| Summary: | Dissertation (Ph.D.)--Stellenbosch University, 2002. === ENGLISH ABSTRACT: The deposition of platinum catalyst on cation-exchange membranes was achieved by
a counter diffusion deposition method known as the Takenaka- Torikai method. The
morphology of the platinum catalyst on the membranes were controlled by varying
the conditions of the platinum deposition process, such as, temperature, type of
reducing agent and concentration of the platinic acid solution. The effect of the
sonication of platinic acid solution and the pre-treatment of membranes on the
morphology of a platinum catalyst was also investigated.
Platinum loading on cation-exchange membranes was determined by UV
spectrophotometric and gravimetric analyses. Suitable conditions for the quantitative
determination of the platinum loading on membranes by UV spectrophotometric
analysis was established through the development of a protocol.
Membranes were characterised using different techniques such as, Atomic
Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Infrared
spectrometry (IR), Dielectric analysis (DEA) and Brunauer Emmett Teller adsorption
(BET).
The roughness profile of a platinum catalyst embedded on a membrane was
explored by various statistical methods. The statistical analysis of various data sets for
a surface of a platinum-containing membrane was investigated using the Hurst
exponent.
The effect of surface modification of membranes on the deposition process, as
well as the morphology of the platinum catalyst, was investigated. Membranes were
modified with ethylene diamine (EDA) and cetyltrimethylammonium bromide
surfactant. Modification of membranes with cetyltrimethylammonium bromide
surfactant resulted in a unique textured platinum catalyst.
The electrochemical "switching" phenomenon was investigated for EDAmodified
membranes and EDA-modified membranes embedded with platinum
catalyst. The "switching" phenomenon was observed in i-V cyclic curves, which were
obtained by galvanodynamie measurements.
The application of electro catalytic membrane systems in the anodic oxidation
of water was investigated by electrochemical techniques such as galvanostatic and
cyclic voltammetric measurements. === AFRIKAANSE OPSOMMING: Die deponering van 'n platinum katalis op katioon-uitruil membrane is suksesvol
gedoen d.m.v. die Takenaka-Torikai metode. Die morfologie van die platinum katalis
op die membrane is gekontrolleer deur variasie van die kondisies van die platinum
deponeringsproses, bv. temperatuur, tipe reduseermiddel gebruik en konsentrasie van
die platiensuuroplossing, asook die ultrasonifikasie van die platiensuuroplossing en
voorafbehandeling van die membrane.
UV spektrofotometriese asook gravimetriese analitiese metodes is gebruik om
die platinumlading op katioon-uitruil membrane te bepaal. Geskikte kondisies vir die
kwantitatiewe bepaling van die platinumlading op membrane d.m.v. UV
spektrofotometriese analise is ontwikkel deur die skep van 'n protokol.
Membrane is gekarakteriseer d.m.v. die volgende tegnieke: Atoomkrag Mikroskopie,
Skanderingselektron Mikroskopie, Infrarooi Spektrometrie, di-elektriese analise en
Brunauer Emmett Teller adsorpsie.
Die skurtheidsprofiel van 'n platinum katalis op 'n membraan is ondersoek
deur gebruik te maak van verskeie statistiese metodes. Statistiese analises van
verskeie data stelsels van 'n platinum-bevattende membraan is ondersoek deur
gebruik te maak van die Hurst eksponent.
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Die effek van oppervlakmodifikasie op membrane sowel as die
deponeringsproses en morfologie van die platinum katalis is ondersoek deur die
modifikasie van membrane met etileen diamien (EDA) en setieltrimetielammonium
bromied as versepingsmiddel
Die elektrochemiese omswaai van EDA-gemodifiseerde membrane sowel as
gemodifiseerde platinum bevattende membrane is ondersoek d.m.v. galvanodinamiese
metings.
Die gebruik van elektro-katalitiese membraansisteme in die anodiese oksidasie
van water is ondersoek deur gebruik te maak van elektrochemiese tegnieke, bv.
galvanostatiese en sikliese voltammetriese metings.
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