Automated electrodeposition of bimetallic noble-metal nanoclusters via redox-replacement reactions for electrocatalysis

Abstract

Nanoclusters of bimetallic composition involving platinum with gold or ruthenium were sequentially deposited via redoxreplacement of electrodeposited sacrificial Cu adlayers for controlling the deposition of the noble metals. These steps were repeated for a desired number of automated cycles toward: (a) stepwise increase of the size of nanostructures, and (b) stepwise synthesis of the nanostructures in relation to tuning of their electrocatalytic properties. Studies were also performed by eliminating the Cu replacement steps (direct spontaneous deposition) as well as implementing sequential codeposition of the noble-metals with simultaneous Cu redox-replacement steps. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy were implemented to characterize properties of the bimetallic nanoclusters with respect to morphology, elemental composition, and electrocatalytic activity for methanol oxidation. The order of electrocatalytic activity for methanol oxidation in acidic medium was (Ru|Pt) > (Au|Pt) > Pt, in line with the bifunctional mechanism.