Facile electrochemical synthesis of a conducting copolymer from 5-aminoindole and EDOT and its use as Pt catalyst support for formic acid electrooxidation

5-Aminoindole and 3,4-ethylenedioxythiophene (EDOT) were copolymerized electrochemically on a carbon cloth (CC) electrode in an aqueous sulfuric acid solution. The as-prepared copolymer was characterized by cyclic voltammogram, SEM, and UV-vis and FT-IR spectra through which the electrochemical properties, structure, and composition of the as-obtained copolymer were determined. The electrochemical activity and stability of the as-formed copolymer are significantly improved in comparison with poly(5-aminoindole) due to the incorporation of EDOT units into the conjugated chain. The copolymer film-modified CC electrode was used as substrate for Pt particle deposition (denoted as Pt/copolymer/CC), and then, its catalytic activity towards formic acid electrooxidation was studied. Experimental results indicate that the catalytic activity of Pt/copolymer/CC towards formic acid electrooxidation is enhanced in comparison with that of Pt/homopolymer/CC, which can be attributed to the homogeneous distribution of Pt nanoparticles on the copolymer/CC substrate and the improved electrochemical activity of the copolymer film.     

甲酸在Pt-Ru/GC电极上氧化的SERS研究

采用循环伏安(CV)法、计时电流法和电化学原位表面增强拉曼散射光谱(SERS)技术研究了甲酸在Pt-Ru/GC电极上的氧化行为, 发现甲酸在Pt-Ru/GC电极上与在粗糙Pt电极上一样, 也能自发解离出强吸附中间体CO和活性中间体—COO－. 从分子水平证实钌的加入有利于提高电极对甲酸的电催化氧化活性, 当镀液中Pt：Ru的摩尔比从10∶1变化到1∶1, CO的氧化峰电位从0.41 V负移至0.35 V, 约负移了60 mV. Pt-Ru/GC(1∶1)电极与粗糙Pt电极相比, CO在电极表面氧化完毕的电位亦负移了约200 mV. 该研究结果表明, 电化学原位表面增强拉曼散射光谱技术可望成为研究电催化反应机理的普适谱学工具.     

Platinum-macrocycle co-catalyst for electro-oxidation of formic acid

In this work, a new promoter, tetrasulfophthalocyanine (FeTSPc), one kind of environmental friendly material, was found to be very effective in both inhibiting self-poisoning and improving the intrinsic catalysis activity, consequently enhancing the electro-oxidation current during the electro-oxidation of formic acid. The cyclic voltammograms test showed that the formic acid oxidation peak current density has been increased about 10 times compared with that of the Pt electrode without FeTSPc. The electrochemical double potential step chronoamperometry measurements revealed that the apparent activity energy decreases from 20.64 kJ mol⁻¹ to 17.38 kJ mol⁻¹ after Pt electrode promoted by FeTSPc. The promoting effect of FeTSPc may be owed to the specific structure and abundant electrons of FeTSPc resulting in both the steric hindrance of the formation of poisoning species (CO) and intrinsic kinetic enhancement. In the single cell test, the performance of DFAFC increased from 80 mW cm⁻² mg⁻¹ (Pt) to 130 mW cm⁻² mg⁻¹ after the anode electrode adsorbed FeTSPc.     

Electrochemical-reduced graphene oxide-modified carbon fiber as Pt–Au nanoparticle support and its high efficient electrocatalytic activity for formic acid oxidation

A simple electrochemical approach is developed to prepare reduced graphene oxide (RGO)-wrapped carbon fiber (CF) as a novel support for Pt–Au nanocatalysts. The obtained composite electrodes have been characterized by scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDX), thermal gravimetric analysis (TGA), and electrochemical methods. SEM images reveal that the Pt–Au nanoparticles deposited on RGO-wrapped CF (RGO/CF) electrode display smaller particle size and more uniform dispersion than those on the bare CF electrode. Cyclic voltammetry, linear sweep voltammetry, chronoamperometry, chronopotentiometry, Tafel plots, and electrochemical impedance spectroscopy (EIS) analyses demonstrate that the introduced RGO on CF electrode surface is beneficial to the dispersion of Pt–Au nanoparticles, as a consequence, to the enhancement of the electrocatalytic activity and the antipoisoning ability of Pt–Au towards formic acid electrooxidation.     

