Plasma-Induced Phase Transition and Ruthenium Nanoparticle Decoration on 1T/2H WSe2 Nanosheets for Hydrogen Evolution Reaction

Abstract Phase or interface engineering of two-dimensional (2D) transition-metal dichalcogenides is an effective approach for enhancing hydrogen evolution reaction (HER) activity. Herein, we combine both of them by a hybrid top-down and bottom-up strategy that involves first synthesizing heterophase 1T/2H WSe2 nanosheets via dual-cathodic plasma exfoliation from the bulk and then decorating Ru nanoparticles (NPs) (∼3 nm) on WSe2 nanosheets (NSs) through an in situ hydrothermal growth process. The plasma exfoliation process induced defects, compressive strain, and electron injection, promoting partial 2H-to-1T phase conversion of WSe2 NSs. Density functional theory calculations reveal stronger Ru NPs binding on the 1T phase than on the 2H phase with binding energies of −12.93 and −11.88 eV on the 1T basal plane and Se edge, respectively, compared with −7.52 and −10.03 eV on the corresponding 2H sites; this offset binding energy allows homogeneous Ru NP dispersion across basal planes and edge sites and induces hydrogen adsorption free energy (ΔGH) values closer to zero. The optimized Ru7.5−1T/2H WSe2 nanocomposite exhibited excellent HER performance, delivering an overpotential of 154 mV at 10 mA cm−2 and a Tafel slope of 58 mV dec−1, significantly outperforming pristine WSe2 NSs (358 and 101 mV dec−1, respectively). Moreover, negligible degradation of the Ru7.5−1T/2H WSe2 nanocomposite was observed after 5000 cyclic voltammetry cycles, demonstrating its outstanding durability. The combined effects of heterophase formation and Ru−WSe2 interfacial interactions provide an effective route toward producing highly active and durable HER electrocatalysts.