Suppressing hydrogen evolution and enhancing discharge performance of alkaline aluminum-air batteries by constructing Ti3C2Tx MXene functional layer

Parasitic hydrogen evolution reaction (HER) and anode passivation are two intertwined challenges that profoundly limit the energy efficiency and operational lifespan of alkaline aluminum-air (Al-air) batteries. Here, we construct a uniform Ti 3 C 2 T x MXene functional layer on pure aluminum (Al) surface via a facile solution-immersion self-assembly process. The assembled MXene architecture acts a highly effective, selective interfacial regulator with state-dependent dual-functionality. During open-circuit standby, its unique 2D structure impedes water reduction, yielding a ∼46% reduction in the HER rate (from 0.129 to 0.070 ml cm −2 ·min −1 ). Conversely, during discharge, the intrinsically conductive MXene framework facilitates highly uniform anodic dissolution. Consequently, in static alkaline cells (10 mA cm −2 ), the MXene-Al anode delivers an exceptional specific capacity of 2216 mAh·g −1 and an energy density of 3303 Wh·kg −1 , substantially outperforming pure Al (1350 mAh·g −1 , 1818 Wh·kg −1 ). Furthermore, under cyclic on/off discharge with electrolyte flow, the functionalized anode extends operational lifetime by roughly one-third (from 82 to 111 h). Post-discharge characterization confirms that the MXene layer remains structurally intact on the Al surface after prolonged operation. These results establish solution-assembled MXene functional layers as a practical approach for simultaneously addressing HER and passivation in alkaline Al-air batteries.