Adsorbed formate: the key intermediate in the oxidation of formic acid on platinum electrodes

The electrooxidation of formic acid on Pt and other noble metal electrodes proceeds through a dual-path mechanism, composed of a direct path and an indirect path through adsorbed carbon monoxide, a poisoning intermediate. Adsorbed formate had been identified as the reactive intermediate in the direct path. Here we show that actually it is also the intermediate in the indirect path and is, hence, the key reaction intermediate, common to both the direct and indirect paths. Furthermore, it is confirmed that the dehydration of formic acid on Pt electrodes requires adjacent empty sites, and it is demonstrated that the reaction follows an apparently paradoxical electrochemical mechanism, in which an oxidation is immediately followed by a reduction.     

Controlled deposition of Pt on Au nanorods and their catalytic activity towards formic acid oxidation

Platinum submonolayer decorated gold nanorods with controlled coverage were prepared by the addition of Au nanorods into the growth solution of Pt in the presence of NH₂OH · HCl as the growth agent. The properties of Au nanorods decorated by Pt submonolayer were investigated by various techniques including transimission electron microscopy, X-ray diffraction, and electrochemical methods. The Pt decorated Au nanorods on carbon black showed significantly higher activity on formic acid electrooxidation than the conventional Pt/C catalysts. They showed different reaction path of formic acid electrooxidation by suppressing the formation of poisoning intermediate CO.     

A versatile electroless approach to controlled modification of Sb on Pt surfaces towards efficient electrocatalysis of formic acid

A new facile approach towards developing superior Pt-based catalysts for HCOOH electrooxidation has been proposed, which is exemplified with a mimetic underpotential deposition (MUPD) of Sb on Pt surfaces to attain a favorable coverage. Suitable Sb modification was achieved simply through immersing a bulk Pt electrode or dispersing Pt/C powders in a Sb(III) solution mixed with ascorbic acid (AA). AA serves as the mild reducing agent to ensure freshly reduced Pt surfaces for Sb modification, as demonstrated by the negatively shifted open circuit potential. The catalytic activity towards HCOOH electrooxidation on the above Sb-modified Pt/C catalyst far exceeds that on commercial Pt–Ru/C or Sb-modified Pt/C through traditional irreversible adsorption. This electroless approach is generally applicable to all types of Pt surfaces, in particular suited for upgrading Pt/C for practical anode catalysts of direct formic acid 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.     

Electrooxidation of methanol on upd-Ru and upd-Sn modified Pt electrodes

The electrochemical oxidation of methanol has been investigated on underpotentially deposited-ruthenium-modified platinum electrode (upd-Ru/Pt) and on underpotentially deposited-tin-modified platinum electrode (upd-Sn/Pt). The submonolayers of upd-Ru and upd-Sn on a Pt electrode increased the rate of methanol electrooxidation several times as large as that on a pure Pt electrode. The best performance for methanol electrooxidation was obtained on a ternary platinum based catalyst modified by upd-Ru and upd-Sn simultaneously. The influence of the submonolayers of upd-Ru adatoms and upd-Sn adatoms on the oxidation of methanol in acid has been investigated. The effect of Ru on methanol electrooxidation lies on the distribution of Ru adatoms on a Pt surface. It has been shown that as long as the amount of upd-Ru deposits were controlled in a proper range, upd-Ru deposits would enhance the methanol oxidation obtained on a Pt electrode at whichever deposition potential the upd-Ru deposits were obtained. The effects of tin are sensible to the potential range. The enhancement effect of upd-Sn adatoms for the oxidation of methanol will disappear as the electrode potential is beyond a certain value. It is speculated that there exists a synergetic effect on the Pt electrode as adatoms Ru and Sn participate simultaneously in the methanol oxidation.     

