Electrochemical Reduction Of Nitrite Research Articles

High-efficiency electrocatalytic nitrite reduction toward ammonia synthesis on CoP@TiO2 nanoribbon array

Electrochemical reduction of nitrite (NO2-) can satisfy the necessity for NO2- contaminant removal and deliver a sustainable pathway for ammonia (NH3) generation. Its practical application yet requires highly efficient electrocatalysts to boost NH3 yield and Faradaic efficiency (FE). In this study, CoP nanoparticle-decorated TiO2 nanoribbon array on Ti plate (CoP@TiO2/TP) is verified as a high-efficiency electrocatalyst for the selective reduction of NO2- to NH3. When measured in 0.1M NaOH with NO2-, the freestanding CoP@TiO2/TP electrode delivers a large NH3 yield of 849.57μmol h-1 cm-2 and a high FE of 97.01% with good stability. Remarkably, the subsequently fabricated Zn-NO2- battery achieves a high power density of 1.24 mW cm-2 while delivering a NH3 yield of 714.40μg h-1 cm-2.

NiMoO4 nanorods with oxygen vacancies self-supported on Ni foam towards high-efficiency electrocatalytic conversion of nitrite to ammonia

As an eco-friendly and sustainable strategy, the electrochemical reduction of nitrite (NO2–) can simultaneous generation of NH3 and treatment of NO2– contamination in the environment. Herein, monoclinic NiMoO4 nanorods with abundant oxygen vacancies self-supported on Ni foam (NiMoO4/NF) are considered high-performance electrocatalysts for ambient NH3 synthesis by reduction of NO2−, which can deliver an outstanding yield of 18089.39 ± 227.98 μg h−1 cm−2 and a preferable FE of 94.49 ± 0.42% at −0.8 V. Additionally, its performance remains relatively stable during long-term operation as well as cycling tests. Furthermore, density functional theory calculations unveil the vital role of oxygen vacancies in promoting nitrite adsorption and activation, ensuring efficient NO2–RR towards NH3. A Zn-NO2– battery with NiMoO4/NF as the cathode shows high battery performance as well.

Ruthenium doping: An effective strategy for boosting nitrite electroreduction to ammonia over titanium dioxide nanoribbon array

Electrochemical reduction of nitrite (NO2–) not only removes NO2– contaminant but also produces high-added value ammonia (NH3). This process, however, needs efficient and selective catalysts for NO2−-to-NH3 conversion. In this study, Ruthenium doped titanium dioxide nanoribbon array supported on Ti plate (Ru–TiO2/TP) is proposed as an efficient electrocatalyst for the reduction of NO2− to NH3. When operated in 0.1 M NaOH containing NO2–, such Ru–TiO2/TP achieves an ultra-large NH3 yield of 1.56 mmol h−1 cm−2 and a super-high Faradaic efficiency of 98.9%, superior to its TiO2/TP counterpart (0.46 mmol h−1 cm−2, 74.1%). Furthermore, the reaction mechanism is studied by theoretical calculation.

Size−selected Cu4 cluster anchored on C2N monolayer for efficient nitrite electroreduction to ammonia: a computational study

The electrochemical reduction of nitrite (NO2ER) to ammonia (NH3) at ambient conditions is of great significance for environmental remediation and energy conservation. However, developing the promising electrocatalysts with high activity, selectivity, and stability still remains a huge challenge. Herein, by means of density functional theory (DFT) computations, we proposed a series of sub−nano transition metal−based tetrahedral clusters anchored on C2N monolayer (TM4/C2N) as NO2ER catalysts for NH3 synthesis. Our results revealed that the strong hybridization between TM−d orbitals and N−2p orbitals guarantees the high stability of these candidates, endowing the top TM sites lower oxidation state valence and thus leading to their stronger ability to capture the adsorbates. Interestingly, according to the computed free energy changes, Cu4/C2N was identified as the most promising NO2ER catalyst with an ultra−low limiting potential of −0.14 eV due to its optimal binding strength with NO2– reactant. In addition, Cu4/C2N can greatly suppress the generation of NO, N2O, and N2 byproducts, as well as the competing hydrogen evolution reaction, boosting its extreme selectivity for NH3 production from NO2ER. Our simulations may provide a promising size−selected cluster for NO2ER to resolve the environmental pollution and the sustainable ammonia production simultaneously.

Biomimetic catalysis of nitrite reductase enzyme using copper complexes in chemical and electrochemical reduction of nitrite.

