Sn/Pt纳米立方体对乙醇电催化氧化的原位FTIR光谱研究

采用循环伏安电沉积方法制备了Sn修饰的铂纳米立方体,并研究其乙醇的电催化氧化. 结合传统的电化学技术和原位电化学红外光谱技术研究了Sn的作用机理. 循环伏安研究表明,Sn修饰后使其乙醇氧化的起始电位显著负移,Sn覆盖度~ 0.90时乙醇氧化的起始电位为-0.1 V. 原位红外光谱结果表明,修饰Sn后极大地促进了乙酸的生成,更利于乙醇的直接氧化途径,但对乙醇的C—C键断裂促进作用不大.     

酸性溶液中钯催化醇电化学氧化的研究

应用电化学循环伏安法(CV)和现场红外光谱(FTIR),研究了酸性溶液中钯催化甲醇、乙二醇电氧化的过程.结果表明:在酸性和中性介质中,甲醇和乙二醇在多晶Pd电极上氧化须在1.5V以上才能发生.随着溶液pH值的降低,过电位减小且峰电流密度上升.溶液的pH值以及电极表面形成的吸附含氧物种对Pd电催化氧化醇有显著的影响.现场红外光谱电化学测试显示,在高电位和强酸性介质中,乙二醇在Pd电极上的氧化产物主要是CO2和少量的乙二酸.在酸性和中性介质中,无论在低电位或高电位,甲醇和乙二醇在Pd上氧化的主要产物是CO2,没有发现CO的存在,说明该氧化过程CO2是经过非毒化的路径产生的.     

乙醇在粗糙铂电极上解离吸附与氧化的原位SERS研究

采用循环伏安法和原位表面增强拉曼光谱（SERS）研究了乙醇在粗糙铂电极上的吸附和氧化行为,获得了乙醇在粗糙铂电极上解离吸附的表面增强拉曼光谱.研究表明,在酸性介质中,乙醇能在粗糙铂电极上自发地解离出强吸附物种CO,在低波数区检测到桥式和线性吸附CO的铂碳键的伸缩振动信息;乙醇在粗糙铂电极上的氧化反应受扩散步骤控制;从分子水平初步证实乙醇的氧化是通过双途径机理进行的.     

乙醇在碳载Pt纳米薄膜电极上吸附和氧化过程研究——II.酸性介质中EQCM和原位FTIR反射光谱

运用电化学循环伏安 ,石英晶体微天平 (EQCM )和原位FTIR反射光谱等方法研究了酸性介质中乙醇在碳载纳米Pt膜电极上吸附和氧化行为 .结果表明 ,乙醇的电氧化与溶液酸碱性及电极表面氧物种有密切的关系 ,并指出乙醇电催化氧化是通过解离吸附产物和反应中间体双途径机理进行的 .在实验条件下 ,经原位FTIR反射光谱检测 ,解离吸附产物为CO ,反应中间体主要有CH3COOH和CH3CHO等物种 .     

2,4-二氯苯酚的电化学氧化降解反应研究

采用循环伏安法和原位红外光谱技术研究了2,4-二氯苯酚在Pt电极上的电化学氧化降解反应,结合Fukui函数值预测了2,4-二氯苯酚在电化学氧化过程中的反应位点. 结果表明,Pt电极对2,4-二氯苯酚有良好的电催化活性,2,4-二氯苯酚在电极表面反应主要有3个途径：直接通过电化学反应脱去氯离子,生成苯酚;在·OH的进攻下,C—Cl键断裂,4位Cl较2位Cl先脱去,生成苯二酚,并可进一步氧化生成苯醌以及不饱和羧酸;在·OH的进攻下发生苯环开环反应,生成含氯不饱和羧酸. 在1700 mV左右,2,4-二氯苯酚可经电化学氧化生成CO₂.     

