Modulation of Surface Ti-O Species in 2D-Ti 3 C 2 T X MXene for Developing a Highly Efficient Electrocatalyst for Hydrogen Evolution and Methanol Oxidation Reactions.

Developing cost-effective and earth-abundant noble-metal-free electrocatalysts is imperative for the imminent electrochemical society. Two-dimensional Ti 3 C 2 T X (MXene) exhibits tunable properties with high electrical conductivity and a large specific surface area, which improve its electrochemical performance. Herein, the low-temperature annealing method is used to enrich MXene with a maximum number of Ti-O terminals without formation of titanium dioxide (TiO 2 ) under neutral pH conditions. MXene annealed at 200 °C is found to have a large number of Ti-O termination groups, resulting in a large electrochemically active surface area and increased active sites (-O termination groups) and hence excellent electrocatalytic performance compared to other samples as well as previous reported work. The optimized sample is found to show the lowest overpotential value of 0.07 V at 10 mA cm -2 and a Tafel slope of 0.15 V dec -1 toward the hydrogen evolution reaction (HER), whereas for the methanol oxidation reaction (MOR), the current density is 18.08 mA cm -2 , and the onset potential is -0.51 V. In addition, it also shows long-term stability and durability toward HER as well as MOR.