Development of Raney-Ni gas diffusion electrodes for fuel-cells

(1995) Development of Raney-Ni gas diffusion electrodes for fuel-cells. PhD thesis, King Fahd University of Petroleum and Minerals.


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A novel method of preparing the gas diffusion electrodes for fuel-cells is proposed which overcomes the problems of conventional 'Dry Method'. In this method, the catalyst is milled with a polymer binder and a slurry of the milled catalyst is made using a surfactant. This slurry is filtered on a filter paper to give a uniform filter cake. This is rolled with a metallic mesh which works as charge collector. The remaining traces of the surfactant are washed off with boiling solvent to get the final electrode. To demonstrate, test and study the effectiveness of the method, Raney-Ni catalyst and Polytetraflouroethylene (PTFE) binder were used to make electrodes. These electrodes were used as anode in an alkaline fuel-cell. The performance tests of galvanostatic polarization at 25, 45, 55, 65 and 75⁰C showed that the new electrodes performed better. Five parameters which may affect the performance, namely: PTFE content, milling time, cooling while milling, clearance between the calendars and the removal of the surfactant were considered in the experimental design. The PTFE content, milling time, their interaction and cooling were found significant using a partial factorial design (2⁵⁻¹). The performance of these electrodes were best at 8% PTFE and milling for 60 seconds while cooling was ON. The spherical grain model for the performance was modified with the assumptions that the electrode is made of spherical agglomerates of Raney metal and PTFE, flooded with electrolyte, while the gas is occupying the macropores. In addition to the analysis of the diffusion and reaction inside the grains in the spherical grain model, this model includes the resistance of gas diffusion into the macropores and a thin electrolyte film sorrounding the grain. The original and modified models were compared with the experimental polarization data of hydrogen oxidation on a Ni/PTFE electrode in KOH. The newly developed model predicts the experimental data very well in all regions. This model was used to obtain exchange current density (i₀), charge transfer coefficient (α) and activation energy (E) for the best electrode prepared by the filtration method. The values of these parameters at 25⁰C were 24.0x10⁻⁵ mA/cm², 0.62 and 73.9 KJ/mol respectively.

Item Type: Thesis (PhD)
Subjects: Chemical Engineering
Department: College of Chemicals and Materials > Chemical Engineering
Committee Advisor: Al-Saleh, Muhammad A.
Committee Members: Jaber, A. M. Y. and Al-Zakri, Abdullah S. and Abdel-Aal, Hussein K. and Gultekin, Selahattin
Depositing User: Mr. Admin Admin
Date Deposited: 22 Jun 2008 14:03
Last Modified: 01 Nov 2019 14:00