Urchin-like Pd@CuO–Pd yolk–shell nanostructures: synthesis, characterization and electrocatalysis

Abstract

Novel urchin-like Pd@CuO–Pd yolk–shell nanostructures are synthesized through subsequent oxidation of Pd@Cu₂O truncated octahedron core–shell precursors with a PdCl₄²⁻ aqueous solution. The permeable hierarchical CuO shells are constructed by a radially standing 1D single-crystalline nanothorn with Pd nanoparticles. The Pd nanocube cores are encapsulated and confined in the void space of the urchin-like shells. The urchin-like yolk–shell Pd@CuO–Pd nanostructures demonstrate excellent electrocatalytic activity and selectivity for glucose oxidation. Enzyme-free glucose biosensors based on the urchin-like yolk–shell Pd@CuO–Pd electrocatalysts display a higher sensitivity (665.9 μA cm⁻² mM⁻¹) than those of the CuO nanoparticles (455.8 μA cm⁻² mM⁻¹), Cu₂O nanoparticles (220.4 μA cm⁻² mM⁻¹), Pd@Cu₂O truncated octahedra (179.1 μA cm⁻² mM⁻¹), Pd mixtures (65.5 μA cm⁻² mM⁻¹) and Pd nanocubes (1.42 μA cm⁻² mM⁻¹). The outstanding electrocatalytic performance of the urchin-like Pd@CuO–Pd yolk–shell nanostructures might be ascribed to two reasons: the unique hierarchical yolk–shell structures provide highly exposed active sites and act as an individualized nanoreactor to enhance the mass diffusion and transport of reactants at the electrode/electrolyte interface. Moreover, the nanocomposite of metal oxide semiconductor CuO and noble metal Pd would result in a synergetic effect to improve the electrocatalysis.