Pd/C promoted by Au for 2-propanol electrooxidation in alkaline media

Pd/C catalysts promoted by Au are investigated as electrocatalysts for the direct 2-propanol fuel cells in alkaline media. The results show that Pd is a good electrocatalyst for 2-propanol oxidation and the activity for 2-propanol electrooxidation is higher than that for methanol electrooxidation on the Pd/C electrocatalysts in alkaline media. Addition of Au can significantly increase the palladium catalytic activity and stability for the 2-propanol oxidation. PdAu4:1/C has higher electrocatalytic activity and better stability for the electrooxidation of 2-propanol than Pd/C and E-TEK Pt/C electrocatalysts. The present study shows the promising properties of Au promoted Pd/C as effective electrocatalysts for 2-propanol fuel based direct alcohol fuel cells.     

Methanol and ethanol electrooxidation on Pt and Pd supported on carbon microspheres in alkaline media

Noble metal (Pt, Pd) electrocatalysts supported on carbon microspheres (CMS) are used for methanol and ethanol oxidation in alkaline media. The results show that noble metal electrocatalysts supported on carbon microspheres give better performance than that supported on carbon black. It is well known that palladium is not a good electrocatalyst for methanol oxidation, but it shows excellently higher activity and better steady-state electrolysis than Pt for ethanol electrooxidation in alkaline media. The results show a synergistic effect by the interaction between Pd and carbon microspheres. The Pd supported on carbon microspheres in this paper possesses excellent electrocatalytic properties and may be of great potential in direct ethanol fuel cells.     

Pd/Pt core–shell nanowire arrays as highly effective electrocatalysts for methanol electrooxidation in direct methanol fuel cells

Highly ordered Pd/Pt–core–shell nanowire arrays (Pd/Pt NWAs) have been prepared by anodized aluminum oxide (AAO) template-electrodeposition and magnetron sputtering methods. Pd/Pt NWA electrode shows a very high electrochemical active surface area and high electrocatalytic activity for the methanol electrooxidation in acid medium for direct methanol fuel cells (DMFCs). The mass specific anodic peak current density is 756.7 mA mg⁻¹ Pt for the methanol oxidation on the Pd/Pt NWA electrode, an increase by a factor of four as compared to conventional E-TEK PtRu/C electrocatalysts. The mechanism of the significant enhancement of the Pd/Pt core/shell NWA nanostructure in the efficiency and electrocatalytic activity of Pt for the methanol electrooxidation in acid medium is discussed.     

Electrocatalytic oxidation of methanol on Ni modified polyaniline electrode in alkaline medium

Electrolytically deposited Ni on polyaniline film covered carbon paste electrode (Ni/PANI/CPE) was used as anode for the electrooxidation of methanol in alkaline medium. The electrochemical behavior and electrocatalytic activity of the electrode were studied using cyclic voltammetry, impedance spectroscopy, chronomethods, and polarization studies. The morphology and composition of the modified film were obtained using scanning electron microscope and energy dispersive X-ray analysis techniques. The electrooxidation of methanol in NaOH was found to be more efficient on Ni/PANI/CPE than on bare Ni, electrodeposited Ni on Pt, Ni on glassy carbon, and Ni on CPE substrates. Partial chemical displacement of dispersed Ni on PANI with Pt or Pd further improved its performance towards methanol oxidation.     

乙醇在碳修饰的二氧化钛纳米管负载的钯电催化剂上的催化氧化

 通过有机物分解碳化处理TiO2 纳米管制得了TiO2C, 并以其为载体制备了Pd/TiO2C电催化剂,考察了该催化剂对碱性介质中乙醇电催化氧化的活性. 结果表明,碳化导电处理的TiO2C纳米管载体能有效改善催化剂中贵金属的分散度和电极结构,从而提高催化剂的电催化活性. 对催化剂活性组分的优化实验表明, Pd/TiO2C质量比为1/1时催化剂的活性最高. 在1 mol/L KOH溶液中Pd载量均为0.3 mg/cm2的条件下, Pd/TiO2C催化剂对乙醇氧化的催化活性是Pd/C催化剂的3.8倍.     

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.     

