用于乙醛酸电合成的高效表面合金电催化剂研究

运用电化学方法，研制了三种表面合金（Ｐｂ－Ｓｂ－Ｐｔ／ＧＣ，Ｓｂ－Ｐｔ／ＧＣ，Ｐｂ－Ｐｔ／ＧＣ）电催化剂，发现在草酸还原生成乙醛酸的电有机合成中这些表面合金电催化有较高的活性，其起始还原电位分别比在Ｐｂ阴极上（－１．１Ｖ）提前了０．４８～０．７０Ｖ，这三种表面合金电催化剂的活性次序为：Ｐｂ－Ｓｂ－Ｐｔ／ＧＣ〉Ｓｂ－Ｐｔ／ＧＣ〉Ｐｂ－Ｐｔ／ＧＣ。红外光谱结果表明，在这些表面合金电极上草酸还原产物主要     

Studies of surface alloy as high efficient electrocatalyst for glyoxylic acid synthesis

运用电化学方法，研制了三种表面合金（ＰｂＳｂＰｔ／ＧＣ，ＳｂＰｔ／ＧＣ，ＰｂＰｔ／ＧＣ）电催化剂，发现在草酸还原生成乙醛酸的电有机合成中这些表面合金电催化剂有较高的活性，其起始还原电位分别比在Ｐｂ阴极上（１．１Ｖ）提前了０．４８～０．７０Ｖ。这三种表面合金电催化剂的活性次序为：ＰｂＳｂＰｔ／ＧＣ＞ＳｂＰｔ／ＧＣ＞ＰｂＰｔ／ＧＣ。红外光谱结果表明，在这些表面合金电极上草酸还原产物主要为乙醛酸。     

铂基Pb-Sb表面合金电催化剂的制备与结构表征

通过电化学方法,在玻碳载体表面制备以Pt、Pb、Sb为主要成分的铂基Pb Sb表面合金电催化剂.运用电化学循环伏安、石英晶体微天平（EQCM）和扫描隧道显微镜（STM）技术对催化剂电极进行表征.结果表明：酸性溶液中在所制备的表面合金电极上,析氢起始电位负移至－0.45 V,表面合金的起始氧化电位为0.15 V,其稳定性明显高于电催化还原中常用的铅、锑等金属电极.通过EQCM研究表面合金电极的形成过程,结合STM观察和XPS深度剖析,确定电催化剂表面是由粒度均匀的纳米颗粒构成的表面合金层.     

金电极表面聚赖氨酸固定微过氧化物酶-11的电化学研究

通过聚赖氨酸修饰将微过氧化物酶-11(MP-11)固定在金电极表面,制备成MP-11修饰电极.修饰在电极表面上的MP-11的血红素活性中心与电极之间可进行直接的电子传递反应,其氧化还原式电位为-0.39V.该修饰电极对氧的还原具有电催化活性.当MP-11与咪唑发生轴向配位反应时,其氧化还原式电位发生负移,此时对氧的还原不再具有电催化活性.     

稀土贮氢合金电极在乙醛酸电解制备中的应用

研究了以AB5型稀土贮氢合金作催化还原电极恒电位电解草酸制备乙醛酸,合金表面处理和电极活化可提高电解产率和电流效率.确定了最佳电解工艺条件:电流密度120mA·dm-2,电解液温度30℃,草酸浓度1.0mol·L-1,此时电流效率为86%,电解产率为88%.随着电解次数的增加,由于贮氢合金膨胀粉化及表面被电解产物覆盖,电流效率和乙醛酸产率均呈下降趋势,在电解过程中即时分离电解产物有利于提高电流效率和乙醛酸产率.     

TiN基IrO2-Ta2O5涂层析氢电极的催化性能

 采用热分解法制备了以离子镀TiN膜为基体的IrO2-Ta2O5涂层电极,通过循环极化曲线并结合扫描电镜、 X射线能谱和X射线衍射研究了涂层的析氢电催化性能. 结果表明,涂层呈多孔多裂纹的结构,焙烧温度对涂层的表面形貌和电催化活性影响很大. 420 ℃下焙烧的涂层具有最优的电催化活性. 涂层电极的析氢反应电极电位为-0.26 V(vs SCE), 低析氢过电位下的Tafel斜率为-0.04 V, 而在高析氢过电位下,电极表面吸附的大量氢原子改变了氧化物电极的结构,从而抑制了氧的阴极还原反应.     

