Optimizing Active Sites for High CO Selectivity during CO₂ Hydrogenation over Supported Nickel Catalysts

Area of Science:

• Catalysis
• Materials Science
• Chemical Engineering

Background:

• Controlling catalyst selectivity in carbon dioxide (CO2) hydrogenation is crucial for producing valuable chemicals.
• Supported nickel (Ni) catalysts are widely studied but often lack predictable selectivity.

Purpose of the Study:

• To investigate the change in selectivity of supported Ni catalysts during CO2 hydrogenation.
• To understand the mechanism behind the observed selectivity shift.
• To explore methods for controlling CO2 hydrogenation selectivity.

Main Methods:

• Preparation of supported Ni catalysts using the impregnation method.
• Testing catalyst performance in CO2 hydrogenation across a temperature range (100–800 °C).
• In situ spectroscopic studies to analyze surface species and catalyst phases.
• Post-reaction treatments including oxidation and exposure to different gas atmospheres.

Main Results:

• Ni catalysts initially selective for methane (CH4) shifted to full selectivity for carbon monoxide (CO) after the first reaction cycle at high temperatures.
• This selectivity shift was linked to the formation of a nickel carbide-like phase due to carbon accumulation.
• Catalyst selectivity reverted to CH4 production after oxidation (carbon depletion) but shifted back to CO upon re-exposure to CO2 hydrogenation conditions.
• In situ studies showed increased weakly adsorbed CO on the carbide-like surface, explaining CO selectivity.

Conclusions:

• The surface of Ni catalysts can be readily modified by high-temperature CO2 hydrogenation to form a nickel carbide-like phase.
• This phase enhances selectivity towards CO production, a valuable chemical feedstock.
• This finding offers a simple method to tune Ni catalyst selectivity for CO2 hydrogenation, advancing commercial applications.