Synthesis and electrocatalytic activity of Au/Pt bimetallic nanodendrites for ethanol oxidation in alkaline medium

Gold/Platinum (Au/Pt) bimetallic nanodendrites were successfully synthesized through seeded growth method using preformed Au nanodendrites as seeds and ascorbic acid as reductant. Cyclic voltammograms (CVs) of a series of Au/Pt nanodendrites modified electrodes in 1M KOH solution containing 1M ethanol showed that the electrocatalyst with a molar ratio (Au:Pt) of 3 exhibited the highest peak current density and the lowest onset potential. The peak current density of ethanol electro-oxidation on the Au(3)Pt(1) nanodendrites modified glassy carbon electrode (Au(3)Pt(1) electrode) is about 16, 12.5, and 4.5 times higher than those on the polycrystalline Pt electrode, polycrystalline Au electrode, and Au nanodendrites modified glassy carbon electrode (Au dendrites electrode), respectively. The oxidation peak potential of ethanol electro-oxidation on the Au(3)Pt(1) electrode is about 299 and 276 mV lower than those on the polycrystalline Au electrode and Au dendrites electrode, respectively. These results demonstrated that the Au/Pt bimetallic nanodendrites may find potential application in alkaline direct ethanol fuel cells (ADEFCs).     

Kinetics of ethylene glycol electrooxidation on the noble metal-based nano-catalysts

A comparative electrooxidation of Eg in the alkaline solution was investigated over Pt, Pd and Au nanoparticle-modified carbon-ceramic electrode. The kinetic parameters of Eg oxidation, i.e., Tafel slope and activation energy (E _a), were determined on the modified electrodes. The lowest E _a value of 8.9 kJ mol^?1 was calculated on Pt|CCE. In continuation, the reaction orders with respect to the Eg and NaOH concentrations on Pd|CCE were found to be 0.4–0.2 and 0.6, respectively. An adsorption equilibrium constant (b) of 22.36 M^?1 and the adsorption Gibbs energy change (ΔG°) of ?7.7 kJ mol^?1 were obtained on Pd|CCE. The chronopotentiometry (CP) and chronoamperometry (CA) results showed that Pd|CCE and then Au|CCE have better performance stability than Pt|CCE for Eg electrooxidation. Additionally, the electrochemical impedance spectroscopy (EIS) suggested faster electron-transfer kinetics on Pt than that on the Pd and Au electrocatalysts.     

Electrodeposited fabrication of highly ordered Pd nanowire arrays for alcohol electrooxidation

Highly ordered Pd nanowire arrays (NWAs) are prepared using a porous aluminum oxide template by pulse electrodeposition. The obtained Pd nanowire arrays with the diameter of 50 nm and length of 850 nm have been characterized by scanning electron microscopy, energy dispersive X-ray analysis, and high resolution transmission electron microscope. Meanwhile, the electrocatalytic activity of Pd NWAs electrodes for methanol and isopropanol oxidation in alkaline media is studied. It is found that the obtained nanostructures exhibit excellent catalytic activity for alcohol electrooxidation. The isopropanol oxidation shows the higher activity on Pd NWAs electrode than methanol in alkaline medium.     

Electrooxidation of carbon monoxide and methanol on platinum-overlayer-coated gold nanoparticles: effects of film thickness

The electrooxidation of carbon monoxide and methanol on Pt-coated Au nanoparticles attached to 3-aminopropyl trimethoxysilane-modified indium tin oxide electrodes was examined as a function of Pt film thickness and Au particle coverage. For the electrodes with medium and high Au particle coverages, the CO stripping peak position shifts to more negative values with increasing Pt film thickness, from ca. 0.8 V (vs Ag/AgCl) at 1 ML to 0.45 V at 10 ML. Accompanying this peak potential shift is the sharpening of the peak width from more than 150 to 65 mV. For the electrode with low Au particle coverage, similar peak width narrowing was also observed, but the peak potential shift is much smaller, from 0.85 V at 1 ML of Pt to 0.65 V at 10 ML. These observations are compared with the CO oxidation on bulk Pt electrodes and on Pt films deposited on bulk Au electrodes. The film-thickness-dependent CO oxidation is explained by d band theory in terms of strain and ligand effects, the particle size effect, and the particle aggregation induced by Pt film growth. Corresponding to the increasing CO oxidation activity, the current density of methanol oxidation grows with the Pt film thickness. The peak potential and current density reach the same values as those obtained on a polycrystalline bulk Pt electrode when more than 4 ML of Pt is deposited on the Au particle electrodes with a particle coverage higher than 0.25. These results suggest that it is feasible to reduce Pt loading in methanol fuel cells by using Pt thin films as the anode catalyst.     

Physical and electrochemical characterizations of nanostructured Pd/C and PdNi/C catalysts for methanol oxidation

Pd and PdNi nanoparticles supported on Vulcan XC-72 carbon were prepared by a chemical reduction with formic acid process. The catalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry, and chronoamperometry. The results showed that the Pd and PdNi nanoparticles, which were uniformly dispersed on carbon, were 2–10 nm in diameters. The PdNi/C catalyst has higher electrocatalytic activity for methanol oxidation in alkaline media than a comparative Pd/C catalyst and shows great potential as less expensive electrocatalyst for methanol electrooxidation in alkaline media in direct methanol fuel cells.     

