The composition-controlled synthesis of Pt-Ag bimetallic nanochains for catalytic methanol oxidation

Highlights: • Pt-Ag bimetallic nanochains were synthesized using plasma discharge in water. • Composition of Pt-Ag was varied by plasma-assisted oxidation and removal. • Pt₇₁Ag₂₉/C exhibited the best activity toward MOR. • Catalytic activity was enhanced by the electronic and synergistic effects. - Abstract: Controlling the elemental composition of Pt-based bimetallic nanostructures plays an important role in catalytic activity. Herein, we synthesized Pt-Ag bimetallic nanochains with various compositions via bipolar pulsed discharges in water. The composition of Pt-Ag bimetallic nanochains was controlled by varying the pulse duration in a range from 1.3 to 2.3 μs, which could determine the different plasma-assisted oxidation states and subsequent decomposition of the oxide layer that was dependent on the thermal parameters of Pt and Ag. The transmission electron microscopy revealed that the nanochain structure was constructed via the attachment of Pt-Ag alloyed nanoparticles. With increasing Ag content, the higher binding energy of the Pt 4f peak in the XPS spectra due to the electron transfer from Ag to Pt atoms was observed, and subsequently the Ag₂O to metallic Ag ratio increased. The electrochemical measurements for methanol oxidation revealed that the electrocatalytic activity, stability and durability of the Pt₇₁Ag₂₉ bimetallic nanoparticles were superior, which could be attributed to the synergistic effect of the Ag oxide and the downshift of the d-band center via electronic modification