Tungsten-Containing MXene (W₂Ti)C₂T_x from a Nanolaminated Ternary Carbide for Hydrogen Evolution Reaction

Two-dimensional transition metal carbides, nitrides and carbonitrides, known as MXenes, have shown great promise as active materials in catalytic applications such as hydrogen evolution reaction. Tungsten (W) containing MXenes are of particular interest as they are predicted to have overpotentials close to Pt based catalysts in the hydrogen evolution reaction (HER) making them candidates for a more sustainable clean energy application. However, the incorporation of W into MXene structure has proven difficult due to the calculated instability of its hypothetical precursor M<i>_n</i>₊₁AX<i>_n</i> phases (W₃AC₂ and W₂AC). In this study, we discuss the synthesis of W-containing MXene (W₂Ti)C₂T<i>_x</i>, derived from a nanolaminated ternary carbide (W,Ti)₄C_4-<i>x</i>precursor. The synergistic effect of the W-containing basal plane endows W₂TiC₂T<i>_x</i> MXene with remarkable electrocatalytic HER performance in terms of lowest HER overpotential (~162 mV) and long-term stability of &gt;24 hours under acidic conditions over other W_1.33CT<i>_x</i> MXenes (~320 mV) and Mo₂CT<i>_x</i> MXenes (~190 mV). This enhanced HER activity of (W₂Ti)C₂T<i>_x</i> MXene may be linked to W's highly active and ordered basal-plane vacancies. In this direction, more efforts on the continuous exploration of W-containing MXenes with low overpotentials are significant toward the progress of HER catalysts for clean energy applications due to their highly active basal plane.