Au/Pb Interface Allows the Methane Formation Pathway in Carbon Dioxide Electroreduction

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical conversion of carbon dioxide (CO2) offers a route to valuable chemicals and an artificial carbon cycle.
• Achieving high activity, selectivity, and stability in CO2 electroreduction remains a significant challenge.

Purpose of the Study:

• To investigate Au-Pb bimetallic electrocatalysts for CO2 reduction.
• To understand the role of Au/Pb interfaces in product selectivity, particularly for methane (CH4) formation.
• To explore the stability and mechanism of these catalysts under reaction conditions.

Main Methods:

• Synthesis and characterization of Au-Pb bimetallic electrocatalysts with varying interfaces.
• Electrochemical CO2 reduction experiments to determine product distribution and rates.
• In situ Raman spectroelectrochemistry to monitor catalyst stability.
• Density functional theory (DFT) simulations to elucidate reaction mechanisms.

Main Results:

• Au-Pb bimetallic catalysts produced carbon monoxide (CO), formic acid (HCOOH), and methane (CH4).
• Significant CH4 formation, rarely observed on Cu-free electrodes, was achieved, with a maximum rate of 0.33 mA cm-2 at high Au/Pb interface density.
• In situ Raman and DFT studies confirmed the stability of Pb oxide and identified the Au/Pb interface with subsurface oxygen as crucial for CH4 pathway by moderating intermediate binding.

Conclusions:

• Bimetallic nanoparticles, specifically Au-Pb, can effectively tune CO2 electroreduction selectivity towards CH4.
• The Au/Pb interface and associated subsurface oxygen play a critical role in overcoming reaction barriers for CH4 formation.
• This work demonstrates a strategy to overcome scaling relations in CO2 reduction using tailored bimetallic catalysts.