Evaluation of covalently and ionically cross-linked PBI-excess blends for application in SO<inf>2</inf> electrolysis
International Journal of Hydrogen Energy
DST HySA Infrastructure Centre of Competence, Faculty of Engineering, North-West University, Potchefstroom, South Africa; Focus Area: Chemical Resource Beneficiation, Faculty of Natural Science, North-West University, Potchefstroom, South Africa; Institute of Chemical Process Engineering, University of Stuttgart, Stuttgart, Germany
Abstract Proton exchange membranes (PEM) containing various combinations of PPOBr (pol(2,6-dimethylbromide-1,4-phenylene oxide, covalently cross-linked) or PWN (poly(tetrafluorostyrene-4-phosphonic acid), ionically cross-linked) were evaluated for their suitability in an SO<inf>2</inf> electrolyser environment. Since H<inf>2</inf>SO<inf>4</inf> is produced during the oxidation of SO<inf>2</inf> in the presence of water, the membranes used in the electrolyser must be both chemically and electrochemically stable. Acid stability tests showed that the blend membranes are stable in 80 wt % acidic media at 80°C for 120 h. The electrochemical characterisation included polarisation curves, voltage stepping and long term operation. Using polarisation curves two blend combinations were selected for the voltage stepping. Both types of blend membranes showed high stability up to 110 cycles while the F<inf>6</inf>PBI/PPOBr blend membrane had comparable (to N115®) long term operating voltage, while the F<inf>6</inf>PBI/PWN blend membrane showed improved voltage, attaining 0.781 V compared to the 0.812 V obtained when using N115 at 0.1 A cm-2. © 2015 Hydrogen Energy Publications, LLC.
Blending; Electrolysis; Membranes; Polarization; Covalently cross-linked; Ionically cross-linked; Long term operation; Operating voltage; Polarisation curves; Presence of water; Proton exchange membranes; Proton-exchange membrane; Proton exchange membrane fuel cells (PEMFC)
KE 673/11-1, DFG, Department of Science and Technology, Republic of South Africa; DST, Department of Science and Technology, Republic of South Africa