Integrative Ni₁-P_x Catalytic Pairs for Low-Concentration CO₂ Electroreduction

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis
• Sustainable Chemistry

Background:

• Electrochemical CO2 reduction (CO2RR) is a key technology for sustainable carbon utilization using renewable energy.
• Low CO2 concentrations (5-15 vol.%) significantly hinder CO2RR efficiency and selectivity due to limited CO2 supply and competing hydrogen evolution reaction (HER).
• Development of advanced catalysts is crucial to overcome these limitations for industrial applications.

Purpose of the Study:

• To design and investigate integrative Ni1-Px catalytic pairs (Ni1-Px/ICPs) for enhanced CO2RR performance under low CO2 conditions.
• To elucidate the reaction mechanism and understand the role of phosphorus (P) in modulating catalytic activity and selectivity.
• To demonstrate efficient CO2-to-CO conversion, suppressing HER at industrially relevant low CO2 concentrations.

Main Methods:

• Synthesis and characterization of Ni1-Px/ICPs.
• In situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and X-ray absorption spectroscopy (XAS) for mechanistic studies.
• H/D isotopic substitution experiments and theoretical calculations to determine reaction pathways and intermediates.
• Electrochemical performance evaluation under low CO2 concentrations.

Main Results:

• Ni1-Px/ICPs exhibited superior CO2-to-CO conversion efficiency under low CO2 concentrations.
• P incorporation modulated the electrochemical microenvironment, accelerating reaction kinetics and enhancing CO2 activation.
• A mechanistic transition to a Langmuir-Hinshelwood pathway was observed, facilitated by cooperative adsorption on adjacent Ni and P sites.
• A unique hydrogen-bonded six-membered ring intermediate (Ni-C-O-H-O-P-Ni) was identified, promoting proton-coupled electron transfer and lowering the reaction barrier.
• Suppression of HER and efficient CO generation were achieved at low CO2 levels.

Conclusions:

• Integrative Ni1-Px catalytic pairs are highly effective for CO2RR under industrially relevant low CO2 concentrations.
• The cooperative effect between Ni and P sites and the formation of a specific hydrogen-bonded intermediate are key to enhanced performance.
• Atomically dispersed catalytic pairs offer a promising strategy for advancing carbon utilization and addressing selectivity challenges in electrochemical hydrogenation.