碱性直接醇燃料电池非铂阳极催化剂

以纳米Pd,Pd-Ru,Au和Au-Ru为碱性直接醇燃料电池非Pt阳极催化剂,考察了其对甲醇、乙醇和乙二醇的电氧化性能.结果表明,Pd在酸中对醇电氧化的催化活性很低,但在碱中表现出较高的催化活性,起波电势约为0.4V(vsRHE);引入Ru助催化剂后,起波电势负移约0.15V;Pd-Ru对乙醇的电氧化表现出很高的活性,在0.3～0.4V电势范围内其活性为Pt-Ru的4倍.Au在酸中几乎不催化醇类分子的电氧化,但在碱中表现出一定的催化活性,在高于0.6V(vsRHE)的电势范围内可观察到醇氧化阳极电流.Au-Ru的催化活性高于Au,但起波电势没有明显负移,这可能表明当电势不足够正时醇分子在Au表面的吸附脱氢步骤是速率控制步骤.     

Catalytic influence of underpotential-deposited submonolayers of heavy metals on d-glucose oxidation on various noble metal electrodes in alkaline media

The catalytic influence of underpotential-deposited (upd) submonolayers of heavy metals (i.e. Pb, Tl, Bi) on the electrooxidation of D-glucose on various noble metal electrodes (i.e. Pd, Rh, Ir) is studied in alkaline media, and the results are compared with those observed for these systems when Pt was used as the electrode. In the case of Rh and Ir electrodes the catalytic activity is expressed mainly through the considerable increase of the respective current peaks as well as through the negative shift of the oxidation peak in the double-layer region, while in the case of the Pd electrode no significant catalytic action of upd ad-layers on the oxidation of D-glucose is observed. An explanation of the enhancement of the catalytic action of these electrodes (except Pd) is given on the basis that the upd ad-atoms decrease the electrode poisoning, due to an intermediate gluconolactone-type adsorbate, according to the third body mechanism in electrocatalysis. Finally, from a volcano-type diagram it is found that for the catalysis of D-glucose oxidation by upd Pb, Tl and Bi ad-atoms the catalytic activity of the electrode metal used decreases according to the order: Pt > Pd > Rh > Ir.     

电沉积制备钯铂电极上乙醇的电催化氧化

研究了乙醇在碱性介质（１．０ｍｏｌ·Ｌ－１ＮａＯＨ）中电沉积制备的Ｐｄ／ＧＣ、Ｐｔ／ＧＣ和Ｐｄ．Ｐｔ／ＧＣ电极上的电催化氧化．实验结果表明：由此法制备的钯铂系列合金电极对乙醇的电催化氧化表现出明显的协同效应─—乙醇在含把原子分数ｙｐｂ＝０．３３６的Ｐｄ－Ｐｔ／ＧＣ合金电极上的阳极交换电流密度是其在纯铂电极上的３０多倍．     

电沉积制备钯铂电极上乙醇的电催化氧化

研究了乙醇在碱性介质（１．０ｍｏｌ．Ｌ＾－１ＮａＯＨ）中电沉积制备的Ｐｂ／ＧＣ、Ｐｔ／ＧＣ和Ｐｄ－ｐｔ／ＧＣ电极上的电催化氧化,实验结果表明：由此法制备的钯铂系列合金电极对乙醇的电催化氧化表现出明显的协同效应－乙醇的含钯原子分数ｙｐｄ＝０．３３６的ｐｄ－ｐｔ／ＧＣ合金电极上的节极交换电流密度是其在纯铂电极上的３０多倍。     

分级结构AgAu纳米合金用于高效电催化乙醇氧化

乙醇由于具有无毒、理论能量密度高、易存储等优点,被广泛用于直接醇类燃料电池研究.乙醇电氧化是直接醇类燃料电池中重要的阳极反应,通常涉及C1和C2反应路径.C1路径中乙醇分子主要转化成二氧化碳,但该过程涉及C-C键断裂,会有COad和CH(x)ad等中间体产生;C2路径中乙醇分子转化成乙醛,最终转化成乙酸或乙酸根.为提升...     

