Conversion of a Bi–Sn complex to Bi nanoparticles for the enhancement of V(ii)/V(iii) redox kinetics

Abstract

In this work, evidence for ligand formation between Sn and Bi during the colloidal synthesis of Bi metal nanoparticles (NP) in an aqueous suspension is provided utilizing time-resolved X-ray absorption and ¹¹⁹Sn Mössbauer spectroscopy. SnCl³⁻ is used simultaneously as a reducing agent and stabilizing agent. Auto-reducible complex formation between Sn and Bi using this approach has not been previously reported. A distorted pyramidal Bi–SnCl³⁻ complex is found to form on the surface of the Bi metal NP which enables its incorporation into electrostatic layer-by-layer (LbL) assemblies of graphene nanoplatelets. These assemblies are shown to act as a bifunctional electrocatalyst to simultaneously suppress capacitance loss associated with the hydrogen evolution reaction (HER) and enhance the activity of the V³⁺ ↔ V²⁺ redox couple. Sustainable aqueous-based colloidal synthesis of Bi metal NPs utilizing SnCl³⁻ surface ligands provides a convenient method to introduce Bi into macroscopic electrodes for various electrochemical applications.