Electrochemical Reduction of Nitrates on CoO Nanoclusters‐Functionalized Graphene with Highest Mass Activity and Nearly 100% Selectivity to Ammonia

Abstract

NO3− is a prominent waste byproduct in ammunition industries, and valorization of NO3− into NH3 is desired. NH3 synthesized from waste using renewable energy could be used as an energy storage medium. For such a process, higher selectivity, stability, and enhanced activity per unit mass of catalyst is required. This work reports CoO nanoclusters functionalized on graphene as an efficient catalyst for electrochemical NO3− reduction to NH3 with >98% NH3 Faradaic efficiency and an NH3 current density (geometric) of ≈400 mA cm−2. A highest NH3 yield of 25.63 mol g−1 h−1 is obtained. The developed catalyst prevents the NN coupling step which is required for promoting the selectivity of NH3 over N2. Density functional theory calculations reveal that CoO NC/graphene has similar selectivity to that of polycrystalline Co and that higher activity can be obtained with lower catalyst loading.

Laser-controlled tandem catalytic sites of CuNi alloys with ampere-level electrocatalytic nitrate-to-ammonia reduction activities for Zn–nitrate batteries

“…3,4 However, the performance of Zn–NO 3 − batteries currently cannot meet the requirements of driving electrical appliances, due to the difficulty in breaking NO bonds (204 kJ mol −1 ) and the slow kinetics of NO 3 − reduction reaction (NIRR) coming from the complex eight-electron transfer process. 5 Moreover, reacting in an ultrahigh concentration NO 3 − solution is the requirement for achieving high current output capability of Zn–NO 3 − batteries. 6 Unfortunately, most NIRR catalysts cannot maintain their performance at high concentrations of NO 3 − solution.…”

Tungsten Nitride/Tungsten Oxide Nanosheets for Enhanced Oxynitride Intermediate Adsorption and Hydrogenation in Nitrate Electroreduction to Ammonia

“…To verify the catalytic mechanism, in situ FT-IR spectroscopy was employed to detect the reaction intermediates on WO 3 , WN/WO 3 , and WN during the electrocatalytic reactions (Figures a–c). The downward peaks at 1120 cm –1 and the upward peaks at 1210 cm –1 correspond to the consumption of *NO 3 and the generation of *NO 2 (O–N–O) intermediates, respectively. − It can be seen that the vibrational band at 1210 cm –1 of WO 3 is downward, while the bands of WN/WO 3 and WN are clearly upward, indicating that *NO 2 can be accumulated on WN/WO 3 and WN surfaces, while it showed a trend of desorption on the WO 3 surface. This result reveals that *NO 3 and *NO 2 can be strongly adsorbed and exhibit enhanced NO 3 RR processes on WN/WO 3 and WN surfaces compared to WO 3 .…”

Decoration of boron nanoparticles on a graphene sheet for ammonia production from nitrate

“…6 However, these compounds do not decompose and end up in the surface water and groundwater, 7,8 where they increase the concentration of nitrates in water that is eventually irrigated back into the soil. Nitrates can have devastating effects on aquatic ecosystems and on human health, 9 including the development of methemoglobinemia, thyroid effects, and cancer. [10][11][12] Thus, to eliminate this harmful pollutant, we need to purify the contaminated water and simultaneously produce ammonia (one of the products that can be synthesized from nitrate).…”