Dual-site synergy via interfacial engineering for enhanced CO₂ electroreduction to methanol

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrocatalytic conversion of carbon dioxide (CO2) to methanol (MeOH) is crucial for sustainable energy, but efficiency is limited by low concentrations of key intermediates like CO.
• Single-site catalysts often struggle with insufficient intermediate generation and subsequent reaction steps, hindering overall methanol production.

Purpose of the Study:

• To design and synthesize a dual-site catalyst that synergistically enhances both CO2-to-CO conversion and CO hydrogenation for improved methanol synthesis.
• To investigate the cooperative mechanism at the catalyst interface using in situ spectroscopy.

Main Methods:

• Fabrication of a dual-site catalyst ((SAs Ni + CoPc-NH2)/N-CNT) by integrating single-atom Nickel (SAs Ni) for CO2 reduction and amino-functionalized cobalt phthalocyanine (CoPc-NH2) for methanol formation on N-doped carbon nanotubes.
• Electrochemical performance evaluation in H-cell, flow cell, and membrane electrode assembly (MEA) electrolyzer under various conditions, including simulated flue gas.
• In situ attenuated total reflectance-surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) to analyze reaction intermediates and confirm the synergistic mechanism.

Main Results:

• The dual-site catalyst achieved a high methanol Faradaic efficiency (FE_MeOH) of 48.7% and a current density of 45.6 mA cm-2 at -1.05 V vs. RHE in an H-cell, significantly outperforming single-component and physical mixture catalysts.
• In a flow cell, peak FE_MeOH reached 51.9% with a methanol partial current density of 103.8 mA cm-2.
• In an MEA electrolyzer using simulated flue gas, the catalyst delivered 500 mA cm-2 current density with an FE_MeOH of 67.1%.
• In situ ATR-SEIRAS confirmed enhanced *CO coverage and the presence of *CHO intermediates, elucidating the synergistic mechanism.

Conclusions:

• The developed dual-site catalyst effectively promotes CO2-to-methanol conversion through synergistic interactions between SAs Ni and CoPc-NH2 sites.
• The catalyst design paradigm offers a promising strategy for constructing cooperative interfaces to enhance multistep electrocatalytic reactions.
• This work provides fundamental insights into optimizing catalyst design for efficient and selective electrocatalytic CO2 valorization.