Small PdC_x interstitial compound for efficient acidic CO₂ electroreduction to formic acid.

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Efficient acidic carbon dioxide reduction reaction (CO₂RR) to formic acid (HCOOH) at high current densities is critical for chemical synthesis.
• Existing catalysts face challenges in achieving high efficiency, low potential, and stability simultaneously under acidic conditions.

Purpose of the Study:

• To develop an efficient catalyst for acidic CO₂RR to HCOOH that overcomes the triple challenge of low overpotential, high current density, and high stability.
• To engineer interstitial atoms in PdCₓ compounds to modulate catalyst properties for improved CO₂RR performance.

Main Methods:

• Synthesis of small PdCₓ interstitial compounds.
• Utilized density functional theory (DFT) calculations and experimental characterization.
• Investigated the effect of interstitial carbon on catalyst electronic structure and reaction pathways.

Main Results:

• Interstitial carbon infusion modulated the soft acid strength of Pd, weakening the Pd-O bond energy for efficient HCOOH formation and desorption.
• Optimized catalyst (PdC₀.₁₃/CNT) achieved >95% Faradaic efficiency (FE) for HCOOH with suppressed hydrogen evolution reaction (HER).
• Demonstrated stability in a proton exchange membrane (PEM) electrolyzer, maintaining 1000 mA cm⁻² for 500 hours at 1.8 V.

Conclusions:

• Engineered PdCₓ interstitial compounds effectively overcome the challenges in acidic CO₂RR to HCOOH.
• The optimized catalyst exhibits excellent selectivity, efficiency, and stability for industrial applications.
• This approach provides a pathway for designing advanced catalysts for electrochemical CO₂ conversion.