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2017 Volume 80 Issue 6
2017, 80(6): 507-516
Abstract:
During subzero startup process, water generated in oxygen reduction reaction at cathode side of a proton exchange membrane fuel cell (PEMFC) is susceptible to freeze, hindering transport of reactants, covering active sites, reducing electrochemical surface area, leading to significant loss of cell performance and even ending up with a failure to startup. Meanwhile, freeze/thaw cycling will destroy the structure of the membrane electrode assembly (MEA) and impair the life time of PEMFC. Thereby, studies on the subzero startup processes of PEMFCs are crucial to the commercial promotion of fuel cell vehicles. In this article, the experimental studies, mechanistic insights, modeling analysis and coping strategies of the subzero startup operation are reviewed with great details. Furthermore, patents reporting mitigation strategies are also included.
During subzero startup process, water generated in oxygen reduction reaction at cathode side of a proton exchange membrane fuel cell (PEMFC) is susceptible to freeze, hindering transport of reactants, covering active sites, reducing electrochemical surface area, leading to significant loss of cell performance and even ending up with a failure to startup. Meanwhile, freeze/thaw cycling will destroy the structure of the membrane electrode assembly (MEA) and impair the life time of PEMFC. Thereby, studies on the subzero startup processes of PEMFCs are crucial to the commercial promotion of fuel cell vehicles. In this article, the experimental studies, mechanistic insights, modeling analysis and coping strategies of the subzero startup operation are reviewed with great details. Furthermore, patents reporting mitigation strategies are also included.
2017, 80(6): 517-523
Abstract:
The thermodynamic analysis of photosynthesis efficiency is critical to understand the photosynthesis mechanism, and also an important approach to achieve artificial photosynthesis with high efficiency. In this review, research progresses in the thermodynamic energy balance, entropy and exergy analysis of photosynthesis processes are discussed with particular focus on the models and development of exergy efficiency calculations. At the same time, the latest progress of artificial photosynthesis is also discussed in this paper.
The thermodynamic analysis of photosynthesis efficiency is critical to understand the photosynthesis mechanism, and also an important approach to achieve artificial photosynthesis with high efficiency. In this review, research progresses in the thermodynamic energy balance, entropy and exergy analysis of photosynthesis processes are discussed with particular focus on the models and development of exergy efficiency calculations. At the same time, the latest progress of artificial photosynthesis is also discussed in this paper.
2017, 80(6): 524-532, 543
Abstract:
Organophosphorus compounds are widely used in pharmacy chemistry, material science, and organic synthesis. So how to construct C-P bonds become a focus in the field of organic synthesis chemistry. In this paper, recent progress in the construction of C-P bonds including traditional synthetic methods, conventional C-P coupling reactions, direct oxidative dehydrogenation coupling, the domino reactions between phosphorus radicals with unsaturated bonds, asymmetric C-P cross-coupling were reviewed. Their advantages and disadvantages, challenges, development directions were also discussed.
Organophosphorus compounds are widely used in pharmacy chemistry, material science, and organic synthesis. So how to construct C-P bonds become a focus in the field of organic synthesis chemistry. In this paper, recent progress in the construction of C-P bonds including traditional synthetic methods, conventional C-P coupling reactions, direct oxidative dehydrogenation coupling, the domino reactions between phosphorus radicals with unsaturated bonds, asymmetric C-P cross-coupling were reviewed. Their advantages and disadvantages, challenges, development directions were also discussed.
2017, 80(6): 533-538
Abstract:
N-Heterocyclic carbene (NHCs) metal complexes as a class of significant catalysts have been a hot research field in organic synthesis. In recent years, water-soluble NCHs transition metal complexes obtained by the introduction of water-soluble ligands have attracted more and more attention from researchers. In this paper, the classification and syntheses of water-soluble NHCs and their application in the C-C coupling reaction, metathesis reaction and catalytic hydrogenation were summarized, and the development trend of water-soluble NHCs metal complexes was also discussed.
N-Heterocyclic carbene (NHCs) metal complexes as a class of significant catalysts have been a hot research field in organic synthesis. In recent years, water-soluble NCHs transition metal complexes obtained by the introduction of water-soluble ligands have attracted more and more attention from researchers. In this paper, the classification and syntheses of water-soluble NHCs and their application in the C-C coupling reaction, metathesis reaction and catalytic hydrogenation were summarized, and the development trend of water-soluble NHCs metal complexes was also discussed.
