Nanoporous Nitrogen-Doped Ti₃C₂ Nanosheets as Efficient Electrocatalysts for Oxygen Reduction

MXene (e.g., Ti3C2), a group of two-dimensional materials with high electrical conductivity, high specific surface area, and excellent mechanical properties, have been widely used in energy storage and conversion devices. Herein, nitrogen-doped Ti3C2 nanosheets with porous structures are simply prepared by etching Ti3C2 nanosheets in ammonia solution. Under alkaline conditions, the surface of the Ti3C2 nanosheets is attacked by hydroxyl ions, breaking Ti–C bonds and forming a porous structure. Meanwhile, the Ti3C2 nanosheets are doped by nitrogen atoms during ammonia etching. The porous structure of the Ti3C2 nanosheets is beneficial to the adsorption and transfer of oxygen and supplies active edge sites for oxygen reduction. In addition, the nitrogen doping enhances the catalytic activity of the Ti3C2 nanosheets. Therefore, the porous nitrogen-doped Ti3C2 nanosheets exhibit highly improved electrocatalytic oxygen reduction activity and superior stability. This study provides a synthesis strategy for MXene nanosheets with controllable structures and expands the applications of MXene nanosheets in the fields of energy storage and conversion.