Characterisation of electrode materials for electrochemical reactors

Three different electrode materials for use in electrochemical reactors were examined in this thesis. Reticulated Vitreous Carbon (RVC), Pt/C proton exchange membrane fuel cell electrodes and nanotubular TiO2 represent a wide variety of established and novel electrode materials. The physical structure of RVC, an open pore foam glassy carbon, was characterised with the help of scanning electron microscopy (SEM) and micro X-ray computer tomography (μCT). A comparison of the results generated by these two techniques was attempted. Electrochemical methods were used to determine the specific electrochemical surface area (SECSA), for high and low Pt loaded electrode samples (4.66 and 0.39 mg Pt cm-2, respectively). Cyclic voltammetry was used to provide active electrode area data based on hydrogen adsorption, underpotential deposition (UPD) of silver and carbon monoxide stripping as routes to the determination of electrode area. The results show that electrochemical methods are useful in providing accurate area measurements for modern, multi-layered fuel cell electrodes. The deposition of previous metals into nanotubular titanates was examined using scanning electron microscopy and transmission electron microscopy imaging. Data for Pt, Pd, Au and Ru deposition is presented with a comparison of three deposition methods. The long-term stability of titanate nanotubes in acidic, basic, and pure water suspensions was studied. It was demonstrated that in basic solution nanotubes are thermodynamically stable and in water suspension nanotubes are kinetically stable. In dilute sulphuric acid (0.1 mol dm-3 H2SO4) at room temperature, the nanotubes are neither thermodynamically nor kinetically stable, slowly transforming to rutile nanoparticles.