2017, 80(6): 539-543
Abstract:
In this article, three kinds of Schiff base containing salicylaldehyde units were synthesized from substituted salicylaldehyde and 3-aminothiophene. The effect of different substituents located in the para position of the phenolic hydroxyl groups on the proton transfer process, the pH response and the metal ion response of the Schiff base probe were investigated. The results showed that changing the electron pushing and withdrawing ability of the substituents can adjust the binding energy of the phenoxy anion to the active hydrogen, and then affect the excited proton transfer properties of these Schiff bases. At the same time, the charge density of the phenoxy anion also determined its ability to coordinate with the metal cation, thus showing different selectivity and sensitivity.
In this article, three kinds of Schiff base containing salicylaldehyde units were synthesized from substituted salicylaldehyde and 3-aminothiophene. The effect of different substituents located in the para position of the phenolic hydroxyl groups on the proton transfer process, the pH response and the metal ion response of the Schiff base probe were investigated. The results showed that changing the electron pushing and withdrawing ability of the substituents can adjust the binding energy of the phenoxy anion to the active hydrogen, and then affect the excited proton transfer properties of these Schiff bases. At the same time, the charge density of the phenoxy anion also determined its ability to coordinate with the metal cation, thus showing different selectivity and sensitivity.
2017, 80(6): 553-557
Abstract:
The binary Co-Al sulfide was grown directly on Ni foams via a two-step hydrothermal method. The CoAl2S4/Ni electrode material were successfully prepared. The structure, surface morphology and supercapacitor property were characterized by X-ray diffraction analysis, field emission scanning electron microscopy (FESEM), and electrochemical method respectively. The results showed that the CoAl2S4/Ni electrode material exhibits 3D porous petal-like structure and rough surface with high conductivity, capacitance and transport rate for electrolyte ions and electrons. The specific capacitance of the electrode can reach 2187.1 F/g under current density of 1A/g. It displayed good electrochemical stability with 90.1% of the initial capacitance over consecutive 100 cycles. The results of this work can provide a reference for the fabrication and properties study of supercapacitor electrode materials.
The binary Co-Al sulfide was grown directly on Ni foams via a two-step hydrothermal method. The CoAl2S4/Ni electrode material were successfully prepared. The structure, surface morphology and supercapacitor property were characterized by X-ray diffraction analysis, field emission scanning electron microscopy (FESEM), and electrochemical method respectively. The results showed that the CoAl2S4/Ni electrode material exhibits 3D porous petal-like structure and rough surface with high conductivity, capacitance and transport rate for electrolyte ions and electrons. The specific capacitance of the electrode can reach 2187.1 F/g under current density of 1A/g. It displayed good electrochemical stability with 90.1% of the initial capacitance over consecutive 100 cycles. The results of this work can provide a reference for the fabrication and properties study of supercapacitor electrode materials.
2017, 80(6): 558-562
Abstract:
Ce0.8Gd0.2O2-α was synthesized by sol-gel method at 900℃, which is much lower than the conventional sintering temperature (1400℃), and was further compounded with (Li/K)2CO3. The XRD pattern showed that there is no chemical reaction between Ce0.8Gd0.2O2-α and (Li/K)2CO3. The SEM images demonstrated that the composite electrolyte is sufficiently dense and does not have holes. The conductivities of the composite electrolyte in dry nitrogen atmosphere were measured using electrochemical analyzer. The highest conductivity was observed to be 6.4×10-2 S·cm-1 at 600℃, which is higher than that of single CeO2 material. The H2/O2 fuel cell performance test showed that the electrolyte impedance and polarization impedance under open-circuit condition are 2.7Ω and 0.8Ω, respectively, and the maximum output power density is 267mW·cm-2 at 600℃.
Ce0.8Gd0.2O2-α was synthesized by sol-gel method at 900℃, which is much lower than the conventional sintering temperature (1400℃), and was further compounded with (Li/K)2CO3. The XRD pattern showed that there is no chemical reaction between Ce0.8Gd0.2O2-α and (Li/K)2CO3. The SEM images demonstrated that the composite electrolyte is sufficiently dense and does not have holes. The conductivities of the composite electrolyte in dry nitrogen atmosphere were measured using electrochemical analyzer. The highest conductivity was observed to be 6.4×10-2 S·cm-1 at 600℃, which is higher than that of single CeO2 material. The H2/O2 fuel cell performance test showed that the electrolyte impedance and polarization impedance under open-circuit condition are 2.7Ω and 0.8Ω, respectively, and the maximum output power density is 267mW·cm-2 at 600℃.
