Heterogeneous nanocomposites composed of silver sulfide and hollow structured Pd nanoparticles with enhanced catalytic activity toward formic acid oxidation

Abstract

Nanocomposites consisting semiconductor and noble metal domains are of great interest for their synergistic effect-based enhanced properties in a given application. Herein, we demonstrate a facile approach for the synthesis of heterogeneous nanocomposites consisting of silver sulfide (Ag2S) and hollow structured Pd nanoparticles (hPd). It begins with the preparation of core–shell nanoparticles with an Ag core and an alloy Ag/Pd shell in an organic solvent via galvanic replacement reaction (GRR) between Ag seed particles pre-synthesized and Pd2+ ion precursors. The Ag component is then removed from the core and shell regions of core–shell Ag-Ag/Pd nanoparticles, and converted into Ag2S by elemental sulfur (S). The Ag2S forms the semiconductor domain in the nanocomposite and shares the solid-state interface with the resultant hollow structured Pd nanoparticle. As demonstrated, the Ag2S-hPd nanocomposites exhibit superior catalytic activity and durability for formic acid oxidation, compared to the pure Pd nanoparticles prepared by oleylamine reduction of Pd ion precursors and commercial Pd/C catalyst, due to the electronic coupling between semiconductor and noble metal domains in the nanocomposites. In addition, the structural transformation from core–shell to heterogeneous nanocomposites may provide new opportunities to design and fabricate hybrid nanostructures with interesting physicochemical properties.