Improved performance of microbial fuel cells using sulfonated polyether ether ketone (SPEEK) TiO2–SO3H nanocomposite membrane

Abstract

The microbial fuel cell (MFC) is a new technology for simultaneous electricity generation and wastewater treatment. An enhancement in the proton exchange membrane (PEM) of MFCs is essential for their scale-up and commercialization. In this work we demonstrate, for the first time, the use of sulfonated inorganic fillers in polyelectrolyte nanocomposite membranes as an effective approach to improve the MFC performance. A new nanocomposite membrane based on a sulfonated polyether ether ketone (SPEEK) hybrid with sulfonated TiO₂ particles (TiO₂–SO₃H) was fabricated and evaluated in a microbial fuel cell. To authenticate the advantages of a SPEEK–TiO₂–SO₃H composite membrane, the IEC value, water uptake, proton conductivity, oxygen crossover, microbial fuel cell (MFC) performance and internal resistance were compared with a SPEEK–TiO₂ membrane and a SPEEK membrane. The SPEEK–TiO₂–SO₃H membrane (7.5 wt%) exhibited the highest peak power density of 1202.5 mW m⁻² compared with the power densities of 766 mW m⁻² and 676 mW m⁻² obtained for the SPEEK–TiO₂ membrane and the SPEEK membrane, respectively, in the single chamber microbial fuel cell (SCMFC) membrane. The electrochemical behaviour of the membrane was improved by adding different amounts of TiO₂–SO₃H into the membrane to enhance the proton conductivity and also to reduce biofouling. Higher power was achieved with the 7.5 wt% TiO₂–SO₃H incorporated SPEEK–TiO₂–SO₃H membrane. In comparison to previously reported work with Nafion 117 (300 mW m⁻²) in MFCs, the composite membrane delivers a 4-fold higher power density. The oxygen mass transfer coefficient (K_O) of the nanocomposite membranes decreased with incorporation of the sulfonated titanate in the nanocomposite membranes. The internal resistance for the SPEEK–TiO₂–SO₃H and SPEEK membranes were estimated to be 37 Ω and 74 Ω, respectively. The improved performance was attributed to the introduction of TiO₂–SO₃H particles, whose high proton conductivity and good water adsorbing/retaining function could facilitate effective proton transfer in the membrane. To the best of our knowledge, this new hybrid SPEEK–inorganic sulfonated nanocomposite is fabricated for the first time and applied to MFCs.