The dual challenges of clean hydrogen production and energy storage are targeted by a system that combines a vanadium-manganese redox flow battery for large-scale stationary energy storage with two catalytic reactors that produce clean hydrogen from fluid running through the battery. Unlike conventional redox flow batteries, the dual-flow battery developed at Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland, can discharge its fluid into the catalytic reactors, thus creating more storage space.

The dual-circuit redox flow battery offers the advantage of two discharging modes, enabling the system to store energy beyond the energy capacity of the electrolytes in the form of renewable hydrogen energy storage. Augmented by the catalytic reactors, the system includes a secondary energy platform in which electrochemical energy can be converted into renewable hydrogen by water-splitting using redox electrocatalysis. A redox mediator on solid electrocatalyst particles in each reactor supports the electrochemical water spitting process.

The battery demonstrated great stability over 50 cycles and an average energy efficiency of 68% at a current density of 50 mA/cm2 and a water-splitting voltage efficiency of 64.1%. The hydrogen production and energy storage technology described in Cell Reports Physical Science is envisioned to be deployed in the transportation sector.

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