Composite of Pt–Ru supported SnO2 nanowires grown on carbon paper for electrocatalytic oxidation of methanol

Platinum–ruthenium (Pt–Ru) nanoparticles were successfully deposited, for the first time, on the surface of SnO₂ nanowires grown directly on carbon paper (Pt–Ru/SnO₂ NWs/carbon paper) by potentiostatic electrodeposition method. The resultant Pt–Ru/SnO₂ NWs/carbon paper composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrocatalytic activities of these composite electrodes for methanol oxidation were investigated and higher mass and specific activities in methanol oxidation were exhibited as compared to Pt–Ru catalysts deposited on glassy carbon electrode.     

Highly dispersed Pt catalysts on single-walled carbon nanotubes and their role in methanol oxidation

Well-dispersed Pt catalysts with very high utilization efficiencies for fuel cell reactions have been prepared by ethylene glycol reduction on polymer-wrapped single-walled carbon nanotubes (SWCNTs). By wrapping the SWCNTs in a polymer such as polystyrene sulfonate, we are able to break up the nanotube bundles to achieve better dispersion. These polymer-wrapped SWCNTs with platinum nanoparticles deposited on them show very high electrochemically active surface areas. The increase in utilization efficiencies for platinum catalysts on these SWCNT supports can be attributed to the increased surface areas and the well-dispersed nature of the carbon support and catalyst. The catalyst dispersion facilitates diffusion of reactant species which in turn results in higher methanol oxidation currents and more positive potentials for oxygen reduction.     

Pt/Au/Fe3O4的制备及其电化学性能

以制得的纳米Fe₃O₄颗粒作为载体,用还原法将还原出的Au与Pt分别负载到Fe₃O₄颗粒表面,制得纳米Pt/Au/Fe₃O₄复合材料。对Pt/Au/Fe₃O₄进行紫外可见光吸收光谱、透射电子显微镜、X射线衍射及光电子能谱等物理表征,结果表明,Au与Pt均匀地沉积到了Fe₃O₄纳米颗粒表面。对纳米Pt/Au/Fe₃O₄复合材料进行循环伏安扫描,当H₂PtCl₆的加入量达到8 mL时,Pt/Au/Fe₃O₄催化性能最佳;正扫电流峰i_p与扫描速率的平方根v^1/2线性相关,Pt/Au/Fe₃O₄催化氧化甲醇的过程受扩散控制;对催化剂进行201次循环伏安扫描,催化剂仍然能保持较好的催化性能且稳定性良好。因此,所合成催化剂Pt/Au/Fe₃O₄是一种具有良好化学稳定性的阳极催化剂材料。     

Titanium vanadium nitride supported Pt nanoparticles as high-performance catalysts for methanol oxidation reaction

Journal of Solid State Electrochemistry - In the present study, Pt nanoparticles (20 wt%) were successfully anchored on vanadium (V)-doped titanium nitride hybrid support, which...     

Platinum-modified polyaniline/polysulfone composite film electrodes and their electrocatalytic activity for methanol oxidation

The polyaniline/polysulfone (PAN/PSF) composite films were prepared by electropolymerization, and then platinum was deposited into this composite film to obtain the platinum-modified polyaniline/polysulfone(Pt/PAN/PSF) composite film electrodes. Their component, morphology and structure were characterized by FTIR spectra, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the composite film has a bi-layer structure with asymmetrical pores, and the platinum particles are homogeneously dispersed in the modified film electrodes. The cyclic voltammetry and electrochemical impedance spectroscopy techniques were applied to investigate the electrochemical properties and the electrocatalytic activity of the modified film electrodes, which show a promotive action for methanol oxidation and the methanol oxidation under a diffusion-controlled process.     

Effect of the microstructure of Pt/CeO2-TiO2 catalysts on their catalytic properties in CO oxidation

The microstructure of 2% Pt/CeO₂-TiO₂ catalysts has an effect on their catalytic properties in CO oxidation. The nanostructured catalysts as platinum clusters 0.3–0.5 nm in size are the most active. These clusters are stabilized at crystal boundaries formed by irregularly intergrown anatase particles. The catalyst containing platinum particles 2–5 nm in size is less active because of the decrease in the extent of dispersion of platinum and the change of its electron state.     