乙醇在碳载Pt纳米薄膜电极上吸附氧化过程研究Ⅰ.碱性介质中循环伏安和原位FTIR反射光谱

运用电化学循环伏安法在玻碳载体上制备纳米级厚度的Pt薄膜电极 ,用STM表征电极表面的形貌 ,测定了电沉积层的厚度、表面积和Pt载量 .同时 ,应用电化学循环伏安法和原位FTIR反射光谱研究了乙醇在碱性介质中的吸附和氧化行为 .结果表明 ,乙醇氧化的主要产物是CH3COO- ,仅存在少量乙醛 ,并未观察到任何CO谱峰 .与酸性介质中乙醇氧化的双途径机理不同 ,碱性介质中乙醇氧化未经过解离吸附中间过程     

镀Pd的GC电极上HCOOH的电催化氧化

在玻璃碳 (GC)基底上电沉积Pd ,应用SEM观测Pd沉积层的表面形貌 ,用循环伏安法研究了Pd/GC电极上HCOOH在HClO4溶液中的电氧化行为 .结果表明 ,Pd的电沉积条件影响电极的催化性能 .在高电流密度下制得的Pd/GC电极对HCOOH的电氧化具有比纯Pd电极更高的催化活性 .当电极表面生成PdO时 ,HCOOH被电氧化的活性很低 ,而在PdO还原后生成的Pd表面 ,HCOOH的电氧化显示极高的活性 .本文还讨论了Pd(Ⅱ )离子对HCOOH电氧化过程的影响 .     

乙二醇在铂电极上吸附和氧化过程的现场FTIR反射光谱研究(Ⅰ)──酸性介质

运用循环伏安法和现场FTIR反射光谱研究了酸性介质中乙二醇在铂电极上的吸附和氧化行为,指出乙二醇电催化氧化是通过解离吸附产物和反应中间体双途径机理进行的。经FTIR反射光谱检测,解离吸附产物为CO,反应中间体主要有CH₂OH─COOH和HOOC─COOH等。本文还在分子水平上解释了铂电极上乙二醇吸附和氧化循环伏安特征的内在原因。     

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     

Pt纳米粒子/Pd纳米线复合材料对乙醇的电催化氧化研究

采用恒电位法在多孔阳极氧化铝模板中电沉积Pd纳米线阵列,再运用循环伏安法在Pd纳米线阵列表面沉积Pt纳米粒子制备出复合纳米材料电极。运用循环伏安法和计时电流法研究了该复合纳米材料电极对乙醇的电催化性能的影响。结果表明,Pt纳米粒子/Pd纳米线复合电极相比于单独的Pd纳米线电极或Pt纳米粒子电极,对乙醇氧化有更高的电催化活性和很好的稳定性。     

FTIR study of the ethanol electrooxidation on Pt(100) modified by osmium nanodeposits

In the present work, ethanol electrooxidation on a Pt(100) electrode modified by different coverage degrees of osmium nanoislands obtained by spontaneous depositions, was extensively studied employing in situ FTIR spectroscopy. A collection of spectra of the ethanol adsorption and oxidation processes was acquired during the first series of a positive potential step, to determine the intermediate species, as well as the main products formed. The spectroscopic results obtained were correlated with conventional electrochemical results obtained by cyclic voltammetry. It was shown that the catalytic activity of Pt(100) for ethanol oxidation increases significantly after osmium deposition and that the mechanistic pathway for this reaction depends directly on the osmium coverage degree. Thus, for low osmium coverage (theta;( Os) up to 0.15) the formation of CO as an intermediate was favored and hence the full oxidation of adsorbed ethanol to CO(2) was increased. For higher osmium coverages (theta;(Os) up to 0.33), the higher the coverage is, the more the direct ethanol oxidation to acetaldehyde and acetic acid is favored. For osmium coverage degree of 0.40, the catalytic activity of the electrode for ethanol oxidation decreased. On an almost complete osmium layer (theta;(Os) = 0.92) obtained by electrodeposition at 50 mV vs reversible hydrogen electrode, the catalytic activity for ethanol oxidation shows a much lower value.     

In situ FTIR spectroelectrochemical study on the mechanism of ethylene glycol electrocatalytic oxidation at a Pd electrode

The adsorption and electrooxidation pathways of ethylene glycol (EG) on polycrystalline palladium surfaces have been investigated in both alkaline and acidic media by in situ FTIR spectroscopy in conjunction with cyclic voltammetry. Palladium exhibits a high electrocatalytic activity in alkaline solution with low onset oxidation potentials and high current densities, depending on the pH, as well as on the supporting electrolyte. Higher potentials are required for EG oxidation in acidic solutions, where the catalytic performance decreases with increasing the pH. The products and intermediates of EG oxidation on Pd are influenced by the pH. In alkaline media, both C(2) species (glycolate, glyoxal, glyoxylate and oxalate) and C(1) species (formate and carbonate) are formed in mutual concentrations depending on the pH. In contrast, CO(2) is selectively produced in acidic aqueous solution.     

