Assembling palladium and cuprous oxide nanoclusters into single quantum dots for the electrocatalytic oxidation of formaldehyde, ethanol, and glucose

Abstract

To effectively manipulate the electronic structure of the catalysts, we present here a simple bottom-up synthesis protocol for agglomerating palladium and cuprous oxide ultrasmall nanoclusters into single nanoparticles, forming so-called quantum dot assemblies (QDAs). Our synthesis is based on the galvanic displacement of copper with palladium cations under O2-free conditions, rendering the simultaneous and unique crystal growth of ∼3 nm Cu2O and Pd clusters. Such assemblies, comprising ultrasmall nanoconstitutes, offer much more phase boundaries, where the interfacial electronic effect becomes prominent in catalysis. This is demonstrated in the electrocatalytic oxidation of formaldehyde, ethanol, and glucose. In all three cases, the QDA catalyst, despite its similar Pd loading, outperforms the monometallic palladium catalyst. Indeed, complementing the experimental results with density functional theory calculations, we could confirm the sharply increased charge density at the Pd-Cu heterojunction and the decreased energy barrier of the formaldehyde oxidation on the QDA catalyst. Finally, we applied these catalysts in electroless copper deposition - an industrially relevant process for manufacturing printed circuit boards. The QDA catalysts gave uniform and robust copper wires at a rate that was three times faster than that of the monometallic Pd catalyst, showing their potential for real-life applications.