直接乙醇燃料电池初探

采用商品化的PtRu/C和Pt/C分别作乙醇阳电极和氧气阴电极的催化剂 ,Nafion 115膜作固体电解质 ,组装成面积为 9cm2 的单池 .考察了电池温度、氧气压力、乙醇浓度及流量等对电池性能的影响 .实验结果表明在电池温度为 85℃ ,乙醇浓度为 1.0mol/L ,流量为 0 .5mL/min ,氧气压力为 0 .5MPa ,流量为 6 8mL/min条件下 ,电池开路电压为 0 .6 0 8V ,电流密度 5 0mA/cm2 时的放电端电压为 0 .32 9V ,电池最大功率密度为 19.2 5mW /cm2     

新型碳纤维负载直接乙醇燃料电池Pt-SnO_2阳极催化剂的性能研究

采用静电纺丝技术制备了碳纤维基纳米Pt-SnO2阳极催化剂(Pt/Sn原子比为3)。通过X射线衍射(XRD)、红外光谱(FT-IR)、扫描电子显微镜(SEM)等技术对该催化剂进行了表征,并采用循环伏安法对其在乙醇燃料电池中的阳极催化活性进行了评价。结果表明,纳米Pt-SnO2催化剂均匀地分散在碳纤维骨架上;随着烧结温度的升高,碳纤维载体的致密度越高、导电性能越好。电催化性能测试表明,烧结温度为800℃时催化剂的峰电流密度最大,达到0.11 A/cm2,抗中毒能力也最强。单电池的发电性能表明,在一定的乙醇浓度下,1.0 mL/min进样流速具有最优的发电效率。     

新型Pt-Sn/C阳极催化剂对乙醇的电催化氧化性能

 研究了用于直接乙醇燃料电池的自制Pt-Sn/C阳极催化剂对乙醇的电催化氧化性能. 采用直流伏安法和交流阻抗法分析了电池温度和极化电位对乙醇电催化氧化性能的影响,比较了不同温度下甲醇和乙醇通过Nafion 117膜的扩散系数. 结果表明,乙醇通过Nafion 117膜的扩散系数小于甲醇的扩散系数. 伏安法测试结果表明,Pt-Sn/C催化剂对乙醇的催化氧化活性高于商品化的Pt-Ru/C催化剂. 在实验温度范围内,乙醇在Pt-Sn/C催化剂上的初始氧化电位比在Pt-Ru/C催化剂上低约0.2 V; 同一电位下Pt-Sn/C催化剂比Pt-Ru/C催化剂的氧化电流密度高出20～60 mA/cm2,且电流密度的差值随温度的升高而增大. 交流阻抗法测试结果表明,Pt-Sn/C催化剂对乙醇具有更高的催化活性. 在90 ℃下,以1 mol/L的乙醇为燃料,氧气为氧化剂时,Pt-Sn/C催化剂显示出良好的电池性能,电池最高功率密度为44 mW/cm2,而Pt-Ru/C催化剂的电池最高功率密度仅为27 mW/cm2.     

钴-聚吡咯-碳载Pt催化剂的制备及其单电池性能研究

采用脉冲微波辅助化学还原法制备了钴-聚吡咯-碳载Pt催化剂(Pt/Co-PPy-C),并将其作为阴极催化剂,组装单电池。考察了电池运行温度和氢气/空气计量比对单电池性能的影响,并与商业Pt/C催化剂进行了耐久性实验比较。 结果表明,运行温度为70 ℃,氢气与空气的计量比为1.2:2.5时单电池性能最佳。600 mA/cm²恒电流稳定运行150 h耐久性测试中,以Pt/Co-PPy-C为阴极催化剂的单电池平均电压衰退率为0.119 mV/h,是商业Pt/C催化剂的26%。耐久性测试前后,单电池的阴极电荷传递阻抗为7.176和8.767 Ω,均比商业Pt/C催化剂阻抗小;Pt颗粒粒径从2.46 nm增长到3.18 nm,均小于商业Pt/C催化剂的粒径。这表明,以Pt/Co-PPy-C催化剂为阴极催化剂制备的单电池性能优良,在质子交换膜燃料电池中有广泛的应用前景。     

在线化学蒸气发生-电感耦合等离子体原子发射光谱法测定废催化剂中的微量铑

使用电感耦合等离子原子发射光谱(ICP-AES)研究了贵金属铑和NaBH4在酸性水溶液中的化学蒸气发生反应的条件,并测定了有机合成催化剂中的铑。研究结果表明:在NaBH4和样品溶液流速为2mL/min、废液排放流速为6mL/min的条件下的最佳蒸气发生条件为:载气流速0.4L/min、HNO3浓度为1.0mol/L、NaBH4浓度为1.2%(m/V)。研究中获得的铑化学蒸气进样效率是常规的气动雾化进样效率的2.7倍;检出限是6.9μg/L,略优于气动雾化法;线性范围20～1500μg/L;线性相关系数是0.9986;RSD是1.6%。样品分析加标回收率分别是94%和97%。用本法测得的样品值与原子吸收法的测得值吻合很好。     

