Shuttle-like core-shell gold nanorod@Ag-Au nanostructures: Shape control and electrocatalytic activity for formaldehyde oxidation

Bimetallic nanostructures have attracted much attention due to their special properties in optics, surface plasmon and catalysis. In this work, two synthesis routes of core/shell gold nanorod/silver (AuNR@Ag) nanostructures were revisited to pursue the control factor of shuttle-like shapes, which demonstrated the key role of residual Au precursor in the formation of shuffle-like shapes. A novel route was adopted to verify the shape control effect of Au and fabricate shuffle-like AuNR@Ag-Au nanostructures. The presence of gold in the shell growth solution leads to shuffle-like shapes of bimetallic nanostructures, and the Au/Ag molar ratio controls shape details of the shuffle-like nanostructures. Then, the electrocatalytic activity of these core-shell nanostructures in the electrochemical oxidation of formaldehyde in alkaline solutions was investigated. In the forward scan the peaks at + 0.22-0.3 V for all samples correspond to the electrochemical oxidation catalyzed by monometallic Ag or Au atoms, but the low potential peak at about - 0.1 V for AuNR@Ag-Au sample with less Au alloy shell displays the oxidation reaction catalyzed by the adjacent Ag and Au atoms. The sample with less Au alloy shell also shows higher catalytic activity. Additionally, the surface reaction mechanism is proposed for the electrocatalytic oxidation of formaldehyde in alkaline conditions.