Unitized reversible fuel cells (URFCs) are a promising grid scale energy storage solution that can leverage intermittent renewable energy sources. URFCs operate in both fuel cell (FC) mode during discharge and water electrolyzer (WE) mode during recharge. Inherent disparity in the requirement of the system components of these two operational modes introduces several technical challenges that must be overcome to make URFCs competitive with other energy storage technologies. The wettability requirements of the porous transport layer (PTL) in the oxygen electrode are different for the two operation modes: hydrophilic PTLs provide optimal H₂O transport in WE mode, while hydrophobic PTLs provide faster O₂ transport in FC mode. PTL design needs to be optimized for both modes in order to resolve this conflicting requirement. We have previously shown that amphiphilic titanium (Ti) felt improved performance in both modes of operations. In this work, a corrosion-resistant micro-porous layer (MPL) is incorporated to facilitate further improvement in the transport of oxygen and water in both operational modes. The MPL is fabricated from corrosion-resistant powders (titanium nitride [TiN], antimony doped tin oxide [ATO], and niobium doped titanium dioxide and polytetrafluoroethylene (PTFE) dispersion. We present experimental results for cell performance and durability through accelerated stress testing of PTLs with amphiphilic MPLs.

Acknowledgment: Financial support from the US Department of Energy through the Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cells Technology Office is gratefully acknowledged.