Stabilization effects in binary colloidal Cu and Ag nanoparticle electrodes under electrochemical CO₂ reduction...

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Nanoparticle catalysts are promising for carbon dioxide (CO2) reduction but suffer from restructuring and sintering under reaction conditions.
• This instability hinders catalyst application and complicates the interpretation of product selectivity.
• Developing stable nanoparticle electrodes is crucial for efficient CO2 electrocatalysis.

Purpose of the Study:

• To investigate the stabilization of metallic copper (Cu) and silver (Ag) nanoparticles during electrochemical CO2 reduction.
• To explore the effect of co-deposition on nanoparticle stability and catalytic selectivity.
• To tune the selectivity of CO2 reduction reaction (CO2RR) products by varying the Cu/Ag nanoparticle ratio.

Main Methods:

• Colloidal synthesis of Cu and Ag nanoparticles with narrow size distribution.
• Electrochemical CO2 reduction reactions using monometallic and bimetallic (Cu-Ag) nanoparticle electrodes.
• Ex situ Scanning Electron Microscopy (SEM) for investigating nanoparticle restructuring and sintering.
• Product selectivity analysis at varying applied potentials.

Main Results:

• Monometallic Cu and Ag nanoparticles exhibited significant sintering at low overpotentials (-0.8 V vs. RHE).
• Co-deposition of Cu and Ag nanoparticles demonstrated a stabilization effect, suppressing sintering.
• Varying the Cu/Ag ratio allowed tuning of CO2RR selectivity towards methane (up to 20.6%) and C2 products (up to 15.7%).
• Synergistic effects between neighboring Ag and Cu nanoparticles were observed.

Conclusions:

• Co-deposition of Cu and Ag nanoparticles effectively stabilizes them against sintering during CO2 electroreduction.
• The stabilization is attributed to the formation of Cu-Ag solid solutions with positive enthalpies.
• This stabilization effect facilitates the design of durable and selective nanocatalysts for CO2 reduction.
• The tunable selectivity offers a pathway for producing valuable chemicals from CO2.