顶空-毛细管气相色谱法测定印刷品中15种痕量挥发性有机物

采用顶空-气相色谱法对印刷品中的挥发性有机物(苯、甲苯、乙苯、二甲苯、乙醇等15种)进行分析,研究了不同升温程序、顶空平衡温度、平衡时间等对分析结果的影响,优化的实验参数为:进样口温度:200℃;检测器温度:250℃。升温程序:初始温度40℃,保持5 min;以20℃/min速率升温至200℃,保持3 min。以高纯氮气作为载气,流速为8.0 mL/min保持5 min,再以0.2 mL/min的速率降至5.0 mL/min(分流比5:1);顶空条件:进样瓶平衡温度为90℃,平衡时间30 min,顶空进样体积1.0 mL。本方法线性关系良好,15种挥发性有机物的相关系数均大于0.9998,高、中、低3个浓度的回收率为77.8%~100.6%;相对标准偏差均低于6.0%(n=6)。方法可用于印刷品中挥发性有机物的分析。     

气相色谱微体积热导检测器测量氙

气相色谱微体积热导检测器(μTCD)是与毛细管柱相连的浓度型检测器。为提高-TCD测量氙的能力,研究了色谱进样条件、分离条件和检测条件对氙响应影响。结果表明,当柱流量为1.5mL/min,1.0mL样品完全进样所需最短时间为0.4min;等量氙响应值随着柱流量的增加而增大,与色谱柱温度无关;在流量比(q)等于2.3时,等量氙响应值达到最大(0.98-V.s/hPa);且当q=2～3时,其均值为0.97-V.s/hPa;相对标准偏差(RSD)为1.2%。     

顶空进样气相色谱法检测啤酒中乙醛

建立了项空自动进样气相色谱法测定啤酒发酵液中乙醛含量的方法.检测条件优化为:顶空进样器平衡温度70℃,平衡时间30 min;色谱柱初始温度40℃,经程序升温10℃/min到180℃;柱流量1.2 mL/min,加盐量1.8g.对不同浓度的乙醛标准溶液进样测定,标准曲线证明线性良好,R2为0.999,线性范围2～64 m...     

超临界CO_2萃取桑叶总黄酮工艺的研究

采用超临界CO2萃取桑叶总黄酮,以得率为指标,对萃取压力、萃取温度、夹带剂乙醇的浓度和流量等影响因素进行正交试验。结果表明最佳工艺条件为:萃取压力35 MPa,温度55℃,乙醇质量分数90%,乙醇流量0.01 mL/min。此条件下桑叶总黄酮得率2.28%。该方法简便、可靠、选择性高,适于工业化生产。     

Bi-Pt催化剂在H-mordenite载体上的甘油选择性氧化

以Bi-Pt/H-mordenite为催化剂,对甘油(GLY, Glycerol)选择性氧化制备二羟基丙酮(DHA, Dihydroxyacetone)进行了研究。采用BET对催化剂进行表征,结果表明,催化剂的比表面积对催化剂的反应性能影响较小。甘油的裂解是主要的副反应,而H-mordenite可以抑制甘油的裂解,提高DHA的选择性。最佳反应条件为温度353 K,反应时间2~4 h,空气流量20 mL/min,甘油(水-乙醇1:1混合溶液的质量分数为10%),催化剂为1%Bi-5%Pt/H-mordenite时,甘油的转化率为70.6%,DHA的选择性为61.0%。     

碱性聚合物电解质膜的表面锥形阵列结构提升燃料电池性能

燃料电池作为一种清洁高效的能量转换装置,被认为是构建未来社会可再生能源结构的关键一环。不同于质子交换膜燃料电池(PEMFC),碱性聚合物电解质燃料电池(APEFC)的出现使非贵金属催化剂的使用成为可能,因而受到了日益广泛的关注和研究。APEFC的关键结构是膜电极,主要由聚合物电解质膜和阴阳极(含催化层、气体扩散层)组成,膜电极是电化学反应发生的场所,其优劣直接决定着电池性能的好坏。因此,基于现有的碱性聚合物电解质及催化剂体系,如何构筑更加优化的膜电极结构,使APEFC发挥出更高的电池性能是亟待开展的研究。本文首先通过模板法在碱性聚合物电解质膜的表面构建出有序的锥形阵列,再将具有阵列结构的一侧作为阴极来构筑膜电极,同时,作为对比,制备了由无阵列结构的聚合物电解质膜构筑而成的膜电极,最后对基于两种不同膜电极的APEFC的电化学性能进行了对比研究。实验结果表明,锥形阵列结构可以将APEFC的峰值功率密度由1.04 W·cm-2显著提高到1.48 W·cm-2,这主要归因于在APEFC的阴极侧具有锥形阵列结构的聚合物电解质膜的亲水性的提升和催化剂电化学活性面积的增加。本工作为碱性聚合物电解质燃...     

