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Title: Non-noble electrocatalysts for hydrogen oxidation in acidic fuel cells
Author: Brady, C. D. A.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2009
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The objective of this project was to advance the development of cost effective, low-temperature hydrogen fuel cells, by creating non-noble anode electrocatalysts for application in acidic electrolytes. The electrocatalytic activity of nanocrystalline tungsten carbides, WC and W2C, towards the anodic oxidation of hydrogen is presented. The tungsten carbides, which were synthesised by solid-state reduction of W(VI) using carbon, are both electrocatalytic. The WC phase shows greater electrocatalysis than the W2C phase, and also shows a greater degree of passivity against corrosion. Silver was co-deposited on the WC phase which results in ca. 25% higher electrocatalytic activity towards the hydrogen electrode reactions relative to WC alone. WC synthesised with Co or Ni additions shows reduced passivity because of the formation of corrodible Ni2W4C and Co3W10C3.4 phases, neither of which show any significant electrocatalytic activity. Furthermore, Ni and Co catalyse the crystal growth of WC during thermal synthesis. This lowers the catalytic performance of electrodes relative to those fabricated from nanocrystalline WC. The Frey-Farthing-Chen electrodeoxidation of NiTa2O6, CoTa2O6 and NiWO4 in the presence of carbon produces TaC or WC particulate electrocatalysts and corrodible Ni or Co containing side-products. TaC shows increased passivity against corrosion but reduced electrocatalytic activity relative to WC. The electrocatalytic activity of the carbides was not enhanced by this synthetic procedure or by the presence of Ni or Co. A compositional range of amorphous, Ni-C and Co-C thin films were synthesised. Ni-C thin films show higher catalytic activity than Co-C thin films of equivalent metal concentration. Films containing less than 20 atm% metal passivate in sulphuric acid. Films containing more than 20 atm% metal do not passivate fully in acid but still show much greater corrosion resistance than the pure metals.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available