贮氢合金表面分析和金属氢化物电极电催化活性

贮氢合金表面状态和组成是影响金属氢化物(MH)电极电催化活性的重要因素, MH电极的表面改性处理是改善电极性能的有效方法。用XPS, ICP, BET方法分析了处理后贮氢合金表面组成和状态的变化。讨论了化学还原处理对MH电极电催化活性的影响, 结果表明: 化学还原处理大大提高了MH电极反应的交换电流密度和减低了电极反应活化能。     

碳载Pt和PtRu催化剂的甲醇电氧化比较

利用电化学方法对商用Pt/C和PtRu/C催化剂在酸性介质中的甲醇电氧化进行了比较研究.动电位和恒电位氧化实验结果皆表明PtRu/C比Pt/C对甲醇电催化活性高.PtRu合金的形成不仅改变了催化剂表面对氢的吸附性质,而且使氧化物还原峰电位向阴极方向移动.Ru与甲醇的相互作用为温度活化过程,需要较高的温度.     

铜-锑双金属合金高效电催化还原二氧化碳制乙烯

随着全球工业化进程的快速发展,日益增多的人类活动不仅加速化石燃料的消耗,还会导致温室气体二氧化碳(CO2)的大量排放.同时,CO2也是廉价、无毒无害、储量丰富的C1资源,将其转化为有价值的化学品具有碳资源合理利用和环境保护的双重意义.近年来,采用电化学方法温和条件下还原CO2为重要化学品和燃料引起广泛关注.其中,探索廉价电催化剂,高效催化还原CO2为C2产物仍是一个具有挑战性的课题.铜基催化剂由于自身低成本和可还原CO2为多种碳氢产物的优点而备受关注.然而,铜基电催化材料具有选择性差、失活严重和效率低等缺点,并且在电催化还原CO2过程中需要较高的过电位,反应过程中会受到氢气析出副反应的影响.为了得到一种化学性质稳定、高电流密度和高选择性等优点的材料在电催化CO2还原中得到了广泛的研究.然而,单纯的铜催化剂对CO2分子的活化以及反应中间体的吸附能力较低,导致了铜基材料催化剂电催化CO2还原活性及选择性较低.因此,开发出可实际应用的高效率和高选择性的电极材料是当前该技术研究中亟待解决的关键科学问题.近年来,铜基二元合金在电催化CO2还原反应中受到广泛关注.由于二元金属的电子结构和各元素的电子结合能发生变化,其催化活性明显优于单金属催化剂.因此,铜基双金属合金在提高CO2还原产物选择性方面具有广阔的前景.本文采用低温还原的方法制备了一系列不同组成的Cu-Sb双金属合金,系统研究了一系列不同配比的Cu-Sb双金属合金对电催化还原CO2为乙烯的影响.研究发现,当Cu/Sb比例为10/1(Cu10-Sb1)时,可有效提高乙烯的法拉第效率及电流密度.当以0.1 M KCl水溶液作为电解液,电位为-1.19 V vs.RHE时,乙烯的法拉第效率和电流密度分别为49.73%和28.5 mA cm-2.实验结果表明,Cu-Sb双金属合金催化剂优异的催化性能主要源于适宜的电子态、良好的CO2吸附性能、较大的电化学比表面积和较高的电子传输速率.迄今,用Cu-Sb作为催化剂进行电催化还原CO2制乙烯尚未见报道.     

铜–锑双金属合金高效电催化还原二氧化碳制乙烯（英文）

随着全球工业化进程的快速发展,日益增多的人类活动不仅加速化石燃料的消耗,还会导致温室气体二氧化碳(CO_2)的大量排放.同时,CO_2也是廉价、无毒无害、储量丰富的C_1资源,将其转化为有价值的化学品具有碳资源合理利用和环境保护的双重意义.近年来,采用电化学方法温和条件下还原CO_2为重要化学品和燃料引起广泛关注.其中,探索廉价电催化剂,高效催化还原CO_2为C_2产物仍是一个具有挑战性的课题.铜基催化剂由于自身低成本和可还原CO_2为多种碳氢产物的优点而备受关注.然而,铜基电催化材料具有选择性差、失活严重和效率低等缺点,并且在电催化还原CO_2过程中需要较高的过电位,反应过程中会受到氢气析出副反应的影响.为了得到一种化学性质稳定、高电流密度和高选择性等优点的材料在电催化CO_2还原中得到了广泛的研究.然而,单纯的铜催化剂对CO_2分子的活化以及反应中间体的吸附能力较低,导致了铜基材料催化剂电催化CO_2还原活性及选择性较低.因此,开发出可实际应用的高效率和高选择性的电极材料是当前该技术研究中亟待解决的关键科学问题.近年来,铜基二元合金在电催化CO_2还原反应中受到广泛关注.由于二元金属的电子结构和各元素的电子结合能发生变化,其催化活性明显优于单金属催化剂.因此,铜基双金属合金在提高CO_2还原产物选择性方面具有广阔的前景.本文采用低温还原的方法制备了一系列不同组成的Cu–Sb双金属合金,系统研究了一系列不同配比的Cu–Sb双金属合金对电催化还原CO_2为乙烯的影响.研究发现,当Cu/Sb比例为10/1(Cu_(10)–Sb_1)时,可有效提高乙烯的法拉第效率及电流密度.当以0.1 M KCl水溶液作为电解液,电位为–1.19 V vs.RHE时,乙烯的法拉第效率和电流密度分别为49.73%和28.5 mA cm~(–2).实验结果表明,Cu–Sb双金属合金催化剂优异的催化性能主要源于适宜的电子态、良好的CO_2吸附性能、较大的电化学比表面积和较高的电子传输速率.迄今,用Cu–Sb作为催化剂进行电催化还原CO_2制乙烯尚未见报道.     

