Revealing the Active State of a Cu/ZnO:Al Catalyst During Reverse Water-Gas Shift Reaction in an Operando Microwave...

Area of Science:

• Catalysis
• Materials Science
• Surface Chemistry

Background:

• Cu/ZnO:Al (CZA) is an industrially significant catalyst.
• CZA is a dynamic system that changes with reaction conditions.
• Understanding structure-function relationships requires in situ/operando methods.

Purpose of the Study:

• To investigate the dynamic behavior of a CZA catalyst.
• To correlate catalytic activity with bulk properties during activation and reaction.
• To elucidate the reaction mechanism of the reverse water gas shift (RWGS) reaction.

Main Methods:

• In situ/operando microwave cavity perturbation technique.
• Electron paramagnetic resonance (EPR) spectroscopy.
• Studied a CZA catalyst composition similar to industrial standards.

Main Results:

• Catalytic activity transiently tracked dielectric property changes, highlighting the importance of bulk properties.
• Confirmed a redox reaction mechanism for the RWGS reaction.
• Demonstrated that H2 and CO2 uptake are not kinetically competing.
• Showed that H2 and CO2 reservoir in the catalyst is governed by chemical potential, directly linked to activity.
• Supported a Schottky barrier model at the Cu/ZnO:Al interface, influenced by gas composition.

Conclusions:

• Bulk properties significantly influence CZA catalyst activity.
• The RWGS reaction proceeds via a redox mechanism.
• Catalyst behavior is explained by a gas-phase-composition-modulated Schottky barrier at the Cu/ZnO:Al interface.