Electrochemical Activation of Cobalt Hexacyanoferrate for High‐Performance Aqueous Hydrogen Gas‐Proton Battery

Abstract Hydrogen gas‐proton batteries (HPBs) continue to gain attention due to their rapid kinetics and excellent stability. However, the lack of high‐capacity and stable cathode materials hinders their further development. Herein, a cubic cobalt‐based Prussian blue analogue (CoHCF) is synthesized via a straightforward coprecipitation method and is first employed as a proton cathode material for HPB. Notably, by optimizing the electrolyte, the cubic CoHCF undergoes an electrochemical activation process under the synergistic effect between Co 2+ and high‐concentration protons, thereby enhancing the discharge plateau and rate capability of HPBs. The characterization tests demonstrate that the activation process stems from the stripping of K + in the CoHCF structure, which can effectively optimize the proton insertion and extraction. Thus, the HPB with the cubic CoHCF after activation exhibits an outstanding cycling stability (68.5% capacity retention after 250 000 cycles at 20 A g −1 ) and superb rate capability (≈62% of the initial value at 50 A g −1 ). This work provides new opportunities to design a high‐performance proton cathode for HPBs.