One-pot synthesis of monodisperse copper–silver alloy nanoparticles and their composition-dependent electrocatalytic activity for oxygen reduction reaction

Abstract

Development of an economical, well-defined and efficient electrocatalyst having a potential to replace Pt/C is crucial for oxygen reduction reaction (ORR). In this respect, we report herein one-pot wet-chemical protocol for the composition-controlled synthesis of monodisperse CuAg alloy nanoparticles (NPs) and their composition-dependent electrocatalytic activities in ORR for the first time under an alkaline condition. The presented synthetic procedure yields CuAg NPs that exhibit monodisperse size distribution with an average particle diameter of ∼8 nm. Almost homogenous CuAg alloy formation is proved by using many advanced analytical techniques despite the considerable lattice mismatch between Cu and Ag. At all compositions investigated, the ORR activities of CuAg electrocatalysts are found to be significantly higher than monometallic Ag NPs. Improved ORR kinetics of CuAg alloy NPs are demonstrated by Tafel slopes (85 mV/dec for Cu30Ag70, 84 mV/dec for Cu40Ag60 and 78 mV/dec for Cu60Ag40 which are all smaller than that of monometallic Ag (113 mV/dec). Electrochemical impedance measurements support these findings and represent that charge transfer resistance strongly depends on composition of CuAg electrocatalyst. The ORR activity and surface analysis results put Cu40Ag60 forward since Cu oxidation is suppressed in Cu40Ag60 NPs, caused by Ag enhancement in the surface.