Carbon is a ubiquitous element on earth, with 6 protons, electrons, and neutrons. It is tetravalent, with a range of hybridised bonding configurations, it can form materials with superlative and varied properties. These materials range from soft and conductive sp2 bonded allotropes like graphite and carbon nanotubes, to the insulating and hardest natural material on earth, sp3 bonded diamond. The first half of this thesis presents an investigation of the properties of a promising novel carbon nanomaterial, CNS, and its application to ultracapacitor electrodes for the first time. High surface area conductive carbon nanomaterials are capable of high power and long service life energy storage in ultracapacitors, a critical green technology. The development of this technology to increase energy density to compete with chemical batteries could accelerate a transition to sustainable energy infrastructure. CNS/polymer composite electrodes were assembled using a conductive diamond collector substrate, then characterised using electrochemical techniques to measure capacitative performance. The second half of this thesis concerns the development of amperometric dissolved oxygen sensors for extreme environments. Diamonds controllable electronic properties, corrosion resistance, wide electrochemical window, and resistance to fouling make it an ideal potential material for this application. Conductive boron doped diamond electrodes were functionalised with platinum nanoparticles. Aphotolithographyprocesswasusedtoproduceanarrayofmicrodiscelectrodesusingan SU-8 photoresist mask, for the first time in this application and material system. A custom electrochemical cell was designed and built to provide a new electrochemical capability to the lab at approximately 1/10th the cost of a commercial solution; the project will be made open source. The microdisc array was tested as an oxygen sensor using the cell; calibration standards were produced by controlling the flow of oxygen and nitrogen gasses through the cell. A control measurement was provided for by a calibrated oxygen gauge incorporated into the test cell
