Reversible Hydrogen Acceptor-Donor Enables Relay Mechanism for Nitrate-to-Ammonia Electrocatalysis

Area of Science:

• Electrochemistry
• Materials Science
• Sustainable Chemistry

Background:

• Electrocatalytic nitrate reduction is key for sustainable ammonia production.
• Current methods require highly negative potentials, increasing energy use and hydrogen evolution.
• A more efficient catalytic system operating at less negative potentials is needed.

Purpose of the Study:

• To develop a novel electrocatalytic system for ammonia production with reduced energy consumption.
• To enable nitrate-to-ammonia conversion at potentials positive to 0 V vs. RHE.
• To investigate the mechanism of a hydrogen tungsten bronze-copper catalytic system.

Main Methods:

• Utilizing hydrogen tungsten bronze (HₓWO₃) as a hydrogen donor-acceptor material.
• Partnering HₓWO₃ with copper (Cu) to create a relay mechanism for nitrate reduction.
• Employing electrochemical analysis and continuous flow cell experiments.

Main Results:

• Achieved a high ammonia yield rate of 3332.9±34.1 mmol g_cat⁻¹ h⁻¹ with ~100% Faraday efficiency at 0.10 V vs. RHE.
• Demonstrated a record-low estimated energy consumption of 17.6 kWh kg_ammonia⁻¹.
• Successfully implemented continuous ammonia production in a flow cell with real energy consumption of 17.0 kWh kg_ammonia⁻¹.

Conclusions:

• The HₓWO₃-Cu catalyst system enables efficient electrocatalytic nitrate-to-ammonia conversion at potentials positive to 0 V vs. RHE.
• This approach significantly lowers energy consumption for ammonia production.
• The developed relay mechanism offers a promising pathway for sustainable ammonia synthesis.