Electrocatalytic nitrate reduction: Selectivity at the crossroads between ammonia and nitrogen

Rethinking nitrate reduction: redirecting electrochemical efforts from ammonia to nitrogen for realistic environmental impacts

“…In summary, electrochemical NO 3 − reduction to NH 3 may show some scientific merits, but when considering practical and industrial implementations, this process will likely play an insignificant role in either NO 3 − contaminants removal or NH 3 production. 35,36 When dealing with NO 3 − contaminants in real wastewater, NO 3 − should not be converted to NH 3 at any concentration range: at high concentrations, NO 3 − is a more valuable feedstock (as it has to be produced from NH 3 ), with the production costs and energy consumption of NH 3 using the electrochemical NO 3 − reduction process being 2.04 times higher than those of the Haber–Bosch process (the detailed calculation is provided in Table S1, ESI†); 37 at low concentrations, NH 3 produced from reducing NO 3 − becomes a more serious contaminant. For a more feasible and meaningful N-cycle to address nitrate pollution issues, following directions are recommended.…”

Crystal facet engineering of electrocatalysts for nitrate reduction to ammonia: recent advances and future perspectives

“…First, NO 3is adsorbed on the catalyst surface and then reduced to * NO 2through electron transfer [Equation ( 3)], which is typically considered as the rate-limiting step [22] . This is because * NO 2has a high energy of the lowest unoccupied molecular π * orbital (LUMO π * ), which makes it difficult for charges to be injected into this orbital [11] . Next, * NO 2can rapidly react with protons on the electrode surface to produce * NO.…”

“…Currently, many studies focus on electrocatalytic nitrogen reduction reaction (NRR) [10] [N 2 + 6e -+ 6H 2 O → 2NH 3 + 6OH -, 0.09 V vs. reversed hydrogen electrode (RHE)], which drives the conversion of N 2 to ammonia under ambient conditions. However, the ammonia Faraday efficiency and yield of NRR are generally low due to the difficulty in breaking the extremely stable N≡N bonds (941 kJ•mol -1 ) and the low solubility of N 2 in aqueous electrolyte [11] . Instead, the electrocatalytic nitrate reduction reaction to ammonia (NtrRR) becomes a promising option since it is thermodynamically more feasible.…”

Bioinspired Tandem Electrode for Selective Electrocatalytic Synthesis of Ammonia from Aqueous Nitrate

“…Nitrogen is one of the most plentiful essential elements on earth and commonly present in the forms of nitrate (NO 3 – ), nitrite (NO 2 – ), ammonia (NH 3 ), and amino acids. , It has played a central role in biological activities and industrial processes for centuries. However, in recent decades, intensified human manufacturing and agricultural activities have resulted in the substantial accumulation of “waste nitrogen”, notably in the form of NO 3 – .…”