Issue 31, 2024

Electrochemical reduction of nitrate to ammonia on ultra-stable amorphous Co–P electrocatalyst

Abstract

Electrocatalytic reduction of nitrate (NO3) to ammonia (NH3) is garnering increasing interest due to its potential to reduce CO2 emissions as a substitute for the Haber-Bosch process, while also mitigating NO3 pollution. However, it remains a challenge to achieve a current density exceeding 300 mA cm−2 while maintaining the stability of catalysts. Additionally, the anodic oxygen evolution reaction, characterized by slow kinetics and high energy barriers, severely impedes the widespread adoption of NH3 formation from NO3 reduction. Therefore, in this study, we introduce amorphous phosphorus-doped cobalt catalysts (Co–P@NF) prepared via a facile electrodeposition process for efficient NO3 reduction and hydrazine oxidation. The incorporation of phosphorus in Co–P@NF facilitates electron migration from phosphorus to cobalt, enhancing *H provision for efficient hydrogenation of the intermediate *NO2. This results in a current density of 2 A cm−2 at −0.3 V, with a faradaic efficiency for NH3 of 91% in an electrolyte containing 1 M NO3. Moreover, the Co–P@NF catalyst exhibits remarkable long-term stability, maintaining an NH3 faradaic efficiency exceeding 90% and a current density of 799 mA cm−2 after 82 hours of electrolysis. Furthermore, Co–P@NF displays high catalytic activity in promoting the rate-determining step of hydrazine oxidation, from *N2H2 to *N2H. The incorporation of the HzOR (hydrazine oxidation reaction)-assisted NO3RR (nitrate reduction reaction) unit significantly reduces the cell voltage to 0.34 V at 300 mA cm−2.

Graphical abstract: Electrochemical reduction of nitrate to ammonia on ultra-stable amorphous Co–P electrocatalyst

Supplementary files

Article information

Article type
Paper
Submitted
04 Mme 2024
Accepted
13 Jan 2024
First published
14 Jan 2024

J. Mater. Chem. A, 2024,12, 20077-20087

Electrochemical reduction of nitrate to ammonia on ultra-stable amorphous Co–P electrocatalyst

J. Fan, S. Liu, M. Chen, Z. Wu, S. Sun and Y. Lou, J. Mater. Chem. A, 2024, 12, 20077 DOI: 10.1039/D4TA02299H

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