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.