Preparation, Characterization And Electrochemical Properties Of Small Size Ag And Au@Ag Nanoparticles Carrying Of Pt Electrocatalysts

Pt is rare in nature.However,it is an essential element for many catalyst of chemical reactions.Therefore,it has been a significant task for chemical scientists to design and synthesize pretinium catalysts with high-performance catalytic surface.In this study,we synthesized a serious of Pt nano catalysts employing nanoparticles of Ag and Au@Ag(core@shell),which are cheaper and less active than Pt,to load nano or subnano scale Pt entities.The Pt particles loaded on Ag and Au@Ag using different methods was examined and the effect of Pt content on the size(or dispersion) of Pt particles and the corresponding specific surface area for electronic catalysis acitivity were investigated.Also,the composition,structure,and catalytic properties of as-synthesized Pt-based catalyst were evaluated by the electrochemical oxidation of formic acid and methanol.Firstly,Ag nanoparticles of 2.7±0.4 nm and 2.7±0.7 nm were prepared respectively using PVP protecting and reverse micelles method.With these particles, Pt^Ag particles as well as series of Pt_m^Ag-B/C(m for Pt/Ag atomic ratio) catalysts were then prepared by reverse micelles method using K₂PtCl₄ as precursor.It is found that the Pt utilization increased with the lowering of m in Pt_m^Ag-B/C samples.Au particles with a diamter of 1.9 nm were prepared using PVP as capping agent, and two series of samples Au@Ag_m-â… and Au@Ag_m-â…¡(m for the Ag/Au atomic ratio) were prepared by seed-mediated growth method using Au particles as seed and hydrogen or sodium citrate as reducing agent.Furthermore,Pt_0.5^Au@Ag_m catalyst was obtained by depositing Pt on the surface of Au@Ag_m particles.It was demonstrated that the tunning of Pt utilization in catalyst was realized by adjusting the thickness of Ag shell.The catalystic activities of as-synthesized samples for the electro-oxidation of methanol and formic acid were examined.The results show that when Pt utilization is lower,the peak potential(0.45 V) of Pt_0.5^Au@Ag_m-â…¡/C series catalysts for the electrooxidation of formic acid is lower than that of the conventional Pt/C and Pt_m^Ag-B/C samples(0.75 V).In the meanwhile,the specific catalytic activity of Pt_0.5^Au@Ag_m-â…¡/C catalysts for formic acid electroxidation was found to be 4-9 times as high as that of conventional Pt/C catalyst.