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Electrochemical and electrocatalytic properties of iron(II) and cobalt(II) phthalocyanine complexes integrated with multi-walled carbon nanotubes
Thesis (PhD)--University of Pretoria, 2011.
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University of Pretoria
2013
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| _version_ | 1867613636190535680 |
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| access_status_str | Open Access |
| author2 | Ozoemena, Kenneth I. |
| author_browse | Ozoemena, Kenneth I. |
| author_facet | Ozoemena, Kenneth I. |
| collection | Thesis |
| dc_rights_str_mv | © 2010 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Thesis (PhD)--University of Pretoria, 2011. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/28834 |
| institution | University of Pretoria (South Africa) |
| last_indexed | 2026-06-10T12:39:17.781Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2013 |
| publishDateRange | 2013 |
| publishDateSort | 2013 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/28834 Electrochemical and electrocatalytic properties of iron(II) and cobalt(II) phthalocyanine complexes integrated with multi-walled carbon nanotubes Ozoemena, Kenneth I. almanto1@yahoo.com Mamuru, Solomon Almanto Multi-walled carbon nanotubes Electrocatalytic properties Electrochemical properties UCTD Thesis (PhD)--University of Pretoria, 2011. For the first time, new metallophthalocyanine (MPc) complexes: (i) nanostructured MPc (nanoMPc, where M = iron or cobalt); (ii) octabutylsulphonylphthalocyanine (MOBSPc, where M = iron or cobalt); and (iii) iron (II) tetrakis(diaquaplatinum)octacarboxyphthalocyanine (PtFeOCPc) were synthesized and characterized using advanced microscopic and spectroscopic techniques such as MS, AFM, HRTEM, FESEM, and EDX. Electrochemical techniques such as cyclic voltammetry, square wave voltammetry, chronoamperometry, rotating disk electrode, and electrochemical impedance spectroscopy, were used to explore the redox chemistry, heterogeneous electron transfer kinetics (HET), and electrocatalytic properties of these MPc complexes towards oxygen reduction reaction (ORR), oxidation of formic acid, thiocyanate and nitrite on a edge plane pyrolytic graphite electrode (EPPGE) platform pre-modified with or without acid functionalized multi-walled carbon nanotubes (MWCNTs). The MWCNT-MPc platforms exhibit enhanced electrochemical response in terms of (i) HET towards an outer-sphere redox probe ([Fe(CN)6]3-/[Fe(CN) 6]4-), and (ii) catalytic activities towards the investigated analytes. The MWCNTnanoMPc electrode exhibits faster HET constant (kapp ≈ 30 – 56 x 10-2 cms-1 compared to their bulk MPc counterparts (≈ 4 – 25 x 10-2 cms-1). The MWCNT-nanoMPc exhibited enhanced electrocatalytic properties (in terms of sensitivity and limit of detection, LoD) towards the detection of thiocyanate and nitrite in aqueous solutions. ORR was a 4- electron process with very low onset potential (-5 mV vs. Ag|AgCl saturated KCl). HET and ORR at MOBSPc complexes supported on MWCNTs showed that the MWCNT–MOBSPc exhibited larger Faradaic current responses than the electrodes without MWCNTs. The rate constant at the MWCNT-MOBSPc electrodes (kapp ≈ (22 – 37) x 10-2 cms-1) is about a magnitude higher than the electrodes without MWCNT (kapp ≈ (0.2 – 93) x 10-3 cms-1). The MWCNT–FeOBSPc electrode gave the best ORR activity involving a direct 4-electron mechanism with low onset potential (0.0 mV vs. Ag|AgCl saturated KCl). The onset potential is comparable and even much lower than recent reports. The HET and electrocatalytic properties of PtFeOCPc supported on a MWCNT platform (MWCNT-PtFeOCPc) gave enhanced electrochemical response in terms of (i) HET (kapp ≈ 78 x 10-2 cms-1), (ii) catalytic rate constant (kcat ≈ 41 cm3mol-1s-1) and (iii) tolerance towards CO poisoning during formic acid oxidation. The ORR activity is a direct 4-electron transfer process at a rate constant of 2.78 x 10-2 cms-1; with a very low onset potential approximately 0.0 mV vs. Ag|AgCl saturated KCl. The electrooxidation of formic acid at MWCNT-PtFeOCPc follows the preferred ‘direct pathway’. This work clearly proves that the MWCNT-MPcs hybrid exhibit enhanced electrochemical and electrocatalytic activities towards the selected analytes compared to the MPcs alone. Considering the ease of fabrication of these electrodes (drop-dry method), these nanocomposite materials are promising platform for potential application in sensing and cataly. Chemistry unrestricted 2013-09-07T14:20:11Z 2011-10-24 2013-09-07T14:20:11Z 2011-09-09 2011-10-24 2011-10-18 Thesis Mamuru, SA 2010, Electrochemical and electrocatalytic properties of iron(II) and cobalt(II) phthalocyanine complexes integrated with multi-walled carbon nanotubes, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://hdl.handle.net/2263/28834 > D11/9/155/ag http://hdl.handle.net/2263/28834 http://upetd.up.ac.za/thesis/available/etd-10182011-200312/ © 2010 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf application/pdf application/pdf application/pdf application/pdf application/pdf application/pdf University of Pretoria |
| spellingShingle | Multi-walled carbon nanotubes Electrocatalytic properties Electrochemical properties UCTD Electrochemical and electrocatalytic properties of iron(II) and cobalt(II) phthalocyanine complexes integrated with multi-walled carbon nanotubes |
| title | Electrochemical and electrocatalytic properties of iron(II) and cobalt(II) phthalocyanine complexes integrated with multi-walled carbon nanotubes |
| title_full | Electrochemical and electrocatalytic properties of iron(II) and cobalt(II) phthalocyanine complexes integrated with multi-walled carbon nanotubes |
| title_fullStr | Electrochemical and electrocatalytic properties of iron(II) and cobalt(II) phthalocyanine complexes integrated with multi-walled carbon nanotubes |
| title_full_unstemmed | Electrochemical and electrocatalytic properties of iron(II) and cobalt(II) phthalocyanine complexes integrated with multi-walled carbon nanotubes |
| title_short | Electrochemical and electrocatalytic properties of iron(II) and cobalt(II) phthalocyanine complexes integrated with multi-walled carbon nanotubes |
| title_sort | electrochemical and electrocatalytic properties of iron ii and cobalt ii phthalocyanine complexes integrated with multi walled carbon nanotubes |
| topic | Multi-walled carbon nanotubes Electrocatalytic properties Electrochemical properties UCTD |
| url | http://hdl.handle.net/2263/28834 http://upetd.up.ac.za/thesis/available/etd-10182011-200312/ |