YSZ传导膜H_2S固体氧化物燃料电池

研究了Y2O3稳定的ZrO2(YSZ)氧离子传导膜H2S固体氧化物燃料电池性能。掺杂NiS、电解质、Ag粉和淀粉制备了双金属复合MoS2阳极催化剂,掺杂电解质、Ag粉和淀粉制备了复合NiO阴极催化剂,用扫描电镜对YSZ和膜电极组装(MEA)进行了表征,比较了不同电极催化剂的性能和极化过程,考察了不同温度对电池性能的影响。结果表明,双金属复合MoS2/NiS阳极催化剂在H2S环境下比Pt和单金属MoS2催化剂稳定,复合NiO阴极催化剂比Pt性能好,在电极催化剂中加入Ag可显著提高电极的导电性;与Pt电极相比,复合MoS2阳极和复合NiO阴极催化剂的过电位较小,阳极的极化比阴极侧小;温度升高,电池的电流密度与功率密度增加,电化学性能变好。在750℃、800℃、850℃和900℃及101.13 kPa时,结构为H2S、(复合MoS2阳极催化剂)/YSZ氧离子传导膜/(复合NiO阴极催化剂)、空气的燃料电池最大功率密度分别为30 mW/cm2、70 mW/cm2、155 mW/cm2及295 mW/cm2、最大电流密度分别为120 mA/cm2、240 mA/cm2、560 mA/cm2和890 mA/cm2。     

含氧煤层气流化床催化燃烧脱氧特性研究

利用自制的铜基球形甲烷催化燃烧催化剂,在小型流化床反应器中对模拟含氧煤层气进行了流化床催化燃烧脱氧的实验研究,考察了床层温度、催化剂粒径、空速对脱氧效率和CO₂选择性的影响。结果表明,较高的反应床层温度使催化剂活性增强,进而提高催化脱氧效率。床层温度在450 ℃以上,脱氧效率可稳定保持在95%以上。较小的催化剂粒径降低了内扩散阻力对催化反应的影响,提高催化反应的CO₂选择性。床层温度在450 ℃以下时,降低空速可提高氧气转化率,但温度高于450 ℃时,脱氧反应速率加快,空速变化对脱氧效率影响不明显。此外,通过调节CH₄/Air比例模拟不同含氧量的煤层气,考察流化床反应器及催化剂对含氧煤层气中O₂浓度变化的适应性。模拟含氧煤层气中氧气体积分数在5%~15%,该催化剂均表现出高的脱氧活性和选择性,反应器出口气体中氧气体积分数低于0.2%,CO₂选择性高于98%。     

A nanometer-ZnO catalyst to enhance the ozonation of 2,4,6-trichlorophenol in water

Removal of 2,4,6-trichlorophenol (TCP) from water has been accomplished through zinc oxide (ZnO) catalytic ozonation. In the presence of ZnO catalyst, aqueous ozone (O₃) can be described by a two-stage behavior, first involving a short-term rapid decomposition followed by a second slow decomposition. The low reaction rate (k_d2) of second stage for O₃-ZnO systems suggested that most of O₃ was transferred into OH radical by ZnO catalyst and was rapidly consumed during the first stage. The combined use of O₃ and ZnO catalyst leads to a conspicuous 99.8% of TCP conversion in 30 min which compares favorably to the hardly 75% reached in the absence of the catalyst. The high reactivity of hydroxyl radicals that were generated by O₃-ZnO during the oxidation process effectively degraded TCP. Without regard to the O₃ dose, the catalytic–oxidation kinetics of the process depends on the concentration of ZnO catalyst and size of ZnO particles. At the same concentration of three different ZnO size in batch tests, TCP degradation rates were in the order of nanometer > submicrometer > micrometer. The effect of pore diffusion on the rate of TCP–ZnO reactions was determined by examination of the effectiveness factor using different particle sizes of ZnO. Calculations show that the rate of TCP decomposition by nano-size ZnO was strongly controlled by surface reaction with little influence of pore diffusion, as indicated by the high effectiveness factors.     