乙醇在不同介质中电氧化的原位表面增强拉曼光谱研究

采用常规电化学伏安技术和电化学原位表面增强拉曼光谱(in-situ SERS)技术研究了不同介质中乙醇在粗糙铂电极上的电催化氧化行为. 发现不论在酸性、中性还是碱性介质中, 乙醇均能在粗糙铂电极上自发氧化解离生成强吸附中间体CO; 碱性介质中, CO在粗糙铂电极上基本氧化完全的电位(0.20 V)比中性和酸性介质中(0.50 V)负移了约0.30 V. 而乙醇在粗糙铂电极上CV正向扫描的氧化峰电位(-0.20 V)比酸性介质中(0.65 V)负移了约0.85 V. 比较不同介质中乙醇和CO在粗糙铂电极上的氧化峰电流和峰电位可以发现, 粗糙铂电极在碱性介质中对乙醇和CO的电催化氧化活性比中性和酸性介质中更强; 可以推测, 不论在酸性、中性还是碱性介质中, 乙醇在粗糙铂电极上的氧化过程均按双途径机理进行.     

Au Nanoparticles Modified with Pt,Ru and SnO2 as Electrocatalysts for Ethanol Oxidation Reaction in Acids

The anodic reaction in direct ethanol fuel cells (DEFCs), ethanol oxidation reaction (EOR) faces challenges, such as incomplete electrooxidation of ethanol and high cost of the most efficient electrocatalyst, Pt in acidic media at low temperature. In this study, core‐shell electrocatalysts with an Au core and Pt‐based shell (Au@Pt) are developed. The Au core size and Pt shell thickness play an important role in the EOR activity. The Au size of 2.8 nm and one layer of Pt provide the most optimized performance, having 6 times higher peak current density in contrast to commercial Pt/C. SnO₂ as a support also enhances the EOR activity of Au@Pt by 1.73 times. Further modifying the Pt shell with Ru atoms achieve the highest EOR current density that is 15 and 2.5 times of Pt/C and Au@Pt. Our results suggest the importance of surface modification in rational design of advanced electrocatalysts.     

Palladium monolayer and palladium alloy electrocatalysts for oxygen reduction

We investigated the oxygen-reduction reaction (ORR) on Pd monolayers on various surfaces and on Pd alloys to obtain a substitute for Pt and to elucidate the origin of their activity. The activity of Pd monolayers supported on Ru(0001), Rh(111), Ir(111), Pt(111), and Au(111) increased in the following order: Pd/Ru(0001) < Pd/Ir(111) < Pd/Rh(111) < Pd/Au(111) < Pd/Pt(111). Their activity was correlated with their d-band centers, which were calculated using density functional theory (DFT). We found a volcano-type dependence of activity on the energy of the d-band center of Pd monolayers, with Pd/Pt(111) at the top of the curve. The activity of the non-Pt Pd2Co/C alloy electrocatalyst nanoparticles that we synthesized was comparable to that of commercial Pt-containing catalysts. The kinetics of the ORR on this electrocatalyst predominantly involves a four-electron step reduction with the first electron transfer being the rate-determining step. The downshift of the d-band center of the Pd "skin", which constitutes the alloy surface due to the strong surface segregation of Pd at elevated temperatures, determined its high ORR activity. Additionally, it showed very high methanol tolerance, retaining very high catalytic activity for the ORR at high concentrations of methanol. Provided its stability is satisfactory, this catalyst might possibly replace Pt in fuel-cell cathodes, especially those of direct methanol oxidation fuel cells (DMFCs).     

Performance study of palladium modified platinum anode in direct ethanol fuel cells: A green power source

The direct ethanol fuel cell is a green and renewable power source alternative to fossil fuels and produces less emissions compared to a combustion engine. Ethanol can be generated in great quantity from renewable resources like biomass through a fermentation process. Bio-generated ethanol is thus attractive fuel since growing crops for biofuels absorbs much of the carbon dioxide emitted into the atmosphere from the oxidation of ethanol. The platinum and palladium were co-deposited on graphite substrate by the galvanostatic technique and employed as anode catalyst for ethanol electrooxidation. The information on surface morphology, structural characteristics and bulk composition of the catalyst was obtained using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) spectroscopy. The cyclic voltammetry (CV) were used for the estimation of the electrochemically active surface area (ECSA) of the synthesized catalysts in alkaline medium. The CVs for ethanol oxidation revealed superior catalytic activity of Pt–Pd/C compared to Pd/C and Pt/C. The effect of OH^? on ethanol oxidation at Pt–Pd/C catalyst was studied using cyclic voltammetry, quasisteady-state polarization, chronoamperometry, and electrochemical impedance spectroscopy (EIS). The Pt–Pd/C catalyst shows good stability and enhanced electrocatalytic activity is ascribed to the synergistic effect of higher electrochemical surface area, preferred OH^? adsorption on the surface and palladium ad-atom contribution on the alloyed surface.