Batch-to-Batch Variations in Lab-Scale Performance of Commercial Catalyst-Coated Membranes for PEM Water Electrolysis

High Resolution Image Download MS PowerPoint Slide This study systematically investigates the reproducibility of commercially available catalyst-coated membranes (CCMs) for proton exchange membrane water electrolysis (PEMWE). Reliable measurements are essential for benchmarking materials and isolating the effects of components and operating conditions, yet CCM variability remains insufficiently understood. To address this gap, six CCM types from five different suppliers were evaluated across two production batches using standardized electrochemical protocols, including polarization (I–V) and Distribution of Relaxation Times (DRT) analysis, under identical laboratory conditions. Reproducibility was assessed across three dimensions: repeated measurements of a single sample, variation within a batch, and variation across batches. The results show that reproducibility strongly depends on CCM type and operating conditions. Some CCMs reach steady state rapidly, while others exhibit significant voltage drift despite extended conditioning. Median deviations in cell voltage of less than 10 mV at 0.5 A cm –2 were observed, which increased to up to 23 mV at 2.0 A cm –2 and to over 65 mV at 3.5 A cm –2 . Cross-batch variations are considerably larger, exceeding 100 mV cell voltage deviation at high current densities, highlighting batch-dependent inconsistencies. I–V breakdown identifies HFR as a key contributor to these variations, while DRT analysis highlights variations in charge transfer resistance and mass transport limitations. Based on these findings, six practical guidelines are proposed: (1) include repetitive measurements in characterization routines to verify completeness of CCM conditioning; (2) use expected deviation ranges as a benchmark for reproducibility; (3) only attribute performance differences to materials if they exceed intrinsic CCM variability; (4) apply deviation thresholds when evaluating operational or component changes; (5) regularly verify reproducibility in long-term studies, especially across batches; and (6) treat CCM variants from the same supplier as independent systems. Overall, this work provides quantitative benchmarks and practical guidance to improve data reliability and comparability in PEMWE research.