低温等离子体协同Cu-Mn-Ce-Zr/TiO2催化降解甲苯

以TiO₂为载体,采用等体积浸渍法制备了负载型Cu_xMn_1-xCe_0.75Zr_0.25/TiO₂(x=1.0、0.75、0.5、0.25、0)负载型催化剂,采用XRD、H₂-TPR、O₂-TPD和XPS等方法对催化剂进行了表征,并通过低温等离子体协同催化剂对大流量的甲苯模拟废气进行了催化降解反应研究。结果表明,Cu和Mn单主金属催化剂的活性优于Cu-Mn双主金属催化剂,其原因是双金属催化剂中Mn的添加减弱了Cu与助剂Ce之间的相互作用,使得催化剂的晶格氧减少,低温还原性能降低。在反应初期,甲苯降解主要依赖于催化剂的活性,具有较好的低温还原性以及丰富的氧空穴和晶格氧含量的CuCe_0.75Zr_0.25/TiO₂的活性最好;Mn具有较强的O₃分解能力,当等离子体比能密度(SED)增加到一定值后,等离子体与催化剂的协同作用增强,从而使得MnCe_0.75Zr_0.25/TiO₂催化剂活性高于CuCe_0.75Zr_0.25/TiO₂,强化了甲苯的脱除。     

A novel MEA architecture for improving the performance of a DMFC

Direct methanol fuel cell (DMFC) consisting of a double-catalytic layered membrane electrode assembly (MEA) provide higher performance than that with the traditional MEA. This novel structured MEA includes a hydrophilic inner catalyst layer and a traditional electrode with an outer catalyst layer, which was made using both catalyst coated membrane (CCM) and gas diffusion electrode (GDE) methods. The inner catalyst was PtRu black on anode and Pt black on cathode. The outer catalyst was carbon supported Pt–Ru/Pt on anode and cathode, respectively. Thus in the double-catalytic layered electrodes three gradients were formed: catalyst concentration gradient, hydrophilicity gradient and porosity gradient, resulting in good mass transfer, proton and electron conducting and low methanol crossover. The peak density of DMFC with such MEA was 19 mW cm⁻², operated at 2 M CH₃OH, 2 atm oxygen at room temperature, which was much higher than DMFC with traditional MEA.     

Investigation of POM Reaction Over Rh/SiO2 Catalyst Using XPS

By means of XPS, the binding energy and the concentration of the surface element were characterized, before and after the catalyst was exposed to CH₄ and/or O₂ at different temperature (from room temperature to 773 K) and at different amounts with different sequence. It was found that CH_x(x=l~3) species were formed over the catalyst closed to CH₄ or CH₄/O₂. For CH₃,CH₂ and CH species, the C_1Sbinding energies were ca. 285.5 eV, 284.5 eV and 283.5 eV, respectively.     

Decomposition of toluene using an atmospheric pressure plasma/TiO2 catalytic system

Application of atmospheric pressure plasma as an alternative technology for the destruction of toluene is demonstrated in this study. Used TiO₂ colloidal solution was obtained by an improved sol–gel method, and coated on glass beads to prepare decomposition of toluene. The physical property of synthesized TiO₂ catalyst film was analyzed by XRD and SEM spectroscopy. From these results, it was identified that the catalyst film exhibited anatase structure with particle size of about 50–100 nm after calcination at 500 °C for 1 h. The decomposition of toluene in TiO₂/O₂ plasma system was investigated. Amounts of the catalyst and toluene concentration were fixed as 3 wt.% and 1000 ppm, respectively. The analyses for performance of toluene decomposition and intermediates in reaction were done by the in situ method using the mass spectroscopy and gas chromatography. The toluene of 40% was decomposed at pulse voltage of 13 kV in the only O₂ plasma condition without TiO₂ catalyst. Furthermore, the conversion enhanced remarkably in the TiO₂/O₂ plasma system, and it reached 70% at pulse voltage of 13 kV after 120 min. This result was very notable compared with that in photocatalytic system, with below 40% after 120 min reaction.     

NiWO_4/g-C_3N_4的制备及其在离子液体中氧化脱硫性能的研究

采用水热法合成了NiWO_4纳米粒子,然后通过混合煅烧法成功地制备了负载型催化剂NiWO_4/g-C_3N_4。采用XRD、FT-IR、EDS、SEM、BET和XPS表征了NiWO_4/g-C_3N_4的形貌和结构特征。以NiWO_4/g-C_3N_4为催化剂,过氧化氢为氧化剂,1-丁基-3-甲基咪唑四氟硼酸盐离子液体([BMIM]BF4)为萃取剂。考察了催化剂的负载量,过氧化氢、离子液体和催化剂使用量,反应温度,反应时间,不同种类的含硫化合物对脱硫效果的影响。结果表明,在5 m L模拟油,0.2 m L过氧化氢,1.0 m L的[BMIM]BF4,0.03 g的NiWO_4/g-C_3N_4,反应温度为80℃,反应时间为140 min的最佳的反应条件下,脱硫率可以达到97.35%。实验表明,NiWO_4/g-C_3N_4具有很好的催化稳定性,催化剂重复使用五次后催化活性并没有明显地降低。