Edge vs. Basal Plane of Ti₃C₂Tₓ MXene: Enhanced Inherent Electrochemistry, Electron Transfer, and Catalytic Activity at the Edge

Abstract

The electrochemistry at the edge and basal plane of two-dimensional (2D) layered materials has been of immense interest recently. While significant advances have been made in this direction for layered graphite, graphene, transition metal dichalcogenides (TMDs), and monoelemental black phosphorus, understanding the fundamental differences in the electrochemical behavior of 2D Ti3C2Tx MXene edges compared to the basal plane remains elusive. This work employs a simple and scalable fabrication technique to fabricate edge and basal plane Ti3C2Tx MXene electrodes and to explore their fundamental electrochemical and electrocatalytic properties. Compared to the basal plane, the innate oxidation of MXene is found to be significantly higher at the edge plane electrodes, with a limited working potential window for a series of electrolytes. The heterogeneous electron transfer rate for the edge is found to be ~3.3-fold higher than the basal plane for common redox mediators such as Ferrocyanide[Fe(〖CN)¬〗_6^(3-)], and hexaammineruthenium[Ru(〖〖NH〗_3)¬〗_6^(3+)], respectively. In addition, the preferentially exposed edge sites offer low potential detection of biomarkers and significantly improved catalytic activity for H2 evolution. This work elucidates how exposed edge sites can dramatically impact the innate electrochemical properties, enabling new opportunities for catalysis and other electrochemical applications.