In the present study, Pt(20wt%)/C electrocatalysts for oxygen reduction reaction in the cathode of fuel cells were synthesized with different amounts of trisodium citrate as stabilizing agent, to achieve higher efficiency of platinum electrocatalyst. The electrocatalyst More
In the present study, Pt(20wt%)/C electrocatalysts for oxygen reduction reaction in the cathode of fuel cells were synthesized with different amounts of trisodium citrate as stabilizing agent, to achieve higher efficiency of platinum electrocatalyst. The electrocatalysts containing platinum and trisodium citrate with ratios of 1:12, 1:9, 1:6, and 1:3 (Pt/C:TC) were prepared by using the saturation-reduction method. To evaluate the oxygen reduction reaction in the cathode catalyst layer in an acidic environment cyclic voltammetry (CV), linear sweep voltammetry (LSV), rotating disk electrode (RDE), and finally electrochemical impedance spectroscopy (EIS) techniques were applied. Also, morphology of the catalysts was studied with scanning electron microscopy (SEM). The results showed that the efficiency of the synthesized electrocatalysts at a ratio of 1:3 (Pt/C:TC) was better for oxygen reduction. It also had lower charge transfer resistance, more suitable distribution, and higher electrochemically active surface area (14.7 m2gPt). In addition, the number of electrons involved in the oxygen reduction reaction was calculated to follow the four-electron pathway for the electrocatalyst prepared at ratio of 1:3.
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n this work, the carbon nanotubes/platinum black composite was prepared by easy, efficient, and cheap method and morphology of composite was investigated by using tunnelling electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The TEM images showed More
n this work, the carbon nanotubes/platinum black composite was prepared by easy, efficient, and cheap method and morphology of composite was investigated by using tunnelling electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The TEM images showed that Pt was immobilized like rosary seeds on external walls of carbon nanotubes and the Pt in EDX spectra confirmed presence of Pt element in composite. Then catalytic activity of this nanocomposite was investigated using carbon paste electrode modified with this nanocomposite for hydrogen evolution reaction in acidic media by electrochemical methods such as linear sweep voltammetry. The linear sweep voltammetry of Pt-CNT/CPE electrode exhibits higher current density and less negative value of potential towards hydrogen evolution reaction than the CPE. Effects of different parameters such as electrolyte type, electrolyte concentration, and platinum black/carbon nanotubes ratio were studied for electrocatalysis of hydrogen evolution reaction. The results showed that sulphuric acid 0.1 M and 2:5 ratio was choice as optimum condition for hydrogen evolution reaction. The deposition of this nanocomposite on the electrode caused onset potential of -0.2 V and the lowest Tafel slope of 4.0 V-1 dec-1 for hydrogen evolution reaction. The electron transfer coefficient and exchange current density for the Pt-CNT/CPE were calculated by Tafel plot about 1.3 and 0.12 mA cm-2, respectively for hydrogen evolution reaction.
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In this study, the nanocomposite of palladium-carbon nanotubes-chitosan was synthesized and characterized by XRD and TEM techniques. The synthesized nanocomposite was used for the modification of glassy carbon electrods surfaces. Using cyclic voltammetry (CV) technique, More
In this study, the nanocomposite of palladium-carbon nanotubes-chitosan was synthesized and characterized by XRD and TEM techniques. The synthesized nanocomposite was used for the modification of glassy carbon electrods surfaces. Using cyclic voltammetry (CV) technique, the electrochemical activity of modified electrode (GC/PdNPs-MWCNTs-CH) toward methanol oxidation was investigted in a solution of 0.5 M sodium hydroxide and 1.0 M methanol. The results revealed that the synthesized nanocomposite shows a high catalytic activity toward methanol oxidation and thus has an efficiency for use as anode for the methanol fuel cells. The effects of different parameters such as methanol and electrolyte concentrations, potential range, and potential scan reate on the anodic current density and the peak potential of methanol oxidation were also investigted. Moreover, comparing the electrochemical activity of the palladiun nanocatalyst for methanol oxidation with that of the platinum-type, it was concluded that the former has a considerable activity closed to the platinum one. Therefore, it coulde be a souitable substituer for platinum in the methonl oxidation process. This substitution, also reduces the catalyst price.
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In this paper, the effect of adding a low amount of platinum to slurry Si-modified aluminide coatings containing silicon less than the amount required to provide complete protection in these coatings is investigated. In addition to the coatings characterization, the rol More
In this paper, the effect of adding a low amount of platinum to slurry Si-modified aluminide coatings containing silicon less than the amount required to provide complete protection in these coatings is investigated. In addition to the coatings characterization, the role of platinum on the type II hot corrosion behavior of coatings has been discussed. To create silicon and silicon-platinum aluminide coatings, a slurry silicoaluminzing method was applied to samples of Ni-base superalloy GTD-111 specimens, which was previously Pt-electroplated on some of them with a thickness of 2 μm. The amount of silicon in the slurry was 10% by weight relative to total solid of the slurry, so that the amount of silicon in the coating is less than the critical amount required for complete protection. The type II hot corrosion test was carried out using a furnace method with Na2SO4-60mol% V2O5 at 700 °C. After 20 hours of hot corrosion, Al2O3 protective oxide and non-protective oxide NiAl2O4 were detected in silicon-platinum- and silicon-aluminide coatings, respectively. In the absence of platinum, the Ni3V2O8 phase was also found to be a product of NiO and NiAl2O4 dissolution in type-II hot corrosion condition. At the end of the 80-hour hot corrosion, unlike the silicon-aluminide coating, silicon remained in the silicon-platinum-aluminide coating structure.
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