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The preparation of multi-walled carbon nanotubes-NiO nanoparticles composites (MWCNT-NiO) and their application as modifier for methanol electrooxidation in NaOH are presented. Nickel oxide nanoparticles were accumulated on multi-walled carbon nanotubes (MWCNT) by pulsed potential electrodeposition. The structure and nature of the GC/MWCNTs/NiO were characterized by Transmission electron microscopy (TEM), the results indicated that NiO nanoparticles were homogeneously electrodeposited on the surfaces of MWCNT. Also, the electrochemical behavior of carbon nanotubes-NiO nanoparticles composites in the alkaline solutions of methanol has been studied by cyclic voltammetry, and electrochemical impedance spectroscopy. The observed peak on the potentiodynamic curve for MWCNT-NiO composite electrode in alkaline solutions of methanol is observed which is ascribed to the methanol oxidation in alkaline medium. The achieved results obtained, are discussed for the MWCNT-NiO composites for the catalytic electrodes of fuel cells.

This work tries to study the problem of methanol crossover through the polymer electrolyte in direct methanol fuel cells (DMFCs) by developing new cathode electrocatalysts. For this purpose, a series of gas diffusion electrodes (GDEs) were prepared by using single-walled carbon nanotubes (SWCNTs) supported Pt-Pd (Pt-Pd/ SWCNT) with different Pd contents at the fixed metal loading of 50 wt%, as bimetallic electrocatalysts, in the catalyst layer. Pt-Pd/SWCNT was prepared by depositing the Pt and Pd nanoparticles on a SWCNTs support. The elemental compositions of bimetallic catalysts were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES) system. The performances of the GDEs in the methanol oxidation reaction (MOR) and in the oxygen reduction reaction with/without the effect of methanol oxidation reaction were investigated by means of electrochemical techniques: cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The results indicated that GDEs with Pt-Pd/SWCNT possess excellent electrocatalytic properties for oxygen reduction reaction in the presence of methanol, which can originate from the presence of Pd atoms and from the composition effect.

The objective of this study is to improve the catalytic activity of platinum by alloying with transition metal (Pd) in gas diffusion electrodes (GDEs) by oxygen reduction reaction (ORR) at cathode site and comparison of the acidic and alkaline electrolytes. The high porosity of single-walled carbon nanotubes (SWCNTs) facilitates diffusion of the reactant and facilitates interaction with the Pt surface. It is also evident that SWCNTs enhance the stability of the electrocatalyst. Functionalized SWCNTs are used as a means to facilitate the uniform deposition of Pt on the SWCNT surface. The structure of SWCNTs is nearly perfect, even after functionalization, while other types of CNTs contain a significant concentration of structural defects in their walls. So catalysts supported on SWCNTs are studied in this research.The electrocatalytic properties of ORR were evaluated by cyclic voltammetry, polarization experiments, and chronoamperometry. The morphology and elemental composition of Pt alloys were characterized by X-ray diffraction (XRD) analysis and inductively coupled plasma atomic emission spectroscopy (ICP-AES) system. The catalytic activities of the bimetallic catalysts in GDEs have been shown to be not only dependent on the composition, but also on the nature of the electrolytes. The GDEs have shown a transition from the slow ORR kinetics in alkaline electrolyte to the fast ORR kinetics in the acidic electrolyte. The results also show that introduction of Pd as transition metal in the Pt alloys provides fast ORR kinetics in both acidic and alkaline electrolytes. The performance of GDEs with Pt-Pd alloy surfaces towards the ORR as a function of the alloy's overall composition and their behavior in acidic electrolyte was also studied. These results show that the alloy's overall composition and also the nature of the electrolytes have a large effect on the performance of GDEs for ORR.

The aim of this study is to extend the knowledge of possible improvements in graphene-supported PtCoFe electrocatalysts synthesized through different thermal treatment procedures. Electrocatalysts are prepared via the reduction of precursors followed by thermal treatment at three different temperatures. A freeze-drying procedure is also used instead of conventional drying to extend the knowledge of possible improvements in electrocatalysts. In the single cell tests, the electrocatalyst nanoparticles, which are synthesized by freeze-drying procedures, show higher performance than the other electrocatalysts. This may be due to more triple-phase boundaries being created in the freeze-dried electrocatalyst because of the increased d 002 and its well-arranged spacing of the nanostructure. The power density of the proton exchange membrane fuel cell (PEMFC) with the synthesized cathode electrocatalyst with low metal loading (0.1 mg cm −2 Pt) can reach a maximum of 450 mW cm −2 at 75 °C, which indicates its potential application in PEMFCs.