| Samenvatting: | This thesis reports experimental work with two main aims: the first is the detection and characterisation of single graphene and polymer nanoparticles with an emphasis on their electrocatalysis; the second is to develop a more comprehensive understanding of nanoscale interfacial reactions kinetically and mechanistically.
Understanding adsorption processes underpins applications in advanced catalysts and ultra-sensitive sensors. The adsorption of catechol on graphene nanoplatelets (GNPs) is first investigated and quantified electrochemically and spectroscopically. Two electrochemical techniques are applied, notably cyclic voltammetry of ensembles and nano-impacts of single particles to study catechol adsorbed on GNPs. Generic methodologies are developed for the study of surface adsorption on GNPs and a molecular phase transition is seen. This is further applied to first investigate the adsorption of phenyl hydroquinone, where a more complicated flat-edge-end adsorption manner is seen with two phase transitions, and second the role of adsorption in electrocatalysis, where a lower overpotential of dopamine oxidation at a single GNP as compared to glassy carbon is observed. This approach is then further protocolised and proposed as an accurate surface area characterisation technique for both graphene and graphene oxide materials with high surface areas and complex internal structures.
In a second set of studies, the electrocatalytic behaviour of Nafion nanoparticles, a cation exchange polymer widely applied in fuel cells, is investigated. The catalytic oxygen reduction by ensembles and single Nafion particles doped with methyl viologen is investigated. The results reveal the relative kinetics of the ensembles and single particles and a generic novel approach to catalysis is proposed applying homogeneous electron mediators heterogeneously by immobilising the former in particles used to modify electrode interfaces. ‘Fake’ catalytic features of undoped Nafion particles are then fully explored, revealing the complexity in the voltammetry of electrodes modified by ensembles of nanoparticles.
The ion transport and charge transfer within Nafion films and particles are then characterised and compared. The contrasting behaviour shows the transport in the particles is significantly faster than in films of similar thickness. This leads to the investigation and development of a novel type of reference electrode based on immobilisation of both components of redox couples within Nafion films. The proposed Nafion film reference electrodes demonstrate superior stability with respect to life-time and multiple cycling.
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