2017, 80(6): 563-567
Abstract:
A novel electrogenerated chemiluminescence (ECL) method for the determination of pyrocatechol has been developed in this paper based on the quenching effect of pyrocatechol on the cathodic ECL intensity of the Ru(bpy)32+-CdTe quantum dots (QDs) system in phosphate buffer solution (pH=7.0). The effects of buffer concentration, pH, CdTe QDs concentration, Ru(bpy)32+ concentration, scan rate and potential windows on the luminescence of the system were investigated. Under the optimal experimental conditions, the log value of ECL intensity and the log value of pyrocatechol concentration showed a good linear relationship in the range of 7.0×10-8~4.0×10-5mol/L with the detection limit of 2.3×10-8mol/L (3σ). The relative standard deviations (RSD) of the ECL intensity for 4.0×10-6mol/L standard pyrocatechol solution was 1.1% (n=6). The present method has been successfully used to determine pyrocatechol in simulated environmental water samples with average recoveries from 95.0% to 105.7%.
A novel electrogenerated chemiluminescence (ECL) method for the determination of pyrocatechol has been developed in this paper based on the quenching effect of pyrocatechol on the cathodic ECL intensity of the Ru(bpy)32+-CdTe quantum dots (QDs) system in phosphate buffer solution (pH=7.0). The effects of buffer concentration, pH, CdTe QDs concentration, Ru(bpy)32+ concentration, scan rate and potential windows on the luminescence of the system were investigated. Under the optimal experimental conditions, the log value of ECL intensity and the log value of pyrocatechol concentration showed a good linear relationship in the range of 7.0×10-8~4.0×10-5mol/L with the detection limit of 2.3×10-8mol/L (3σ). The relative standard deviations (RSD) of the ECL intensity for 4.0×10-6mol/L standard pyrocatechol solution was 1.1% (n=6). The present method has been successfully used to determine pyrocatechol in simulated environmental water samples with average recoveries from 95.0% to 105.7%.
2017, 80(6): 568-572
Abstract:
A kind of single-electrode tip discharge plasma reaction systems at atmospheric pressure was built for non-thermodynamic conversion of benzene, one of tar compounds in the CO2 plasma assisted gasification process. The gas analyzer was used to study the syngas production, and emission spectrum was used to diagnose the plasma. The results showed that the main gaseous product of benzene conversion in this reaction system is CO, and the H element is directly oxidized to H2O. The energy density plays a dominant role in the conversion of benzene. At the same energy density, the decrease of benzene concentration can also increase the conversion ratio of benzene, However, the conversion of benzene can not be improved by changing the gas velocity and increasing the reaction time. In addition, based on spectral analysis, the non-thermal conversion of benzene can be triggered by O-radicals generated by direct dissociation of CO2.
A kind of single-electrode tip discharge plasma reaction systems at atmospheric pressure was built for non-thermodynamic conversion of benzene, one of tar compounds in the CO2 plasma assisted gasification process. The gas analyzer was used to study the syngas production, and emission spectrum was used to diagnose the plasma. The results showed that the main gaseous product of benzene conversion in this reaction system is CO, and the H element is directly oxidized to H2O. The energy density plays a dominant role in the conversion of benzene. At the same energy density, the decrease of benzene concentration can also increase the conversion ratio of benzene, However, the conversion of benzene can not be improved by changing the gas velocity and increasing the reaction time. In addition, based on spectral analysis, the non-thermal conversion of benzene can be triggered by O-radicals generated by direct dissociation of CO2.
2017, 80(6): 573-578
Abstract:
Effect of low-cost packing γ-Al2O3 modified with different coupling agents on one-step catalytic oxidation of 1, 2, 4-trimethylbenzene (TMB) to 2, 3, 5-trimethylbenzoquinone was studied. Results showed that packing γ-Al2O3 modified with 2, 3-epoxypropoxy propyltrimethoxysilicane (KH560) has better catalytic effect. The effects of KH560 amount, hydrolysis time, adsorption time, adsorption temperature on the catalytic reaction were investigated. Packing γ-Al2O3 is coated by KH560 in some extent. Conversion(14.3%) of TMB and selectivity (72.4%) of TMBQ are obtained under optimal conditions:2mL of KH560/EtOH (V:V=1:25) solution, hydrolysis for 1h, adsorption time of 4h at 50℃. TMB is mildly catalyzed and oxidized by the modified packing γ-Al2O3, which leads to less side reactions.
