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Tuning excitability by alloying: the Rh(111)/Ni/H2 + O2 system
T Smolinsky1, M Homann1, R Imbihl1
1Institut für Physikalische Chemie und Elektrochemie, Leibniz Universität Hannover, Callinstrasse 3a, D-30167 Hannover, Germany. imbihl@pci.uni-hannover.de.
Physical Chemistry Chemical Physics : PCCP
|December 15, 2015
Summary
This study investigated the O2 + H2 reaction on a Ni-alloyed Rh(111) surface. A critical nickel coverage of 0.13 monolayers is needed for excitability, leading to chemical waves and oscillations.
Area of Science:
- Surface chemistry
- Heterogeneous catalysis
- Chemical kinetics
Background:
- The O2 + H2 reaction on metal surfaces is a model system for studying surface dynamics.
- Alloying surfaces can significantly alter their catalytic and dynamic properties.
Purpose of the Study:
- To investigate the dynamic behavior of the O2 + H2 reaction on a Rh(111) surface alloyed with Ni.
- To map the bifurcation diagram as a function of Ni coverage and identify critical parameters for excitability.
Main Methods:
- Photoemission electron microscopy (PEEM) was used for spatially resolved studies.
- Experiments were conducted in the 10(-5) mbar pressure range at T = 773 K.
Main Results:
- A critical Ni coverage of Θ(Ni,crit) = 0.13 monolayers (ML) was identified for surface excitability.
- Pulse trains and irregular chemical wave patterns were observed in the excitable regime.
- The frequency of oscillations increased linearly with Ni coverage from 0.13 to 1.3 ML, while propagation speed showed no clear dependence.
Conclusions:
- Nickel alloying on Rh(111) can induce complex dynamic behaviors in the O2 + H2 reaction.
- The Ni coverage is a critical parameter controlling the excitability and oscillation frequency of the reaction system.
