KOH-Enabled Axial-Oxygen Coordinated Ni Single-Atom Catalyst for Efficient Electrocatalytic CO₂ Reduction

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Precise control over metal center coordination is crucial for effective electrochemical reduction of carbon dioxide (CO2).
• Developing stable and selective catalysts for CO2 reduction remains a significant challenge.

Purpose of the Study:

• To develop a KOH activation strategy for preparing hierarchically porous materials with Ni single-atoms coordinated by axial-oxygen.
• To investigate the role of KOH in material synthesis and its impact on electrocatalytic performance for CO2 reduction.

Main Methods:

• Hierarchically porous material synthesis using a KOH activation strategy.
• Spectroscopic measurements (e.g., X-ray photoelectron spectroscopy, Raman spectroscopy) for material characterization.
• Electrochemical testing to evaluate catalytic performance (Faradaic efficiency, turnover frequency).
• Density functional theory (DFT) calculations to understand reaction mechanisms.

Main Results:

• The KOH activation strategy successfully produced a porous material with a high surface area (1801 m2 g-1) and anchored Ni single-atoms with axial-oxygen coordination.
• The material exhibited excellent electrocatalytic performance for CO2 reduction, achieving a Faradaic efficiency of 94% and a turnover frequency of 11,362 h-1.
• Spectroscopic and DFT analyses confirmed KOH's multiple roles as an oxygen source, pore-forming agent, and promoter of the phthalocyanine structure, facilitating CO2 reduction.

Conclusions:

• The KOH-enabled hierarchical porous structure with Ni single-atoms and axial-oxygen coordination is highly effective for selective electrochemical CO2 reduction to CO.
• The axial-oxygen ligand enhances electronic delocalization at the Ni site, promoting key intermediates (*COOH formation and *CO desorption) for efficient catalysis.
• This approach offers a promising pathway for designing advanced catalysts for CO2 utilization.