Evaluation of s-PIM as an Alternative Binder to Nafion in Proton-Exchange Membrane Electrolyzers

Binders play a crucial role in ensuring the structural stability and efficient transport of reactants and products at the catalyst surface in Proton-Exchange Membrane (PEM) electrolyzers. This study presents a comprehensive comparative analysis of an innovative material, s-PIM (sulfur-containing Polymer of Intrinsic Microporosity), as a polymeric binder in PEM electrolyzers. The research focuses on investigating the advantages/disadvantages of using s-PIM instead of the traditional Nafion binder, with a specific emphasis on assessing the electrochemical performance of the electrodes. The research started with a screening of s-PIM as a binder at the cathode and anode within a three-electrode cell. Linear sweep voltammetry (LSV) and chronoamperometry (CA) were employed to analyze the electrocatalytic activity and stability over time. The results revealed s-PIM's significant potential as an anode binder, exhibiting either similar or superior performance than those of Nafion, while its performance at the cathode was comparatively lower. Additionally, two anodes (one containing NAfion and the other containing s-PIM as binder) were prepared and subjected to an Accelerated Durability Test (ADT) in the same three-electrode cell to assess their long-term. The results showed slightly higher activity for s-PIM highlighting its good durability and stability. Subsequent tests in a PEM electrolyzer were conducted, including optimization of the anodic catalyst and gas diffusion layers (GDL) for both the anode and cathode, with the aim of achieving higher current densities. LSV results indicated that s-PIM as binder at the anode exhibits lower performance compared to Nafion, but after one hour of CA, they showed similar current densities. These results suggest that s-PIM is a promising binder material for PEM electrolyzers, particularly at the anode. However, further research is necessary to maximize its utilization in industrial applications.