Preparation and characterization of PtIr alloy dendritic nanostructures with superior electrochemical activity and stability in oxygen reduction and ethanol oxidation reactions

Abstract

Pt-based alloy dendritic nanostructures have been known to exhibit improved electrocatalytic properties due to their particularly modulated surface and electronic structures favorable for alcohol oxidation and oxygen reduction reactions. We prepared PtIr alloy nanoparticles (NPs) with a dendritic shape as three-dimensional structures for enhanced ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR) by thermal decomposition in the presence of cetyltrimethylammonium chloride (CTAC) as surfactant. The PtIr alloy dendritic nanoparticles show a well-defined three-dimensional alloy nanostructure analyzed using TEM, XPS, and XRD. In particular, the PtIr alloy nanostructures exhibit 2.74 times higher electrochemical active surface areas (EASAs) than commercial Pt/C. Also, in the EOR, the PtIr alloy dendritic electrocatalyst exhibits excellent electrochemical properties, including high I_f/I_b ratio and current density, high negative onset potential, and good electrochemical stability compared to the commercial Pt/C electrocatalyst. In addition, the PtIr alloy dendritic electrocatalyst exhibits enhanced electrochemical activity and stability, i.e., 3.19 times higher specific mass-kinetic activity than the commercial Pt/C electrocatalyst, and an 8 mV reduction of the half-wave potential in the ORR. The improved electrochemical activity and stability of the PtIr alloy dendritic electrocatalyst in the EOR and ORR are ascribed to the dendritic structures, the surface state of the electrocatalyst, and the controlled electronic structure due to the Ir atoms in the alloy phase.