innovation Fund for Graduate Students(KC-22221892)the Open Research Fund of School of Chemistry and Chemical Engineering of Henan Normal Universitythe Workstation of Academician Chen Jing of Yunnan Province(202105AF150012)the Free Exploration Fund for Academician(202205AA160007)。
文摘The base-free aerobic oxidation of 5-hydroxymethylfurfural(HMF) to 2,5-furandicarboxylic acid(FDCA)in water is recognized as an important and sustainable upgrading process for cellulosic carbohydrates.However,selectivity control still remains a challenge.Here,we disclose that the unique synergy in magnetic Ni_(x)Co_(1)O_(y)(x=1,3 and 5) bimetallic oxides can induce reactive oxygen defects and simultaneously stabilize small-sized metallic Au nanoparticles in the Au/Ni_(x)Co_(1)O_(y)catalysts.Such catalytic features render effective adsorption and activation of O_(2),OH and C=O groups,realizing selective oxidation of HMF to FDCA.On a series of magnetic Au/Ni_(x)Co_(1)O_(y)catalysts with almost identical Au loadings(ca.0.5 wt%) and particle sizes(ca.2.7 nm),the variable Ni/Co molar ratios give rise to the tunable electron density of Au sites and synergistic effect between NiO and CoO_(y).The initial conversion rates of HMF and its derived intermediates(i.e., DFF,HMFCA and FFCA) show a volcano-like dependence on the number of oxygen defects(i.e.,O_(2)^(-)and O^(-)) and electron-rich Au0sites.The optimum Au/Ni3Co1Oycatalyst exhibits a highest productivity of FDCA(12.5 mmol_(FDCA)mol_(Au)^(-1)h^(-1)) among all the Au catalysts in the literature and achieves> 99% yield of FDCA at 120℃ and 10 bar of O_(2).In addition,this catalyst can be easily recovered by a magnet and show superior stability and reusability during six consecutive cycling tests.This work may shed a light on Au catalysis for the base-free oxidation of biomass compounds by smartly using the synergy in bimetallic oxide carriers.
基金the National Natural Science Foundation of China(Nos.22025206,21991094)supported by the Ministry of ScienceTechnology of the People’s Republic of China(No.2018YFE0118100)+1 种基金the CAS-NSTDA Joint Research Project(No.GJHZ2075)Dalian Science and Technology Innovation Fund(No.2019J11CY009).
文摘Selective oxidation of saturated C(sp^(3))-H bonds in hydrocarbon to target chemicals under mild conditions remains a signifi-cant but challenging task because of the chemical inertness and high dissociation energy of C(sp^(3))-H bonds.Semiconductor photocatalysis can induce the generation of holes and oxidative radicals,off ering an alternative way toward selective oxidation of hydrocarbons under ambient conditions.Herein,we constructed N-doped TiO_(2) nanotubes(N-TNTs)that exhibited remark-able activity and selectivity for toluene oxidation under visible light,delivering the conversion of toluene and selectivity of benzaldehyde of 32% and>99%,respectively.Further mechanistic studies demonstrated that the incorporation of nitrogen induced the generation of N-doping level above the O 2p valance band,directly contributing to the visible-light response of TiO_(2).Furthermore,hydroxyl radicals generated by photogenerated holes at the orbit of O 2p were found to be unselective for the oxidation of toluene,aff ording both benzaldehyde and benzoic acid.The incorporation of nitrogen was able to inhibit the generation of hydroxyl radicals,terminating the formation of benzoic acid.
文摘A nematode Caenorhabditis elegans(C. elegans) is a filter feeder, which draws a suspension of bacteria and separates bacteria from the solvent by using pharyngeal pumping motions and specific mouth parts. This mechanism has not been fully understood. We investigated the mechanism of filtering of bacteria in the pharynx of C. elegans by visualization by fluorescent particles and dyed E. coli. We succeeded in quantifying the selectivity of bacteria-sized particles by C. elegans. The most accumulated particles were those of 0.5 μm in diameter. The quantity of accumulated particles of 0.2 μm or 1.0 μm in diameter was about one third of that of particles of 0.5μm in diameter. The least accumulated particles were those of 0.05 μm in diameter. These results suggest that the pharyngeal structures of C. elegans would be suitable for eating bacteria because the size of bacteria ingested by C. elegans worms is about 0.5 μm in diameter. We also succeeded in visualizing pharyngeal structures and pumping motions and flow in the pharynx. We found that there were phase differences in the motions among procorpus, metacorpus and isthmus. This result suggests filtering would occur at the two tips of procorpus and isthmus by the phase differences. We found that bacteria-sized particles and bacteria were flowed and trapped in the channels, which existed along the central lumen from tip of procorpus to isthmus. From our results, we proposed the novel mechanism of filtering of bacteria through the channels for flowing and trapping. In future, this selective filtering mechanism of C. elegans would be applied to development of microfluidic filtration devices for medical and biological equipment.
