Bio-inspired design: bulk iron-nickel sulfide allows for efficient solvent-dependent CO₂ reduction

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science
• Environmental Science

Background:

• Electrocatalytic reduction of carbon dioxide (CO₂RR) is crucial for pollution control and sustainable energy storage.
• Enzyme active sites, like CODH_Ni, provide inspiration for designing efficient CO₂RR catalysts.
• Iron and nickel sulfides are promising materials for electrocatalytic applications.

Purpose of the Study:

• To investigate the potential of bulk Fe/Ni sulfides for efficient CO₂RR.
• To explore pentlandite (Fe_4.5Ni_4.5S₈) as an electrocatalyst for CO₂ reduction.
• To understand the influence of reaction conditions on CO₂RR selectivity.

Main Methods:

• Electrochemical synthesis and characterization of pentlandite electrodes.
• Testing pentlandite electrodes for CO₂RR and hydrogen evolution reaction (HER) under varying conditions.
• Analysis of product selectivity (CO, methane) using faradaic efficiency measurements.

Main Results:

• Pentlandite electrodes exhibited significant CO₂RR activity alongside HER.
• A peak faradaic efficiency of 87% for CO and 13% for methane was achieved at 3 mA cm^-2.
• Solvent choice, water/proton presence, and CO₂ solubility were identified as critical factors influencing selectivity.

Conclusions:

• Bulk Fe/Ni sulfides, specifically pentlandite, are effective electrocatalysts for CO₂ reduction.
• Optimized reaction conditions can tune the selectivity towards valuable chemical products.
• These findings support the use of such materials in gas diffusion electrodes for CO₂ utilization.