Copper nitrite reductase mimetics were synthesized using three new tridentate ligands sharing the same N,N,N motif of coordination. The ligands were based on L-proline modifications, attaching a pyridine and a triazole to the pyrrolidine ring, and differ by a pendant group (R = phenyl, n-butyl and n-propan-1-ol). All complexes coordinate nitrite, as evidenced by cyclic voltammetry, UV-Vis, FTIR and electron paramagnetic resonance (EPR) spectroscopies. The coordination mode of nitrite was assigned by FTIR and EPR as κ2O chelate mode. Upon acidification, EPR experiments indicated a shift from chelate to monodentate κO mode, and 15N NMR experiments of a Zn2+ analogue, suggested that the related Cu(II) nitrous acid complex may be reasonably stable in solution, but in equilibrium with free HONO under non catalytic conditions. Reduction of nitrite to NO was performed both chemically and electrocatalytically, observing the highest catalytic activities for the complex with n-propan-1-ol as pendant group. These results support the hypothesis that a hydrogen bond moiety in the secondary coordination sphere may aid the protonation step.

Nitrite Electroreduction to Ammonia Promoted by Molecular Carbon Dioxide with Near-unity Faradaic Efficiency.

Electrochemical reduction of nitrite (NO2 - ) offers an energy-efficient route for ammonia (NH3 ) synthesis and reduction of the level of nitrite, which is one of the major pollutants in water. However, the near 100 % Faradaic efficiency (FE) has yet to be achieved due to the complicated reduction route with several intermediates. Here, we report that carbon dioxide (CO2 ) can enhance the nitrite electroreduction to ammonia on copper nanowire (Cu NW) catalysts. In a broad potential range (-0.7∼-1.3 V vs. RHE), the FE of nitrite to ammonia is close to 100 % with a 3.5-fold increase in activity compared to that obtained without CO2. In situ Raman spectroscopy and density functional theory (DFT) calculations indicate that CO2 acts as a catalyst to facilitate the *NO to *N step, which is the rate determining step for ammonia synthesis. The promotion effect of CO2 can be expanded to electroreduction of other nitro-compounds, such as nitrate to ammonia and nitrobenzene to aniline.

Highly Efficient Electrosynthesis of Nitric Oxide for Biomedical Applications.

Nitric oxide (NO) constitutes one of the most versatile therapeutics for biomedical applications. The efficient and on-demand NO generation essentially dictates its concentration dependent therapeutic activity. Here, we report an electrochemical system employing a rationally designed single-iron atom based biomimetic catalyst (i.e., Fe SAC), for high-efficient and controlled NO generation. The Fe SAC shows superior catalytic ability in electrochemical reduction of nitrite, with maximal NO generation rate achieving 2.1 μM (min μg)-1 . Theoretical studies suggest the significant decrease of Gibbs-free energy of NO2 - adsorption on single-iron atom accounts for its high catalytic efficiency. Moreover, ample amount of NO can be controllably generated in a potential dependent manner. For antibacterial application, the generated NO overwhelmingly disrupts both gram-negative and gram-positive strains, highlighting a great promise to expedite NO research in both basic and applied sciences.

Highly Efficient Electrosynthesis of Nitric Oxide for Biomedical Applications

AbstractNitric oxide (NO) constitutes one of the most versatile therapeutics for biomedical applications. The efficient and on‐demand NO generation essentially dictates its concentration dependent therapeutic activity. Here, we report an electrochemical system employing a rationally designed single‐iron atom based biomimetic catalyst (i.e., Fe SAC), for high‐efficient and controlled NO generation. The Fe SAC shows superior catalytic ability in electrochemical reduction of nitrite, with maximal NO generation rate achieving 2.1 μM (min μg)−1. Theoretical studies suggest the significant decrease of Gibbs‐free energy of NO2− adsorption on single‐iron atom accounts for its high catalytic efficiency. Moreover, ample amount of NO can be controllably generated in a potential dependent manner. For antibacterial application, the generated NO overwhelmingly disrupts both gram‐negative and gram‐positive strains, highlighting a great promise to expedite NO research in both basic and applied sciences.

Selectivity and efficiency of nitrite electroreduction catalyzed by a series of Keggin polyoxometalates

In this paper we have studied the influence of the charge and redox potential for a series of polyoxometalates (POMs) belonging to the Keggin family on the electrochemical reduction of nitrite or nitrous acid (NO2– or HNO2). We have focused on the correlation of gaseous products and the redox properties of the POMs. Analysis by differential electrochemical mass spectrometry (DEMS) showed that the gaseous products (NO and N2O) are formed at pH 2 and 5 by reaction of HNO2 or NO2– with the reduced POM. Only NO is detected when the POM ([PW12O40]3- , [SiW12O40]4-, [BW12O40]5-) undergoes the first one-electron reduction wave. However, N2O is obtained along with NO as soon as the POM undergoes two-electron reduction. The potential of the first reduction wave of the POM is correlated with its charge. Consequently NO and/or N2O appear at lower overpotential for [PW12O40]3- and [SiW12O40]4- followed by [BW12O40]5- and [H2W12O40]6-. Microkinetic simulations of the experimental current–potential curves were used to estimate the rate constant kc of the reaction between the reduced POM and HNO2 or NO2– in solution and the turnover frequency (TOF). At low overpotentials, the values of TOF are decreasing in a trend following the redox potential of the POM: [PW12O40]3- > [SiW12O40]4- > [BW12O40]5- while at high overpotentials the TOFs are dominated by kc following the reverse order. At pH 5 kc values are about 70 times lower than at pH 2. This is attributed to the decrease in the proton concentration and to the electrostatic repulsion between the negatively charged POMn- and NO2–.