A combination of SERS and electrochemistry in Pt nanoparticle electrocatalysis: Promotion of formic acid oxidation by ethylidyne

In this paper, formic acid electrooxidation on ethylidyne modified Pt nanoparticles is reported. The formation as well as the stability electrochemical range of the ethylidyne adlayers was studied by surface enhanced Raman spectroscopy (SERS) and cyclic voltammetry. The presence of adsorbed ethylidyne on platinum nanoparticles improved their electrocatalytic activity towards formic acid oxidation, which could be attributed to an instabilization of the carbon monoxide poisonous species as evidenced by SERS. The use of in situ spectroscopic measurements with electrocatalysts similar to those applied in practice is highlighted.     

Oscillatory behavior in the electrochemical oxidation of formic acid on Pt(100): rotation and temperature effects

We investigated the oscillatory behavior in the kinetics of formic acid electrooxidation on Pt(100) in 1 mM HClO₄ solution. We studied the effect of different experimental parameters on the oscillatory behavior, viz. defined HCOOH mass-transport to the electrode surface by using the rotating disk electrode technique, the temperature of the supporting electrolyte, and the nature of anions. We suggest that the interdependence of the reaction steps during HCOOH oxidation, the adsorption of anions and the competition for adsorption sites among the reaction partners and intermediates lead to complex non-linear kinetics. It was evident that once the individual reactions in the dual path mechanism reach steady state the oscillations vanish. These conditions can be reached either by enhanced formic acid reaction rates induced by electrode rotation or by increased temperature. Under specific conditions of anion and formic acid concentration, relaxational oscillations can be transformed into mixed-mode oscillations.     

Electrocatalytic oxidation of methanol on Pt/NiZn electrode in alkaline medium

In this study, a platinum electrode was coated with NiZn layer (Pt/NiZn) in a nickel-zinc bath by electrodeposition for use as anode material for methanol electrooxidation in alkaline solution. The electrode prepared was etched in a concentrated alkaline solution (30% NaOH) to produce a porous and electrocatalytic surface suitable for use in the methanol electrooxidation (Pt/NiZn). The surface morphologies and compositions of coating before and after alkaline leaching were determined by energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) techniques. The effect of NiZn coated platinum electrode for methanol electrooxidation was investigated in 1 M NaOH solution by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Methanol electrooxidation on Pt/NiZn electrode was studied at various temperatures and potential scan rates. The results showed that Pt/NiZn electrode behaved as an efficient catalyst for the electrooxidation of methanol in alkaline medium.     

PS-b-PEO模板法制备Pt纳米线

以PS-b-PEO纳米孔膜为基体电极,采用电沉积技术制备了Pt纳米线,用扫描电化学显微镜(SECM)、扫描电镜(SEM)和X-射线能谱(EDS)分析法表征了基体电极和Pt纳米线。利用循环伏安法考察了Pt纳米线的电化学性能。实验结果表明,Pt纳米线对甲酸氧化表现出优异的电催化活性。此外,Pt纳米线具有良好的稳定性和重现性,可望用于实际样品中甲酸的测定。     

Kinetic isotope effects in complex reaction networks: formic acid electro-oxidation.

The determination of kinetic isotope effects (KIEs) for different reaction pathways and steps in a complex reaction network, where KIEs may affect the overall reaction in various different ways including dominant and minority pathways or the buildup of a reaction-inhibiting adlayer, is demonstrated for formic acid electrooxidation on a Pt film electrode by quantitative electrochemical in situ IR spectroscopic measurements under controlled mass-transport conditions. The ability to separate effects resulting from different contributions--which is not possible using purely electrochemical kinetic measurements--allows conclusions on the nature of the rate-limiting steps and their transition state in the individual reaction pathways. The potential-independent values of approximately 1.9 for the KIE of formic acid dehydration (CO(ad) formation) in the indirect pathway and approximately 3 for the CO(ad) coverage-normalized KIE of formic acid oxidation to CO2 (direct pathway) indicate that 1) C-H bond breaking is rate-limiting in both reaction steps, 2) the transition states for these reactions are different, and 3) the configurations of the transition states involve rather strong bonds to the transferred D/H species, either in the initial or in the final state, for the direct pathway and--even more pronounced--for formic acid dehydration (CO(ad) formation).     

