Facile synthesis of PtAu alloy nanoparticles with high activity for formic acid oxidation

We report the facile synthesis of carbon supported PtAu alloy nanoparticles with high electrocatalytic activity as anode catalysts for direct formic acid fuel cells (DFAFCs). PtAu alloy nanoparticles are prepared by co-reducing HAuCl₄ and H₂PtCl₆ with NaBH₄ in the presence of sodium citrate and then deposited on Vulcan XC-72R carbon support (PtAu/C). The obtained catalysts are characterized with X-ray diffraction (XRD) and transmission electron microscope (TEM), which reveal the formation of PtAu alloy nanoparticles with an average diameter of 4.6 nm. Electrochemical measurements show that PtAu/C has seven times higher catalytic activity towards formic acid oxidation than Pt/C. This significantly enhanced activity of PtAu/C catalyst can be attributed to noncontinuous Pt sites formed in the presence of the neighbored Au sites, which promotes direct oxidation of formic acid.     

Proton exchange membrane fuel cells with nanoengineered AuPt catalysts at the cathode

The report describes the findings of an investigation of nanoengineered gold-platinum (AuPt) catalysts in proton exchange membrane fuel cells. The membrane electrode assembly was prepared using carbon-supported Au_nPt_100−n nanoparticles with controlled sizes and bimetallic compositions that were thermally treated under controlled temperature, atmosphere, and time. Examples shown in this report included Au₂₂Pt₇₈/C and Au₄₉Pt₅₁/C catalysts treated at 400-500 °C. The electrocatalytic performances of these catalysts in the fuel cells was found to be dependent on the bimetallic composition and the nanoscale phase properties which are controlled by the thermal treatment parameters (temperature and time). Excellent fuel cell performance was observed for the catalysts which are characteristic of an alloyed AuPt phase with a lattice parameter approaching that for an Pt-rich alloy phase. The results have also demonstrated excellent stability of the nanoengineered AuPt catalysts in fuel cells. The observed combination of high activity and high durability of the selected AuPt catalysts indicated that this nanoengineered bimetallic catalyst system, upon further refinement and optimization of the nanoscale phase properties and durability serve as a promising candidate of electrocatalysts for the practical application in Proton Exchange Membrane fuel cells.     

Effective PtAu nanowire network catalysts with ultralow Pt content for formic acid oxidation and methanol oxidation

Pt is the ideal anode catalyst in fuel cells. In this paper, in order to increase the utilization of Pt, the PtAu nanowire networks (NWNs) with ultralow content of Pt are fabricated by a simple silicon monoxide (SiO) reduction method without any capping agent. PtAu NWNs supported on carbon black with Pt content of 1 wt% (Pt₀.₀₅Au NWNs) are employed as catalysts for formic acid oxidation (FAO) and methanol oxidation reaction (MOR), whose mass activities are as high as 4998.9 and 2282.3 mA∙mg_Pt⁻¹, respectively. The network structure facilitates the electron transfer and increases the stability of the catalysts. The PtAu composite experiences compressive lattice strain as confirmed by X-ray powder diffraction (XRD). The Pt₀.₀₅Au NWNs catalyst with low Pt content results in the largest strain variation compared with PtAu composited of other ratios, which may downshift the d-band center of Pt and lead to the higher electrocatalytic activity in oxidation reaction.     

Pt-modified Au/C catalysts for direct glycerol electro-oxidation in an alkaline medium

Au-based catalysts promoted with Pt were prepared by using polyvinyl alcohol protection method. Different amounts of Pt (5, 10 and 15% of total metal) were added in the Au sol formation step to improve the activity of Au/C toward glycerol electro-oxidation in an alkaline medium. The physical and electrochemical properties of the as-prepared catalysts were explored. The average particle sizes of the Au/C and Pt-modified Au/C catalysts measured by transmission electron microscopy (TEM) were the same at around 4 nm. The PtAu/C alloy formation in the PtAu/C catalysts was confirmed by the increase of lattice parameter calculated from the X-ray diffraction (XRD) patterns and by the absence of Pt ring in the electron diffraction pattern. The change of binding energy in X-ray photoelectron spectroscopy (XPS) results indicated the interaction between Pt and Au. For glycerol electro-oxidation in an alkaline medium, the PtAu/C catalysts were more active than the Au/C catalyst as observed from an early onset potential and a shift of potential at maximum current density to a lower potential. Among the Pt-modified Au/C catalysts, the most active catalyst was Pt₁Au₉/C. The synergistic effects between Pt–Au was proven by a better performance of the PtAu/C compared to the physical mixed catalyst of Au/C and Pt/C at the same Pt:Au ratio. The Pt-modified Au/C catalysts were more stable than the Au/C, especially in a high potential region. This enhancement may be caused by the promotion effect of highly active PtO on the surface of the bimetallic catalyst.     

