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Liu and co-workers report a molecular engineering study of ferricyanide and ferrocyanide catholytes for pH neutral aqueous organic redox flow battery applications using a strategy of cation modulation. Compared with traditional potassium or sodium ferricyanide and ferrocyanide catholytes, the newly designed (NH 4 ) 3 [Fe(CN) 6 ] and (NH 4 ) 4 [Fe(CN) 6 ] catholytes manifest unprecedented electron storage capacities and robust battery performance, which promise sustainable and economical energy storage. Meanwhile, this work presents an efficient pathway to the development of high-performance redox active electrolytes for redox flow batteries.

Redox‐active anthraquinone molecules represent promising anolyte materials in aqueous organic redox flow batteries (AORFBs). However, the chemical stability issue and corrosion nature of anthraquinone‐based anolytes in reported acidic and alkaline AORFBs constitute a roadblock for their practical applications in energy storage. A feasible strategy to overcome these issues is migrating to pH‐neutral conditions and employing soluble AQDS salts. Herein, we report the 9,10‐anthraquinone‐2,7‐disulfonic diammonium salt AQDS(NH4)2, as an anolyte material for pH‐neutral AORFBs with solubility of 1.9 m in water, which is more than 3 times that of the corresponding sodium salt. Paired with an NH4I catholyte, the resulting pH‐neutral AORFB with an energy density of 12.5 Wh L−1 displayed outstanding cycling stability over 300 cycles. Even at the pH‐neutral condition, the AQDS(NH4)2 /NH4I AORFB delivered an impressive energy efficiency of 70.6 % at 60 mA cm−2 and a high power density of 91.5 mW cm−2 at 100 % SOC. The present AQDS(NH4)2 flow battery chemistry opens a new avenue to apply anthraquinone molecules in developing low‐cost and benign pH‐neutral flow batteries for scalable energy storage.

Instead of catalyzing electrochemical reduction of N 2 , we found that tetragonal Mo 2 N undergoes decomposition and results in the generation of ammonia. The present results call urgent attention to the need to carefully evaluate the catalytic nature of the dinitrogen reduction reaction by nitrogen-containing materials.

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