碱性介质中甘氨酸在Pt电极上解离吸附和氧化反应的原 …

运用原位红外反射光谱研究了碱性介质中甘氨酸在Ｐｔ电极上的解离吸附和氧化反应行为,并利用纳米Ｐｔ膜极的异常红外效应鉴定反应过程中生成的表现吸附物种。结果表明,甘氨酸在Ｐｔ电极上极易发生解离,生成强吸附于电极表面上的氰基负离子。     

中性介质中L-丝氨酸在Pt电极上解离吸附和氧化的原位FTIR研究

运用电化学循环伏安(CV)和原位红外反射光谱(in situ FTIRS)研究了中性介质中L-丝氨酸在Pt电极上的解离吸附和氧化过程. 结果表明, 在中性溶液中, 以两性离子形式存在的丝氨酸可以在很低的电位下(-0.6 V, vs. SCE)在Pt电极表面发生解离吸附, 生成强吸物种一氧化碳(COL)、(COB)和氰负离子(CN-). 研究结果还表明, 当电位低于0.7 V(vs. SCE)时, CN-能稳定存在于电极表面, 抑制丝氨酸的进一步反应. 在更高电位时则主要为丝氨酸分子的氧化过程.     

酸性和碱性介质中甘氨酸解离吸附和氧化的EQCM研究

用电化学石英晶体微天平(EQCM)研究酸性和碱性介质中甘氨酸在Pt电极上的吸附和氧化过程.结果表明,甘氨酸的解离吸附和氧化行为与溶液的酸碱性密切相关.酸性溶液中甘氨酸吸附较弱,碱性溶液中则产生强吸附物,且当电位低于0V(vs.SCE)时可吸附于Pt电极表面.此外,碱性溶液中甘氨酸还表现出较高的电氧化活性.通过EQCM定量检测上述过程中Pt电极表面的质量变化,测定了不同电位区间(氢区、双电层区和氧区)每传递一个电子所对应的电极表面吸附物种的平均摩尔质量.     

碱性介质中甘氨酸在纳米金膜电极上的吸附和氧化

运用原位红外反射光谱（in situ FTIRS）和电化学石英晶体微天平（EQCM）在分子水平上研究了碱性介质中甘氨酸在纳米金膜电极上的解离吸附和氧化过程.结果表明,甘氨酸在很低的电位下（－0.8 V, vs SCE）就可发生解离吸附.其解离产物氰基(CN－)与电极表面存在较强的化学吸附作用，形成AuCN－物种(红外吸收谱峰位于2100 cm－1附近).吸附在纳米金膜表面的CN－给出红外吸收显著增强、红外谱峰方向倒反和半峰宽增加的异常红外效应特征.吸附态CN－在低电位抑制H2O和OH－的吸附，当电位高于0.2 V可氧化产生OCN－；进一步升高电位到0.3 V则形成.溶液相物种OCN－和对应的红外吸收峰分别为2169 cm－1和2145 cm－1.实验结果指出，金以的形式溶解是导致电极表面质量显著减少的主要原因.     

酸性介质中1,2-丙二醇在铂电极上吸附和氧化过程的原位FTIR反射光谱研究

应用电化学循环伏安和原位FTIR反射光谱研究1,2-丙二醇在Pt电极上吸附和氧化过程。结果指出1,2-丙二醇的电氧化可按双途径进行。其一经1,2-丙二醇在Pt上解离吸附产物氧化至CO_2。但在较低电位下这些解离吸附产物(红外检测为CO_(ad)、[﹥C=CH_2]_(ad)等)累积吸附于电极上, 毒化Pt表面抑制其它反应。当电位大于0.3 V后它们一经生成即氧化脱附, 从而使1,2-丙二醇得以在未毒化Pt表面经反应中间体氧化至CO_2。在实验条件下,原位FTIR反射光谱检测到的反应中间体可能有HOC-CHOHCH_3(或CH_2OHCOCH_3)和HOOC-COCH_3(或HOOC-CHOHCH_3)等物种。     

酸性介质中1,2-丙二醇在铂电极上吸附和氧化过程的原位FTIR反射光谱研究

应用电化学循环伏安和原位FTIR反射光谱研究1,2-丙二醇在Pt电极上吸附和氧化过程。结果指出1,2-丙二醇的电氧化可按双途径进行。其一经1,2-丙二醇在Pt上解离吸附产物氧化至CO_2。但在较低电位下这些解离吸附产物(红外检测为CO_(ad)、?C=CH_2]_(ad)等)累积吸附于电极上,毒化Pt表面抑制其它反应。当电位大于0.3V后它们一经生成即氧化脱附,从而使1,2-丙二醇得以在未毒化Pt表面经反应中间体氧化至CO_2。在实验条件下,原位FTIR反射光谱检测到的反应中间体可能有HOC-CHOHCH_3(或CH_2OHCOCH_3)和HOOC-COCH_3(或HOOC-CHOHCH_3)等物种。     

二十四面体Pt纳米晶电极上甲酸解离吸附反应动力学研究

研究了甲酸在二十四面体Pt纳米晶（THHPtNCs）电极表面解离吸附反应过程.电化学原位红外反射光谱结果显示,甲酸在低电位（-0.20V（SCE））即可在THHPtNCs电极上氧化到CO2,同时发生分子内化学键断裂生成吸附态CO物种.运用程序电位阶跃暂态方法定量研究甲酸解离吸附反应动力学,测得5×10^-3mol·L^-1 HCOOH＋0.1mol·L^-1 H2SO4溶液中甲酸在THHPtNCs电极上解离吸附的最大平均速率υamax为13.19×10^-10mol·cm^-2·s^-1,是商品Pt/C催化剂电极上υamax的1.5倍.研究结果揭示了THHPtNCs的反应活性显著高于Pt/C催化剂.     

