Bifunctional Amorphous Phosphate Layer Simultaneously Boosts Proton Transfer and Stabilizes Zn Active Sites for...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Zinc (Zn) is a promising electrocatalyst for CO2 reduction reaction (CO2RR) but suffers from poor selectivity and stability.
• Conventional methods using crystalline modifiers or bulk buffers have limitations in enhancing Zn performance.

Purpose of the Study:

• To develop a bifunctional strategy using an amorphous phosphate layer to improve proton transfer and stabilize Zn active sites for CO2RR.
• To synthesize and characterize amorphous phosphate-modified zinc nanoflakes (Zn-HPO4 NF) for enhanced CO2RR.

Main Methods:

• Synthesis of amorphous phosphate-modified zinc nanoflakes (Zn-HPO4 NF) via a two-step method.
• Electrochemical characterization including CO2RR performance testing at various potentials.
• In situ spectroscopy and operando electrochemical impedance spectroscopy (EIS) to investigate reaction mechanisms.

Main Results:

• Zn-HPO4 NF achieved a high CO Faradaic efficiency (FE_CO) of 86.4% at -1.3 V vs RHE.
• The catalyst demonstrated exceptional durability, maintaining a stable current of ~17 mA for over 20 h with FE_CO > 80% at -1.4 V vs RHE.
• Amorphous hydrogen phosphate (HPO4^2-) modification promoted intermediate adsorption, facilitated proton transfer via a hydrogen-bonding network, and stabilized Zn active sites by buffering local pH.

Conclusions:

• The amorphous phosphate layer effectively enhances proton transfer and stabilizes Zn active sites, leading to superior CO2RR performance and durability.
• The Zn-HPO4 NF catalyst significantly outperforms pure Zn in selectivity and stability for CO2 conversion.
• The findings offer a promising bifunctional strategy for designing advanced electrocatalysts for CO2RR.