Electrochemical and operation performance of electrolytic air dehumidification with different catalyst coated membrane methods

Proper catalyst coated membrane (CCM) methods are significant for membrane electrode assembly (MEA) of PEM-based electrolytic dehumidification. In this work, four CCM processes, doctor blade, decal, electrostatic spraying, and modified pneumatic spraying methods, were employed for fabricating dehumidifier assemblies with low-load (0.6 mg/cm2) IrO2 catalyst layers (CLs). The physical and electrochemical properties of the as-prepared CLs were characterized, and the mass transfer resistance and dehumidification rate of the MEA were tested during actual operations. The optimal hot-pressing parameters were also determined. Results showed that the modified pneumatic spraying method can significantly improve the pore distribution and CL flatness by promoting the evaporation of solvent from catalyst slurry. The charge-transfer and ohmic resistances of MEA was 25.3 and 27.8 mΩ/cm2, respectively, which are the best values for those prepared using the four methods. The dehumidification rate was also the highest (0.105 g/h), 20–40% higher than that of other methods. Although the overall mass transfer resistance of assembly prepared by the electrostatic spraying was low, the CL structure was obviously loose and unable to bind to the membrane surface tightly, leading to high electrochemical resistance (6.6-fold that of pneumatic spray method). Besides, catalyst particles tend to agglomerate using the doctor blade method. The pore size of the CL prepared using the decal method was found to be too small (<300 nm), hindering reactant transfer and resulting in a low overall mass transfer coefficient. This study provides a practical direction for the preparation of economical and high-performance dehumidifiers or electrolyzers.