Electrooxidation of ethanol and glycerol on carbon supported PtCu nanoparticles

Four carbon supported PtCu nanostructured catalysts with Pt:Cu atomic ratios of 1:3.20, 1:2.23, 1:0.61 and 1:0.35 were synthesized by a two-step route, involving the chemical reduction of Cu ions on the carbon support, followed by the partial galvanic replacement of Cu atoms by Pt. Bimetallic nanostructured particles with average sizes in the range of 2.3–3.2 nm were obtained. The bimetallic catalysts with surface Pt contents between 20 and 55 at. % were formed by a Cu-rich core surrounded by a Pt-Cu shell, while that with the highest Pt content presented a uniform alloy structure instead of a core-shell arrangement. The electrocatalytic performance of the as-prepared materials toward ethanol electrooxidation in acid and alkaline media and glycerol oxidation in alkaline environment was investigated by cyclic voltammetry and chronoamperometry. It was observed that the electrocatalytic activity of PtCu nanoparticles was found to depend on the surface composition, platinum utilization efficiency, structure and Pt ensemble. Among the as-prepared catalysts, Pt_0·62Cu_0·38/C core-shell material showed the best performance for ethanol oxidation in both acid and alkaline environments, while Pt_0·24Cu_0·76/C and Pt_0·31Cu_0·69/C core-shell catalysts exhibited the highest activity for glycerol oxidation in alkaline medium. The electrochemical results showed that the catalytic activity of the bimetallic Cu@PtCu core-shell nanostructured nanoparticles is between four and ten times higher than that of a commercial Pt_0·51Ru_0·49/C catalyst.     

Electrochemical deposition of Au–Pt alloy particles with cauliflower-like microstructures for electrocatalytic methanol oxidation

Au–Pt alloy particles with cauliflower-like microstructures of varying Pt/Au ratios were electrodeposited on indium tin oxide (ITO) substrates by constant potential electrolysis at E = −0.25 V. The results of X-ray diffraction and X-ray photoelectron spectroscopy confirm that the bimetallic alloys can be obtained for different Pt/Au ratios including 4/1, 1/1 and 1/4. The formation of alloyed cauliflower-like microstructures may be the result of the fast formation of gold seeds as the core and subsequent simultaneous deposition of Au and Pt from cyclic voltammetric study. The effect of surface composition of Au–Pt alloy particles on electrocatalytic methanol oxidation were investigated in H₂SO₄ solution. The electrocatalytic abilities including electrochemical surface area, peak current density and the turnover number of methanol oxidation follow the order of Pt₄Au₁ > Pt > Pt₁Au₁. The results can be ascribed to that electronic effect may be prominent while bifunctional effect is insignificant for Au–Pt alloy systems because the electrocatalytic activity of Au is negligible in acidic media. Additionally, the Pt₄Au₁ electrode has superior kinetics of methanol electro-oxidation than monometallic Pt electrode by calculating the electron transfer coefficient (α).     

A novel binary Pt3Tex/C nanocatalyst for ethanol electro-oxidation

The Pt₃Te_x/C nanocatalyst was prepared and its catalytic performance for ethanol oxidation was investigated for the first time. The Pt₃Te/C nanoparticles were characterized by an X-ray diffractometer (XRD), transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy equipped with TEM (TEM-EDX). The Pt₃Te/C catalyst has a typical fcc structure of platinum alloys with the presence of Te. Its particle size is about 2.8 nm. Among the synthesized catalysts with different atomic ratios, the Pt₃Te/C catalyst has the highest anodic peak current density. The cyclic voltammograms (CV) show that the anodic peak current density for the Pt₃Te/C, commercial PtRu/C and Pt/C catalysts reaches 1002, 832 and 533 A g⁻¹, respectively. On the current–time curve, the anodic current on the Pt₃Te/C catalyst was higher than those for the catalysts reported. So, these findings show that the Pt₃Te/C catalyst has uniform nanoparticles and the best activity among the synthesized catalysts, and it is better than commercial PtRu/C and Pt/C catalysts for ethanol oxidation at room temperature.     

