Abstract:

A nano-composite Li₂SO₄ proton-conducting electrolyte and a new preparation procedure of membrane-electrode assembly (MEA) were developed for the electrochemical oxidation of H₂S. Instead of the traditional screen-printing method , in the MEA , both the anode and cathode catalysts were simultaneously pressed to form the cell with nano-composite electrolyte. This allows the design to possess some advantageous configurations that can diminish the Ohmic resistance between the electrolyte and the electrodes , enhance the mechanical and electrical properties , and improve the performance of fuel cells due to the membrane thickness reduction and the good contact between the electrolyte and the electrodes. The electrolyte was then characterized by scanning electron microscope (SEM) and electrochemical impedance spectrum techniques. The results indicate that the nano-composite materials improve the electrolyte integrity , and that no cross-over of H25 through the improved electrolyte occurs due to its high density , good compactivity and gas-impermeability. Moreover , MEA is stable in H25 stream. For a single cell with the configuration of H₂S, (MoS₂/NiS + Ag + electrolyte + starch)/Li₂SO₄ + Al ₂O₃/ ( NiO + Ag + electrolyte + starch) and air in a MEA thickness of 0. 8 mm and a Li₂ SO₄ to Al₂O₃ weight ratio of 65: 35 , the maximum power density is about 130 m W/cm² and the corresponding current density is about 200 mA/ cm² at 680 ℃ .

Key words: solid oxide fuel cell, membrane-electrode assembly, hydrogen sulfide, proton-conducting membrane