MXenes as a promising practical and long durance catalyst in cathodic oxygen reduction reaction

The current commercial Pt/C catalysts used in fuel cells rely on carbon supports, which are prone to rapid corrosion and instability [1]. Therefore, there is a pressing need to develop alternative supports that offer a stable structure and high electrical conductivity. In 2011, the first 2D MXene was discovered through the selective etching of a Ti3AlC2 MAX phase by a team at Drexel University [2]. MXenes are highly valued materials for their remarkable chemical and thermal stability, excellent mechanical properties, exceptional electrical conductivity (up to 24,000 S cm⁻¹), high adsorption capacity arising from their 2D structure (higher surface area compared to traditional 2D materials), and unique topological properties (catalytically active basal planes with exposed metal sites), leading to their use in many applications such as electromagnetic shielding, wireless communication, chemical sensing, energy storage, optoelectronics, catalysis, and flexible electronics [3]. Herein we adopted different synthetic routes towards MXene and investigated their catalytic activity towards oxygen reduction reaction in alkaline media. Direct HF and in-situ HF-etching (clay-like and MILD) were taken as low cost and ease-handled procedure to obtain MXene with different characteristics. Using direct HF (named Mx-HF) leads to higher fluorine terminal group on the surface and accordion-like morphology (Fig. 1b), while in clay-like and MILD routes - which uses LiF and HCl as etchant to produce in-situ HF - leads to more delaminated sheets and higher oxygen group on the surface (named Mx-LiF and Mx-Mild respectively).