Large scale energy storage challenges are increasing with increasing energy demand. Unitized reversible fuel cells (URFCs) coupled with intermittent renewable power sources could be instrumental in enabling the transition away from non-renewable sources. URFCs operate as a fuel cell (FC) and electrolyzer (E) in a single cell/stack (1, 2). However, several technical barriers must be overcome to make URFCs competitive with other energy storage technologies. For low-temperature membrane-based systems, the optimal operation in E mode requires high liquid water saturation, while FC mode requires just enough water to maintain ionic conductivity. The conflicting saturation requirements prevent transport optimization for either mode, while also causing inefficiencies when switching between the operating modes.

In this work, we present a novel binary array structure that could lead to improved operation in both E and FC mode while avoiding any need for gas purging when switching between operating modes. This is achieved by patterning the electrodes and diffusion media to induce localized hydrophilic and hydrophobic domains. The hydrophobic domain enables improved gas transport during switching between the different operating modes. However, electrodes with only hydrophobic domains can provide an improvement in FC mode, but E mode performance suffers due to poor water transport as seen in Figure 1. Binary array electrode enhances water management and thereby increases performance in both the operating modes.

Acknowledgments

This research is supported by DOE Fuel Cell Technologies Office; Technology manager: Nancy Garland.

References

1. B. Paul and J. Andrews, Renewable and Sustainable Energy Reviews, 79, 585 (2017).
2. Y. Wang, D. Y. C. Leung, J. Xuan and H. Wang, Renewable and Sustainable Energy Reviews, 65, 961 (2016).