NH₄ ⁺ Deprotonation at Interfaces Induced Reversible H₃ O⁺ /NH₄ ⁺ Co-insertion/Extraction

Ion insertions always involve electrode-electrolyte interface process, desolvation for instance, which determines the electrochemical kinetics. However, it's still a challenge to achieve fast ion insertion and investigate ion transformation at interface. Herein, the interface deprotonation of NH₄ ⁺ and the introduced dissociation of H₂ O molecules to provide sufficient H₃ O⁺ to insert into materials' structure for fast energy storages are revealed. Lewis acidic ion-NH₄ ⁺ can, on one hand provide H₃ O⁺ itself via deprotonation, and on the other hand hydrolyze with H₂ O molecules to produce H₃ O⁺ . In situ attenuated total reflection-Fourier transform infrared ray method probed the interface accumulation and deprotonation of NH₄ ⁺ , and density functional theory calculations manifested that NH₄ ⁺ tend to thermodynamically adsorb on the surface of monoclinic VO₂ , and deprotonate to provide H₃ O⁺ . In addition, the inserted NH₄ ⁺ has a positive effect for stabilizing the VO₂ (B) structure. Therefore, high specific capacity (>300 mAh g^-1 ) and fast ionic insertion/extraction (<20 s) can be realized in VO₂ (B) anode. This interface derivation proposes a new path for designing proton ion insertion/extraction in mild electrolyte.