Studies of electrochemical performance of carbon supported Pt-Cu nanoparticles as anode catalysts for direct borohydride-hydrogen peroxide fuel cell

Carbon supported Pt-Cu bimetallic nanoparticles are prepared by a modified NaBH₄ reduction method in aqueous solution and used as the anode electrocatalyst of direct borohydride-hydrogen peroxide fuel cell (DBHFC). The physical and electrochemical properties of the as-prepared electrocatalysts are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), cyclic voltammetry (CV), chronoamperometry (CA), chronopotentiometry (CP) and fuel cell test. The results show that the carbon supported Pt-Cu bimetallic catalysts have much higher catalytic activity for the direct oxidation of BH₄⁻ than the carbon supported pure nanosized Pt catalyst, especially the Pt₅₀Cu₅₀/C catalyst presents the highest catalytic activity among all as-prepared catalysts, and the DBHFC using Pt₅₀Cu₅₀/C as anode electrocatalyst and Pt/C as cathode electrocatalyst shows as high as 71.6 mW cm⁻² power density at a discharge current density of 54.7 mA cm⁻² at 25 °C.     

Carbon nanotube-supported Pt-Alloyed metal anode catalysts for methanol and ethanol oxidation

To improve the electrocatalytic activity of alcohol oxidation, functionalized carbon nanotubes (CNTs) decorated with various compositions of metal alloy catalyst nanoparticles (Pt_xM_y, where M = Au and Pd; x and y = 1–3) have been prepared via reduction. The CNTs were treated with an nitric acid solution to promote the oxygen-containing functional groups and further load the metal nanoparticles. X-ray diffraction (XRD) scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to probe the formation of catalyst microstructure morphologies. A uniform dispersion of the spherical metal particles with diameters of 2–6 nm was acquired. The catalytic properties of the catalyst for oxidation were thoroughly studied by electrochemical methods that involved in the cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). To maximize the electrocatalytic performance and minimize the metal integration of the loaded CNTs, various compositions of active catalysts with large active surface areas are expected to increase the activity of the enhanced catalysts for alcohol oxidation. Most of the prepared bimetallic catalysts have better alcohol oxidation kinetics than commercial PtRu/C. Among the prepared catalysts, the PtAu/CNTs and PtPd/CNTs catalysts with high electrochemically active surface area (ECSA) show excellent activities for alcohol oxidation resulting in their low onset potentials, small charge transfer resistances and high peak current densities and I_f/I_b ratios, stability, and better tolerance to CO for alcohol oxidation. The integration of Pt and different metal species with different stoichiometric ratios in the CNTs support affects the electrochemical active surface area achieved in the catalytic oxidation reactions.     

High activity of Au-Cu/C electrocatalyst as anodic catalyst for direct borohydride-hydrogen peroxide fuel cell

Carbon supported Au-Cu bimetallic nanoparticles are prepared by a modified NaBH₄ reduction method in aqueous solution at room temperature. The electrocatalytic activities of the Au-Cu/C catalysts are investigated by cyclic voltammetry, chronoamperometry, chronopotentiometry and fuel cell experiments. It has been found that the Au-Cu/C catalysts have much higher catalytic activity for the direct oxidation of BH₄⁻ than Au/C catalyst. Especially, the Au₆₇Cu₃₃/C catalyst presents the highest catalytic activity for BH₄⁻ electrooxidation among all as-prepared catalysts, and the DBHFC using Au₆₇Cu₃₃/C anode catalyst and Au/C cathode catalyst shows the maximum power density of 51.8 mW cm⁻² at 69.5 mA cm⁻² and 20 °C.     

Catalytic activities of Ag/C decorated with small amounts of Au and Pt for glycerol oxidation

The two-step decoration of the Ag nanoparticles supported on carbon black (Ag/C) with Au and Pt, the electrooxidation of glycerol on the Pt/Au/Ag/C catalysts in alkaline solution, and the effect of the amounts of Au and Pt on the catalytic activity of Pt/Au/Ag/C are investigated. The decoration of Ag/C is performed by electrochemically depositing a small amount of Au and then Pt on Ag/C, and the Pt_x/Au_y/Ag₁₀₀/C catalysts with different x:y:100 ratios (0.15 ≤ x ≤ 1.9 and 0.2 ≤ y ≤ 1.5) are obtained. Physical and electrochemical characterizations reveal that small parts of the Ag surfaces are covered by the deposited Au and Pt. Pt_x/Au_y/Ag₁₀₀/C mainly shows Pt-relevant behaviors in glycerol oxidation, and Pt_1.3/Au_y/Ag₁₀₀/C exhibits high catalytic activities. The results reveal that the surface decoration is a useful method of fabricating efficient ternary catalysts at low cost.     