Graphene-nickel nitride hybrids supporting palladium nanoparticles for enhanced ethanol electrooxidation

Electrocatalysts for ethanol oxidation reaction(EOR)are generally limited by their poor durability because of the catalyst poisoning induced by the reaction intermediate carbon monoxide(CO).Therefore,the rapid oxidation removal of CO intermediates is crucial to the durability of EOR-based catalysts.Herein,in order to effectively avoiding the catalyst CO poisoning and improve the durability,the graphene-nickel nitride hybrids(AG-Ni₃N)were designed for supporting palladium nanoparticles(Pd/AG-Ni₃N)and then used for ethanol electrooxidation.The density functional theory(DFT)calculations demonstrated the introduction of AG-Ni₃N depresses the CO absorption and simultaneously promotes the adsorption of OH species for CO oxidation removal.The fabricated Pd/AG-Ni₃N catalyst distinctively exhibits excellent electroactivity with the mass catalytic activity of 3499.5 m A mg^-1 on EOR in alkaline media,which is around 5.24 times higher than Pd/C(commercial catalyst).Notably,the Pd/AG-Ni₃N hybrids display excellent stability and durability after chronoamperometric measurements with a total operation time of 150,000 s.     

CoPt nanoparticles and their catalytic properties in electrooxidation of CO and CH(3)OH studied by in situ FTIRS

CoPt nanoparticles supported on a glassy carbon electrode (denoted as CoPt/GC) were prepared by galvanic replacement reaction between electrodeposited Co nanoparticles and K(2)PtCl(6) solution. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were both employed to characterize the CoPt nanoparticles. It was shown that the CoPt nanoparticles have irregular shapes and most of them exhibit a core-shell structure with a porous Co core and a shell of Pt tiny particles. The composition of the CoPt nanoparticles was analyzed by energy-dispersive X-ray spectroscopy (EDX), which depicts a Co : Pt ratio of ca. 21 : 79. Studies of cyclic voltammetry (CV) demonstrated that CoPt/GC possesses a much higher catalytic activity towards CO and methanol electrooxidation than a nanoscale Pt thin film electrode. In situ FTIR spectroscopic studies have revealed for the first time, that a CoPt nanoparticles electrode exhibits abnormal IR effects (AIREs) for IR absorption of CO adsorbed on it. In comparison with the IR features of CO adsorbed on a bulk Pt electrode, the direction of the IR bands of CO adsorbed on the CoPt/GC electrode is inverted completely, and the intensity of the IR bands has been enhanced up to 15.4 times. The AIREs is significant in detecting the adsorbed intermediate species involved in electrocatalytic reactions. The results demonstrated a reaction mechanism of CH(3)OH oxidation on CoPt/GC in alkaline solutions through evidencing CO(L), CO(M), HCOO(-), CO(3)(2-), HCO(3)(-) and CO(2) as intermediate and product species by in situ FTIRS.     

丙酮对Pd电极上异丙醇电氧化的毒化作用

采用循环伏安法和计时电流法研究了丙酮浓度和反应温度对Pd电极上异丙醇直接电氧化的影响. 研究发现, 丙酮对Pd电极上异丙醇电氧化存在严重的毒化作用, 并提出了其发生竞争吸附的毒化作用机理.     

Pd/FeOx催化剂动态生成Pdδ+-Fe2+界面高效催化逆水煤气变换反应

通过一系列原位、非原位表征,包括透射电子显微镜(TEM)、傅里叶变换红外光谱(FTIR)、程序升温解吸/还原/氧化(TPD/TPR/TPO)、X射线光电子能谱(XPS)等,系统地研究了Pd/FeOx催化剂的逆水煤气变换反应(RWGS)。以Pd(acac)2为前驱体合成了高度分散的Pd/FeOx催化剂,在400℃下,RWGS的CO2转化率高达29%,CO选择性超过98%,在目前文献中报道的催化剂中处于领先水平。通过原位表征方法,我们进一步研究了Pd/SiO2和Pd-Fe/SiO2,并明确指出了Pd-FeOx界面对促进RWGS反应的重要作用。准原位XPS实验进一步揭示了Pd/FeOx界面上动态形成的Pd^δ+-Fe^2+物种是高效催化C=O离解的活性位点。因此,实验结果证明,反应过程中动态形成的Pd^δ+-Fe^2+界面可以显著提高RWGS的活性和选择性,对CO2吸附、C=O解离和CO脱附都起到的促进作用。     

