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© Springer Nature Switzerland AG 2020
R. Adzic, N. Marinkovic, Platinum Monolayer Electrocatalysts,
https://doi.org/10.1007/978-3-030-49566-4_7
Chapter 7
Platinum Monolayer Electrocatalysts
7.1 Concept of Pt Monolayer Electrocatalysts
Electrocatalytic reactions are heterogeneous reactions that occur at the interface of
catalyst and electrolyte with dissolved gaseous or liquid reactants. Thus, adsorption,
desorption, dissociation, surface diffusion, recombination and product desorption
all take place at the surface, and all these processes depend on distribution of surface
atoms or surface sites. This view is supported by the well-known structural dependence of electrocatalytic reactions. In addition, the pronounced effect of metal
adlayers, adatoms, and submonolayers obtained by underpotential deposition
(UPD) clearly show that surface atoms play a key role in determining the kinetics of
electrocatalytic reaction, reaction mechanism, and the nature of intermediates and
products. Thus, the notion of the role of top layers of atoms on solid catalysts has
been a part of the understanding of electrocatalytic reactions for some time.
However, the techniques to control and modify surface structures and to study these
effects were not readily available. The research in electrocatalysis of fuel cell reactions has been directed to address the questions that hampered a wide-scale application of fuel cells. These included decreasing amounts of platinum in catalysts and
increasing the catalysts’ durability and utilization.
Two main approaches used over the last several decades to improve the Pt electrocatalysts include:
1. Decreasing the particle size
2. Alloying Pt to form bimetallic or multimetallic catalysts
Decreasing the particle size brings about an increase in a Pt-specific surface,
resulting in an increased reaction rate. However, for some reactions, oxygen reduction for example, this is limited by extensive oxidation of small nanoparticles below
a certain size, which causes a decrease in the reaction rate. The alloying approach
gives the best results with Pt 3 M stoichiometry, which for lighter metals, such as Fe,
Co, Ni, is mostly Pt.
© Springer Nature Switzerland AG 2020
R. Adzic, N. Marinkovic, Platinum Monolayer Electrocatalysts,
https://doi.org/10.1007/978-3-030-49566-4_7
Chapter 7
Platinum Monolayer Electrocatalysts
7.1 Concept of Pt Monolayer Electrocatalysts
Electrocatalytic reactions are heterogeneous reactions that occur at the interface of
catalyst and electrolyte with dissolved gaseous or liquid reactants. Thus, adsorption,
desorption, dissociation, surface diffusion, recombination and product desorption
all take place at the surface, and all these processes depend on distribution of surface
atoms or surface sites. This view is supported by the well-known structural dependence of electrocatalytic reactions. In addition, the pronounced effect of metal
adlayers, adatoms, and submonolayers obtained by underpotential deposition
(UPD) clearly show that surface atoms play a key role in determining the kinetics of
electrocatalytic reaction, reaction mechanism, and the nature of intermediates and
products. Thus, the notion of the role of top layers of atoms on solid catalysts has
been a part of the understanding of electrocatalytic reactions for some time.
However, the techniques to control and modify surface structures and to study these
effects were not readily available. The research in electrocatalysis of fuel cell reactions has been directed to address the questions that hampered a wide-scale application of fuel cells. These included decreasing amounts of platinum in catalysts and
increasing the catalysts’ durability and utilization.
Two main approaches used over the last several decades to improve the Pt electrocatalysts include:
1. Decreasing the particle size
2. Alloying Pt to form bimetallic or multimetallic catalysts
Decreasing the particle size brings about an increase in a Pt-specific surface,
resulting in an increased reaction rate. However, for some reactions, oxygen reduction for example, this is limited by extensive oxidation of small nanoparticles below
a certain size, which causes a decrease in the reaction rate. The alloying approach
gives the best results with Pt 3 M stoichiometry, which for lighter metals, such as Fe,
Co, Ni, is mostly Pt.