酸性和碱性介质中甘氨解离吸附和氧化的EQCM研究

用电化学石英晶体微天平（EQCM）研究酸性和碱性介质中甘氨酸在Pt电极上的吸附和氧化过程，结果表明，甘氨酸的解离吸附和氧化行为与溶液的酸碱性密切相关，酸性溶液中甘氨酸吸附软弱，碱性溶液中则产生强吸附物，且当电位低于0V（vs.SCE)时可吸附于Pt电极表面，此外，碱性溶液中甘氨酸还表现出较高的电氧化活性，通过EQCM定量检测上述过程中Pt电极电极表面的质量变化，测定了不同电位区间（氢区、双电层区和氧区）每传递一个电子所对应的电极表面吸附物的平均摩尔质量。     

原位红外光谱法研究对氯苯酚在Pt电极上的电氧化行为

采用原位红外光谱法研究了碱性条件下对氯苯酚(PCP)在Pt电极上电化学氧化的脱氯反应机理. 研究结果表明Pt电极对PCP有良好的电化学反应活性, 其氧化过程首先是对氯苯酚负离子氧化生成对氯苯氧自由基, 该自由基可与对氯苯酚负离子作用生成芳香醚低聚物; 随着电位升高, 对氯苯酚负离子经电化学氧化生成了苯二酚盐(还可能存在其氧化产物不饱和羧酸盐); 当电位继续升高, 苯二酚盐进一步氧化形成苯醌; 最后, 在Pt表面生成小分子羧酸盐, 同时生成了最终产物CO2. 但由于芳香醚低聚物等不溶性聚合物膜的形成并吸附在Pt电极表面, 可造成Pt电极毒化, 使得Pt电极在使用过程中逐渐失去活性.     

二甲醚在Pt电极上吸附和氧化的循环伏安和原位FTIR光谱研究

运用电化学循环伏安法(CV)和原位傅立叶变换红外(FTIR)反射光谱, 研究了不同pH值溶液中二甲醚(DME)在Pt电极上的解离吸附和氧化过程. 稳态CV结果给出, 在0.1 mol·L-1 H2SO4溶液中, 当电位处于0.05-0.35 V (vs RHE)区间, 约70%的Pt表面位被DME的解离吸附产物占据. DME电氧化反应的活性随pH值增加而下降, 在0.1 mol·L-1 NaOH溶液中, 氢的吸脱附几乎不受抑制且观察不到明显的氧化电流, 表明DME醚键上氧原子的质子化是其发生解离吸附和氧化的必要条件. 原位FTIR光谱研究给出DME解离吸附和氧化过程的分子水平信息, 指出DME在低电位区间解离生成线型吸附态CO(COL)毒性中间体. 当电位高于0.55 V(vs RHE)时, COL开始氧化为CO2; 在0.75-1.00 V(vs RHE)的电位区间则可同时发生经活性中间体(HCOOH)的氧化过程.     

Adsorption and oxidation of glycine on Au electrode: An in situ surface-enhanced infrared study

The adsorption and oxidation of glycine on Au surface are studied by cyclic voltammetry coupled with in situ surface-enhanced infrared spectroscopy. The infrared spectra definitely indicate that glycine is adsorbed on the electrode with two oxygen atoms directing the C_α–C bond perpendicular to the surface. During glycine oxidation, cyanide is formed and oxidized to cyanate at high potentials. It is also shown that ureylene biradical species (deprotpnated urea) bonded to the surface via two nitrogen atoms is formed on oxidized Au surface. Combining experimental results reported in the literature, the mechanism of glycine electrooxidation is discussed.     

丙三醇在Pt电极上吸附和氧化过程的原位FTIR反射光谱研究

运用电化学循环伏安(CV)和原位FTIR反射光谱方法, 研究了丙三醇在Pt电极上的氧化过程。结果指出, 丙三醇的氧化是一个复杂的表面过程。其间包括脱水、吸附、解离等步骤。根据CV和红外实验数据, 本文提出了Pt电极上丙三醇解离吸附的表面反应机理和不同电位下丙三醇氧化的分子过程。     

Manipulation of electrocatalytic reaction pathways through surface chemistry: in situ Fourier transform infrared spectroscopic studies of 1,3-butanediol oxidation on a Pt surface modified with Sb and S adatoms

