Facile synthesis of self-assemblies of ultrathin round Pd nanosheets or nanorings and their enhanced electrocatalytic activities

Abstract

Self-assemblies consisting of ultrathin round Pd nanosheets with a thickness of three to six atomic layers for an individual Pd nanosheet are fabricated in a one-pot process by reducing Pd(acac)₂ with CO as a reducing agent in the presence of sodium acetate at 100 °C for 3 h. The synergistic effect of CO and acetate ions is crucial to the formation of the ultrathin round Pd nanosheet self-assemblies. The selective adsorption of I⁻ ions on the side (100) faces as well as CO on the (111) flat surfaces results in the production of Pd nanosheets, while the van der Waals forces between acetate ions adsorbed on the surfaces of the nanosheets promote the formation of a self-assembly of Pd nanosheets. Based on the Pd nanosheet self-assemblies, Pd nanoring self-assemblies are generated by means of oxidative etching arising from I⁻/O₂ pairs. Both the as-prepared self-assemblies of ultrathin round Pd nanosheets and the self-assemblies of Pd nanorings exhibit outstanding electrocatalytic activities.