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Shedding new light onto the fundamental understanding of heterogeneous gold catalysis

last modified May 26, 2017 01:50 PM
Shedding new light onto the fundamental understanding of heterogeneous gold catalysis

Size of gold particles supported on titania affects adsorption and reactivity of glycerol over the catalyst surface. Click to see larger version.

A newly published research study in ACS Catalysis conducted by Dr Carmine D'Agostino from the CEB department has shed new light onto the fundamental understanding of heterogeneous gold catalysis. Gold is well-known to be the most noble of all metals and is usually thought to be the least reactive metal, which is one of the main reasons for using it in the making of jewels. For this reason, its use in catalysis has for a long time been overlooked. However, in the mid 80s, Hutchings and Haruta discovered that tiny gold nanoparticles can be an excellent catalyst. Since then, research in gold catalysis has been growing rapidly. In particular, its applications in sustainable chemistry have shown that gold-based catalysts can be very effective in converting bio-renewable platform chemicals, such as glycerol, to value-added chemicals.

T1/T2 ratio (an indicator of adsorption strength) of glycerol and water over Au/TiO2 catalysts as a function of gold mean particle size. Larger gold particles decrease the affinity of the glycerol reactant for the catalyst surface relative to the water solvent.
One of the main peculiarities of gold catalysis is its sensitivity to particle size. Small gold particles are known to be very effective catalysts in such reactions; however, an increase in particle size can have a dramatic effect and reduce significantly catalyst activity. Theoretical studies have suggested that smaller gold particles show stronger binding properties with substrates such as glycerol. In his research, Dr Carmine D'Agostino has been able to validate with experiments such a conclusion, using the protocols that he has been developing in recent years to characterise adsorption in catalytic materials. In particular, studying the aerobic oxidation of glycerol in water over gold nanoparticles supported on titania, the work shows as an increase of gold particle size leads to a dramatic decrease in adsorption strength of the glycerol reactant relative to the water solvent, leading to a greater extent of solvent inhibition, which results in a lower catalyst activity.

This result is of great significance in understanding the reactivity of polyols over supported gold catalysts and gives the first experimental evidence that smaller gold particles tend to be stronger adsorption sites for glycerol, in agreement with computational and theoretical studies.

DOI: 10.1021/acscatal.7b01255

 

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