Reveal the source of protons in aqueous hydrogen proton battery

In this work, we have discovered and investigated the reaction mechanism of Aqueous Hydrogen Proton Battery (AHPB), which differ from conventional rocking-chair batteries. The hydrogen protons in the battery reaction is provided by the dissociation of H₂O molecules in the electrolyte. Thus, the charging and discharging processes of the battery are also accompanied by changes in electrolyte concentration. To explore this, we have designed a AHPBs with a 2 M Zn(ClO₄)₂ electrolyte. The experimental results demonstrate excellent performance of the AHPBs, with a discharge specific capacity of up to 700.6 mAh g⁻¹ and a charge-discharge power conversion efficiency of 83.638 %. Both experimental and simulation results confirm that H⁺ in the battery is primarily provided by H₂O molecules solvating Zn²⁺. As the electrolyte concentration increases, ClO₄⁻ replaces some of the solvating H₂O molecules of Zn²⁺, resulting in the remaining unsaturated solvating H₂O molecules having a stronger propensity for deprotonation, thus facilitating the release of H⁺. This elucidates the specific source of H⁺ in AHPBs.