Preparation and Comparative Evaluation of Membrane Separators for Aqueous Electrochemical Nitrogen Reduction Reaction Measurements

Catalyst screening for electrochemical nitrogen (N₂) reduction to ammonia (NH₃) suffers from spurious results caused by various sources of contamination associated with the experimental setup and the environment. As a crucial component of the electrochemical cell, a separator membrane is necessary to prevent the oxidation of as-synthesized NH₃, specifically for low-yield aqueous electrochemical nitrogen reduction reactions (EC-N₂RR). However, there remains a key need for a robust and contamination-free membrane, including systematic assessments of its electrochemical suitability for this reaction. Here, we report a simple yet effective cleaning process for the recently introduced microporous Celgard membrane. We show that the cleaned Celgard membrane outperforms other commonly used EC-N₂RR membranes in alkaline electrolytes, exhibiting superior ion transport compared to a Nafion proton exchange membrane and enhanced chemical inertness and structural stability compared to a Fumasep anion exchange membrane. Beyond guiding membrane selection, this study provides a comprehensive strategy for managing contamination and a framework for designing and operating nearly contamination-free EC-N₂RR workstations, enabling reliable catalyst screening for aqueous EC-N₂RR.