Enhanced proton pseudocapacitive of Ti₃C₂T_x in neutral electrolyte activated by acid regulation dynamic pillars

Aqueous Zinc ion capacitors (ZICs) using 2D transition metal carbides or nitrides (MXenes) have extraordinary energy density and wide potential range. However, low pseudocapacitance and slowly divalent charges (e.g., zinc ions) transfer in MXene nano sheets are the essential issues in exploring MXene-based ZICs of greater energy densities. Herein, the strategy of using Al³⁺ as dynamic acid regulation pillars is demonstrated to address these issues. Attributing to dynamically expanded layer spacing, adjustable acid of electrolyte and excited proton pseudocapacitance, enhanced capacity values of 277.9 F g^-1 with a high voltage range from -1 to 0.3 V is achieved. The energy density of asymmetric ZICs constructed applied this strategy exhibits superior energy densities of 37.7 Wh kg^-1 with outstanding cycling stability, which has been greatly improved compared with traditional acidic and neutral electrolytes. DFT calculations reveal the enhancement mechanism of acid regulation dynamic pillars on electrochemical performance. Our study provides a pathway for precise control of Ion selectivity in MXene energy storage process, and could be further used for other electrolyte systems and aqueous Zn-ion electrodes as well.