Practical Considerations for Understanding Surface Reaction Mechanisms Involved in Heterogeneous Catalysis

Area of Science:

• Heterogeneous catalysis
• Surface reaction mechanisms
• Chemical kinetics

Background:

• Determining catalyst active sites, reactant interactions, and reaction mechanisms is challenging, particularly for heterogeneous catalysts due to complex surface dynamics.
• The Eley-Rideal mechanism is often invoked but can be confused with other surface reaction models.
• Bibliometric analysis is used to examine common reactions attributed to the Eley-Rideal mechanism.

Purpose of the Study:

• To clarify confusion surrounding complex surface reaction mechanisms in heterogeneous catalysis.
• To critically evaluate the applicability of the Eley-Rideal mechanism for specific reactions.
• To identify and discuss experimental and computational approaches for distinguishing between surface reaction mechanisms.

Main Methods:

• Bibliometric analysis to identify reactions commonly associated with the Eley-Rideal mechanism.
• Review of experimental and computational studies on H2 activation, CO oxidation, esterification, and selective catalytic reduction (SCR) of NO with NH3.
• Analysis of methodologies for differentiating surface reaction mechanisms.

Main Results:

• Four common reactions (H2 activation, CO oxidation, esterification, SCR of NO with NH3) were identified as frequently, but incorrectly, attributed to the Eley-Rideal mechanism.
• Evidence suggests these reactions predominantly occur via the Langmuir-Hinshelwood mechanism, incorporating nonideal surface behavior.
• The Eley-Rideal mechanism is unlikely for these specific catalytic processes.

Conclusions:

• The Eley-Rideal mechanism is not the primary pathway for H2 activation, CO oxidation, esterification, and SCR of NO with NH3.
• The Langmuir-Hinshelwood mechanism, accounting for surface nonidealities, better describes these reactions.
• Careful application of experimental characterization, differential kinetics, and computational modeling is crucial for accurate mechanistic determination in heterogeneous catalysis.