Platinum supported on hydroxyl-grafted poly (3,4-ethylenedioxythiophene)-modified RuCo,N-tridoped bamboo-like carbon nanotubes for direct methanol fuel cell

The development of highly active and efficient heterogeneous catalytic oxidation system has become an attractive research field. In this paper, a catalyst (RuCo/N-CNT@PEDOT-OH/Pt) from platinum nanoparticles (Pt NPs) supported on hydroxyl-grafted poly(3,4-ethylenedioxythiophene) (PEDOT–OH)-modified RuCo, N-tridoped bamboo-like carbon nanotubes (RuCo/N-CNT) are used for direct methanol fuel cell (DMFC). The electrocatalytic activity of RuCo/N-CNT@PEDOT-OH/Pt is systematically compared with RuCo/N-CNT/Pt (Pt NPs supported on RuCo/N-CNT without PEDOT-OH) in the methanol oxidation reaction (MOR). The growth mechanism of carbon nanotubes and the role of heteroatom doping in the electrocatalytic process is explored. The catalysts show excellent electrocatalytic performance with high stability for MOR. It is found that the mass activity (MA) of the RuCo/N-CNT@PEDOT-OH/Pt (1961.3 mA mg^?1_Pt) for MOR was higher than that of RuCo/N-CNT/Pt (1470.1 mA mg^?1_Pt) and the commercial Pt/C catalysts (281.0 mA mg^?1_Pt), indicating the positive effect of the PEDOT-OH in the electrocatalytic MOR. In addition, density functional theory (DFT) calculations verify the possible mechanism pathways of the obtained RuCo/N-CNT@PEDOT-OH/Pt catalyst. This presented catalyst offers new inspiration for designing efficient electrocatalysts for methanol oxidation.     

Platinum-nickel bimetallic catalyst doped with rare earth for enhancing methanol electrocatalytic oxidation reaction

Platinum (Pt) is often used as anodic catalyst for direct methanol fuel cell (DMFC). However, platinum is difficult to achieve large-scale application because of its low stability and high cost. In this work, the electrocatalytic activity and stability of the Pt-based catalyst for methanol oxidation (MOR) are significantly improved by adding Ce and Ni to the catalyst. Additionally, the rare earth element-Pr (Dy) is also chosen to be added into the catalysts for comparison. A series of PtMNi (M = Ce, Pr, Dy) catalysts are prepared by impregnation and galvanic replacement reaction methods using carbon black as support. The electrocatalytic mass activity of PtCeNi/C, PtDyNi/C, PtPrNi/C and Pt/C is 3.92, 1.86, 1.69 and 0.8 A mg_Pt⁻¹, respectively. The mass activity of these the above four catalysts after stability measurement is 3.14, 1.49, 1.27 and 0.72 A mg_Pt⁻¹. Among them, PtCeNi/C has the highest catalytic activity. These as-prepared catalysts are also characterized by various analyzing techniques, such as TEM, HRTEM, XRD, XPS, ICP-OES, STEM, STEM-EDS elemental mapping and line-scanning etc. It shows that PtCeNi/C exhibits best catalytic activity (3.92 A mg_Pt⁻¹) among the as-obtained catalysts, 4.9 times higher than that of commercial Pt/C (0.8 A mg_Pt⁻¹). PtCeNi/C is also with excellent anti-CO poisoning ability. The outstanding catalytic performance of PtCeNi/C for the MOR is mainly attributable to uniform-sized PtCeNi nanoparticles, uniform Ni, Ce and Pt element distribution, and electron interaction among Pt-, Ni- and Ce-related species (electron transferring from Pt to CeO₂).     

Ethanol electro-oxidation on carbon-supported Pt,PtRu and Pt3Sn catalysts: A quantitative DEMS study

The electrocatalytic activity of commercial carbon supported PtRu/Vulcan and Pt₃Sn/Vulcan bimetallic catalysts (E-TEK, Inc.) for ethanol oxidation under well defined electrolyte transport conditions and their selectivity for complete oxidation were evaluated using cyclic voltammetry combined with on-line differential electrochemistry mass spectrometry (DEMS) measurements and compared to the activity/selectivity of standard Pt/Vulcan catalysts. The main reaction products CO₂, acetaldehyde and acetic acid were determined quantitatively, by appropriate calibration procedures, current efficiencies and product yields were calculated. Addition of Ru or Sn in binary Pt catalysts lowers the onset potential for ethanol electro-oxidation and leads to a subtle increase of the total activity of the Pt₃Sn/Vulcan catalyst. It does not improve, however, the selectivity for complete oxidation to CO₂, which is about 1% for all three catalysts under present reaction conditions—incomplete ethanol oxidation to acetaldehyde and acetic acid prevails on all three catalysts. The results demonstrate that the performance of the respective catalysts is limited by their ability for C–C bond breaking rather than by their activity for the oxidation of poisoning adsorbed intermediates such as CO_ad or CH_x,ad species.     

