Cu-Doped Iron Oxide for the Efficient Electrocatalytic Nitrate Reduction Reaction

Abstract

The electrochemical nitrate reduction reaction (NO3RR) is a promising alternative synthetic route for sustainable ammonia (NH3) production, because it not only eliminates nitrate (NO3 –) from water but also produces NH3 under mild operating conditions. However, owing to the complicated eight-electron reaction and the competition from the hydrogen evolution reaction, developing catalysts with high activities and Faradaic efficiencies (FEs) is highly imperative to improve the reaction performance. In this study, Cu-doped Fe3O4 flakes are fabricated and demonstrated to be excellent catalysts for electrochemical conversion of NO3 – to NH3, with a maximum FE of ∼100% and an NH3 yield of 179.55 ± 16.37 mg h–1 mgcat –1 at −0.6 V vs RHE. Theoretical calculations reveal that doping the catalyst surface with Cu results in a more thermodynamically facile reaction. These results highlight the feasibility of promoting the NO3RR activity using heteroatom doping strategies.

Recent developments and prospects for engineering first-row transition metal-based catalysts for electrocatalytic NOx− reduction to ammonia

“…In addition to Fe single-atom catalysts, oxides of iron have received considerable attention. Wang et al synthesized Fe 3 O 4 doped with appropriate amounts of Cu, 79 achieving an ammonia yield of 222.75 ± 12.15 mg h −1 mg cat −1 and an excellent FE of 95.7% ± 4.8 at −0.7 V. More intriguingly, in addition to enhancing the adsorption of various intermediates (Fig. 8a), the doping of Cu alters the state of *NO adsorbed on the metal − reduction copied with permission.…”

“…8a), the doping of Cu alters the state of *NO adsorbed on the metal − reduction copied with permission. 79 Copyright 2023, American Chemical Society. (c) ECSA and contact angles of different catalysts copied with permission.…”

Sustainable ammonia synthesis from air by the integration of plasma and electrocatalysis techniques

“…To bridge the gap, some researchers have proposed employing nitrogen oxides (NO x − ) as precursors because they own comparatively low N–O bond dissociation energy and superior water solubility. 15–17 Nevertheless, the direct use of NO x − chemicals (NO 2 − or NO 3 − ) obviously contradicts the objectives of green ammonia synthesis since they are produced by using NH 3 as a reactant via the Haber–Bosch process (NH 3 synthesis), which is combined with the Ostwald process (NH 3 oxidation to NO x − ). 18 Gratifyingly, the rapid development of plasma techniques, especially the non-thermal plasma (NTP) technique, has offered the prospect of converting atmospheric N 2 into NO x on a large scale with low energy consumption, thereby realizing indirect N 2 fixation to NH 3 when coupled with the electrocatalysis technique.…”

Electrodeposited copper–nickel nanoparticles as highly efficient electrocatalysts for nitrate reduction to ammonia

“…20,21 Clean electricity-driven NO 3 − –NH 3 transformation (NO 3 − RR) is thus depicted as a two-pronged route to simultaneously synthesize value-added NH 3 and alleviate environmental problems. 22–26…”

“…20,21 Clean electricitydriven NO 3 − -NH 3 transformation (NO 3 − RR) is thus depicted as a two-pronged route to simultaneously synthesize valueadded NH 3 and alleviate environmental problems. [22][23][24][25][26] Electrochemically reducing NO 3 − into NH 3 requires the transfer of eight electrons, simultaneously producing a handful of byproducts including nitrite (NO 2…”