Direct Electrochemical Ammonia Synthesis from Nitric Oxide

Abstract

NO removal from exhausted gas is necessary owing to its damage to environment. Meanwhile, the electrochemical ammonia synthesis (EAS) from N2 suffers from low reaction rate and Faradaic efficiency (FE). Now, an alternative route for ammonia synthesis is proposed from exhaust NO via electrocatalysis. DFT calculations indicate electrochemical NO reduction (NORR) is more active than N2 reduction (NRR). Via a descriptor‐based approach, Cu was screened out to be the most active transition metal catalyst for NORR to NH3 owing to its moderate reactivity. Kinetic barrier calculations reveal NH3 is the most preferred product relative to H2, N2O, and N2 on Cu. Experimentally, a record‐high EAS rate of 517.1 μmol cm−2 h−1 and FE of 93.5 % were achieved at −0.9 V vs. RHE using a Cu foam electrode, exhibiting stable electrocatalytic performances with a 100 h run. This work provides an alternative strategy to EAS from exhaust NO, coupled with NO removal.

The impact of nitrogen oxides on electrochemical carbon dioxide reduction

“…Cu primarily produced NH 3 and N 2 , with no NH 2 OH, Ag produced a mixture of NORR products, and Sn primarily produced NH 2 OH. These observations are consistent with previous reports, in which Cu has been demonstrated as an effective catalyst for NORR to NH 3 26 , and Sn has been used as a dopant in Pt to shift the selectivity from NH 3 to NH 2 OH in nitrate reduction 30 .…”

“…Among all the catalysts, the Cu catalyst suffers the largest FE loss on all NO x impurities, followed by Ag and Sn catalysts. Indeed, Cu has been demonstrated as one of the more active metals for the electroreduction of NO 26 and N 2 O 25 , in which Cu achieved high FE in N 2 ORR to N 2 at relatively low overpotentials. The results suggest that Cu is an effective electrocatalyst for NO x reduction, which may be further explored in future studies.…”

“…The electrochemical reduction products of NO, the major component of NO x in industrial point sources, were further investigated. As NH 3 , NH 2 OH, N 2 , and N 2 O have been suggested as the main products in NORR 26,28,29 , NH 3 and NH 2 OH were detected via spectrophotometry ( Supplementary Figs. 13 and 14), and N 2 was detected via GC ( Supplementary Fig.…”

Theoretical Insights into the Mechanism of Selective Nitrate‐to‐Ammonia Electroreduction on Single‐Atom Catalysts

“…Interestingly, no overt barrier impedes the process from *NO 3 to *NO, it is thus reasonably inferred that the electroreduction of NO 2 − , NO 2 , and NO to produce NH 3 can be realized as well, in agreement with recent experimental results. [ 7b,23 ]…”

Structural insight into [Fe–S2–Mo] motif in electrochemical reduction of N2 over Fe1-supported molecular MoS2

“…For example, it has been reported that contaminants such as NO x may also participate in the synthesis of ammonia. 30,31 NaClO 2 is known to be one of the most efficient chemicals for NO x oxidation due to its strong oxidation power. 32,33 Thus, to remove the interference of NO x , two traps lled with 0.2 M NaClO 2 solution and 1 mM H 2 SO 4 solution were used to purify the feed gas before it was owed into the three-electrode single cell.…”