Kinetics and Surface Composition of Au/Pt Nanoparticles Synthesized in Microemulsion Template Using a Prediction Model

Abstract

The objective of this study is producing tailor-made Au/Pt nanoparticles. The presence of Au on the surface of Au/Pt nanocatalysts has been shown to improve the Pt catalytic activity. That is why the ability to exert control over surface composition is key to improve catalysts efficiency of bimetallic nanoparticles. A computer simulation study was carried out in order to comprehend how the resulting surface can be modified by the simple strategy of varying Au:Pt ratio. We present an in-depth kinetic simulation study on the influence of Au:Pt ratio on the formation of Au/Pt nanoparticles synthetized in microemulsions. The resulting nanostructures and surface compositions are explained as a function of kinetic parameters such as Au:Pt ratio, concentration and intermicellar exchange rate. It should be stressed that the compartmentalization of the reaction medium play a fundamental role in the synthesis because micelles act as dosing pump of the faster precursor metal (Au). It allows us to explain that a higher Au precursor amount in feeding solution results in a Au reduction which takes place over a longer period of time. As a result, Au is deposited until longer stages of the synthesis, so that Au is present at nanoparticle surface. Micelles as reaction media produces a minor impact on Pt due to its slower reduction. By adjusting the Au:Pt ratio, it is possible to create surfaces with specific compositions based on the distinct kinetic behaviors of Au and Pt. The conclusions on the degree of atomic mixing under varied Au:Pt ratios are further supported by numerical results on surface composition, which correctly mirror experimental data.