Synthesis of polymeric ionic liquid microsphere/Pt nanoparticle hybrids for electrocatalytic oxidation of methanol and catalytic oxidation of benzyl alcohol

Herein, we present a facile approach for the synthesis of polymeric ionic liquids (PILs) microspheres for metal scavenging and catalysis. Crosslinked poly(1‐butyl‐3‐vinylimidazolium bromide) microspheres with the diameter of about 200 nm were synthesized via miniemulsion polymerization, in which 1,4‐di(vinylimidazolium) butane bisbromide was added as the crosslinker. Anion exchange of PIL microspheres with Pt precursor and followed by the reduction of Pt ions produced PIL microsphere supported Pt nanoparticle hybrids. The synthesized Pt nanoparticles with a diameter of about 2 nm are uniformly dispersed and strongly bound to the surface of PIL microspheres. The catalytic performances of PIL/Pt nanoparticle hybrids were evaluated for both the electrocatalytic oxidation of methanol and oxidation of benzyl alcohol. The PIL/Pt nanoparticle hybrids show better electrocatalytic activity towards the electrooxidation of methanol than pure Pt nanoparticles. Furthermore, they are effective and easily reusable catalysts for the selective oxidation of benzyl alcohol in aqueous reaction media, demonstrating that the synthesized PIL microspheres are suitable scaffolds for heterogeneous catalysts Pt. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

电化学石英晶体微天平研究碱性介质中单层级铂原子修饰的金电极上甲醇的电催化氧化

通过在Au电极表面欠电位沉积(UPD)Cu、再与Pt源(H2PtCl6或K2PtCl4)进行置换反应,制得单层级Pt原子修饰的金电极(对H2PtCl6或K2PtCl4,所制电极分别记为Pt(CuUPD-Pt4+)n/Au或Pt(CuUPD-Pt2+)n/Au,n表示欠电位沉积-置换过程的重复次数).用电化学石英晶体微天平(EQCM)技术定量研究了所制电极,评估了其在碱性环境中催化甲醇氧化的质量比活性(SECA).结果表明,以H2PtCl6为Pt源所制电极(Pt(CuUPD-Pt4+)3/Au)的活性更高,最大SECA高达35.7mAμg-1.根据EQCM结果计算了置换效率,籍此讨论了Pt原子在Au电极表面的层层组装结构,发现所制电极表面的裸Au位点分布百分数与实验结果(由AuOx还原峰电量测算)吻合.我们认为,EQCM技术是一种定量研究电极支撑的超薄催化剂的有效手段,这种高效的单层级贵金属催化剂有望在生物、能源、环境相关的电催化研究中进一步应用.     

Electrochemical quartz crystal microbalance study on Au-supported Pt adlayers for electrocatalytic oxidation of methanol in alkaline solution

Underpotential deposition (UPD) of Cu on an Au electrode followed by redox replacement reaction (RRR) of Cu_UPD with a Pt source (H₂PtCl₆ or K₂PtCl₄) yielded Au-supported Pt adlayers (for short, Pt(CuUPD-Pt⁴⁺)n/Au for H₂PtCl₆, or Pt(CuUPD-Pt²⁺)n/Au for K₂PtCl₄, where n denotes the number of UPD-redox replacement cycles). The electrochemical quartz crystal microbalance (EQCM) technique was used for the first time to quantitatively study the fabricated electrodes and estimate their mass-normalized specific electrocatalytic activity (SECA) for methanol oxidation in alkaline solution. In comparison with Pt(CuUPD-Pt²⁺)n/Au, Pt(CuUPD-Pt⁴⁺)n/Au exhibited a higher electrocatalytic activity, and the maximum SECA was obtained to be as high as 35.7 mA μg^?1 at Pt(CuUPD-Pt⁴⁺)3/Au. The layer-by-layer architecture of Pt atoms on Au is briefly discussed based on the EQCM-revealed redox replacement efficiency, and the calculated distribution percentages of bare Au sites agree with the experimental results deduced from the charge under the AuO _x -reduction peaks. The EQCM is highly recommended as an efficient technique to quantitatively examine various electrode-supported catalyst adlayers, and the highly efficient catalyst adlayers of noble metals are promising in electrocatalysis relevant to biological, energy and environmental sciences and technologies.     

Low Pt content Pt–Ru–Ir–Sn quaternary catalysts for anodic methanol oxidation in DMFC

In this communication we report our research work on low Pt content Pt–Ru–Ir–Sn quaternary catalysts for use in DMFC anodes. The carbon-supported quaternary metal alloy catalyst was synthesized according to the solution reduction method and was deposited onto a carbon fiber paper or a carbon aerogel nanofoam to form the anode for direct methanol fuel cells. The Pt loading of the electrode is 0.1 mg/cm². The testing results from a three-electrode electrochemical cell show that the simultaneous use of higher Ir (25–35 wt.%) and Sn (10 wt.%) content gives satisfactory stability and higher activity for methanol oxidation than the commercially available E-TEK anode (80%[0.5Pt 0.5Ru]/C on carbon cloth). Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), scanning electron microscope (SEM), and Bruner–Emmett–Teller method (BET) measurements were carried out to characterize the composition, structure, morphology, and surface area of the developed catalysts.     

