Electrochemical modification of electrodes with metal nanoparticles

In this thesis, the use of boron-doped diamond and Au (111) as electrode materials with special physical and electrochemical properties was investigated in a number of electrochemical and photoelectrochemical applications. The surface chemistry of the aforementioned electrodes was modified utilising such strategies as electrochemical and hydrogen plasma treatment as well as coating treatment. Extended attention was paid to metal alloys and/or core-shell metal nanostructures. The modified surface of the diamond and Au (111) electrodes was studied using a wide spectrum of techniques. The electrochemical activity of these materials was investigated in order firstly to expand the knowledge of diamond electrochemistry and secondly to establish an understanding of how the electrochemical modification with metal nanoparticles of core-shell structure impacts their electrochemical performance.
In the first study, the nanostructuring strategies of boron-doped diamond surface with Pt-Cu and Cu nanoparticles were developed for two different applications. Pt-Cu modified diamond electrode was explored for methanol oxidation, which is of relevance to the direct methanol fuel cell. The motivation of this work was to understand how these core-shell structures on diamond compare to similar structures on other forms of carbon. The second objective was the development of a simple Cu-modified diamond electrode that can be used as a sensitive non-enzymatic amperometric glucose sensor.
The second work involves two fundamental electrochemical studies. The first one reports the overpotential growth of Pd metallic nanoparticles on Au (111). For the first time, this study contradicts the classical theories for electrochemical nucleation and growth which proceed only by the fresh reduction of ions. It demonstrates that electrochemical nucleation and growth at the early stages is overpotential dependent and in fact proceed also by the aggregation of small clusters through surface diffusion when deposited at relatively higher overpotentials. The second study reports the influence of two dissimilar surface terminations of diamond: hydrophobic H-terminated and hydrophilic O-terminated. The latter work provides a useful insight of how the chemical terminations of diamond with electrodeposited Pd nanoparticles impact their overall electrochemical performance.
The third project extends the discussion on the study of the diamond electrodes modified with core-shell metal nanoparticles along with two different chemical terminations. In this work, a H-terminated diamond electrode was modified with Pd-Sn nanoparticles and an O-terminated diamond electrode was electrochemically modified with Pd-Ni nanoparticles. The enhanced electrodes’ performance with regard to the ethanol electrooxidation reaction was demonstrated.
The fourth study reports on the development of a novel photocatalyst comprised of Cu2O nanoparticles coated with Ni supported on boron-doped diamond electrodes, of relevance to water splitting and CO2 reduction reactions. Similarly to the previous works, an insight is provided on how a co-catalyst contributes not only to the protection of semiconductor materials from self-photo-corrosion issues in aqueous solutions, but also to improved stability and enhanced photoelectrochemical performance.
Overall, the electrochemical and photoelectrochemical performance of the boron-doped diamond and Au (111) electrodes for sustainable energy applications is reported in this thesis.

Advisor: Foord, J
Compton, R