A Scalable and Robust Water Management Strategy for PEMFCs: Operando Electrothermal Mapping and Neutron Imaging Study.

Effective water management is crucial for the optimal operation of low-temperature polymer electrolyte membrane fuel cells (PEMFCs). Excessive liquid water production can cause flooding in the gas diffusion electrodes and flow channels, limiting mass transfer and reducing PEMFC performance. To tackle this issue, a nature-inspired chemical engineering (NICE) approach has been adopted that takes cues from the integument structure of desert-dwelling lizards for passive water transport. By incorporating engraved, capillary microchannels into conventional flow fields, PEMFC performance improves significantly, including a 15% increase in maximum power density for a 25 cm2 cell and 13% for a 100 cm2 cell. Electro-thermal maps of the lizard-inspired flow field demonstrate a more uniform spatial distribution of current density and temperature than the conventional design. Neutron radiography provides evidence that capillary microchannels in the lizard-inspired flow field facilitate the efficient transport and removal of generated liquid water, thereby preventing blockages in the reactant channels. These findings present a universally applicable and highly efficient water management strategy for PEMFCs, with the potential for widespread practical implementation for other electrochemical devices.

High-speed 4D neutron computed tomography for quantifying water dynamics in polymer electrolyte fuel cells.

In recent years, low-temperature polymer electrolyte fuel cells have become an increasingly important pillar in a zero-carbon strategy for curbing climate change, with their potential to power multiscale stationary and mobile applications. The performance improvement is a particular focus of research and engineering roadmaps, with water management being one of the major areas of interest for development. Appropriate characterisation tools for mapping the evolution, motion and removal of water are of high importance to tackle shortcomings. This article demonstrates the development of a 4D high-speed neutron imaging technique, which enables a quantitative analysis of the local water evolution. 4D visualisation allows the time-resolved studies of droplet formation in the flow fields and water quantification in various cell parts. Performance parameters for water management are identified that offer a method of cell classification, which will, in turn, support computer modelling and the engineering of next-generation flow field designs.