Novel cross-linked partially fluorinated and non-fluorinated polyaromatic PBI-containing blend membranes for SO2 electrolysis

PBI-Blended Membrane Evaluated in High Temperature SO2Electrolyzer

“…Membrane material (01-CEM) was prepared as discussed in earlier work (22).The characterization entailed an 80 wt% H2SO4 treatment (ex-situ) at 80 and 120 °C for 5 days, where after the membrane material was characterized using weight and thickness changes, ion-exchange capacity (IEC) and Thermo Gravimetric Analysis (TGA) measurements before and after treatment. This was completed in reference to earlier work (22,24).…”

“…For SO2 electrolysis the membrane material (01-CEM) was pretreated as discussed previously (22). Subsequently, the membrane electrode assembly (MEA) was prepared by hot pressing (Carver, Model #3912) the membrane (60 µm) between two pieces of a commercial GDE (0.5 mg Pt C/cm 2 catalyst loading -Fuel Cell Etc.)…”

“…General procedure: The cell and H2O heater were switched on, allowing 1 hour reaching 120 °C before starting with a break-in of the membrane. A constant current density of 0.1 A/cm 2 was held for 10 minutes and thereafter incrementally increased by 0.1 A/cm 2 until the voltage limit of 1.1 V had been reached (22). Initially a flow rate of 150 mL/min SO2 was supplied with 5 mL/min H2O which was increased with increasing current density to maintain a constant voltage on the system.…”

“…Polybenzimidazole (PBI) type membranes have been considered most promising due to their known thermal stability and good ionic conductivity with limited water supply (19)(20)(21). One example entails a study in our group on a cross-linked partially fluorinated polyaromatic PBI-blended membrane (01-CEM), which proved promising at operating temperatures of both 80 and 95 °C within the SO2 electrolyzer (22). It has become evident that these type membranes possess the ability to conduct protons from the acid produced during electrolysis which insures the continuous doping of the membrane during operation and an improved performance (10, 23).…”

“…In this study, in comparison to earlier characterization studies, the membrane 01-CEM will be evaluated ex-situ in an 80 wt% H2SO4 environment at 120 °C to determine its stability and hence suitability for higher temperature SO2 electrolysis. For operation at elevated temperatures, the previously used SO2-electrolyzer setup was adapted to maintain operations at 120 °C, while supplying steam (120 °C) and SO2 directly to the anode (22). Polarization curves were recorded and the voltage monitored at both a lower (0.3 A/cm 2 ) and higher (0.6 A/cm 2 ) current density limit for 360 minutes.…”