Enhanced Nitrate-to-Ammonia Activity on Copper–Nickel Alloys via Tuning of Intermediate Adsorption

Abstract

Electrochemical conversion of nitrate (NO 3 − ) into ammonia (NH 3 ) recycles nitrogen and offers a route to the production of NH 3 , which is more valuable than dinitrogen gas. However, today's development of NO 3 − electroreduction remains hindered by the lack of a mechanistic picture of how catalyst structure may be tuned to enhance catalytic activity. Here we demonstrate enhanced NO 3 − reduction reaction (NO 3 − RR) performance on Cu 50 Ni 50 alloy catalysts, including a 0.12 V upshift in the half-wave potential and a 6-fold increase in activity compared to those obtained with pure Cu at 0 V vs reversible hydrogen electrode (RHE). Ni alloying enables tuning of the Cu d-band center and modulates the adsorption energies of intermediates such as *NO 3 − , *NO 2 , and *NH 2 . Using density functional theory calculations, we identify a NO 3 − RR-to-NH 3 pathway and offer an adsorption energy−activity relationship for the CuNi alloy system. This correlation between catalyst electronic structure and NO 3 − RR activity offers a design platform for further development of NO 3 − RR catalysts.

Restoring the Nitrogen Cycle by Electrochemical Reduction of Nitrate: Progress and Prospects

“…[30] Twofold coordination is sterically favorable for the cleavage of the NO bond and had been employed in the first principles calculation for the mechanism of electrochemical reduction on catalysts. [30][31][32]…”

“…The dissolved NO 2 will react with NH 2(ad) to produce NH 2 NO 2(ad) following Reaction (30). NH 2 NO 2(ad) can be protonated by the intense acidity and yield NH 2 NO (ad) (Reaction (31)…”

“…In the implementation of the construction of cathode, porous substrates, such as Ni foam, [85,87,[135][136][137][138] Cu foam, [31,139] and carbon fiber products [140,141] can generate high surface area for the hosting of active sites. Moreover, the tunable porosity in these substrates strongly influences both the process performance and product distribution.…”

Single‐Atom Cu Catalysts for Enhanced Electrocatalytic Nitrate Reduction with Significant Alleviation of Nitrite Production

“…From the perspective of environmental scientists, the most desirable solution for nitrate removal is to selectively reduce it to harmless gaseous nitrogen, but few non‐noble metal catalysts available today can convert nitrate into nitrogen with a high selectivity. In this regard, recent studies [ 13–16 ] by chemical scientists have attempted to promote the selectively electrocatalytic reduction of nitrate to ammonia, a value‐added product utilized as a precursor to fertilizer.…”

Recent Advances in the Application of Structural‐Phase Engineering Strategies in Electrochemical Nitrogen Reduction Reaction

“…From simple inorganic salts and fertilizers to complex organic dyes and drugs, ammonia plays an important role in the chemical industry. [ 1–2 ] However, the use of the Haber–Bosch method to synthesize ammonia consumes an extremely large amount of energy (its usage accounts for about 1% of the global total energy consumption), and the problems of obvious pollution emissions, low raw material conversion rates, and complex equipment maintenance cannot always be fundamentally solved. In addition, the highly purified hydrogen required by the Haber–Bosch process is derived from the reformation of fossil fuels, which means that in addition to the extremely high energy consumption and the accompanying huge carbon dioxide emissions, this process will also consume a large amount of national strategic fossil fuel reserves.…”