Shapeshifting Nanocatalyst for CO₂ Conversion.

Area of Science:

• Materials Science
• Catalysis
• Surface Chemistry

Background:

• Photoreduction of carbon dioxide (CO2) to valuable chemicals offers a sustainable alternative to fossil fuels.
• Silver-copper (Ag-Cu) alloys show promise for enhancing selectivity in CO2 conversion.
• The precise surface state and dynamic evolution of Ag-Cu alloys under reaction conditions remain poorly understood.

Purpose of the Study:

• To elucidate the underlying mechanisms and dynamic evolution of Ag-Cu nanoparticles during CO2 reduction reaction (CO2RR).
• To investigate the morphological and chemical changes of Ag and Cu species under photocatalytic CO2 reduction conditions.
• To identify the active species and restructuring processes governing CO2 conversion.

Main Methods:

• Multi-modal in situ X-ray experiments were employed to track changes in Ag-Cu nanoparticles.
• Morphological and chemical transformations of Ag and Cu species were monitored during nanocatalyst operation.
• In situ analysis captured diffusion mechanics and surface evolution under CO2RR conditions.

Main Results:

• Initial Ag-Cu nanoparticles exhibit a Cu-rich shell and Ag-rich core, with Ag migration to the surface upon reduction.
• During CO2RR, Cu atoms migrate back to the surface, forming Ag-Cu-O species and leading to Cu(0) oxidation to Cu+.
• Nanoparticles undergo shape changes, reducing specific surface area due to Cu diffusion, with Ag present in the sub-surface region.

Conclusions:

• The study reveals the dynamic restructuring of Ag-Cu catalysts under CO2RR conditions.
• Copper diffusion is identified as a key driver for nanoparticle shape changes and surface chemistry evolution.
• These findings provide critical insights into the active species and mechanisms responsible for efficient CO2 conversion.