HF-free microwave-assisted synthesis of MXene as an electrocatalyst for hydrogen evolution in alkaline media.

Abstract

MXenes, characterized by their robustness, flexibility, and large surface-to-volume ratio facilitating efficient energy transfer with fast response times, have emerged as promising electrocatalysts for hydrogen generation through electrochemical water-splitting. However, the conventional synthetic route to MXenes typically involves the use of hydrofluoric acid (HF) to obtain MXenes with terminal F-functional groups. Unfortunately, these fluorine groups can negatively impact the electrocatalytic performance of MXenes. Moreover, HF is highly toxic, necessitating the development of more environmentally friendly synthetic methods. In response to these challenges, we have developed a novel HF-free microwave-assisted synthesis approach for MXenes. This method harnesses the benefits of uniform heating, homogeneous nucleation, and rapid crystal development, resulting in MXene crystallites with limited size. Importantly, our microwave-assisted approach utilizes a fluoride-free, less hazardous etchant as compared to HF for the synthesis and functionalization of MXene. The as-obtained MXene exhibits significantly improved performance towards the electrochemical hydrogen evolution reaction in alkaline media. Specifically, it demonstrates an overpotential of 140 mV at a current density of 10 mA cm^-2 and a Tafel slope of 84 mV dec^-1. These results highlight the potential of our HF-free microwave-assisted synthesis approach for producing high-quality MXenes with enhanced electrocatalytic activity for hydrogen generation.