Recent discoveries in the reaction mechanism of heterogeneous electrocatalytic nitrate reduction

Abstract

We review advances in the electrocatalytic nitrate reduction mechanism and evaluate future efforts. Existing work could be supplemented by controlling reaction conditions and quantifying active sites to determine activity on a per-site basis.

Splicing the active phases of copper/cobalt-based catalysts achieves high-rate tandem electroreduction of nitrate to ammonia

“…3a ), where NO 2 − is generated as a stable intermediate 17 , 36 . A fast NO 3 − -to-NH 3 conversion requires the simultaneous acceleration of the sequential NO 3 − -to-NO 2 − and NO 2 − -to-NH 3 reactions 35 , 36 . To rationalize the high Y NH3 on CuCoSP at low overpotentials, we firstly compared the potentials of the three catalysts required to reach −1 mA cm −2 (kinetic area with negligible mass transport limitation) in 0.01 M NO 3 − and NO 2 − , respectively (Supplementary Fig.…”

“…However, NO 3 − typically shows low binding affinity to transition metals in aqueous electrolytes due to its symmetrical (D 3h ) resonant structure and strong hydrogen bonding to H 2 O 31 , 33 , 34 . Moreover, the NO 3 − -to-NH 3 pathway involves a complex eight−electrons transfer and multiple intermediates 17 , 35 , 36 . As a result, there is a scaling relation between the binding strengths of NO 3 − , NO 2 − and other oxygen−containing intermediates (e.g., NO) on the transition metal surface 37 .…”

Ambient Ammonia Synthesis via Electrochemical Reduction of Nitrate Enabled by NiCo2O4 Nanowire Array

“…[18] However, reduction NO 3 − to NH 3 is a complex reaction involving eight electrons transfer and can produce various byproducts. [19,20] Therefore, eNO 3 RR highly requires efficient electrocatalyst with high selectivity for NH 3 generation.Although noble metals (such as Pt, [21][22][23] Rh, [23] Ru, [24] etc.) are favorable for NO 3 − reduction electrocatalysis, they suffer from scarcity and high price, limiting their large-scale uses.…”

Efficient electrocatalytic reduction of nitrate to nitrogen gas by a cubic Cu2O film with predominant (111) orientation

“…Although the electrocatalytic reduction mechanism and pathway of nitrate were complicated and mysterious, two main strategies are widely accepted: deoxygenation to generate N 2 and hydrogenation to generate ammonia/ammonium. 31 In acid conditions, rich protons promoted the hydrogenation of intermediate species, resulting in the favorable generation of NH 4 + . On the contrary, in basic solution, deoxygenation of intermediate species was predominant, resulting in the favorable generation of N 2 .…”