Stratified Porous Transport Layers for Unitized Reversible Fuel Cells

Unitized reversible fuel cells (URFCs) are promising grid-scale energy storage and conversion technologies that can enable increased deployment of intermittent renewable energy sources. URFCs operate in fuel cell mode for power generation and water electrolyzer mode for hydrogen production, but the two operational modes have conflicting transport requirements, limiting the round-trip efficiency. In this study, we report stratification of porous transport layers (PTLs) with different architectures that facilitate gas and water transport in both operational modes. The stratified PTL is composed of two or more layers of titanium felts and/or sinters. Combination of layers with different porosities produces a PTL with a hierarchical porosity gradient, enabling faster transport and increased performance in both operating modes.