Plasmon-assisted spatially selective grafting of Ti3C2TX flakes for prevention of MXene oxidation and stability increase

Abstract

The MXene flakes are considered excellent materials for a range of applications and device construction. Especially attractive is the utilization of MXenes as the catalysts or co-catalysts for water splitting, including both half-reactions – hydrogen (HER) and oxygen (OER) evolution. However, the MXenes exhibit a strong tendency to oxidize during utilization, especially in water media and at oxygen presence. The oxidation of the MXene flakes commonly starts from the edges and then proceeds to the basal planes. Since the catalytic activity of flakes is mostly related to the basal plane, strong covalent blocking of flake edges can significantly protect MXene in oxidative conditions and increase the flake’s lifetime without the loss of their catalytic activity. In this work, we demonstrated the combination of plasmon-assisted chemistry and electrochemistry for spatial-selective and precise modification of MXene (Ti3C2TX) flake edges. Our approach is based on the spatial distribution of plasmon energy under the flake’s illumination with infrared (IR) light. Plasmon local excitation leads to homolysis of the modification agent – iodonium salt, the formation of highly reactive radicals, and their immediate grafting to the edges of MXene flakes in the neighborhood. As a result, the edges of the flakes are protected, and the initial stage of their oxidation is prevented. After optimization of plasmon-assisted grafting, the modified flakes were tested in HER and OER and a significant increase in flakes stability was validated.