Bacterial cellulose as a scaffold for electrode materials in electrochemical energy storage and conversion
- Autores: Wenhai Wang
- Directores de la Tesis: Dino Tonti (dir. tes.)
- Lectura: En la Universitat Autònoma de Barcelona ( España ) en 2022
- Idioma: inglés
- Tribunal Calificador de la Tesis: Eduardo Enciso Rodríguez (presid.), Stefanos Chaitoglou (secret.), Bernd Wicklein (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencia de Materiales por la Universidad Autónoma de Barcelona
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Bacterial cellulose (BC) is a biopolymer with various outstanding properties, such as pure composition, nanosized fibers, and high water retention. Based on these properties, BC was employed in this thesis as a scaffold to process electrodes for electrochemical energy storage and conversion (EESC) applications. In general, the nanofibers allow high specific area and open porosity for optimal transport, but their insulating character prevents direct use. To obtain suitable conductivity, carbonization and metal coating were studied, respectively. Then, their electrochemical performance in EESC applications was investigated. The following main aspects of this work can be highlighted, each dedicated to the development of a novel material: 1. Carbons with appropriate porosity are ideal cathodes of Li-O2 battery. Mesoporous carbons were obtained from carbonization of alcohol-treated BC. Soaking purified, wet BC in alcohol removes the initial water and prevents its collapse when drying. Compared with conventional methods, such as freeze-drying, or using templating agents, the proposed route to fabricate porous carbons is more convenient. In contrast with carbon derived from untreated BC that shows compact structure, carbon derived from 1-butanol treated BC presents to be porous, exhibits high capacity (5.6 mA h cm-2) and has good cycle life.
2. Manganese dioxide (MnO2) is an interesting cathode for Zn ion battery (ZIB), while it suffers from poor conductivity, greatly impairing the electrochemical performance. N-doped carbon nanosheets derived from urea-soaked BC were utilized to improve the conductivity of MnO2. BC possesses high water-absorbing capacity and it can absorb urea to obtain the nitrogen source. N-doped carbon nanosheet/MnO2 as the cathode of ZIB shows a high capacity and long cycle life (114 mAh g-1 at 2 A g-1 after 1800 cycles).
3. Low-cost electrodes for hydrogen evolution reaction (HER) in neutral electrolytes usually show poor performance. A free-standing Ni-P/BC electrode was obtained, showing high conductivity and high HER activity at the same time. Ni-P was in situ grown on BC by electroless deposition (ELD). The thin fibers of BC are beneficial to form small Ni-P particles, providing more catalytic sites. The obtained Ni-P/BC presents a small overpotential (141 mV dec-1) and good stability in 1 M potassium phosphate-buffered saline (pH=7) electrolyte.
