Low-Valence Zn^δ+ (0<δ2 Reduction

Area of Science:

• Catalysis
• Materials Science
• Electrochemistry

Background:

• Developing efficient catalysts for CO2 reduction is critical for sustainable energy solutions.
• Single-atom catalysts offer high atom utilization and unique catalytic properties.
• Understanding the role of coordination environment and valence state in catalysis is essential.

Purpose of the Study:

• To synthesize and characterize a nitrogen-stabilized single-atom catalyst with low-valence zinc atoms (Zn^δ+-NC).
• To investigate the catalytic performance of Zn^δ+-NC for electrochemical CO2 reduction to CO.
• To elucidate the relationship between the catalyst's structure, valence state, and its catalytic activity.

Main Methods:

• Synthesis of nitrogen-stabilized single-atom catalyst with low-valence zinc.
• Electrochemical characterization including CO2 reduction reaction (CO2RR) measurements.
• Spectroscopic techniques (XPS, XAS, EPR) for material characterization.
• Density functional theory (DFT) calculations to understand reaction mechanisms.

Main Results:

• The catalyst features both saturated (Zn-N4) and unsaturated (Zn-N3) sites, with the latter indicating a low-valence zinc state.
• Zn^δ+-NC exhibits high selectivity (>95%) for CO2 to CO conversion in water at a low overpotential (310 mV).
• Achieved high current density up to 1 A cm⁻² in a flow cell, demonstrating industrial relevance.
• DFT calculations indicate that the unsaturated Zn-N3 sites stabilize the key COOH* intermediate.

Conclusions:

• The coordination number and valence state of single-atom catalysts significantly impact their performance.
• Low-valence zinc sites in Zn^δ+-NC are key to achieving efficient and selective electrochemical CO2 reduction.
• This catalyst design offers a promising pathway for developing highly active and stable electrocatalysts for CO2 conversion.