Adsorption and oxidation of ethanol on colloid-based Pt/C, PtRu/C and Pt3Sn/C catalysts: in situ FTIR spectroscopy and on-line DEMS studies

The interaction of colloid-based, carbon supported Pt/C (40 wt%), PtRu/C (45 wt%) and Pt3Sn/C (24 wt%) catalysts with ethanol and their performance for ethanol electrooxidation were investigated in model studies by electrochemical, in situ infrared spectroscopy and on-line differential electrochemical mass spectrometry measurements. The combined application of in situ spectroscopic techniques on realistic catalysts and under realistic reaction (DEMS, IR) and transport conditions (DEMS) yields new insight on mechanistic details of the reaction on these catalysts under the above reaction and transport conditions. Based on these results, the addition of Sn or Ru, though beneficial for the overall activity for ethanol oxidation, does not enhance the activity for C-C bond breaking. Dissociative adsorption of ethanol to form CO2 is more facile on the Pt/C catalyst than on PtRu/C and Pt3Sn/C catalysts within the potential range of technical interests (<0.6 V), but Pt/C is rapidly blocked by an inhibiting CO adlayer. In all cases acetaldehyde and acetic acid are dominant products, CO2 formation contributes less than 2% to the total current. The higher ethanol oxidation current density on the Pt3Sn/C catalyst at these potentials results from higher yields of C2 products, not from an improved complete ethanol oxidation to CO2.     

The electrocatalytic behavior of electrodeposited Ni–Mo–P alloy films towards ethanol electrooxidation

Ternary Ni–Mo–P thin films have been electrodeposited from citrate‐based electrolyte onto graphite substrates for application as anode catalysts for ethanol electrooxidation. The operating deposition parameters were optimized to produce Ni–Mo–P alloy films of outstanding catalytic activity. The phase structure of the deposits was evaluated employing X‐ray diffraction technique. Morphology and chemical composition of the deposited alloy films were studied using scanning electron microscopy and energy‐dispersive X‐ray analysis, respectively. The results demonstrated that the rate of Ni–Mo–P deposition increases with increasing the ammonium molybdate concentration in the plating electrolyte up to 10 g l^?1. Also, the amount of Mo in the deposits increases with increasing the ammonium molybdate concentration up to 7.5 g l^?1, and the maximum Mo content in the film was 9.1 at.%. The catalytic activity of Ni–Mo–P/C alloy films has been evaluated towards electrooxidation of ethanol in 1.0 M NaOH solution by using cyclic voltammetry and chronoamperometry. The catalytic performance of the prepared anodes as a function of the amount of Mo was studied. The results showed an increase in the oxidation peak current density of ethanol with increasing the Mo at.% in the deposited alloy films. Additionally, Ni–Mo–P/C electrodes displayed significantly improved catalytic activity and stability towards electrooxidation of ethanol compared with that of Ni–P/C electrode. Copyright © 2013 John Wiley & Sons, Ltd.     

Ethanol electrooxidation on Pd/C nanoparticles in alkaline media

Carbon-supported Pd nanoparticles were prepared by microwave heating-glycol reduction method, and characterized by a wide array of experimental techniques including X-ray diffraction spectroscopy(XRD) and transmission electron microscopy(TEM). The electrooxidation behaviors of ethanol on the Pd/C electrode in alkaline media were investigated using cyclic voltammetry(CV), chronoamperometry(CA), electrochemical impedance spectroscopy(EIS) and single cell performance methods. Pd/C electrode for ethanol oxidation showed high electro-catalytic activity and long term stability. However, it is observed that the current density decreases with the increasing of the potential and negative impedance presents in the potential from-0.1 to0.1 V. The decreasing current density and the negative impedance could be due to the adsorbed intermediates species that inhibited the further oxidation of ethanol. Based on the chemical reaction analysis and EIS spectra, equivalent circuits relating to various potential zones have been obtained. These results reveal the dynamic adsorption of intermediates species on Pd surfaces. Significantly, it is clarified that the adsorption behavior begins from the maximum catalysis of electro-catalysis and ends in the formation of the palladium(II) oxide layer on the electrode surface.