MXenes are highly promising materials for the substitution of platinum metals in electrocatalysis. They have implicitly impacted materials science and engineering, nanoscience, and nanotechnology with their excellent properties. These 2D carbides and nitrides have shown great promise in several research domains, including clean energy (hydrogen evolution reaction (HER), carbon capture and conversion, storage devices, etc.). The interlayer spacing of MXenes provides enough space for embedding of different intercalant species, which can enhance the conductivity, and chemical properties of MXenes. In this direction, alkali metal decoration of MXene 2D sheets leads to the increased surface area, stability and adds ionic conductivity, exhibiting better electrocatalytic performance. Molybdenum-containing MXenes have shown the highest catalytic efficiency among all MXenes. We present a detailed study of Mo2Ti2C3 MXenes by decorating cations of variable sizes (Li+, Zn2+, Na+, Ca2+). The electrocatalytic results show a strong dependence of cations on the HER. The overpotential (208 mV, 305 mV, 340 mV, 401 mV) at 10 mA/cm2 directly correlates with atomic radii of cation ((Li+, Zn2+, Na+, Ca2+) decorated on Mo2Ti2C3 MXenes. The synergistic effect between the unique chemical properties and nanostructure endows Li+-decorated Mo2Ti2C3 MXenes with remarkable electrocatalytic performance for HER with the lowest overpotential under acidic conditions over other cation-decorated MXenes. These Li+-decorated MXenes show excellent stability without any noticeable degradation after 48 h of operation over control, making them a promising efficient electrocatalyst for HER. Our findings have broad fundamental implications because by choosing the cation, one can tune the MXenes for electrocatalytic (hydrogen evolution reaction, carbon dioxide reduction reaction, oxygen evolution reaction, nitrogen reduction reaction, etc.) applications.

Cation-decorated Mo2Ti2C3 MXenes as an efficient electrocatalyst for hydrogen evolution reaction

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