Improved Nitrate-to-Ammonia Electrocatalysis through Hydrogen Poisoning Effects

Area of Science:

• Electrochemistry
• Materials Science
• Sustainable Chemistry

Background:

• Electrochemical conversion of nitrate to ammonia is crucial for sustainable ammonia production.
• Current methods face challenges with low efficiency and high energy demands due to inadequate electrocatalysts.

Purpose of the Study:

• To develop novel electrocatalysts for efficient nitrate-to-ammonia conversion.
• To investigate the catalytic mechanism and optimize energy consumption in ammonia synthesis.

Main Methods:

• Synthesis and characterization of nickel cobalt phosphide (NiCoP) catalysts.
• Electrochemical testing for nitrate reduction to ammonia.
• Theoretical calculations to understand catalytic mechanisms.

Main Results:

• NiCoP catalysts achieved a record current density of -702 mA cm⁻² and ammonia production rate of 5415 mmol g⁻¹ h⁻¹.
• A high Faraday efficiency of 99.7% was observed at -0.3 V vs. RHE.
• Estimated energy consumption as low as 22.7 kWh kg⁻¹ ammonia, with a real-world value of 18.9 kWh kg⁻¹.

Conclusions:

• NiCoP catalysts demonstrate superior performance in nitrate electrocatalysis.
• The mechanism involves selective hydrogen poisoning, enhancing nitrate hydrogenation.
• These findings pave the way for energy-efficient, continuous ammonia production.