Advanced Design Strategy in Polymer Electrolyte Membrane Fuel Cells: Micro‐channeling Architectures in Carbon Nanotube Sheets

Abstract Maintaining high performance under varying relative humidity (RH) conditions remains a significant challenge for polymer electrolyte membrane fuel cells (PEMFCs). This difficulty arises from the delicate balance required between mass transport and water management. This study presents an alternative PEMFC design that replaces conventional bipolar plates by incorporating a carbon nanotube sheet (≈30 µm) as a functional interlayer. The engraved channel‐rib CNT sheet, fabricated via laser processing, is located between the gas diffusion layer and the catalyst layer. This configuration improves performance under all tested RH conditions (40–100% RH), primarily due to the effective distribution of reactants and water within the channels. The proposed design yields up to a ≈270% increase in power density, along with significant reductions in charge transfer resistance (≈76.1%) and ohmic resistance (≈27.0%) compared to the conventional. Furthermore, it demonstrates remarkable stability, showing a 87.5% reduction in performance variation across the tested RH range compared to the conventional. This strategy offers a potential solution to minimize performance fluctuations under varying operating conditions, thereby enhancing the commercial viability of PEMFC applications.