草酸电还原反应机理的研究

以硫酸钠溶液作底液,用快速循环伏安和电势阶跃法研究了草酸在铅电极上的电还原机理,测定了草酸电还原第一步反应的动力学参数,并根据循环伏安图比较相同条件下草酸,乙醛酸和乙醇酸的还原峰峰电势,推断出草酸还原的中间产物.研究结果表明,草酸电还原遵从不可逆2电子EE反应机理.     

Identification of iron(III) oxides and hydroxy-oxides by voltammetry of immobilised microparticles

In this paper, we propose the use of an electroanalytical technique based on the direct oxidation or reduction of the electroactive components of the sample on the surface of the working electrode, called voltammetry of immobilised microparticles (VMPs). The sample is easily deposited on the electrode by abrasion and then the electrode is transferred to the electrochemical cell where the square wave potential scan is performed. Electroactive species showed peaks whose peak potential is related to the standard formal potentials. We applied this technique to the identification of iron oxides and hydroxy-oxides in cosmetics. To characterise and identify the iron(III) oxides and hydroxy-oxides VMP was performed in two different media: oxalic acid and hydrochloric acid, that is, a complexing and a slightly complexing media. Two electrode processes were observed. They were influenced by the media and the synthesis procedure of the oxides. The reduction peak at negative potentials (−0.50 V in hydrochloric acid and −0.60 V in oxalic acid) is related to the direct reduction of the iron(III) oxide and it does not appear in the case of the more reactive phases (hydroxy-oxides). The peak at positive potentials (0.90 V in hydrochloric acid and 0.60 V in oxalic acid) involves the reduction of iron(III) in solution. The same electrode process were observed for binary mixtures but the peak potentials are shifted from the pure components peak potentials. This allowed us to distinguish between their mixtures. Finally, VMP was used to characterise iron oxides in cosmetic powders.     

草酸电还原制取乙醛酸的研究

研究了由草酸电解还原制备乙醛酸时，温度、草酸纯度、电解时间、电极状态和电解产物对电流效率和产率的影响。实验发现，除温度和原料纯度是重要的影响因素外，电极表面的有机物吸附和电解产物－乙醛酸的浓度具有更大的影响。     

草酸处理对丙烷氨氧化催化剂Sb-V-O结构和催化性能的影响

以不同量的草酸处理钒的起始原料,采用共沉淀法制备了VSb3混合氧化物催化剂,运用N2低温吸附、X射线衍射、X射线光电子能谱和H2程序升温还原等方法对催化剂进行了表征,并考察了其在丙烷氨氧化反应中的催化性能.结果表明,草酸的处理可使所得样品中V处于较低的价态,从而有利于活性相SbVO4的生成.当草酸/V(摩尔比)为3时,所制VSb3混合氧化物中存在较多的活性相SbVO4,且其表面具有适量Sb和V的分布,使催化剂具有良好的氧化/还原性能平衡,因而在丙烷氨氧化反应中表现出更高的活性和丙烯腈选择性.     