Effect of low-cost packing γ-Al2O3 modified with different coupling agents on one-step catalytic oxidation of 1, 2, 4-trimethylbenzene (TMB) to 2, 3, 5-trimethylbenzoquinone was studied. Results showed that packing γ-Al2O3 modified with 2, 3-epoxypropoxy propyltrimethoxysilicane (KH560) has better catalytic effect. The effects of KH560 amount, hydrolysis time, adsorption time, adsorption temperature on the catalytic reaction were investigated. Packing γ-Al2O3 is coated by KH560 in some extent. Conversion(14.3%) of TMB and selectivity (72.4%) of TMBQ are obtained under optimal conditions:2mL of KH560/EtOH (V:V=1:25) solution, hydrolysis for 1h, adsorption time of 4h at 50℃. TMB is mildly catalyzed and oxidized by the modified packing γ-Al2O3, which leads to less side reactions.
2017, 80(6): 579-584
Abstract:
The effects of adding dosage and the size of the slags, the temperature, and the initial pH on the adsorption of ammonia nitrogen from water were studied by using the titanium blast furnace slag as the adsorbent. The kinetic analysis showed that the pseudo-second-order model can better describe the adsorption of ammonia on titanium-bearing blast furnace slags. Adsorption isotherm fitting showed that the Langmiur equation can better simulate the adsorption process. Under the conditions of 20℃, reaction time of 4h, 8 g (80~120mesh) slags, and 100mL (100mg/L) ammonia nitrogen solution, the removal rate of ammonia nitrogen could reach 32%. With the increasing of temperature, removal rate basically showed ascendant trend. Initial pH had a certain influence on the ammonia nitrogen removal, and it has a better removal effect under the alkaline condition.
The effects of adding dosage and the size of the slags, the temperature, and the initial pH on the adsorption of ammonia nitrogen from water were studied by using the titanium blast furnace slag as the adsorbent. The kinetic analysis showed that the pseudo-second-order model can better describe the adsorption of ammonia on titanium-bearing blast furnace slags. Adsorption isotherm fitting showed that the Langmiur equation can better simulate the adsorption process. Under the conditions of 20℃, reaction time of 4h, 8 g (80~120mesh) slags, and 100mL (100mg/L) ammonia nitrogen solution, the removal rate of ammonia nitrogen could reach 32%. With the increasing of temperature, removal rate basically showed ascendant trend. Initial pH had a certain influence on the ammonia nitrogen removal, and it has a better removal effect under the alkaline condition.
2017, 80(6): 544-552
Abstract:
Abstract Methyl 2-aminobenzoate was reacted with iodomethane to get methyl N-methylanthranilate. The key intermediate 2-(6-chloro-1-methyl-2, 4-dioxo-1, 2-dihydroquinazolin-3(4H)-yl)acetohydrazide (7) was synthesized from methyl N-methylanthranilate via substitution, hydrolysis, cyclization and hydrazinolysis reactions. Then the key intermediate 7 was reacted with various substituted aromatic aldehydes or ketones to afford a series of quinazolin-2, 4-dione acetyl hydrazone compounds 9a~9t. The structures of all target compounds were characterized by means of 1H NMR, 13C NMR and MS. The preliminary bioassay indicated that the as-synthesized compounds had certain antibacterial activities against the tested strains. At the same time, some of them showed better antibacterial activities than the commercial drugs such as streptomycin sulfate and polyoxin B.
Abstract Methyl 2-aminobenzoate was reacted with iodomethane to get methyl N-methylanthranilate. The key intermediate 2-(6-chloro-1-methyl-2, 4-dioxo-1, 2-dihydroquinazolin-3(4H)-yl)acetohydrazide (7) was synthesized from methyl N-methylanthranilate via substitution, hydrolysis, cyclization and hydrazinolysis reactions. Then the key intermediate 7 was reacted with various substituted aromatic aldehydes or ketones to afford a series of quinazolin-2, 4-dione acetyl hydrazone compounds 9a~9t. The structures of all target compounds were characterized by means of 1H NMR, 13C NMR and MS. The preliminary bioassay indicated that the as-synthesized compounds had certain antibacterial activities against the tested strains. At the same time, some of them showed better antibacterial activities than the commercial drugs such as streptomycin sulfate and polyoxin B.
