乙醇电氧化的研究进展

简要地叙述了国内外乙醇电催化氧化的研究进展，着重介绍不同电极材料对乙醇电氧化的影响及目前所提山的机理，并对其可能的研究方向提出了建议。     

无隔膜电解槽内羟基新戊醛的间接电氧化

在无隔膜电解槽内,电解溴离子生成溴单质作为氧化剂,氧化羟基新戊醛为羟基新戊酸。研究了pH、反应温度、反应物浓度和阳极电位对电流效率及选择性的影响。结果表明,在无隔膜电解槽内,以Br-/Br2为媒质的间接电氧化法可以制取羟基新戊酸,电流效率最高可达61 9%,选择性可达90%。     

Paired electrooxidation IV. Decarboxylation of sodium gluconate to D-arabinose

A paired electrooxidative method has been developed to synthesize D-arabinose in a divided cell. D-arabinose is a material which has an important role in the production of vitamin B2 and DNA. Sodium gluconate was directly oxidized at the anode and indirectly oxidized in the catholyte by bubbling oxygen which was reduced to H₂O₂ and OH free radicals. In the catholyte, indirect oxidation of sodium gluconate was mediated by Fe³⁺ and OH free radicals. The optimal current efficiencies for D-arabinose production in the anolyte and catholyte were found to be 88.37% and 39.12%, respectively, and the total current efficiency of the paired electrooxidation was 127.49%. The paired electrosynthesis of D-arabinose is more economical in terms of power consumption than electrosynthesis that employ a single anode or cathode as the working electrode. The influence of cathodic/anodic CV and I/E curves, redox mediators and the amount of charge passed were also examined.     

Preparation of methanol oxidation electrocatalysts: ruthenium deposition on carbon-supported platinum nanoparticles

Methanol oxidation electrocatalysts were prepared from Ru electrochemical or spontaneous deposition on commercial-grade carbon-supported Pt nanoparticles (Pt-Vulcan XC72, E-TEK). The resulting Ru coverage was estimated by cyclic voltammetry in supporting electrolyte. The maximum electrocatalytic activity for methanol oxidation at room temperature was observed at lower Ru coverage for spontaneous deposition than for electrodeposition; _Ru 10% vs 20%, respectively. On the other hand, higher current densities for methanol oxidation were obtained in the case of electrodeposited Ru. These two results were related to the presence of non-reducible ruthenium oxides in the spontaneous deposit. The present work provides evidence that (i) efficient DMFC electrocatalysts can be achieved by Ru deposition on Pt nanoparticles, and (ii) formation of a PtRu alloy is not a required condition for effective methanol electrooxidation.     

Electrooxidation of methanol at platinum–ruthenium catalysts prepared from colloidal precursors: Atomic composition and temperature effects

The electrocatalytic oxidation of methanol was investigated on PtRu electrodes of different atomic compositions at several temperatures (from 25 to 110 °C). Very active catalyst nanoparticles supported on active carbon (Vulcan XC 72) were obtained using the colloidal synthesis developed by Bönnemann et al. [11], allowing easy variation of the atomic composition. These electrocatalysts were characterized by TEM, EDX and XRD; results indicate that they consist of platinum nanoparticles decorated by ruthenium. Methanol oxidation was studied as a function of composition, temperature and methanol concentration. Two effects were investigated: the effect of the working temperature and the effect of the atomic composition. It appeared that for lower methanol electrooxidation overvoltages, the best catalysts are ruthenium-rich, whereas at higher overvoltages the best one is the Pt + Ru (80:20)/C composition, irrespective of the working temperature, either in half-cell or in a single DMFC.     

Enhancement of the electrooxidation of ethanol on a Pt–PEM electrode modified by tin. Part I: Half cell study

The direct platinisation of a solid polymer electrolyte (Nafion^® membrane) was realized by chemical reduction of a platinum salt. The Pt–PEM electrodes thus obtained were modified by tin to improve the electrocatalytic activity towards the electrooxidation of ethanol. The Pt–PEM and Pt–Sn–PEM electrodes were characterized by TEM, EDX and XRD analysis, cyclic voltammetry, and their polarisation curves for the electrooxidation of ethanol were determined under quasisteady state conditions.     

