Oxygen reduction at Pt and Pt70Ni30 in H2SO4/CH3OH solution

Journal of Physical Chemistry C, 2011

Electrochimica Acta, 2009

Carbon-supported Pt and Pt 3 Co catalysts with a mean crystallite size of 2.5 nm were prepared by a colloidal procedure followed by a carbothermal reduction. The catalysts with same particle size were investigated for the oxygen reduction in a direct methanol fuel cell (DMFC) to ascertain the effect of composition. The electrochemical investigations were carried out in a temperature range from 40 to 80 • C and the methanol concentration feed was varied in the range 1-10 mol dm −3 to evaluate the cathode performance in the presence of different conditions of methanol crossover. Despite the good performance of the Pt 3 Co catalyst for the oxygen reduction, it appeared less performing than the Pt catalyst of the same particle size for the cathodic process in the presence of significant methanol crossover. Cyclic voltammetry analysis indicated that the Pt 3 Co catalyst has a lower overpotential for methanol oxidation than the Pt catalyst, and thus a lower methanol tolerance. Electrochemical impedance spectroscopy (EIS) analysis showed that the charge transfer resistance for the oxygen reduction reaction dominated the overall DMFC response in the presence of high methanol concentrations fed to the anode. This effect was more significant for the Pt 3 Co/KB catalyst, confirming the lower methanol tolerance of this catalyst compared to Pt/KB. Such properties were interpreted as the result of the enhanced metallic character of Pt in the Pt 3 Co catalyst due to an intra-alloy electron transfer from Co to Pt, and to the adsorption of oxygen species on the more electropositive element (Co) that promotes methanol oxidation according to the bifunctional theory.

International Journal of Hydrogen Energy, 2008

Electrocatalysts of Pt, PtCo and PtNi powders for the oxygen reduction reaction (ORR) were processed by Mechanical Alloying. Physical characterization was made by X-ray diffraction, scanning electron microscopy and scanning transmission electron microscopy. It was found that milled powders formed agglomerates in the range of 0.2-20 mm formed by nanometric size crystallites. The synthesized powders were alloys of PtFe, PtCoFe and PtNiFe due to iron incorporation during the milling process. The binding energies of Pt in the alloys were determined by XPS. Polarization curves were obtained by Rotating Disk Electrode technique in 0.5 M H 2 SO 4 to determine the electrocatalytic activity of the mechanically alloyed powders. Tafel curves were plotted and kinetic parameters for the ORR were calculated. The PtFe alloy showed the highest electrocatalytic activity for the ORR. However, the lowest overpotential was found for the PtCoFe alloy and it also showed a higher current exchange density. A linear relationship was found between the Pt-binding energy in the alloys and the overpotential at the same current density independent of the Pt alloy composition.

Journal of Solid State Electrochemistry, 2008

High surface area carbon-supported Pt and bimetallic Pt-Fe catalysts are investigated for the oxygen electroreduction reaction (ORR) in low-temperature direct methanol fuel cells (60°C). The electrocatalysts are prepared using a combination of colloidal and incipient wetness methods allowing the synthesis of carbon-supported bimetallic nanoparticles with a particle size of about 2-3 nm. These materials are studied in terms of structure, morphology and composition using X-ray diffraction, X-ray fluorescence and transmission electron microscopy techniques. The electrocatalytic behaviour of these catalysts for ORR is investigated by employing the rotating disc technique. An enhancement of the ORR is observed with the bimetallic Pt-Fe catalyst in the oxygen-saturated electrolyte solution, with and without methanol.

Applied Catalysis B: …, 2005

The electrocatalysis of the oxygen reduction reaction on carbon supported Pt and Pt–Co (Pt/C and Pt–Co/C) alloy electrocatalysts was investigated in sulphuric acid (both in the absence and in the presence of methanol) and in direct methanol fuel cells (DMFCs). In pure sulphuric ...

2015

Gas diffusion electrode was used for providing better conditions in fuel cell systems for oxygen reduction reaction (ORR). Because the slow kinetics of the oxygen reduction reaction at the proton exchange membrane fuel cell cathode restricts fuel cell efficiency. To this end, researchers have used platinum-coated carbon. In the present study, due to the reduction of carbon corrosion, Zinc oxide nanoparticles have been employed as a support material for platinum. The Pt/ZnO nanoparticles catalyst was made via a combined process of impregnation and seeding method. The microstructure of coating was characterized using scanning electron microscopy (SEM) which indicates that Pt nanoparticles are uniformly dispersed on the surface of ZnO. In order to investigate the chemical composition and crystalline phases of coating, X-ray analysis was carried out. Electrochemical Impedance Spectroscopy (EIS) was carried out for comparing the charge transfer effect during the ORR. The catalytic perfor...

