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 (H2) and oxygen (O2). 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 H2 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.