Controlling the Surface Reactivity of Hybrid Ti 3 CN MXene via In‐situ Electrocatalysis

Abstract Two‐dimensional (2D) carbide and nitride MXenes possess properties that are desirable for a broad range of electrocatalytic applications including the hydrogen evolution reaction (HER). These properties include high surface area, hydrophilicity, heterogeneity of redox‐active transition metals, and tunable surface functionalities allowing for low HER overpotentials. In this paper, we report on the cathodic etching and −O/−OH functionalization of hybrid Ti 3 CN upon the application of an external potential for improved HER performance and show that the active sites for HER on this MXene catalyst are located primarily on the −O− and −OH functional groups. The overpotential for the hybrid Ti 3 CN improves by 350 mV upon in‐situ −O/−OH functionalization and etching, reaching −0.46 V vs. RHE at a current density of 10 mA cm −2 , much lower than those reported for the benchmark Ti 3 C 2 carbide MXene. These results provide a path forward to tuning the electrocatalytic activity of MXenes and related electrocatalysts for water splitting.