Size Stability and H₂/CO Selectivity for Au Nanoparticles during Electrocatalytic CO₂ Reduction

Area of Science:

• Nanomaterials Science
• Electrocatalysis
• Surface Chemistry

Background:

• Gold nanoparticles (AuNPs) are promising electrocatalysts for CO2 reduction.
• Controlling AuNP size and stability during catalysis is critical for understanding their function.
• Citrate and low-generation dendrimers fail to stabilize small AuNPs during electrocatalysis.

Purpose of the Study:

• To investigate the effect of dendrimer generation on AuNP stability during CO2 electrocatalysis.
• To determine if higher-generation dendrimers can prevent AuNP growth under reductive conditions.
• To correlate AuNP size and stability with electrocatalytic performance.

Main Methods:

• Electrocatalytic reduction of CO2 using AuNPs stabilized by citrate, G6-OH DENs, and G8-OH DENs.
• Characterization of AuNP size and polydispersity before and after electrolysis using techniques like TEM (implied).
• Electrochemical measurements to assess catalytic activity and product selectivity (H2 vs. CO).

Main Results:

• Citrate-stabilized and G6-OH DEN-stabilized AuNPs (∼2 nm) grew significantly (to 6-7 nm) during electrolysis at -0.80 V.
• G8-OH DENs effectively stabilized AuNPs (1.7 ± 0.3 nm to 2.2 ± 0.5 nm) even at -1.20 V.
• Stable, smaller G8-OH DEN-encapsulated AuNPs favored H2 production over CO, challenging previous findings attributed to AuNP growth.

Conclusions:

• Higher-generation dendrimers, like G8-OH DENs, are superior stabilizers for AuNPs in electrocatalytic CO2 reduction.
• AuNP growth during catalysis can lead to misinterpretation of intrinsic catalytic properties.
• Stable, small AuNPs exhibit distinct catalytic behavior compared to larger, grown nanoparticles.