PAMAM-stabilized Pt-Ru nanoparticles for methanol electro-oxidation

This work utilizes poly(amidoamine) dendrimers (PAMAM) as a protective ligand in solution to produce carbon-supported, Pt-Ru bimetallic nanoparticles for use as methanol electro-oxidation catalysts. UV-vis spectra show that after initial Pt²⁺ complexation with PAMAM G4OH dendrimer in water, appropriate adjustment of solution pH permits subsequent Ru³⁺ complexation without displacing Pt²⁺, demonstrating the formation of an aqueous, bimetallic solution complex. Catalysts (nominally 20 wt% metals, confirmed by AA spectroscopy) are produced by impregnating high surface area carbon black with G4OH-(Pt²⁺)_x(Ru³⁺)_y complex solution, drying, and activation in H₂ gas at elevated temperature. XPS results show that activation in H₂ at 400 °C removes virtually all of the PAMAM and reduces all of the Pt and most of the Ru to zero valence. TEM and XRD results show that the use of G4OH in the recipe is crucial for controlling metal particle size, and that the particles are crystalline with lattice parameters indicative of bimetallic Pt-Ru alloys. XRD data also suggest that G4OH promotes greater Pt-Ru alloying when Pt:Ru = 1:1. Catalytic activity for methanol oxidation increases with Ru content and is greatest for the catalyst with 1:1 Pt:Ru ratio. Per unit mass of Pt, the methanol oxidation activity of 20 wt% G4OH-PtRu/C catalyst is about 60% greater than that of E-Tek's commercially available 20 wt% PtRu catalyst.     

Enhancement of anodic oxidation of formic acid on Pd–Fe bimetallic nanoparticles by thermal treatment

The surface composition and catalytic properties of Pd–Fe bimetallic catalysts with identical bulk composition can be continuously tuned by treatment at different temperatures. The activity of these catalysts in formic acid oxidation was related to the treatment temperature. The thermal treatment temperatures ranged from 400 to 600 °C. The Pd–Fe nanoparticles are characterized by an array of analytical techniques including TEM (transmission electron microscopy), XRD (X-ray diffraction), ICP (inductively coupled plasma) and HS-LEIS (low energy ion scattering spectroscopy). The electrocatalytic activity is examined using cyclic voltammetric and chronoamperometric measurements. The Pd–Fe/C catalyst with 500 °C shows the highest electrocatalytic activity for formic acid oxidation, with a current activity 3 times higher than that of before treated Pd–Fe/C catalyst, 5.6 times higher than that of commercial Pt/C catalyst. The migration of Pd to the surface on the nanoparticle catalysts as well as the electrochemical active surface area of the PdFe–H catalysts was shown to play a major role in enhancing the electrocatalytic activity for catalyst. These findings provided important insights into the correlation between the electrocatalytic activity and the treatment temperature of the nanoengineered bimetallic catalysts.     

Catalytic activity,stability and impedance behavior of PtRu/C,PtPd/C and PtSn/C bimetallic catalysts toward methanol and formic acid oxidation

PtRu, PtPd and PtSn with weight ratios of (2:1) on carbon black (Vulcan XC-72) supported bimetallic catalysts were prepared by using microwave method via chemically reduction of H₂PtCl₆·6H₂O, RuCl₃, PdCl₂ and SnCl₂·2H₂O precursors with ethylene glycol (EG). These prepared catalysts were systematically investigated and obtained results were compared with commercial Pt black, PtRu black catalysts and with each other. The catalysts were characterized with XRD, ICP-MS, EDS and TEM. The electrocatalytic activities, stability and impedance of the catalysts were investigated in sulfuric acid/methanol and sulfuric acid/formic acid mixtures using electrochemical measurements. The results showed that PtSn/C catalyst showed comparable activity and durability with commercial Pt/C catalyst toward methanol oxidation. The synthesized PtRu/C catalyst was found to completely oxidize methanol and it showed more catalytic activity than commercial PtRu catalyst. Bimetallic PtPd/C catalyst gave better activity than both commercial Pt black and synthesized Pt/C catalyst for oxidation of formic acid. Higher electrochemical active surface areas were obtained with supported bimetallic catalysts.     