Preparation and characterization of nano-sized Pt-Ru/C catalysts and their superior catalytic activities for methanol and ethanol oxidation

Carbon-supported PtRu nanoparticles (Ru/Pt: 0.25) were prepared by three different methods; simultaneous reduction of PtCl(4) and RuCl(3) (catalyst I) and changing the reduction order of PtCl(4) and RuCl(3) (catalysts II and III) to enhance the performance of the anodic catalysts for methanol and ethanol oxidation. Structure, microstructure and surface characterizations of all the catalysts were carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM) coupled with energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The results of the XRD analysis showed that all catalysts had a face-centered cubic (fcc) structure with different and smaller lattice parameters than that of pure platinum, showing that the Ru incorporates into the Pt fcc structure by different ratios in all the catalysts. The typical particle sizes of all catalysts were in the range of 2-3 nm. The most active and stable catalyst for methanol and ethanol oxidation is catalyst III, in which a large amount (more than 90%) of PtRu alloy formation was observed. It has been found that this catalyst is about 8.0 and 33.4 times more active at ～0.60 V towards the methanol and ethanol oxidation reactions, respectively, compared to the commercial Pt catalyst.     

CO oxidation on Ta-Modified SnO2 solid solution catalysts

Co-precipitation method was adopted to prepare Sn–Ta mixed oxide catalysts with different Sn/Ta molar ratios and used for CO oxidation. The catalysts were investigated by N₂-Brunauer–Emmett–Teller (N₂-BET), X-ray diffraction patterns (XRD), H₂-temperature programmed reduction (H₂-TPR), Thermal Gravity Analysis – Differential Scanning Calorimetry (TGA–DSC) techniques. It is revealed that a small amount of Ta cations can be doped into SnO₂ lattice to form solid solution by co-precipitation method, which resulted in samples having higher surface areas, improved thermal stability and more deficient oxygen species on the surface of SnO₂. As a result, those Sn rich Sn–Ta solid solution catalysts with an Sn/Ta molar ratio higher than 4/2 showed significantly enhanced activity as well as good resistance to water deactivation. It is noted here that if tantala disperses onto SnO₂ surface instead of doping into its lattice, it will then have negative effect on its activity.     

Facile synthesis of NiCo2O4 nanorods for electrocatalytic oxidation of methanol

Fuel cell performance largely relies on the activity of catalyst; hence development of high performance electrocatalysts for the electrooxidation of methanol is highly essential for the further development in fuel cell technology. Herein, we demonstrate a facile hydrothermal approach for the growth of NiCo₂O₄ nanorods and their application in the methanol electrooxidation. The morphology and surface area investigation reveal the growth of NiCo₂O₄ nanorods with an average length of 500 nm and a specific surface area of 123 m²/g, respectively. The NiCo₂O₄ nanorods displayed a larger electrochemical activity towards the electrooxidation of methanol in alkaline pH than the quasi-spherical NiCo₂O₄ nanoparticles. On the NiCo₂O₄ nanorod based electrode a higher catalytic current density of 129 mA/cm² and a high stability with 86% current retention was achieved, signifying that the current non-Pt based catalyst could be a non-expensive alternative candidate for high performance fuel cell application.     

Formation of polyaniline/Pt nanoparticle composite films and their electrocatalytic properties

Polyaniline (PANI) thin films modified with platinum nanoparticles have been prepared by several methods, characterised and assessed in terms of electrocatalytic properties. These composite materials have been prepared by the in situ reduction of a platinum salt (K₂PtCl₄) by PANI, in a variety of solvents, resulting in the formation of platinum nanoparticles and clusters of different sizes. The further deposition of platinum clusters at spin cast thin films of PANI/Pt composites from a neutral aqueous solution of K₂PtCl₄ has also been demonstrated. Thin-film electrodes prepared from these materials have been investigated for their electrocatalytic activity by studying hydrazine oxidation and dichromate reduction. The properties of the composite materials have been determined using UV–visible spectroscopy, atomic force microscopy and transmission electron microscopy. The nature of the material formed is strongly dependent on the solvent used to dissolve PANI, the method of preparation of the PANI/Pt solution and the composition of the spin cast thin film before subsequent deposition of platinum from the aqueous solution of K₂PtCl₄.Dedicated to Professor Dr. Alan Bond on the occasion of his 60th birthday.     

