Theory-Guided Modulation of Optimal Silver Nanoclusters toward Efficient CO₂ Electroreduction

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical CO2 reduction (CO2RR) is crucial for closing the carbon cycle and mitigating greenhouse gas emissions.
• Renewable energy integration into CO2RR offers a sustainable pathway for converting CO2 into valuable products.
• Developing efficient electrocatalysts is key to enhancing CO2RR performance and practicality.

Purpose of the Study:

• To investigate the potential of crystallographically defined silver nanoclusters (Ag NCs) for high-performance CO2RR.
• To synthesize and characterize ultrasmall Ag NCs (∼2 nm) for optimized CO2 electroreduction.
• To demonstrate the structure-performance relationship in Ag-based catalysts for CO2-to-CO conversion.

Main Methods:

• Density functional theory (DFT) calculations to model CO2RR-preferred electroactive sites.
• Theoretical work function calculations.
• Synthesis of homogeneously distributed ∼2 nm Ag NCs and characterization.
• Electrochemical evaluation of CO2RR performance, including partial current density, Faraday efficiency, onset overpotential, energy efficiency, and stability.

Main Results:

• Optimal Ag NC size for CO2RR performance was theoretically predicted to be around 2 nm.
• Synthesized 2 nm Ag NCs achieved a significantly higher CO partial current density and >93.8% CO Faraday efficiency.
• The 2 nm Ag NCs exhibited a lower onset overpotential (146 mV), higher energy efficiency (62.8%), and superior stability (45 h) compared to Ag NPs and bulk Ag.

Conclusions:

• Crystallographically explicit atomic structures, particularly ultrasmall Ag NCs, significantly promote electrochemical CO2 reduction to CO.
• The 2 nm Ag NCs demonstrate a novel and effective design for advancing large-scale CO2RR applications.
• This study provides a benchmark metal-based platform for efficient CO2 conversion.