Sulfur-doped graphene for efficient electrocatalytic N₂-to-NH₃ fixation

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Current industrial ammonia synthesis relies on the energy-intensive and carbon-emitting Haber-Bosch process.
• Electrocatalytic nitrogen reduction reaction (NRR) offers a sustainable alternative under ambient conditions, reducing energy consumption and carbon footprint.

Purpose of the Study:

• To propose and investigate sulfur-doped graphene (S-G) as an efficient and stable electrocatalyst for NRR.
• To evaluate the performance of S-G in ammonia synthesis under ambient conditions.

Main Methods:

• Electrocatalytic synthesis of ammonia using sulfur-doped graphene (S-G) as the catalyst.
• Performance evaluation in 0.1 M HCl, measuring ammonia yield and Faradaic efficiency at various potentials.
• Density functional theory (DFT) calculations to elucidate the catalytic mechanism and active sites.

Main Results:

• S-G demonstrated a high ammonia yield of 27.3 μg h-1 mgcat.-1 and a Faradaic efficiency of 11.5% at -0.5 V vs. reversible hydrogen electrode.
• Performance significantly surpassed undoped graphene, which showed a yield of 6.25 μg h-1 mgcat.-1 and 0.52% efficiency.
• DFT calculations identified carbon atoms adjacent to sulfur as the active sites for NRR.

Conclusions:

• Sulfur-doped graphene is a promising electrocatalyst for efficient and stable ammonia synthesis under ambient conditions.
• The study provides insights into the NRR mechanism on S-G, paving the way for further catalyst development.