Ag Nanoparticle-Decorated V2CTX MXene Nanosheets as Catalysts for Water Splitting

Two-dimensional (2D) MXenes and their composites are increasingly performing as efficient catalysts for the production of hydrogen (H-2) and oxygen (O-2). Herein, we report a strategy for the surface modification of V2CTx MXene as an efficient bifunctional hybrid electrocatalyst for water splitting application by optimized loading of spherical silver nanoparticles (Ag-NPs) on V2CTx nanosheets (NSs). In 1.0 M KOH solution, the V2CTx/Ag-NPs nanohybrid (labeled as HII) attained an overpotential of 310 mV (vs RHE) and a Tafel slope of 62 mV/dec for the oxygen evolution reaction (OER), and an overpotential of 32 mV (vs RHE) and a Tafel slope of 114 mV/dec for the hydrogen evolution reaction (HER). The hybrid showed significantly improved values than those of their constituents (MXene nanosheets and Ag-NPs) and was even comparable to the industrial RuO2 and Pt electrocatalysts. The uniform loading of silver nanoparticles (Ag-NPs) on 2D MXene sheets acted as a conductive agent and their large surface area facilitated ion transport by ensuring short conductive pathways at the electrode- electrolyte interface. Moreover, the strong contact and electrical coupling with charge transfer between Ag-NPs and V2CTx MXene provided much higher water-splitting performance and structural stability as well as low charge transfer resistance, which eventually enhanced the intrinsic activity of the catalyst. This HER reaction followed the Volmer-Heyrovsky mechanism for H-2 production at the cathode. The dispersion of Ag-NPs increases the Raman signals of V2CTx for the hybrid, demonstrating the surface-enhanced activity of Raman scattering. The three-dimensional frame structure of nickel foam helped in easing the release of oxygen and hydrogen gas bubbles from the reaction sites.