聚茜素红-多壁碳纳米管复合膜修饰电极的研制及叶酸含量测定

采用电聚合方法将茜素红（AR）非共价修饰到多壁碳纳米管（MWCNTs）上,制得了PAR/MWCNTs/GC电极,该电极对叶酸（FA）具有良好的电催化作用. 结果表明,在最佳实验条件下,在-0.63 V处叶酸还原峰电流与浓度（1.25×10^-6 ~ 4.00×10^-5 mol·L^-1）呈现良好线性关系,相关系数0.9985. 用标准加入法检测了回收率,其值达92.0% ~ 102.0%. 该电极制作简单,有良好的稳定性．     

痕量铅在草酸修饰电极上阳极溶出伏安的研究

本文对草酸修饰电极的制作、痕量铅在草酸修饰电极上的反应机理和电化学特性作了研究。采用阳极溶出伏安法,测定铅的灵敏度比玻碳电极提高7.5倍,在1.0～15.0ng·/mL铅浓度范围内溶出峰高与铅浓度呈良好的线性关系。连续测定12次变异系数为3.0％。利用草酸修饰电极对人尿中痕量铅进行了测定,结果良好。     

二氧化碳电还原制草酸研究进展

近年来, 二氧化碳过量排放所引发的全球变暖等气候问题引起了全世界的广泛关注, 碳减排已成为人类社会可持续发展面临的共同挑战. 利用电化学方法将二氧化碳转化为高附加值化学品是实现碳减排和二氧化碳高附加值利用的理想途径之一, 但仍面临能耗高、 二氧化碳转化率低、 产物选择性差和难分离等问题. 本文以电还原二氧化碳制草酸为例, 从反应机理、 催化剂、 电解液、 催化电极及反应器等方面介绍该反应的研究进展, 对当前二氧化碳电还原制草酸存在的关键问题进行了分析, 并对其未来研究方向进行了展望.     

Determination of oxalate in urine, using an amperometric biosensor with oxalate oxidase immobilized on the surface of a chromium hexacyanoferrate-modified graphite electrode

A novel enzymatic amperometric method is described for the determination of oxalic acid in urine. An amperometric biosensor was made by immobilizing oxalate oxidase on the surface of a chromium(III) hexacyanoferrate-modified graphite electrode by using a bovine serum albumin and glutaraldehyde cross-linking procedure. The enzyme biocatalyzes oxalate decomposition in the presence of oxygen into carbon dioxide and hydrogen peroxide. The oxalate concentration, which is proportional to the amount of hydrogen peroxide, was determined amperometrically by measuring the current resulting in the reduction of hydrogen peroxide at a very low working potential (0.05 V versus the Hg ?Hg2Cl2? 3M KCl electrode), which minimized the influence of the possible interferences present in human urine. All experiments were performed with succinic buffer, pH 3.8, containing 0.1M KCl and 5.4mM ethylenediaminetetraacetic acid. In an aqueous solution of pure oxalic acid, the biosensor showed good linearity in a concentration range of 2.5-100 microM without the use of a dialysis membrane. For untreated urine samples, a high correlation (R2 = 0.9949) was obtained between oxalate concentrations added to urine samples and oxalate recoveries calculated for determinations with the described oxalate biosensor.     

Adsorption of dicarboxylic acids on lithiated nickel oxide electrode

Adsorption of dicarboxylic acids on NiO electrodes was studied by means of the galvanostatic transient method, mainly for oxalic acid. The oxalate or hydrogen oxalate anion or both were concluded to adsorb on the electrode. The adsorption was maximal at a potential less positive than the flat-band potential of the electrode, owing to preferential adsorption of hydroxyl anion in the region above the maximum adsorption potential. The quantity of adsorption was dependent on carrier concentration of the electrode, and high for the electrode of high carrier concentration. This phenomenon is connected to the charged condition of the electrode that when the maximum adsorption takes place, positively charged sites remain on the surface of the electrode which is charged negatively as a whole and the amount of the sites is much more different between the electrodes of different N than their bulk carrier concentrations. Adsorptions of malonic and succinic acid were distinctly low compared with that of oxalic acid. The adsorbability was in the order; oxalic acid>malonic acid>succinic acid. This order was in accord with the stability constants of nickel dicarboxylic acid chelates.     

Improvement of the Selectivity of Amperometric Biosensors by Using a Permselective Electropolymerized Film

Abstract

Dichlorophenolindophenol (DCPIP) was electrochemically deposited onto the surface of glassy carbon and platinum electrodes to form a permselective film. Cyclic voltammetry of the DCPIP coated electrode exhibited a reversible oxidation/reduction current at +0.14 V, behavior similar to monomeric DCPIP. However, such an electrode did not mediate glucose oxidase in the presence of β-D-glucose. For operation at +0.7 V vs Ag/AgCl, the DCPIP electrodeposited film behaved like a permselective membrane and virtually eliminated oxidative interference currents resulting from 0.2 mM acetaminophen, uric acid and glutathione. For ascorbic acid, interfering current due to 0.2 mM ascorbate was decreased by 80%. Improvement of the selectivity due to ascorbic acid was achieved using an electrodeposited film prepared from a mixture of DCPIP with diaminobenzene or resorcinol.