Electrochemical Nitric Oxide Reduction on Metal Surfaces

Abstract

Electrocatalytic denitrification is a promising technology for removing NOx species (NO3−, NO2− and NO). For NOx electroreduction (NOxRR), there is a desire for understanding the catalytic parameters that control the product distribution. Here, we elucidate selectivity and activity of catalyst for NOxRR. At low potential we classify metals by the binding of *NO versus *H. Analogous to classifying CO2 reduction by *CO vs. *H, Cu is able to bind *NO while not binding *H giving rise to a selective NH3 formation. Besides being selective, Cu is active for the reaction found by an activity‐volcano. For metals that does not bind NO the reaction stops at NO, similar to CO2‐to‐CO. At potential above 0.3 V vs. RHE, we speculate a low barrier for N coupling with NO causing N2O formation. The work provides a clear strategy for selectivity and aims to inspire future research on NOxRR.

Efficient nitric oxide electroreduction toward ambient ammonia synthesis catalyzed by a CoP nanoarray

“…3,9 Notably, ambient NO reduction by electrocatalysis is being investigated as a sustainable approach for NO hydrogenation to other harmless or valuable nitrogen species, using only water and electrical energy. 10–23 Among these products, NH 3 as a critical chemical for producing fertilizers and a potential carbon-free energy carrier with high energy density is a notable target molecule. 24,25 Although NH 3 can be produced by N 2 electroreduction, 26–29 it is extremely challenging from both thermodynamic and kinetic points of view since N 2 is chemically inert and poorly dissolves in water.…”

Effect of Electrolyte and Electrode Configuration on Cu‐Catalyzed Nitric Oxide Reduction to Ammonia

“…Due to the small EC‐MS cell volume and relatively high reduction currents for H 2 evolution, a pH change induced by proton reduction might allow for partial transformation of NH 4 + to NH 3 and thus allows for detection of ammonia. Note that m/z: 17 is only detected at highly negative potentials while NH 4 + formation at more positive potentials should not be excluded, as shown by theory as well as experimental work [12,21] . Further work is required to rule out any contribution of water to m/z 17, potentially changing in concentration during NO reduction (see eq.…”

“…+ formation at more positive potentials should not be excluded, as shown by theory as well as experimental work. [12,21] Further work is required to rule out any contribution of water to m/z 17, potentially changing in concentration during NO reduction (see eq. 1-4).…”

“…So far only a few materials have been proposed for electrochemical formation of ammonia from NO. Besides Bi, Au/C, [11] Ag [17] and Fe [18] electrodes, copper was demonstrated to be a promising material for NH 3 formation by both theoretical and experimental investigations in neutral and alkaline conditions [12,19–21] . Using Cu foam electrodes, ammonia production rates of 517 μmol h −1 cm −2 (faradaic efficiencies of 93.5 %) were achieved in neutral pH electrolyte at −0.9 V vs RHE using a pure NO (100 %) stream provided by sparging into the solution close to the electrode surface [12] .…”

“…Besides Bi, Au/ C, [11] Ag [17] and Fe [18] electrodes, copper was demonstrated to be a promising material for NH 3 formation by both theoretical and experimental investigations in neutral and alkaline conditions. [12,[19][20][21] Using Cu foam electrodes, ammonia production rates of 517 μmol h À 1 cm À 2 (faradaic efficiencies of 93.5 %) were achieved in neutral pH electrolyte at À 0.9 V vs RHE using a pure NO (100 %) stream provided by sparging into the solution close to the electrode surface. [12] It is worth noting that NO feeds are usually not purified and thus higher nitrogen oxides [22] might be present in the feed, complicating a precise performance evaluation.…”