Structure dependent electrooxidation of small organic molecules on Pt-decorated nanoporous gold membrane catalysts

We describe the electrocatalytic properties of self-supported Pt-decorated nanoporous gold (Pt-NPG) membranes towards the electrooxidation of formic acid and some other small organic molecules. By effectively enhancing the Pt utilization and providing a unique surface structure, the electrooxidation of formic acid on Pt-NPG was found to be highly sensitive to its surface structure. An unparalleled increase by nearly two orders of magnitude in catalytic activity was achieved on NPG electrodes decorated with sub-monolayer Pt atoms, as compared to the commercial Pt/C catalyst under the same testing conditions.     

金属间化合物PtBi对甲酸的电催化氧化

从 1839 年 Grove 首次提出了燃料电池理论, 并 证实了氢/氧燃料电池能直接把化学能转化为电能 以来, 氢/氧燃料电池迅速发展起来。但是由于氢气 在储存、运输以及供应方面存在很多难以克服的困 难, 而有机分子的重整制氢成本太高以及电池构造 复杂等因素[1,2], 使得人们将目光     

Structural design and facile synthesis of a highly efficient catalyst for formic acid electrooxidation

The pathway of formic acid electrooxidation strongly depends on the amount of three neighbouring Pt or Pd atoms in the surface of Pd- or Pt-based catalysts. Here, Pt decorated Pd/C nanoparticles (the optimal atomic ratio, Pd?:?Pt = 20?:?1) were designed and then synthesized through a facile galvanic replacement reaction where the amount of three neighbouring Pt or Pd atoms markedly decreased. As a result, discontinuous Pd and Pt atoms suppressed CO formation and exhibited unprecedented catalytic activity and stability toward formic acid electrooxidation while the cost was almost the same as that of Pd/C.     

磷钼酸修饰铂电极的电化学行为及对甲醇氧化的电催化作用

通过循环伏安扫描法制备了PMo₁₂修饰Pt/Pt电极,并研究了该修饰电极在硫酸溶液中的电化学行为。研究结果表明:虽然磷钼酸具有较大的分子尺寸,但在Pt/Pt电极上仍能发生吸附作用,并且由于PMo₁₂在电极上的吸附,降低了Pt/Pt电极上氢区和氧区的荷电量,另外在0.02V左右还观察到磷钼酸的氧化-还原峰。通过稳态极化曲线和循环伏安曲线研究了PMo₁₂修饰Pt/Pt电极对甲醇氧化的电催化作用。测试结果表明:PMo₁₂修饰铂基电极不但对甲醇的电氧化具有较高的活性,而且还有一定的抗CO中毒性。该修饰电极还具有较高的稳定性。     

One-step electrochemical synthesis of Pt–CeO2 composite thin films on a glassy carbon electrode

A Pt–CeO₂ composite thin film was prepared on a glassy carbon electrode by one-step electrochemical deposition technique. The film was constructed of Pt particles well dispersed and embedded in a porous CeO₂ substrate. The prepared Pt–CeO₂/GC electrode showed a better catalytic performance toward methanol electrooxidation compared with the bulk Pt electrode.     

Methanol electrooxidation in alkaline solutions on platinum-based electrodes: Classical and dynamical approach

The electrochemical oxidation of methanol has been carefully studied due to its application in fuel cells. In this work electrooxidation of methanol was investigated on bare platinum electrode, the platinum electrode covered with Nafion and platinum supported on zeolite 13X. Along with classical electrochemical methods, attractor reconstruction was used to make rough distinction among possible reaction mechanisms on different forms of Pt. The obtained transient voltammogram records were used to calculate apparent rate constants for methanol oxidation limiting steps in transient period. All samples contributed to methanol oxidation by basically same reaction mechanism, but with significantly different apparent rate constants.