Electrocatalytic N₂-to-NH₃ conversion using oxygen-doped graphene: experimental and theoretical studies.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing efficient catalysts for nitrogen electroreduction (NRR) is crucial for sustainable ammonia synthesis.
• Oxygen-doped graphene (O-G) presents a potential alternative to traditional Haber-Bosch processes.

Purpose of the Study:

• To investigate the efficacy of oxygen-doped graphene derived from sodium gluconate as a catalyst for ambient nitrogen electrohydrogenation to ammonia.
• To elucidate the catalytic mechanism and identify key functional groups responsible for NRR activity.

Main Methods:

• Synthesis of oxygen-doped graphene (O-G) from sodium gluconate.
• Electrochemical testing in 0.1 M HCl to evaluate ammonia yield and faradaic efficiency.
• Density functional theory (DFT) calculations to explore the NRR catalytic mechanism.

Main Results:

• O-G achieved a high ammonia yield of 21.3 μg h^-1 mg_cat.^-1 and a faradaic efficiency of 12.6% at specific potentials (-0.55 V and -0.45 V vs. RHE).
• The catalyst exhibited excellent electrochemical and structural stability in 0.1 M HCl.
• DFT calculations indicated that C[double bond, length as m-dash]O and O-C[double bond, length as m-dash]O groups are more significant contributors to NRR than C-O groups.

Conclusions:

• Oxygen-doped graphene is a highly promising catalyst for ambient electrohydrogenation of N₂ to NH₃.
• The study highlights the importance of specific oxygen functional groups (C[double bond, length as m-dash]O and O-C[double bond, length as m-dash]O) in enhancing NRR performance.
• O-G offers a stable and efficient alternative for sustainable ammonia production.