The study of platinum alloy films of thickness on the order of 1 nanometre is an important topic. For the development of viable fuel cell catalysts, there is a necessity to reduce the overall platinum content while maintaining high catalytic performance. Such nanoscale structures are also convenient model systems to gain a fundamental understanding of the correlation between surface structure and reactivity. The work presented within this thesis focusses on the development of a method to electrochemically form Pt1-xPbx nanoscale overlayers of controlled thickness, composition and morphology. By utilising partial surface limited redox replacement (SLRR) , Pt1-xPbx alloys of variable thickness and surface composition have been formed. The electrochemical adsorption of hydrogen and carbon monoxide has been studied with respect to these two variables. A pronounced sensitivity of adsorption to small (on the order of 1 atomic percent) modulations of Pb surface composition has been determined. Electrocatalytic reactions of relevance to fuel cells, carbon monoxide oxidation and formic acid oxidation, have also been examined on Pt1-x Pbx overlayers. Changes in activity with respect to surface Pb content have been assessed by a combination of electrochemical and x-ray photo emission spectroscopy (XPS) depth profiling measurements. It has been established that Pb is concentrated towards the near surface of these films, and that electrochemical treatment results in the dissolution of Pb and a concomitant loss of activity. The study extends knowledge by developing a new methodology to form Pt1-xPbx alloys and by systematically studying the effect of film thickness, surface composition and electrochemical treatment on adsorption and reactivity. However, the described methods and analysis could be applied to other bimetallic systems on the nanoscale
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:683907 |
| Date | January 2015 |
| Creators | Mercer, Michael Peter |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
Page generated in 0.002 seconds