Molecules, 2021

Platinum is a main catalyst for the electroreduction of oxygen, a reaction of primary importance to the technology of low-temperature fuel cells. Due to the high cost of platinum, there is a need to significantly lower its loadings at interfaces. However, then O 2 -reduction often proceeds at a less positive potential, and produces higher amounts of undesirable H 2 O 2 -intermediate. Hybrid supports, which utilize metal oxides (e.g., CeO 2 , WO 3 , Ta 2 O 5 , Nb 2 O 5 , and ZrO 2 ), stabilize Pt and carbon nanostructures and diminish their corrosion while exhibiting high activity toward the fourelectron (most efficient) reduction in oxygen. Porosity of carbon supports facilitates dispersion and stability of Pt nanoparticles. Alternatively, the Pt-based bi-and multi-metallic catalysts, including PtM alloys or M-core/Pt-shell nanostructures, where M stands for certain transition metals (e.g., Au, Co, Cu, Ni, and Fe), can be considered. The catalytic efficiency depends on geometric (decrease in Pt-Pt bond distances) and electronic (increase in d-electron vacancy in Pt) factors, in addition to possible metal-support interactions and interfacial structural changes affecting adsorption and activation of O 2 -molecules. Despite the stabilization of carbons, doping with heteroatoms, such as sulfur, nitrogen, phosphorus, and boron results in the formation of catalytically active centers. Thus, the useful catalysts are likely to be multi-component and multi-functional.

Electrochimica Acta

Mesoporous thin films of PtCo, PtNi and PtCu were prepared by a single-step potentiostatic electrodeposition on carbon substrate. Samples were characterized by SEM, XRD, XRF and BET and their activity for oxygen reduction reaction (ORR) was studied in an acidic three electrode cell. The results were compared with both a commercial nanoparticle Pt/C catalyst and a Pt catalyst prepared using the same method. Additionally, the ORR activity of PtCo was studied in a fuel cell. Onset potential of ORR was found to be higher for all the electrodeposited catalysts compared to commercial Pt/C. The ORR activity of mesoporous Pt was found to be linearly dependent on the amount of deposited platinum within a platinum loading range of 0.1−0.5 mg cm −2. Therefore, the results have been normalized by the mass of platinum and mesoporous Pt, PtCu and PtCo was found to have high activity for ORR. Of these catalysts, PtCo was found to have the highest durability. Similar results were obtained in fuel cell experiments as PtCo exhibited enhanced activity towards ORR, peak powers being 60, 70 and 90 mW gPt −1 for commercial Pt/C, mesoporous Pt and mesoporous PtCo, respectively.

Journal of Power Sources, 2006

PtRh alloy nanoparticles were synthesized for use in enhancing the stability of methanol crossover and electrocatalytic activity for oxygen reduction in direct methanol fuel cells (DMFCs). From the electrochemical results, by comparing Pt in terms of methanol tolerance and oxygen reduction with Pt-based alloys, the PtRh(2:1) was an optimum catalyst for the elimination of CO poisoning during the oxidation of crossover methanol as well as oxygen reduction. A PtRh(2:1) alloy cathode showed a higher power density as well as better performance stability than Pt in DMFC unit cell test.

The Journal of Physical Chemistry C, 2017

Direct methanol fuel cell (DMFC) with noble metals based anode and cathode is a promising energy generator to portable power devices. However, the deterioration of catalyst performance suffered by CO poisoning, crossover of fuel from anode to cathode, and higher economical cost of such devices hinder their commercialization. Herein, all of the above issues have been neutralized and crossed the huge hump of faced challenges. Highly efficient, durable, and surfactant-free catalyst with ultralow Pt 3 Pd 1 loadings supported on CeO 2 /C was synthesized. The ex-situ and in situ spectroelectrochemical techniques such as, CV, in situ FTIR, and online DEMS studies confirm the highly efficient activity of catalyst toward electro-oxidation of methanol. In addition, the critical and detailed analysis of RDE results prove the superiority of the present material for electro-reduction of oxygen along a cathode side. The as-synthesized catalyst has proven itself as a better substitute for commercial Pt/C catalyst, with enhanced and durable performance as anode and cathode material for DMFCs. The obtained remarkable performance of catalysts can be attributed to the accumulative effects of PtPd bimetallic NPs and the enhanced synergistic factors of CeO 2 in a hybrid material.