Nanostructured Bacterial Cellulose-Poly(4-styrene sulfonic acid) Composite Membranes with High Storage Modulus and Protonic Conductivity

abstract

The present study reports the development of a new generation of bio-based nanocomposite proton exchange membranes based on bacterial cellulose (BC) and poly(4-styrene sulfonic acid) (PSSA), produced by in situ free radical polymerization of sodium 4-styrenesulfonate using poly(ethylene glycol) diacrylate (PEGDA) as cross-linker, followed by conversion of the ensuing polymer into the acidic form. The BC nanofibrilar network endows the composite membranes with excellent mechanical properties at least up to 140 degrees C, a temperature where either pure PSSA or Nafion are soft, as shown by dynamic mechanical analysis. The large concentration of sulfonic acid groups in PSSA is responsible for the high ionic exchange capacity of the composite membranes, reaching 2.25 mmol g(-1) for a composite with 83 wt % PSSA/PEGDA. The through-plane protonic conductivity of the best membrane is in excess of 0.1 S cm(-1) at 94 degrees C and 98% relative humidity (RH), decreasing to 0.042 S cm(-1) at 60% RH. These values are comparable or even higher than those of ionomers such as Nafion or polyelectrolytes such as PSSA. This combination of electric and viscoelastic properties with low cost underlines the potential of these nanocomposites as a bio-based alternative to other polymer membranes for application in fuel cells, redox flow batteries, or other devices requiring functional proton conducting elements, such as sensors and actuators.

keywords

FUEL-CELL APPLICATIONS; POLYMER ELECTROLYTE; TRANSPORT-PROPERTIES; MICROBIAL CELLULOSE; ACID MEMBRANES; X-RAY; TEMPERATURE; POLYSTYRENE; DIFFRACTION; HYDROLYSIS

subject category

Science & Technology - Other Topics; Materials Science

authors

Gadim, TDO; Figueiredo, AGPR; Rosero-Navarro, NC; Vilela, C; Gamelas, JAF; Barros-Timmons, A; Neto, CP; Silvestre, AJD; Freire, CSR; Figueiredo, FML

Groups

G1 - Porous Materials and Nanosystems
G3 - Electrochemical Materials, Interfaces and Coatings
G4 - Renewable Materials and Circular Economy

Projects

Bacterial Cellulose Membranes for Proton Exchange Fuel Cells (EXPL/CTM-ENE/0548/2012)

Acid-functionalised hybrid membranes for intermediate temperature proton exchange membrane fuel cells (HyPEM) (PTDC/CTM-CER/109843/2009)

Centre for Research in Ceramics and Composite Materials - CICECO (LA0011: 2013-2014) (PEst-C/CTM/LA0011/2013)

Laboratório de Análises Térmicas (REEQ/515/CTM/2005)

acknowledgements

Work funded by the Portuguese Foundation for Science and Technology (FCT) through projects CelFuelCel - FCOMP-01-0124-FEDER-027691 (Ref. FCT EXPL/CTM-ENE/0548/2012), HyPEM - FCOMP-01-0124-FEDER-014563 (Ref. PTDC/CTM-CER/109843/2009) and CICECO - FCOMP-01-0124-FEDER-037271 (Ref. FCT PEst-C/CTM/LA0011/2013). Andrea G. P. R. Figueiredo and Carla Vilela thank FCT for the post-doctoral grants (SFRH/BPD/63219/2009 and SFRH/BPD/84168/2012). Carmen S. R. Freire acknowledges FCT/MCTES (Portugal) for a contract under Investigador FCT 2012, and Filipe Figueiredo for the Investigador FCT 2013 contract number IF/01174/2013. Thermal Analysis Laboratory was funded by FEDER Funds through Programa Operacional Factores de Competitividade COMPETE and by National Funds through FCT under the project REEQ/515/CTM/2005.