Carbon supported Pt-Y electrocatalysts for the oxygen reduction reaction

Carbon supported Pt₃Y (Pt₃Y/C) and PtY (PtY/C) were investigated as oxygen reduction reaction (ORR) catalysts. After synthesis via reduction by NaBH₄, the alloy catalysts exhibited 10-20% higher mass activity (mA mg_Pt⁻¹) than comparably synthesized Pt/C catalyst. The specific activity (μA cm_Pt⁻²) was 23 and 65% higher for the Pt₃Y/C and PtY/C catalysts, respectively, compared to Pt/C. After annealing at 900 °C under a reducing atmosphere, Pt₃Y/C-900 and PtY/C-900 catalysts showed improved ORR activity; the Pt/C and Pt/C-900 (Pt/C catalyst annealed at 900 °C) catalysts exhibited specific activities of 334 and 393 μA cm_Pt⁻², respectively, while those of the Pt₃Y/C-900 and PtY/C-900 catalysts were 492 and 1050 μA cm_Pt⁻², respectively. X-ray diffraction results revealed that both the Pt₃Y/C and PtY/C catalysts have a fcc Pt structure with slight Y doping. After annealing, XRD showed that more Y was incorporated into the Pt structure in the Pt₃Y/C-900 catalyst, while the PtY/C-900 catalyst remained unchanged. Although these results suggested that the high ORR activity of the PtY/C-900 catalyst did not originate from Pt-Y alloy formation, it is clear that the Pt-Y system is a promising ORR catalyst which merits further investigation.     

Pt/C electrocatalysts based on the nanoparticles with the gradient structure

The architecture of bimetallic nanoparticles has strong influence on durability and activity of PtM/C electrocatalysts in the oxygen electroreduction (ORR) and the methanol electrooxidation reactions (MOR). In the present study the Pt_0.8(Cu)/C electrocatalyst was obtained by the methods of successive multistage reduction of platinum and copper from the solutions of their precursors while platinum concentration in the matrix solution was increasing step by step. The composition, structural characteristics and electrochemical behavior of this material were compared with the Pt_1.0Cu/C catalyst based on the nanoparticles of a solid solution, which was obtained by the combined single-step chemical reduction of precursors, as well as with a commercial Pt/C sample with the same Pt-loading (20% by weight). The catalyst based on the Pt–Cu gradient nanoparticles demonstrated the highest corrosion-morphological stability in the stress-test, as well as the highest activity in ORR and MOR in the HClO₄ solutions. Both of the studied bimetallic catalysts lose a significant amount of copper during the standardizing cycling and the stress-test. In the stabilized composition of the “gradient catalyst” the residual copper content, however, is considerably higher than that of the catalyst with the solid solution nanoparticles. The positive features of the electrochemical behavior of Pt_0.8(Cu)/C catalyst arise apparently due to the faster formation of a durable protective layer of platinum on the surface of nanoparticles in the process of functioning, compared to the analogue based on the nanoparticles of the solid solution. High stability and activity of Pt_0.8(Cu)/C compared to the Pt/C analogue are associated with the larger size of the nanoparticles and the promoting influence of residual copper on the catalytical activity of platinum.     

Direct immobilization of Pt-Ru alloy nanoparticles on nitrogen-doped carbon nanotubes with superior electrocatalytic performance

Taking the advantage of the inherent chemical activity arisen from the nitrogen incorporation for nitrogen-doped carbon nanotubes (NCNTs), we have developed a facile strategy for the construction of binary Pt-Ru/NCNT electrocatalysts. Alloyed Pt-Ru nanoparticles have been directly immobilized onto the outer surface of NCNTs without pre-modification due to the nitrogen participation. The Pt-Ru nanoparticles have a high dispersion, a narrow size distribution of 2.5-3.5 nm and tunable chemical composition. These catalysts have been evaluated for methanol oxidation and show good stability and better CO tolerance than the monometallic Pt/NCNT catalyst due to the bifunctional and electronic effects. The Pt₅Ru₅/NCNT catalyst shows superior electrocatalytic performance to the commercial Pt₅Ru₅/C catalyst. The easy fabrication and excellent performance of the NCNT-based Pt-Ru alloy catalysts indicate their potential application in direct methanol fuel cells.