Neutralization flow batteries in energy harvesting and storage

First studies on electrochemical devices converting chemical energy of neutralization into electricity - neutral-ization (or acid-base) flow batteries (NFB) -are dated 70s, but at the time they did not attract adequate attention due to a moderate performance of first prototypes. A renaissance of NFBs was in the 2010s: researchers proposed various battery designs with unique features. Since available studies overview great diversity of experimental methodology and devices, comparison of NFBs performance is challenging. Therefore, this review focuses on summarizing for the first time the NFB development achievements with special attention to device architecture and their performance metrics. Considering the available data, we highlight two operation modes with distinctive requirements - energy harvesting from acidic and alkaline streams, and stationary energy storage. We hope that this review will provide a clear NFBs state-of-the-art overview, and thereby facilitate further tech-nology improvement.