Direct Electrosynthesis of Metal Nanoparticles on Ti₃C₂T_x-Mxene during Hydrogen Evolution

Herein, we propose a simple yet effective method to deposit metal nanoparticles on Ti₃C₂T_x-MXene via direct electrosynthesis. Without using any reducing reagent or annealing under reducing atmosphere, it allows the conversion of metal salts (e.g., PtCl₄, RuCl₃·yH₂O, IrCl₃·zH₂O, AgNO₃, and CuCl₂·2H₂O) to metal nanoparticles with a small particle size (ca. 2 nm). Under these circumstances, it was realized that the support effect from Ti₃C₂T_x-MXene (electron pushing) is quite profound, in which the Ti₃C₂T_x-MXene support will act as an electron donor to push the electron to Pt nanoparticles and increase the electron density of Pt nanoparticles. It populates the antibonding state of Pt-Pt bonds as well as the adsorbate level that leads to a “weakening” of the ΔG_H* in the optimal position. This rationalizes the outstanding activity of Pt/Ti₃C₂T_x-MXene (5 wt %, η₁₀ = 16 mV) for the hydrogen evolution reaction (HER). In addition, this direct electrosynthesis method grants the growth of two or multiple types of metal nanoparticles on the Ti₃C₂T_x-MXene substrate that can perform dual or multiple functions as desired. For instance, one can prepare an electrocatalyst with Pt (2.5 wt %) and Ru nanoparticles (2.5 wt %) on the Ti₃C₂T_x-MXene support from the same synthetic method. This electrocatalyst (Pt_Ru/Ti₃C₂T_x-MXene) can display good electrocatalytic HER performance in both acid (0.5 M H₂SO₄) and alkaline electrolytes (1.0 M KOH).