Research promotes electrochemical reduction of nitrate synthesis of ammonia

Electrocatalytic reduction converts nitrate pollutants into high value-added ammonia, providing a promising solution for the recycling of nitrogen resources. Recently, Wang Guoxiong, a researcher at the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, and a team of academicians Bao Xinhe have made new progress in the research of electrochemical ammonia synthesis. They developed an in-situ derived high-performance copper nanosheet catalyst, proposed an effective strategy for copper facet tandem catalysis to promote electrochemical reduction of nitrate to ammonia, and deepened the understanding of the reaction mechanism of nitrate to ammonia on copper catalysts. The results were published in the German Journal of Applied Chemistry.

The conversion of nitrate to ammonia requires a complex multi-step process of proton electron transfer, which results in a slow kinetic rate and high overpotential. At the same time, the competitive hydrogen evolution reaction reduces the ammonia faraday efficiency and current density. Therefore, the key to nitrate electrocatalytic reduction is to design and prepare catalysts with high activity, high selectivity and high stability.

Schematic diagram of the electrochemical reduction process. Photo courtesy of Dalian Chemical Properties

This work reports an electrochemical, in situ derived high-performance copper nanosheet catalyst. In the mobile phase electrolytic cell, the catalyst obtained an ammonia current density of 665 mA cm-2 and an ammonia yield of 1.41 mmol h-1 cm-2 at -0.59 V vs. a relative reversible hydrogen electrode. Moreover, the catalyst exhibits high stability of 700h. The results of physicochemical and electrochemical characterization and density functional theory calculations show that the high performance of in-situ derived copper nanosheets is attributed to the tandem catalysis of Cu(100) and Cu(111) crystal faces. Due to the difference in electrostatic potential on different crystal faces of copper, the difference in nitrate adsorption strength is different. Among them, Cu(100) is easier to adsorb nitrate (NO3-) and promote its conversion to NO2-, and the resulting NO2- is subsequently migrated on Cu(111) and further reduced, thereby promoting the production of ammonia. (Source: Sun Danning, China Science News)

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