2017, 80(6): 585-588, 572
Abstract:
A novel process for microwave-assisted synthesis of sulfobutyl ether-β-cyclodextrins was investigated through reaction between β-cyclodextrin and 1, 4-butane sultone with adding the alkali stepwise. The effects of initial amount of alkali on the degree of substitution were evaluated. Under the synthesis conditions:the molar ratios of 1, 4-butane sultone and β-cyclodextrin are 1:1.2, 1:5, 1:8, respectively, the reaction temperature is 85℃, microwave output power is 400 W, and the reaction time is 2~3h, the average degrees of substitution of products are 1.12, 3.96, 6.83, and the yield of sulfobutyl ether β-cyclodextrin derivatives is up to 86.3%, 85.6%, 85.1%, respectively. The average degree of substitution and the characterizations of sulfobutyl ether β-cyclodextrin derivatives were investigated by means of IR, 1H NMR, MS and capillary electrophoresis. The experimental results showed that, compared with the conventional heating process, the novel process for the synthesis of sulfobutyl ether β-cyclodextrins with specific average degree of substitution has the advantages of shorter reaction time, less alkali, milder reaction conditions, etc.
A novel process for microwave-assisted synthesis of sulfobutyl ether-β-cyclodextrins was investigated through reaction between β-cyclodextrin and 1, 4-butane sultone with adding the alkali stepwise. The effects of initial amount of alkali on the degree of substitution were evaluated. Under the synthesis conditions:the molar ratios of 1, 4-butane sultone and β-cyclodextrin are 1:1.2, 1:5, 1:8, respectively, the reaction temperature is 85℃, microwave output power is 400 W, and the reaction time is 2~3h, the average degrees of substitution of products are 1.12, 3.96, 6.83, and the yield of sulfobutyl ether β-cyclodextrin derivatives is up to 86.3%, 85.6%, 85.1%, respectively. The average degree of substitution and the characterizations of sulfobutyl ether β-cyclodextrin derivatives were investigated by means of IR, 1H NMR, MS and capillary electrophoresis. The experimental results showed that, compared with the conventional heating process, the novel process for the synthesis of sulfobutyl ether β-cyclodextrins with specific average degree of substitution has the advantages of shorter reaction time, less alkali, milder reaction conditions, etc.
2017, 80(6): 589-592, 562
Abstract:
Screen printed electrodes were modified with reduced oxide graphene (rGO), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) and graphite phase carbon nitride (g-C3N4). The SPME modification conditions were optimized and the electrochemical properties of the SPME were characterized by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The oxidation induction time of safflower seed oil, almond oil, wheat germ oil and olive oil were determined by EIS in the mixture of 1.0×10-3mol/L LiCl-ethanol and chloroform (V:V=20:3) which was used as supporting electrolyte. F-test and t-test results showed that there was no significant difference of oxidation induction time between the proposed method and the national standard method. Moreover, the proposed method is more simple, rapid and sensitive than that of the national standard method.
Screen printed electrodes were modified with reduced oxide graphene (rGO), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) and graphite phase carbon nitride (g-C3N4). The SPME modification conditions were optimized and the electrochemical properties of the SPME were characterized by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The oxidation induction time of safflower seed oil, almond oil, wheat germ oil and olive oil were determined by EIS in the mixture of 1.0×10-3mol/L LiCl-ethanol and chloroform (V:V=20:3) which was used as supporting electrolyte. F-test and t-test results showed that there was no significant difference of oxidation induction time between the proposed method and the national standard method. Moreover, the proposed method is more simple, rapid and sensitive than that of the national standard method.
2017, 80(6): 593-599
Abstract:
The time from the late nineteenth to the early twentieth century was an important period in the development of physical chemistry and biochemistry. It was a time when the isotope tracer method received many achievements in a series of tracer experiments. It was Hungarian Swiss chemist George de Hevesy (1885-1966) who applied tracer technology to the field of biology. And his invention of the isotope tracer method made him receive the 1943 Nobel Prize in Chemistry. This paper introduces the life and academic experience of Hevesy which reflects that the growth of Hevesy is inseparable from the academic exchanges with many European scientists at the time.
The time from the late nineteenth to the early twentieth century was an important period in the development of physical chemistry and biochemistry. It was a time when the isotope tracer method received many achievements in a series of tracer experiments. It was Hungarian Swiss chemist George de Hevesy (1885-1966) who applied tracer technology to the field of biology. And his invention of the isotope tracer method made him receive the 1943 Nobel Prize in Chemistry. This paper introduces the life and academic experience of Hevesy which reflects that the growth of Hevesy is inseparable from the academic exchanges with many European scientists at the time.
