• By utilizing water vaporization to increase the surface area of graphene and precisely controlling the ratio of oxygen-containing functional groups, the optimal –COOH:–OH ratio of 1:1 was successfully achieved, resulting in a maximum pseudocapacitance of 430.5 F g−1.
• Through hydrazine-assisted hydrothermal reaction, –F groups on the MXene surface were substituted with –NH2, while gas generation facilitated the creation of a porous structure, boosting the capacitance to 500.5 F g−1 under high mass loading conditions.
• The assembled asymmetric proton pseudocapacitor achieved high energy and power densities of 58.9 Wh kg−1 and 3802 W kg−1, respectively, with excellent stability.
• Density functional theory calculations revealed that –COOH groups on graphene and –NH2 groups on MXene enhance proton adsorption/desorption and conductivity, providing a synergistic design strategy for high-performance flexible energy storage.