Evaluation of MEA manufacturing parameters using EIS for SO2 electrolysis

Membrane electrode assembly (MEA) manufacturing parameters such as hot pressing pressure and pressing time were investigated for the use in a SO2 electrolyser. The SO2 electrolysis was optimised in terms of cell temperature, membrane thickness and catalyst loading. The electrolysis efficiency was evaluated using polarisation curves while electrochemical impedance spectroscopy (EIS) was used to determine the membrane resistance, activation energy and mass transport limitations. An electrical circuit, which included inductance, ohmic resistance, charge transfer, constant phase and Warburg elements, was used to fit the experimental data. The optimum hot pressing conditions were 50 kg cm−2 for 5 min at 120 °C. Increased cell temperature (80 °C) resulted in a reduction of mass transport, while thicker membranes resulted in an increased mass transport due to lower water transport through the membrane. Increased catalyst loading (from 0.3 to 1 mgPtC.cm−2) improved the cell performance due to improved kinetics confirmed by the EIS data.