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

[Display omitted] •Two synthesis routes were revisited to pursue the control factor of shuttle-like shape.•A novel route was adopted to verify the shape control effect of the Au precursor.•The Au/Ag ratio in shell growth solution controls the shape details of nanostructures.•Bimetallic nanostructures can catalyze the electrochemical oxidation of formaldehyde.•The catalytic activity lies on the surface structure/component of the bimetallic shells. 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 shuttle-like shapes. A novel route was adopted to verify the shape control effect of Au and fabricate shuttle-like AuNR@Ag-Au nanostructures. The presence of gold in the shell growth solution leads to shuttle-like shapes of bimetallic nanostructures, and the Au/Ag molar ratio controls shape details of the shuttle-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.