Hydrogen Fuel Exhaling Zn−Ferricyanide Redox Flow Battery

Electrochemical water splitting reaction provides a reaction pathway for green fuel synthesis, which in turn offers a carbon neutral energy platform for stabilizing global mean temperatures. However, it is a thermodynamically unfavorable reaction often requiring substantial electrical driving force. Second, the concurrent generation of hydrogen and oxygen in close proximity in the state-of-the-art water electrolyzer may pose potentially dangerous consequences. We offer a unique approach for fuel synthesis and report a hydrogen fuel synthesizing a Zn–ferricyanide battery by exploiting the concept of dual electrolytes, where exclusive hydrogen fuel synthesis is spontaneously coupled with electric power production. The key to our approach is short-circuited electrodes housed in dual electrolytes without ionic communication, where oxidative Zn dissolution and reductive hydrogen fuel synthesis are spontaneously driven at the two poles during electric power generation. This battery chemistry eventually amplifies the voltage output of the Zn–ferricyanide battery from ∼1.7 to ∼3 V and boosts the energy density from ∼9.5 to ∼16 W h/L while concomitantly synthesizing ∼932 μmol/h of clean hydrogen fuel. We believe that coupling hydrogen fuel synthesis with electric power harnessing distinctly integrates an extra dimension to battery functionality and articulates a pathway toward balancing global mean temperatures.