Chemical scissor-enabled synthesis of Ti₃C₂T_x MXene nanowires for selective oxygen reduction to hydrogen peroxide

Transition metal carbides, especially Ti₃C₂T_x, display appealing prospects in the field of energy conversion and storage due to the unique combination of good conductivity and abundant functional groups. The physical structure as well as surface terminations of Ti₃C₂T_x have significant impact on its properties when scaling down from 3D bulk to 2D sheets. However, moving toward 1D nanowire remains a great challenge because of the absence of anisotropic skeleton in Ti₃C₂T_x. Herein, we demonstrate a facile strategy to convert Ti₃C₂T_x nanosheets into crosslinked Ti₃C₂T_x nanowires in hybrid alkaline solutions. The experimental results and theoretical calculation reveal that both OH⁻ and O₂ play important roles in the controllable cutting of Ti₃C₂T_x nanosheets into nanowires. Compared to Ti₃C₂T_x nanosheets, crosslinked Ti₃C₂T_x nanowires expose much higher density of active sites at edges and surfaces, making them ideal catalysts for oxygen reduction reaction (ORR). Unexpectedly, Ti₃C₂T_x nanowires can selectively reduce oxygen through a 2e⁻ pathway to hydrogen peroxide. The structural modulation of MXene opens a new avenue toward improved performance in emerging application fields.