Core-Shell Nanocatalysts Obtained in Reverse Micelles: Structural and Kinetic Aspects

C Tojo ,David Buceta,M Arturo López‐Quintela

doi:10.1155/2015/601617

C Tojo , David Buceta + Show 1 more

Open Access

https://doi.org/10.1155/2015/601617

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Abstract

Ability to control the metal arrangement in bimetallic nanocatalysts is the key to improving their catalytic activity. To investigate how metal distribution in nanostructures can be modified, we developed a computer simulation model on the synthesis of bimetallic nanoparticles obtained in microemulsions by a one-pot method. The calculations allow predicting the metal arrangement in nanoparticle under different experimental conditions. We present results for two couples of metals, Au/Pt (Δε=0.26 V) and Au/Ag (Δε=0.19 V), but conclusions can be generalized to other bimetallic pairs with similar difference in standard reduction potentials. It was proved that both surface and interior compositions can be controlled at nanometer resolution easily by changing the initial reactant concentration inside micelles. Kinetic analysis demonstrates that the confinement of reactants inside micelles has a strong effect on the reaction rates of the metal precursors. As a result, the final nanocatalyst shows a more mixed core and a better defined shell as concentration is higher.

Highlights

The development of new improved nanocatalysts has attracted extensive research due to scientific and technological interest [1,2,3]
The ability to control the metal arrangement in bimetallic nanoparticles is the key to improving the catalytic activity
The fact that reactants are trapped into micelles plays a key role in metal arrangement in bimetallic nanocatalysts, because it affects the metals reduction in different ways

Summary

Introduction

The development of new improved nanocatalysts has attracted extensive research due to scientific and technological interest [1,2,3]. In the research at hand, a comprehensive analysis of the resulting nanostructures is performed, based on the hypothesis that metal arrangement is due to the particular combination of three main factors: the difference in reduction rate of both metals (characteristic of the pair of metals), the intermicellar exchange rate (determined by microemulsion composition), and the amount of metal precursors inside micelles. To investigate how metal distribution in the nanostructure can be modified by changing reactant concentration, two couples of metals were chosen, and microemulsion composition was kept unvariable Because of their high catalytic activity the nanocatalysts chosen for the study were Au/Pt [12, 13, 39,40,41,42] and Au/Ag [43,44,45,46].

Simulation Model

Changing the Metal Salt Concentration

Conclusions