Membranas à base de celulose bacteriana para pilhas de combustível
authors Tiago Daniel Oliveira Gadim
supervisors Filipe Miguel H Lebre R Figueiredo
thesis type Mestrado
abstract This study aims to develop a new generation of renewable polymeric electrolytes based on bacterial cellulose with acid functionalization, for application in fuel cells. The selected bacterial cellulose is produced by bacteria in laboratory Gluconacetobacter sacchari, within which poly (4-styrene sulfonic acid) is polymerized in its acid form, thus giving a high proton conducting membrane. The polymer is stabilized by crosslinking inside the cellulose nanostructure. The physicochemical properties of this new generation membranes were evaluated by various techniques, including thermo-gravimetric analysis, X-ray diffraction, infrared spectroscopy, and also by measurements of the ion exchange capacity and water absorption capacity. The microstructure was analyzed by scanning electron microscopy. Finally, the proton conductivity of the electrolyte was evaluated by electrochemical impedance spectroscopy at different conditions of temperature and relative humidity. The results show that these membranes are thermally stable up to 165 °C, maintaining a concentration of acid ranging from 1.8 to 2.3 mmol [H+].g-1 depending on the amount of crosslinking agent incorporated (between 10 and 40% of the mass of monomer used). These values are substantially higher than those cited for the commercial polymers Nafion® (1 mmol [H+].g-1) and Aquivion ® (1.2 mmol [H+].g-1). The proton conductivity at 94 °C ranges between 1.410-3 at a relative humidity of 30% and 1.110-1 at 98%, values comparable or even higher than those obtained with the mentioned commercial references, being a clear indication of the potential of the membranes developed here for use as electrolytes in fuel cells.
year published 2013