Full text
| |
| Author(s): |
Vinicius Del Colle
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | São Carlos. |
| Institution: | Universidade de São Paulo (USP). Instituto de Química de São Carlos (IQSC/BT) |
| Defense date: | 2006-10-26 |
| Examining board members: |
Germano Tremiliosi Filho;
Antonio Carlos Dias Angelo;
Paulo Olivi;
Giuseppe Abíola Câmara da Silva;
Teresa Benita Iwasita de Vielstich
|
| Advisor: | Germano Tremiliosi Filho |
| Abstract | |
This work reports the electrochemical and spectroscopic results of ethanol, acetaldehyde and acetic acid electrooxidation onto low index platinum single crystal surface (110) modified by osmium (Os). The Pt(110) electrode was modified by spontaneous and electroless Os deposition and checked electrochemically in order to obtain low, intermediate and high Os coverages on Pt(110). The ethanol electrooxidation on Pt(110) and Pt(110)/Os, which used voltammetric cycle and cronoamperometric techniques, showed higher currents toward this reaction on Os coverage between 0.51-0.61 ML. The FTIR results reveal that ethanol oxidation has different pathways according to Os coverage. The step one suggests that the cleavage of ethanol CC bond occurs with major intensity forming species such as COlinaer and CHx when the reached coverage is 0.36 0.80 ML and further producing CO2. At the step two, acetaldehyde formation is improved above 0.4 V on Pt(110) and Pt(110)/Os, and at low potentials on HOs > 0.80 ML, this molecule can oxidize and form CO and acetic acid. Studies on acetaldehyde showed that the catalytic activity is slightly higher on electrodes modified by Os. The step three presents the CO2 production through acetic acid onto electrodes with high Os coverage. During the oxidation of this molecule, COlinear is produced in large quantities at low potentials; there is formation of acetic acid and thereupon CO2. Onto Os thick electrode, CO2 production occurs without the presence of COlinear, indicating the possibility of acetic acid oxidation directly to CO2. The acetic acid oxidation on various electrodes modified by Os is possible with cleavage of CC bond to form CO2, though this process is less significant than others organic molecules studied. Since the amount of CO2 produced can arise through the acetate group once this specie is adsorbed onto the electrode surface. (AU) | |
| FAPESP's process: | 02/11007-1 - Electrochemical and spectroscopic study of alloys formed on monocrystalline platinum by surface modification in levels of submonolayers of Ru, Os and Ru/Os: application in the electro-oxidation of ethanol |
| Grantee: | Vinicius Del Colle |
| Support Opportunities: | Scholarships in Brazil - Doctorate |