(519b) Reversible Fuel Cells -Challenges and Perspectives for Energy Conversion (invited)

A reversible fuel cell (RFC) is a system that combines a fuel cell and electrolysis cell together. The RFC is a promising energy storage system for intermittent renewable energy resources, such as solar and wind energy. It stores electricity during off-peak periods (water electrolysis mode) and then produces electricity (fuel cell mode) during peak periods. Compared to a rechargeable battery, a UFC exhibits advantages such as high energy storage capacity (high specific packaged energy density of 400-800 Wh/kg), low cost, simple system design and environmental friendliness, etc.

This work will present recent low temperature RFC technology development, which includes proton exchange membrane (PEM) and anion exchange membrane (AEM). Although the PEM-based RFC technology is more developed with better cell performance and round-trip efficiency, the scarcity and high cost of platinum group metal (PGM) electrocatalysts for the acidic media oxygen electrode reactions still hinder its scalable application. This has driven exploration in AEM-based RFCs, with the potential of low cost electrocatalysts and stack components (membranes, bipolar plates, air looping and cooling, etc.).

We will also present challenges and perspectives of RFCs. A RFC system having both fuel cell and electrolyzer cell can maximize the performance of each individual cell thus the round trip efficiency, but the capital cost can be increased. A unitized RFC integrates fuel cell and electrolyzer cell into one system using bifunctional catalysts; although the capital cost can be tremendously reduced, the RFC round trip efficiency can be sacrificed. Compared to rechargeable battery technology, the RFC does not demonstrate apparent advantage for short-duration (e.g., < 12 hours) energy storage. However, the RFC may demonstrate tremendous advantage for long-duration (e.g., > 24 hours) energy storage. The awareness of the advantages and constrains of RFCs can allow for the selection of the best technology under various application scenarios.