Bipolar‐Interface Hydrogen Fuel Cells: A Review and Perspective on Future High‐Performance, Low Platinum‐Group Metal Content Designs

Abstract

This Review elucidates the state-of-the-art, challenges, and future prospects for bipolar-interface-based fuel cells (BPIFCs), focusing on hydrogen-based systems. On the one side, it provides a summary of state-of-the-art design strategies for BPIFCs from different fields of application. On the other hand, it identifies the two most pivotal areas for a future understanding that particularly refer to the changed mass transport situations introduced by the bipolar fuel cell design, that is, the water management and the bipolar interface layer itself. All operation-relevant components such as the gas diffusion layers, catalyst layers, and membrane designs are discussed within the framework of these two main areas. As non-platinum-group metal (PGM) oxygen reduction is one of the key benefits of bipolar hydrogen fuel cells, a particular focus is put on this configuration. Several additional challenges that exclusively originate from non-PGM-based catalyst layers and possible mitigation approaches are discussed. One key insight is that these thick layers could take over the role of microporous layers in the future. Finally, we emphasize that there is a strong lack in both theoretical and experimental approaches that improve our understanding of the underlying processes in bipolar fuel cell designs.

The influence of the anion exchange membrane on mass-transport limiting phenomena in bipolar interface fuel cells with Fe–N/C based cathode catalyst layers

“…As elaborated in previous theoretical work, the CCL properties (dominated by pore size distribution and wettability) might affect the overall water management as the water formation reaction is shifted to the edge of the said layer. 23 Consequently, the majority of the product water is produced outside of the CCL and the CCL|AEM interface acts as an additional barrier against the water transport. For water to access the pore space of a porous structure, a critical breakthrough pressure must be overcome.…”

“…One of the effects, induced by not having water formation in the electrodes, is a significantly altered cell water management in BPIFCs compared to conventional fuel cell systems. 23 Balanced water management is important for all polyelectrolyte membrane fuel cell types such as anion 24 or cation exchange membrane fuel cells. 25 When balanced water transport management cannot be sustained, increased mass transport resistances are often the result.…”

“…The closer the AEM|PEM interface to the cathode, the more likely it is that product water will be transported into the cathode electrode. 23 Increasing water transport into the cathode also reduces the likelihood of flooding at the anode electrode, as seen in AEMFCs. For PGM-based BPIFCs, this again could allow for eliminating gas feed humidification in the BPIFC and ensuring membrane hydration and water supply for alkaline ORR from interfacial water only.…”

“…And as elaborated more thoroughly in previous theoretical work, the AEM layer is involved in the most important water flows of a BPIFC and therefore inhibits large potential for a better understanding of transport processes within the bipolar system. 23 This work is focused on experimentally understanding the impact of the AEM layer on the polarization behavior of a BPIFC employing Fe–N/C electrodes and its relation to possible MTL.…”

A review on process design and bilayer electrolyte materials of bipolar membrane fuel cell

“…The recent reviews on BPM‐based technologies by Giesbrecht et al, 18 Parnamae et al, 19 and Blommaert et al 20 provide a comprehensive overview of the strategies for the improvement of BPM performance and its recent achievements in various applications of energy storage, carbon oxide capture, and wastewater treatment, but do not specifically focus on fuel cell applications. To the best of the author's knowledge, only a review by Dominik et al 21 described the state‐of‐art design strategies of BPM for fuel cells in terms of cell components design, manufacturing, characterization, and challenges. However, their work does not comprehensively describe the influence of cell components design and does not consider the influence of electrolyte materials and integration techniques on BPMFC performance and self‐humidification behavior.…”