RMIT University (Australia) researchers have developed a concept battery based on storing protons produced by splitting water—a reversible fuel cell with integrated solid proton storage electrode. As only an inflow of water is needed in the charge mode, and air in discharge mode, the system is called a “proton flow battery”.
This new concept has the potential to increase roundtrip efficiency compared to the conventional hydrogen-based electrical energy storage system by eliminating the intermediate steps of hydrogen gas production, storage, and recovery.
The concept integrates a composite metal hydride–nafion electrode into a reversible proton exchange membrane (PEM) fuel cell. During charging, protons produced from splitting water are directly combined with electrons and metal particles in one electrode of a fuel cell, forming a solid-state metal hydride as the energy storage. To resupply electricity, this process is reversed.
The research, published in the International Journal of Hydrogen Energy, found that, in principle, the energy efficiency of the proton flow battery could be as high as that of a lithium-ion battery, while storing more energy per unit mass and volume.
Its hydrogen storage capacity was measured to be 0.6 wt% of hydrogen, although the amount of hydrogen recovered to run the device in fuel cell mode was much lower. These results provide initial confirmatory evidence that the proton flow battery concept is technically feasible, though additional research is still required to enhance both storage capacity and reversibility.—Andrews and Mohammadi
Lead researcher Associate Professor John Andrews said the novel concept combined the best aspects of hydrogen fuel cells and battery-based electrical power.
Powering batteries with protons has the potential to be a much more economical device than using lithium ions, which have to be produced from relatively scarce mineral, brine or clay resources. Hydrogen has great potential as a clean power source and this research advances the possibilities for its widespread use in a range of applications—from consumer electronic devices to large electricity grid storage and electric vehicles.—John Andrews
The published paper is the first to articulate and name the proton flow battery concept, and the first to include an experimental preliminary proof of concept.
John Andrews, Saeed Seif Mohammadi (2014) “Towards a ‘proton flow battery’: Investigation of a reversible PEM fuel cell with integrated metal-hydride hydrogen storage,” International Journal of Hydrogen Energy, Volume 39, Issue 4, Pages 1740-1751 doi: 10.1016/j.ijhydene.2013.11.010