Electrocatalytic oxidation of ethanol on Pt–Mo bimetallic electrodes in acid medium

Pt–Mo alloy electrocatalysts were prepared by an arc-melting furnace process to investigate the origin of their enhanced activity toward ethanol oxidation. Two Mo contents were chosen in zones of the binary phase diagram where they are supposed to form either a pure alloy mixture or a solid solution. Pt–Mo alloy catalysts were more active than Pt-alone. Gradual Mo dissolution at the electrode surface was observed after voltammetric and chronoamperometric measurements. The dissolved Mo contributed to the catalytic effect of the electrode as underpotentially deposited (upd) adatoms. This dissolution probably also leads to an increase in the electrode surface roughness. Low molybdenum content in the electrode material enhances the activity toward ethanol oxidation when compared to Pt-alone. Ethanol oxidation was also investigated by in situ infrared reflectance spectroscopy in order to determine the presence of adsorbed intermediates like CO species. Acetaldehyde, acetic acid and CO₂ were also found by spectroscopic experiments.     

间接电解氧化法合成L-磺基丙氨酸

Nafion417为隔膜的电解槽中,DSA(dimensionalstableanode)为形稳性阳极,Pb为阴极,间接电解氧化L 胱氨酸合成L 磺基丙氨酸。研究了胱氨酸浓度、HBr浓度、电解浴温度、阳极电流密度及电解电量等因素对电合成L 磺基丙氨酸产率的影响。研究表明:由0 1mol/L胱氨酸和3 5mol/LHBr组成的阳极液,以2 5A·dm-2的电流密度于30℃电解至理论电解电量为止,产品产率达70%。     

Selective oxidation of pentachlorophenol on diamond electrodes

The influence of electrode potential on pentachlorophenol (PCP) oxidation on boron doped diamond (BDD) electrodes in a 0.1 mol L^–1 Britton–Robinson buffer (pH 5.5) is described. Controlled potential electrolyses were carried at 0.9, 2.0 and 3.0 V vs Ag/AgCl and the solutions analysed by square wave voltammetry, high performance liquid chromatography, chloride ion selective electrode and spectroscopy in the ultraviolet–visible region. At low positive potential (0.9 V), the formation of an adherent film on the electrode surface involving the transference of 1 electron per PCP molecule was observed. The film was identified as the dimer 2,3,4,5,6-pentachloro-4-pentachlorophenoxy-2,5-cyclohexadienone and the current efficiency was as high as 90%. At potentials close to the onset of O₂ evolution (2.0 V), the formation of the corresponding quinone (p-tetrachlorobenzoquinone) was detected at the beginning of the process. This was followed by further oxidation to the hydroxy-benzoquinone with a practically quantitative yield. Electrolyses carried out well into the region of oxygen evolution (3.0 V) lead to the electrochemical combustion of PCP to CO₂ and H₂O as well as to the release into solution of 5 Cl^– ions per PCP molecule destroyed.     

玻炭电极差分脉冲伏安法测定抗坏血酸的研究

研究差分脉冲伏安法在电活化玻炭电极表面测定抗坏血酸的方法。循环伏安表明经电活化的玻炭电极对抗坏血酸具有明显的氧化作用,且氧化峰电流随着抗坏血酸浓度增大而增大。差分脉冲表明抗坏血酸在pH=3.73的1 mol/L HAc-NaAc缓冲体系中具有较高的电活性,且在0～0.08 g/L的浓度范围内,差分脉冲峰电流密度与抗坏血酸的浓度呈线性关系,线性回归方程为:i=9.256c+1.085,r=0.998 2。该方法可用于抗坏血酸注射液浓度的测定,回收率为98.6%～104.0%。