Ambient ammonia synthesis via nitrite electroreduction over NiS2 nanoparticles-decorated TiO2 nanoribbon array.

Nitrite (NO2-), as a N-containing pollutant, widely exists in aqueous solution, causing a series of environmental and health problems. Electrocatalytic NO2- reduction is a promising and sustainable strategy to remove NO2-, meanwhile, producing high value-added ammonia (NH3). But the NO2- reduction reaction (NO2-RR) involves complex 6-electron transfer process that requires high-efficiency electrocatalysts to accomplish NO2--to-NH3 conversion. Herein, we report NiS2 nanoparticles decorated TiO2 nanoribbon array on titanium mesh (NiS2@TiO2/TM) as a fantastic NO2-RR electrocatalyst for ambient NH3 synthesis. When tested in NO2--containing solution, NiS2@TiO2/TM achieves a satisfactory NH3 yield of 591.9 µmol h-1 cm-2 and a high Faradaic efficiency of 92.1 %. Besides, it shows remarkable stability during 12-h electrolysis test.

Cu nanoparticles decorated juncus-derived carbon for efficient electrocatalytic nitrite-to-ammonia conversion.

Electrocatalytic nitrite reduction to value-added NH3 can simultaneously achieve sustainable ammonia production and N-contaminant removal in natural environments, which has attracted widespread attention but still lacks efficient catalysts. In this work, Cu nanoparticles decorated juncus-derived carbon can be proposed as a high-active electrocatalyst for NO2--to-NH3 conversion, obtaining a high Faradaic efficiency of 93.2% and a satisfactory NH3 yield of 523.5 µmol h-1 mgcat.-1. Density functional theory calculations were applied to uncover insightful understanding of internal catalytic mechanism.

Nitrite reduction over Ag nanoarray electrocatalyst for ammonia synthesis.

Electrochemical reduction of nitrite to ammonia can simultaneously achieve ammonia synthesis and N-contaminant removal under mild conditions, which has attracted widespread attention but still lacks efficient catalysts. In this work, Ag nanoarray using NiO nanosheets array on carbon cloth as support is reported as an efficient electrocatalyst to selectively reduce nitrite to ammonia. In 0.1 M NaOH with 0.1 M NO2-, such catalyst exhibits a maximum ammonia yield of 5,751 µg h-1 cm-2 (57,510 µg h-1 mgAg-1) and high Faradaic efficiency up to 97.7 %. Density functional theory calculations applied to uncover the catalytic mechanism of NO2- reduction reaction on Ag.

High-efficiency NO electroreduction to NH3 over honeycomb carbon nanofiber at ambient conditions.

Electrocatalytic NO reduction is a promising technology for ambient NO removal with simultaneous production of highly value-added NH3. Herein, we report that honeycomb carbon nanofiber coated on carbon paper acts as an efficient metal-free catalyst for ambient electroreduction of NO to NH3. In 0.2 M Na2SO4 solution, such catalyst achieves an NH3 yield of 22.35 µmol h-1 cm-2 with a high Faradaic efficiency of up to 88.33%. Impressively, it also shows excellent stability for 10-h continuous electrolysis. Theoretical calculations reveal that the most active center of functional groups is -OH group for NO reduction with a low energy barrier (ΔG of 0.29 eV) for the potential-determining step (*NO + H → *HNO).