Electrochemical studies of the applications of novel carbon-based materials

Thesis

In this thesis, the electrochemical behaviour of novel carbon-based materials is investigated in respect of supercapacitor applications. The first chapter explains the concern over climate change, potential for renewable energy, and significance of energy storage. Much emphasis is placed on the mechanism (e.g., electric double-layer capacitance and pseudocapacitance) and electrode materials (e.g., carbon and metal oxides) for supercapacitors. The second chapter introduces the basic principles of electrochemistry as well as electrochemical methods and characterisation techniques used in this work.

In the first project, the electrochemical oxidation of Mn2+ ions to manganese dioxides is carried out on boron-doped diamond electrodes via cyclic voltammetry. A composite electrode is fabricated by potentiostatic deposition of MnO2 on boron doped diamond, and its electrochemical performance is then measured. The motivation of this work is to illustrate that MnO2, a cheap material with pseudocapacitance, can improve the overall performance of carbon-based composite electrodes for supercapacitor applications.

The second work exploits carbonised seaweed paper, which is a biomass-derived carbon material. MnO2 is deposited on seaweed paper-derived carbon potentiostatically to form a composite for electrochemical measurements and characterisation. Seaweed paper after carbonisation benefits from electric double-layer capacitance, whilst incorporation of the pseudocapacitive MnO2 further extends the potential window and specific capacitance of the hybrid electrode materials as supercapacitors.

The third study investigates nickel treated filter paper for supercapacitor applications. Carbon derived from filter paper is produced at low carbonisation temperature with in situ nickel treatment. Its electrochemical behaviour is researched by removing or keeping the nickel particles. Particularly, faradaic battery-type characteristics is observed electrochemically on account of conversion of nickel into electroactive nickel hydroxide in aqueous alkaline media. Nickel treated filter paper acts as a promising supercapacitor material which is economical and environmentally friendly.

The fourth research involves a number of carbon materials derived from biomass and biowaste with bimetallic cobalt/manganese metal-organic frameworks (MOFs) modification. The composite materials take advantage of the electric double-layer capacitance from the biomass-derived carbon and faradaic battery-type contributions from the pyrolysed MOFs in alkaline electrolytes. In particular, the bulk carbon-based electrode material bears favourable comparison with its powdery counterpart in supercapacitor applications.

Overall, this thesis reports the electrochemical studies of novel carbon-based materials for supercapacitor applications in regard to renewable energy and energy storage.

Authors: Wang, Y

• DOI: 10.5287/ora-pvne26a4v
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: carbon-based materials; energy storage; supercapacitor
• Subjects: electrochemisttry