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Title: PtNi dendrimer catalysts supported on carbon nanotubes for oxygen reduction reaction in direct methanol fuel cell
Author: Mahmoud, Heaven
ISNI:       0000 0005 0289 9061
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2019
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The work in this thesis focuses on the preparation of bimetallic PtNi catalysts in order to promote oxygen reduction reaction (ORR) in direct methanol fuel cells (DMFC). The approach involves using a dendrimer template method in order to exert control over the size of the bimetallic nanoparticles and to prevent the agglomeration process especially during the dispersion on the carbon nanotubes support. Thermal treatment is an imperative step for the catalyst prepared by this method since the dendrimer loses its porous structure in dry conditions, confining the metal active site and blocking the passage of the reactants, leading to a significant loss of catalytic activity. The Thermal treatment is carried out at two different temperatures 200 °C and 300 °C, at various time periods 1h, 2 h, 3 h, 4 h, and 6 h. The best conditions were specified as 300 oC and 2 h after which the membrane electrode assembly (MEA) featuring 20 wt% Pt/MWCNTs catalyst activated using these conditions showed the best performance in the cell. The performance of the MEA's in the cell is used to indicate the catalytic activities towards oxygen reduction reaction. The MEA featuring the core-shell 20 wt% Ni25@Pt75/MWCNTs with an atomic ratio of 3:1 (75Pt:25Ni), outperformed the standard MEA by 20.5% with a power density of 51.03 mW/cm2 at 2 M and 70 oC in comparison with 40.56 mW/cm2 for the standard MEA utilising the commercial 60% Pt/C at the same temperature of 70 oC. This improvement is due to the ligand effect and the compression stress on Pt metal nanoparticles resulting from the core-shell configuration. The MEA incorporating alloy type 20 wt% Ni25Pt75/MWCNTs surpassed the standard MEA by 12.5% reaching a maximum power density of 46.41 mW/cm2 in comparison to 40.56 mW/cm2 for the standard MEA at the same temperature of 70 oC and 2 M methanol feed.
Supervisor: Holmes, Stuart Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: dendrimer ; CNTs ; bimetallic catalysts ; DMFC