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Title: Development of anodes for low temperature fuel cells
Author: Barnett, C. J.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1997
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Porous gas diffusion electrodes (GDEs) were prepared using; (i) solubilised polymer binders and Au coated porous polymer substrates (ii) sintered PTFE or PVDF binders and porous carbon substrates. Type (i) GDEs were capable of catalysing H2 oxidation at significant rates but rates of CH3OH oxidation were ca. 100 times lower. They also suffered from ohmic limitations, poor long term stability and poor reproductibility between similar electrodes. Type (ii) GDEs showed much improved rates of CH3OH oxidation compared with Type (i) but were highly dependant on PTFE concentration and only marginally affected by the catalyst loading. The rate of H2 and CH3OH oxidation on Type (i) GDEs appeared independent of the catalyst used (Pd or Pt/Ru) while CH3OH oxidation on Type (ii) GDEs altered according to the Pt/Ru ratio. Various base materials ((Ni/C), Ni3C, (W, Fe6W6C), (W, Co6W6C)) were prepared as Type (ii) electrodes but were found to corrode rapidly in H2SO4 making them unsuitable as electrocatalysts. Newly synthesised materials, (Ni/W/C), (Ni/Mo/C) and (Ni/W/Mo/C) were also prepared as Type (ii) GDEs. (Ni/Mo/C) and (Ni/W/Mo/C) were passive in hot H2SO4 at <0.25V(SCE) respectively; beyond this they corroded transpassively which was attributed to the poor corrosion resistance of Mo2C under acidic conditions. Both materials showed some activity for H2 oxidation but (Ni/Mo/C) showed no activity for CH3OH oxidation while (Ni/W/Mo/C) showed a low rate of oxidation in the passive region. (Ni/W/C) was passive throughout the potential range examined and showed electrocatalytic activity for H2 and CH3OH oxidation; CH3OH oxidation occurred at over potentials significantly lower than observed on noble metal catalysed electrodes. The WC component of (Ni/W/C) was thought to passivate the Ni component rendering it catalytically active. Electrodes prepared using Pt/WC and Pt/Ru/WC showed inferior electrocatalytic activity for the oxidation of CH3OH than Pt/Ru of a comparable loading. In addition higher rates of corrosion were observed compared with plain WC.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available