Li₂SO₄-based proton-conducting membrane for H₂S–air fuel cell
By Wei, Guo-Lin; Luo, Jing-Li; Sanger, Alan R.; Chuang, Karl T. & Zhong, Li
Published in Journal of Power Sources
2005
Abstract
The composition and preparation procedure have been developed for a strong, integral Li₂SO₄-based gas-impermeable proton-conducting membrane. Incorporation of both Al₂O₃ and boric acid enhances mechanical and electrical properties. The membrane has been characterized using scanning electron microscope (SEM), energy dispersive X-ray (EDX) and electrochemical impedance spectrum (EIS) techniques. Use of the sodium salt of poly(acrylic acid) as an organic binder provided no improvement in membrane integrity, and caused severe Al₂O₃ segregation to the membrane surface. Addition of H₃BO₃ (2.5 or 5 wt.%) significantly improved membrane integrity and slightly decreased its electrical resistivity. The membrane is stable in H₂S–air fuel cell applications. There was no cross-over of H₂S through the improved membrane. Composite anodes based on metal sulfides had superior performance compared to Pt catalysts for conversion of H₂S. Membranes comprising 75–90 wt.% Li₂SO₄ and 10–25 wt.% Al₂O₃ to which 2.5–5.0 wt.% H₃BO₃ was added showed similar current–voltage and current–power performance, and had maximum current density about 40 mA cm⁻² and maximum power density about 20 mW cm⁻².