Please use this identifier to cite or link to this item: http://hdl.handle.net/2381/30045
Title: Mechanistic studies of bubble evolution
Authors: Gilbert, Sarah Lucy.
Award date: 2000
Presented at: University of Leicester
Abstract: This thesis describes a study of the bubble evolution mechanisms of four systems; H2/HC1O4Au, H2/HCIO4/Pt, Cl2/NaCl/RTO and Cl2/NaCl/Ti as a function of current density, surface composition (RTO) and morphology. Three experimental techniques have been used, fast frame video (FFV), electrochemical quartz crystal microbalance (EQCM) and the pressure release bubble nucleation technique (PRBN). The three complementary techniques were utilised to provide a comprehensive study of bubble behaviour. The FFV was used to study individual bubbles, the EQCM to measure the detachment rate integrated over the nucleating surface area, and the PRBN technique was used to measure the bubble nucleation rate integrated over space and time.;In the current density range 3-44 mA cm-2 nucleation of individual hydrogen bubbles was found to be rapid at vertical gold and platinum electrodes. For both electrode materials, the detachment radius decreased as a function of current density, but the average bubble size on detachment was approximately 50% smaller on the platinum electrode. The detachment rate and number of active nucleation sites both increased as a function of current density, and the dominant detachment mechanism was coalescence between closely paired neighbouring bubbles. EQCM analysis of the overall detachment rates at the electrodes confirmed the visual observations; novel Fast Fourier Transform analysis of the frequency response from the gold electrode showed that the detachment frequency increased with current density, but there was little change in the volume of gas resident on the electrode. On the platinum electrode small bubbles detached rapidly and were characterised by small fluctuations in the EQCM resonant frequency response.;Using the FFV technique, nucleation was found to be the rate-limiting step for chlorine bubble evolution at an RTO electrode in the current density range 18-56 mA cm-2.
Links: http://hdl.handle.net/2381/30045
Type: Thesis
Level: Doctoral
Qualification: PhD
Rights: Copyright © the author. All rights reserved.
Appears in Collections:Theses, Dept. of Chemistry
Leicester Theses

Files in This Item:
File Description SizeFormat 
U129393.pdf17.95 MBAdobe PDFView/Open


Items in LRA are protected by copyright, with all rights reserved, unless otherwise indicated.