Chemical scissor-enabled synthesis of Ti3C2Tx MXene nanowires for selective oxygen reduction to hydrogen peroxide

Abstract

Transition metal carbides, especially Ti3C2Tx, 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 Ti3C2Tx 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 Ti3C2Tx. Herein, we demonstrate a facile strategy to convert Ti3C2Tx nanosheets into crosslinked Ti3C2Tx 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 Ti3C2Tx nanosheets into nanowires. Compared to Ti3C2Tx nanosheets, crosslinked Ti3C2Tx nanowires expose much higher density of active sites at edges and surfaces, making them ideal catalysts for oxygen reduction reaction (ORR). Unexpectedly, Ti3C2Tx 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.