Cyclic voltammetry and in situ Fourier transform infrared (FTIR) spectroscopy were employed to study the electrocatalytic properties of a Pt electrode modified with adatoms of antimony (Sb) or sulfur (S) for 1,3-butanediol (1,3-BD) oxidation. The results demonstrated the possibility of manipulating the reaction pathways involved in 1,3-BD oxidation through chemical modification of the Pt electrode surface. Both Sb and S adatoms (Sb(ad) and S(ad)) can inhibit the dissociative reaction of 1,3-BD into CO, which is the main source of self-poisoning in electrocatalysis of small organic molecules. On Pt electrodes modified with a high coverage of Sb(ad) (Pt/Sb(ad)) the onset oxidation potential of 1,3-BD has been significantly decreased, which is attributed to the fact that the oxidation of Sb(ad) occurs at lower potentials than that of the Pt surface. In situ FTIR results illustrated that, although at potentials below 0.5 V (vs a saturated calomel electrode), at which the Sb(ad) is stable on the Pt electrode surface, both carbonyl and CO2 species have been observed, the principal oxidation products of 1,3-BD are carbonyl species. Such results indicate that the reaction is mainly the dehydrogenation of 1,3-BD molecules. However, at potentials above 0.5 V the proportion of CO2 species in the oxidation products increases quickly, implying that the reaction has turned to the breakage of C-C bonds in 1,3-BD molecules and the subsequent oxidation of the cleaved fragments. In contrast with the cases of 1,3-BD oxidation on Pt and Pt/Sb(ad) electrodes, the reaction of 1,3-BD oxidation on a Pt electrode modified with S adatoms (Pt/S(ad)) is oriented completely to the production of carbonyl species when electrode potentials are below 0.9 V, though the reaction activity is relatively low. When the electrode potential is increased above 0.9 V, the intensity of the CO2 IR band in the FTIR spectra increases rapidly, corresponding to a fast oxidation of 1,3-BD on surface Pt sites recovered by the oxidation and desorption of S(ad) from the Pt surface.     

CO和SCN~-在高分散Pt及Pd表面异常红外光学行为的电化学现场FTIR反射光谱研究

在玻碳基底上沉积Pt和Pd，在以CO和SCN-为探针分子的电化学现场FTIR反射光谱研究中，首次观察到异常红外光学行为，其中包括吸附物种的谱带方向倒反以及谱峰强度显著增强等．     

Formate,an active intermediate for direct oxidation of methanol on pt electrode

The electro-oxidation of methanol on a Pt thin film electrode in acidic solution has been investigated by in situ surface-enhanced IR absorption spectroscopy. A new IR peak is observed at around 1320 cm-1 when the electrode potential is more positive than 0.5 V, where the bulk oxidation of MeOH occurs. This peak has been assigned to the symmetric stretching of formate species adsorbed on the Pt electrode surface. It is the first observation of formate adsorption during the electro-oxidation of methanol on a Pt surface. A near proportional relationship between the intensity of the IR band of the formate species and MeOH electro-oxidation current is observed. A new reaction scheme via non-CO pathway with formate as the active intermediate is proposed for the methanol electro-oxidation process.     

甲酸解离吸附的动力学和时间分辨FTIR特征

 运用电化学暂态（电位阶跃）方法和时间分辨FTIR反射光谱研究甲酸在Pt电极上的解离吸附过程，揭示了这一表面分子过程的反应速率在－0．25至0．25VvsSCE区间呈火山形变化的规律，还测得在含10－3mol•L－1HCOOH的溶液中最大的初始解离速率（－0．06V时）为9.33×10－11mol•cm－2•s－1.     

次亚磷酸根离子在铂电极上氧化的机理研究(英文)

用SNIFTIRS和循环伏安法研究次亚磷酸根离子在多晶铂电极上的电氧化机理 .分析了0 .5mol/LH2 SO4 + 0 .1mol/LNaH2 PO2 溶液中原位红外反射谱图与Pt电极电位的关系 ,发现次亚磷酸根离子在Pt上发生解离吸附 ,其氧化产物是H3 PO4 ,不同于在Ni上的氧化产物H2 PO- 3 ,据此提出了酸性溶液中次亚磷酸根离子在Pt上氧化机理的新看法     

In-situ flow-cell IRAS observation of intermediates during methanol oxidation on low-index platinum surfaces.

Structural effects on intermediate species of methanol oxidation are studied on low-index planes of platinum using in-situ infrared (IR) spectroscopy. A flow cell is designed for rapid migration of reactant and product species on the electrode surface. IR spectra show adsorption of formate and the formation of carbonate species on the Pt(111) surface at potentials higher than that of CO oxidation. The band assignments for carbonate and formate are confirmed by vibrational isotope shifts. On Pt(100), the absorption band of adsorbed formate is much smaller than that on Pt(111). On the other hand, there is no adsorbed formate on Pt(110) in the potential region examined. The band intensity of formate follows the order: Pt(111)>Pt(100)>Pt(110). This order is opposite to that of the current density in the regions of higher potential. Adsorbed formate on Pt(111) behaves like a catalyst-poisoning intermediate, like adsorbed CO.