Solid-State On-SubstrateSynthesis of Size-ControlledCuPt@Cu₂O Core–Shell Nanocubes and Applicationsfor Electrochemical Sensing and ElectrocatalyticMethanol Oxidation Reaction

The development of size- and shape-controlled nanomaterials is essential to tailor their properties and performance for wide-ranging applications from catalysis to sensing. Solid-state synthesis of nanostructures is attractive from a sustainability perspective, but they typically lack the desired size and shape control at small-scale dimensions. This work shows that colloidal precursors can be used in a solid-state route to form hybrid core–shell nanostructures with simultaneous size and morphology control. Encapsulation of PtNPs with a well-defined Cu₂O shell produces CuPt@Cu₂O core–shell nanocubes grown directly from the underlying substrate. The controlled formation of the nanostructures is facilitated by the diamine passivation layer on the Cu substrate. On-substrate growth of the nanocubes gives ease of postsynthesis processing for them to be used directly in electrochemical applications. We show that the synthesized nanostructured substrates have high sensitivity as an electrocatalyst for glucose sensing. We further demonstrate their potential for direct methanol fuel cells by assessing the methanol oxidation reaction (MOR). The mass activity is determined to be 1.656 A mg_Pt^–1 for MOR, and initial studies indicate the substrates show high CO tolerance.