Ru effect on the catalytic performance of Pd@Ru/C catalysts for methanol electro-oxidation

Pd@Ru bimetallic nanoparticles deposited on carbon black electro-catalysts have been fabricated by microwave-assisted polyol reduction method and investigated for methanol electro-oxidation(MEO). The structure and electro-catalytic properties of the as-prepared catalysts were characterized by XRD, SEM, TEM and cyclic voltammetry(CV) techniques. The results showed that the introduction of Ru element(2-10 wt%) into Pd 20 wt%/C(hereafter, denoted as Pd/C) produced a series of core-shell structured binary catalysts. Pd@Ru 5 wt%/C(hereafter, denoted as Pd@Ru5/C) catalyst displayed the highest catalytic activity towards MEO. And the mass activity of Pd@Ru5/C electrode catalyst at E =-0.038 V(vs. Hg/HgO) was 1.42 times higher than that of Pd/C electrode catalyst. In addition, the relationship between the catalytic stability for MEO on Pd@Ru/C catalysts and the value of Jbp/Jfp(the ratio of MEO peak current density in the negative scan and positive scan) were also investigated. The result demonstrated that Pd@Ru5/C offering the smallest value of Jbp/Jfpdisplayed the best stable catalytic performance.     

A high dispersed Pt0.35Pd0.35Co0.30/C as superior catalyst for methanol and formic acid electro-oxidation

Pt：Pd：Co ternary alloy nanoparticles were synthesized by sodium borohydride reduction under nitrogen, and were supported on carbon black as catalysts for methanol and formic acid electro-oxidation. Compared with Pt0.65C00.35/C, Pt/C, Pd0.65C00.35/C, and Pd/C catalyst, Pt0.35Pd0.35Co0.30/C exhibited relatively high durability and strong poisoning resistance, and the Pt-mass activity was 3.6 times higher than that of Pt/C in methanol oxidation reaction. Meanwhile, the Pt0.35Pd0.35Co0.30/C exhibited excellent activity with higher current density and higher CO tolerance than that of Pt0.6sCo0.35/C, Pt/C, Pd0.65C00.35/ C, and Pd/C in formic acid electro-oxidation.     

Studies on State and Structure of Noble Metals in Electrocatalyst Made by Coprecipitation Method

The electrocatalysts of Pt/C,PtRu/C and Ru/C were prepared by the impregnation method.The facet characterization.The dispersion and the particle size for the catalysts were determined by means of X-ray diffraction and transmission electron microscopy,X-ray photoelectron spectroscopy was also used to analyze the state and the valency of the noble metals.The results show that the particle size was in nanometer range and the binary metals have come into being an alloy.The platinum in the catalysts existed in zero valency.The valency of the ruthenium on the surface is different from that in the body,while the ruthenium on the surface existed in oxide-form.PtRu/C and Pt/C are of good activity of the electrooxidation of hydrogen except Ru/C.PtRu/C is more tolerant of CO than Pt/C,and CO is only adsorbed on Pt.     

Electrocatalytic activity of porous nanostructured Fe/Pt-Fe electrode for methanol electrooxidation in alkaline media

An electrochemical approach to fabricate a nanostructured Fe/Pt-Fe catalyst through electrodepo-sition followed by galvanic replacement is presented. An Fe/Pt-Fe nanostructured electrode was prepared by deposition of Fe-Zn onto a Fe electrode surface, followed by replacement of the Zn by Pt at open-circuit potential in a Pt-containing alkaline solution. Scanning electron microscopy and energy-dispersive X-ray techniques reveal that the Fe/Pt-Fe electrode is porous and contains Pt. The electrocatalytic activity of the Fe/Pt-Fe electrode for oxidation of methanol was examined by cyclic voltammetry and chronoamperometry. The electrooxidation current on the Fe/Pt-Fe catalyst is much higher than that on flat Pt and smooth Fe catalysts. The onset potential and peak potential on the Fe/Pt-Fe catalyst are more negative than those on flat Pt and smooth Fe electrodes for methanol electrooxidation. All results show that this nanostructured Fe/Pt-Fe electrode is very attractive for integrated fuel cell applications in alkaline media.     

Co-modified Pd/CeO2-ZrO2 catalysts for methanol decomposition

Pd/Ce0.8Zr0.2O2 catalysts modified by cobalt were prepared by a sequential impregnation method and characterized by X-ray powder diffraction(XRD), N2adsorption/desorption(Brunauer-Emmet-Teller), oxygen storage capacity(OSC), CO-chemisorption, H2-temperature-programmed reduction(H2-TPR) and X-ray photoelectron spectroscopy(XPS). The effect of Co on the performance of methanol decomposition was evaluated at a fixed-bed microreactor. The results showed that the addition of Co can improve the oxygen storage capacity of the catalyst and the dispersion of Pd. XPS results indicated that Pd was in a partly oxidized(Pdδ+, 1δ2) state and Co2+was present in Pd catalysts modified by Co. A 90% conversion of methanol was achieved at around 280°C over Pd-Co/Ce0.8Zr0.2O2 catalyst which was 20°C lower than that over Pd/Ce0.8Zr0.2O2, indicating that both Pdδ+and Co2+play an important role in improving the catalytic activity of methanol decomposition.     

