Abstract:

Composite proton-conducting membranes with Li₂SO₄ as the substrate and with Al₂O₃ as the packing were fabricated, and the electrochemical impedance spectroscopy （EIS） was employed to investigate the ion con ductivity of the composite membranes with different components （ Li₂WO₄ or Na₂SO₄ ） , dosages and thicknesses. Analytical results indicate that the doping of Li₂WO₄or Na₂SO₄ with suitable dosage may increase the ion conductivity and improve the performance of the membrane, especially the doping of Li₂WO₄. SEM photographs show that the doping of Li₂WO₄ helps to improve the integrity more greatly. Experimental results indicate that, with a suitable composition of Li₂SO₄-based composite membranes, namely 75%Li₂SO₄/Li₂WO₄ mixture （with a Li₂SO₄-to- Li₂WO₄ molar ratio of 9：1 ） ＋25% Al₂O₃ , the ion conductivities of the membrane respectively reach 0. 16,0. 38, 0. 46 and 0. 52 S/cm at 600, 650, 700 and 750 ℃ , and the suitable membrane thickness is 0. 8 mm. Moreover, a single fuel cell with the configuration of H₂S ＋ composite Mo-Ni-S anode ＋ Li₂SO₄-based composite proton-conducting membrane ＋ NiO-based composite cathode was fabricated, and the corresponding electrochemical performances were also investigated. The results show that the fuel cell of composite membrane with Li₂SO₄ ＋ Li₂WO₄ ＋ Al₂O₃ is of the most excellent performances.

Key words: proton-conducting membrane, fuel cell, electrolyte, hydrogen sulfide, electrochemical performance