Redox-free reverse electrodialysis using capacitive electrodes for energy generation

• Autor(a) principal: Amaral, Eliana Patrícia da Conceição
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/113080
• topic: Salinity gradient power; reverse electrodialysis; electrode system; capacitive electrodes; capacitance; power density; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Química

The increasing demand for fossil fuels and arising concerns about their impact on the environment creates the need to develop sustainable technologies that make use of natural sources to generate energy, like reverse electrodialysis (RED) that makes use of salinity gradient power (SGP). In this thesis, a possible optimization of the electrode system applied in RED is introduced, including the preparation and study of capacitive slurry electrodes to replace redox electrodes commonly used. Three slurries were prepared with different carbon concentrations (15 %, 20 %, and 22.4 %) in 1 M aqueous solution of NaCl. When pumped through a single membrane cell, it was possible to conclude about their resistance, and without being pumped their capacitance was obtained. The 22.4 %cwt slurry allowed the lowest electro-resistance at different conditions, while the 20 %cwt slurry achieved the highest specific capacitance of 34.52 F/g after 100 cycles. Pumping the slurries through the RED cell at 300 mL/min, while using the 20 %cwt slurry resulted in the best electrochemical performance, since the best trade-off between power density 1.56 W/m2, and energy efficiency 15.6 %, was achieved. The results obtained demonstrate that it is possible to efficiently operate a redox-free RED cell. Further investigation on slurry preparation, charge percolation mechanism, and cell design, should be done aiming for complete validation of capacitive slurries application in RED, thus promoting its industrial application.