SYNTHESIS OF GOLD NANOPARTICLE CATALYSTS USING A BIPHASIC LIGAND EXCHANGE METHOD AND STUDY OF THEIR ELECTROCATALYTIC PROPERTIES

Description

<div><br></div><div><p>Noble
metal nanoparticles have been studied extensively as heterogeneous catalysts
for electrocatalytic and thermal reactions. In particular, the support material
for the catalytic species is known to play a role in influencing the geometric
and electronic properties of the active site as well as its catalytic
performance. Polycrystalline gold electrodes have
been used as a support to modify the
electrocatalytic behavior of adsorbed molecular species. Here, we have
studied two electrocatalytic processes- the hydrogen evolution reaction (HER) and
the oxygen reduction reaction (ORR), using Au nanoparticle-based catalysts.</p>

<p>Transition
metal dichalcogenides are well-known HER catalysts that show
structure-sensitive catalytic activity. In particular, undercoordinated sulfur
sites at the edges of bulk materials as well as amorphous clusters and
oligomers tend to show the highest reactivity. The hydrogen adsorption energy
of MoS_x nanoclusters can be further tuned through the metallic
support. Here, we synthesize colloidal Au@MoS₄^2-, Au@WS₄^2-and
Au@MoS₄^2--WS₄^2- using a biphasic
ligand-exchange method. The MoS₄^2-
and WS₄^2- complexes show higher HER activity when supported on Au nanoparticles than on
to a carbon control, illustrating the
electronic role played by the support material.</p>

<p>In the
second project, Au nanoparticle cores are utilized as supports for Pd
submonolayer and monolayer surfaces in order to catalyze the two-electron
reduction of O₂ to generate hydrogen peroxide. Bulk surfaces of Pt and Pd are excellent catalysts for the four-electron reduction of O₂ to H₂O.
In order to achieve high selectivity for H₂O₂, we postulate that the ensemble geometry of the Pd surface
must be reduced to small islands or single atoms based on literature studies
that have shown that large Pd ensembles are required for O–O bond cleavage. In this study, we synthesize several
submonolayers surface coverages of Au@Pd core-shell nanoparticles using a biphasic ligand-exchange method. As the Pd coverage
decreases from monolayer to submonolayer, the peroxide
selectivity rises but is accompanied by an increase in catalytic overpotential.
The highest peroxide selectivity was observed for 0.1 layers of Pd on Au, which
likely exhibits the highest fraction of isolated atom and small cluster
geometric ensembles of Pd.</p><br></div>

Links & Downloads

1. 10.25394/pgs.14498631.v1

Tags

Inorganic Chemistry

Catalysis

Palladium Catalysts

Gold Nanoparticle

hydrogen evolution electrocatalyst

Oxygen Evolution Reaction

ligand exchange reaction

Additional Fields

Identifer	oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/14498631
Date	06 May 2021
Creators	Toma Bhowmick (10712736)
Source Sets	Purdue University
Detected Language	English
Type	Text, Thesis
Rights	CC BY 4.0
Relation	https://figshare.com/articles/thesis/SYNTHESIS_OF_GOLD_NANOPARTICLE_CATALYSTS_USING_A_BIPHASIC_LIGAND_EXCHANGE_METHOD_AND_STUDY_OF_THEIR_ELECTROCATALYTIC_PROPERTIES/14498631