Multilayered Pt/Ru nanorods with controllable bimetallic sites as methanol oxidation catalysts

A physical synthesis of multilayered Pt/Ru nanorods with controllable bimetallic sites as methanol oxidation catalysts is reported for the first time. The novel nanorods were synthesized via the oblique angle deposition method, deposited prior to the formation of each individual noble metal layer, in a sequential fashion. It has been shown that the oblique angle deposition controls the morphology and electrochemical properties of the resultant nanostructures. Sequentially the multilayered nanorods comprising Pt and Ru segments exhibited superior electrocatalytic activity when compared to equivalent monometallic Pt nanorods with respect to methanol electrooxidation reaction in an acidic medium. Moreover, it has been established that the electrochemical process takes place at the Pt/Ru nanorods followed the bifunctional mechanism. The relative rates of reaction, recorded using chronoamperometry, show a linear relationship between the long-time current density and the number of Pt/Ru interfaces. Interestingly, the best catalyst for methanol oxidation was found to the surface of bimetallic Pt/Ru nanorods produced by the heat treatments via the so-called electronic effect. This reflects the fact that the ensemble effects of combined bifunctional and electronic effects via second elements could be expected in methanol oxidation reactions. Electrocatalytic activities correlate well with bimetallic pair sites and electronic properties analyzed by X-ray photoemission spectroscopy and X-ray absorption near-edge structure.     

In situ synthesis of Pt/carbon nanofiber nanocomposites with enhanced electrocatalytic activity toward methanol oxidation

Pt/carbon nanofiber (Pt/CNF) nanocomposites were facilely synthesized by the reduction of hexachloroplatinic acid (H(2)PtCl(6)) using formic acid (HCOOH) in aqueous solution containing electrospun carbon nanofibers at room temperature. The obtained Pt/CNF nanocomposites were characterized by TEM and EDX. The Pt nanoparticles could in situ grow on the surface of CNFs with small particle size, high loading density, and uniform dispersion by adjusting the concentration of H(2)PtCl(6) precursor. The electrocatalytic activities of the Pt/CNF nanocomposites were also studied. These Pt/CNF nanocomposites exhibited higher electrocatalytic activity toward methanol oxidation reaction compared with commercial E-TEK Pt/C catalyst. The results presented may offer a new approach to facilely synthesize direct methanol fuel cells (DMFCs) catalyst with enhanced electrocatalytic activity and low cost.     

Synthesis of ultrathin FePtPd nanowires and their use as catalysts for methanol oxidation reaction

We report a facile synthesis of ultrathin (2.5 nm) trimetallic FePtPd alloy nanowires (NWs) with tunable compositions and controlled length (<100 nm). The NWs were made by thermal decomposition of Fe(CO)(5) and sequential reduction of Pt(acac)(2) (acac = acetylacetonate) and Pd(acac)(2) at temperatures from 160 to 240 °C. These FePtPd NWs showed composition-dependent catalytic activity and stability for methanol oxidation reaction. Among FePtPd and FePt NWs as well as Pd, Pt, and PtPd nanoparticles (NPs) studied in 0.2 M methanol and 0.1 M HClO(4) solution, the Fe(28)Pt(38)Pd(34) NWs showed the highest activity, with their mass current density reaching 488.7 mA/mg Pt and peak potential for methanol oxidation decreasing to 0.614 V from 0.665 V (Pt NP catalyst). The NW catalysts were also more stable than the NP catalysts, with the Fe(28)Pt(38)Pd(34) NWs retaining the highest mass current density (98.1 mA/mg Pt) after a 2 h current-time test at 0.4 V. These trimetallic NWs are a promising new class of catalyst for methanol oxidation reaction and for direct methanol fuel cell applications.     

Characterization of carbon-supported AuPt nanoparticles for electrocatalytic methanol oxidation reaction

In view of the recent finding that the bimetallic AuPt nanoparticles prepared by molecular-capping-based colloidal synthesis and subsequent assembly on carbon black support and thermal activation treatment exhibit alloy properties, which is in sharp contrast to the bimetallic miscibility gap known for the bulk counterparts in a wide composition range, there is a clear need to assess the electrocatalytic properties of the catalysts prepared with different bimetallic composition and different thermal treatment temperatures. This paper reports recent results of such an investigation of the electrocatalytic methanol oxidation reaction (MOR) activities of the carbon-supported AuPt nanoparticle catalysts with different bimetallic composition and thermal treatment temperatures. Au(m)Pt(100)(-)(m) nanoparticles of 2-3 nm core sizes with different atomic compositions ranging from 10% to 90% Au (m = 10 approximately 90) have been synthesized by controlling the feeding of the metal precursors used in the synthesis. The electrocatalytic MOR activities of the carbon-supported AuPt bimetallic catalysts were characterized in alkaline electrolytes. The catalysts with 65% to 85% Au and treated at 500 degrees C were found to exhibit maximum electrocatalytic activities in the alkaline electrolytes. The findings, together with a comparison with some well-documented catalysts as well as recent experimental and theoretical modeling results, have revealed important insights into the participation of CO(ad) and OH(ad) on Au sites in the catalytic reaction of Pt in the AuPt alloys with approximately 75% Au. The insights are useful for understanding the correlation of the bifunctional electrocatalytic activity of the bimetallic nanoparticle catalysts with the bimetallic composition and the thermal treatment temperatures.