Various operating methods and parameters for SO2 electrolysis

摘要

AbstractThe application of PFSA-based proton exchange membranes was investigated for the production of hydrogen and sulfuric acid using a SO₂-depolarized electrolyzer system. Parameters investigated included hot pressing pressure for the membrane electrode assembly (MEA) manufacturing, cell temperature, membrane thickness, catalyst loading, membrane type, and SO₂ anode feed concentration. The effect of cell temperature, membrane thickness, and acid concentrations was also investigated when using a second method, where clean sulfuric acid as cathode and SO₂ saturated sulfuric acid as anode were used. Electrochemical impedance spectroscopy showed that the pressure exerted in the MEA manufacturing step had a significant influence with 125 kg cm−2 yielding the highest current density. High temperatures (80°C) and thin membranes (≈120 μm) showed the best performance while thicker membranes produced higher acid concentration when using the first system. The SO₂ concentration in the anode had a significant influence with the over potential increasing with decreasing SO₂ concentration. When using the second method, it was found that the SO₂ solubility in sulfuric acid is important as the mass transport of the SO₂ limits the overall reaction rate. From the two systems tested, the first method, that is, dry SO₂ anode and liquid water cathode showed the best operational effectiveness reaching a maximum of 0.32 A cm−2 at 80°C using N115 coated with 1 mgPt cm−2 while the second system under the same conditions achieved a current density of 0.18 A cm−2 when using N117.