Co-modified Pd/CeO_2-ZrO_2 catalysts for methanol decomposition

Pd/Ce0.8Zr0.2O2 catalysts modified by cobalt were prepared by a sequential impregnation method and characterized by X-ray powder diffraction(XRD), N2adsorption/desorption(Brunauer-Emmet-Teller), oxygen storage capacity(OSC), CO-chemisorption, H2-temperature-programmed reduction(H2-TPR) and X-ray photoelectron spectroscopy(XPS). The effect of Co on the performance of methanol decomposition was evaluated at a fixed-bed microreactor. The results showed that the addition of Co can improve the oxygen storage capacity of the catalyst and the dispersion of Pd. XPS results indicated that Pd was in a partly oxidized(Pdδ+, 1δ2) state and Co2+was present in Pd catalysts modified by Co. A 90% conversion of methanol was achieved at around 280°C over Pd-Co/Ce0.8Zr0.2O2 catalyst which was 20°C lower than that over Pd/Ce0.8Zr0.2O2, indicating that both Pdδ+and Co2+play an important role in improving the catalytic activity of methanol decomposition.     

Structure and Performance of Fe-N_x-C Catalyst for Oxygen Reduction Reaction Prepared by Vacuum Casting Method and the Second Pyrolysis

Affordable non-precious metal(NPM) catalysts played a vital role in the wide application of polymer electrolyte membrane fuel cells(PEMFC). In current work, a facile vacuum casting reacting method based on vacuum casting was introduced to prepare Fe-N_x-C oxygen reduction reaction(ORR) catalysts with high efficient in acid medium. The catalysts were prepared with ammonium ferrous sulfate hexahydrate(AFS) and 1,10-phenanthroline monohydrate utilizing homemade mesoporous silica template. The heat treatment and its influence on structure and performance were systematically evaluated to achieve superior ORR performance and some clues were found. And 850 ℃ was found to be the best temperature for the first and second pyrolysis. The linear sweep voltammetry(LSV) results showed that there were only 18 mV slightly negative shifts of half-wave potential(E_(1/2)) of the optimal catalyst(749 mV) compared with the commercial Pt/C(20 μg·Pt·cm~(-2)). Besides, I850 R also showed better electrochemical stability and methanol-tolerance than that of Pt/C. All evidences proved that our vacuum casting reacting strategy and heat treatment process were prospective for the future RD of high performance Fe-N_x-C ORR catalysts.     

Promoter Effects of Rare Earth Ions on Electrocatalytic Oxidation of Methanol

The promoter effects of rare earth ions on the electrocatalytic oxidation of methanol at the Pt electrode were studied using the cyclinc voltammetry and stable polarization techniques. It was found or the first time that Eu、Ho、Dy ions could accelerate the electrocatalytic oxidation of methanol at the Pt electrode,while Lu、Pr、Yb、Sm ions showed inhibitor effects.     

Electrooxidation Mechanism of Methanol at Pt-Ru Catalyst Modified GC Electrode in Electrolytes with Different pH Using Electrochemical and SERS Techniques

The electrochemical and in-situ surface-enhanced Raman spectroscopy （SERS） techniques were used to investigate the electrooxidation behavior of methanol in acidic, neutral and alkaline media at a Pt-Ru nanoparticle modified glassy carbon （Pt-Ru/GC） electrode. The results showed that methanol could be dissociated spontaneously at the Pt-Ru/GC electrode to produce a strongly adsorbed intermediate, CO. It was found that CO could be oxidized more easily in the alkaline medium than in the acidic and neutral media. The peak potential of methanol oxidation was shifted from 0.663 and 0.708 V in the acidic and neutral media to -0.030 V in the alkaline medium, which is due to that the adsorption strength of CO on the Pt surface in the alkaline medium is weaker than that in the acidic and neutral media. The final product of the methanol oxidation is CO2. However, in the alkaline medium, CO2 produced would form CO3^2- and HCO3^- resulting in the decrease in the alkaline concentration and then in the decrease in the performance of DMFC. Therefore, the performance of the alkaline DMFC is not Stable.     

Ni/Al LDH纳米粒子改性的陶瓷碳电极对甲醇和乙醇电催化氧化性能(英文)

A Ni/Al layered double hydroxide(LDH) nanoparticle modified carbon ceramic electrode(Ni/Al LDH/NMCC) was fabricated and used for the electrocatalytic oxidation of methanol and ethanol in alkaline media.Cyclic voltammetric(CV) studies showed that it gave a significantly higher activity for methanol and ethanol oxidation and can be used as an electrocatalytic anode for fuel cells.The kinetic parameters of the electron transfer coefficient(α) and number of electrons involved in the rate determining step(nα) for the oxidation of methanol and ethanol were determined using CV.The anodic currents showed a linear dependence on the concentration of methanol and ethanol.