Te-Doped Pd Nanocrystal for Electrochemical Urea Production by Efficiently Coupling Carbon Dioxide Reduction with Nitrite Reduction.

The renewable electricity-driven reduction of carbon dioxide (CO2RR) is a promising technology for carbon utilization. However, it is still a challenge to broaden the application of CO2RR. Herein, we report a Te-doped Pd nanocrystals (Te-Pd NCs) for promoting urea synthesis by coupling CO2RR with electrochemical reduction of nitrite. The electrochemical synthesis of urea has been achieved with nearly 12.2% Faraday efficiency (FE) and 88.7% N atom efficiency (NE) at -1.1 V versus reversible hydrogen electrode (vs RHE), much higher than those of pure Pd NCs (4.2% FE and 21.8% NE). Significantly, an FE of ∼10.2% and an NE of ∼82.3% for urea solution production via an optimized flow cell system have been realized, where a solution with up to 0.95 wt % of urea has been obtained. Mechanistic insights show that Te-doping not only optimizes the CO2/CO adsorption but also promotes NH3 production, fully meeting the requirements of urea synthesis.

Electrochemically Modulated Nitric Oxide (NO) Releasing Biomedical Devices via Copper(II)-Tri(2-pyridylmethyl)amine Mediated Reduction of Nitrite

A controllable and inexpensive electrochemical nitric oxide (NO) release system is demonstrated to improve hemocompatibility and reduce bacterial biofilm formation on biomedical devices. Nitric oxide is produced from the electrochemical reduction of nitrite using a copper(II)-tri(2-pyridylmethyl)amine (Cu(II)TPMA) complex as a mediator, and the temporal profile of NO release can be modulated readily by applying different cathodic potentials. Single lumen and dual lumen silicone rubber catheters are employed as initial model biomedical devices incorporating this novel NO release approach. The modified catheters can release a steady, physiologically-relevant flux of NO for more than 7 days. Both single and dual lumen catheters with continuous NO release exhibit greatly reduced thrombus formation on their surfaces after short-term 7-h intravascular placement in rabbit veins (p < 0.02, n = 6). Three day in vitro antimicrobial experiments, in which the catheters are “turned on” for only 3 h of NO release each day, exhibit more than a 100-fold decrease in the amount of surface attached live bacteria (n = 5). These results suggest that this electrochemical NO generation system could provide a robust and highly effective new approach to improving the thromboresistance and antimicrobial properties of intravascular catheters and potentially other biomedical devices.

Pencil Lead Electrode Modified with Hemoglobin Film as a Novel Biosensor for Nitrite Determination

AbstractIn the present paper, the electrochemical reduction of nitrite at a hemoglobin modified pencil lead electrode (Hb/PLE) is described. The electrochemical properties of nitrite were studied by cyclic voltammetry and chronoamperometry. Results showed that the hemoglobin film has an excellent electrochemical activity towards the reduction of nitrite. By using voltammetric and chronoamperometric methods, α, nα and n were calculated. Then the ability of the electrode for nitrite determination was investigated using differential pulse voltammetry. The electrocatalytic reduction peak currents were found to be linear with the nitrite concentration in the range from 10 to 220 µM with a detection limit of 5 µM. The relative standard deviation is 2 % for 3 successive determinations of a 100 µM nitrite solution. This modified electrode was successfully used for the detection of low amounts of NO2− in spinach sample and a spiked sample of tap water.

A Simple and Efficient Electrochemical Sensor for Electrocatalytic Reduction of Nitrite Based on Poly(4‐aminoacetanilide) Film Using Carbon Paste Electrode

AbstractIn this study, the electrochemical reduction of nitrite was investigated on poly(4‐aminoacetanilide) (PPAA) forming by cyclic voltammetry at the surface of carbon paste electrode. The electrochemical properties of the modified electrode have been studied by cyclic voltammetry and double potential step chronoamperometry. Results showed that in the optimum condition (pH = 0.00) the reduction of nitrite occurred at a potential about 667 mV more positive than that unmodified carbon paste electrode. This amount of electrocatalytic ability is high compared with other electrocatalysts. Using a chronoamperometric method, the catalytic rate constant (k) was calculated 8.4 × 104 cm3 mol‐1 s‐1. Also, the electrocatalytic reduction peak currents was found to be linear with the nitrite concentration in the ranges of 5 × 10‐4 M to 2.5 × 10‐2 M and 2 × 10‐5 M to 7 × 10‐3 M with detection limits (2σ) were determined as 4.5 × 10‐4 M and 1 × 10‐5 M by cyclic voltammetry (CV) and hydrodynamic amperometry methods respectively. Recovery experiments exhibit the satisfactory results.

Metallophthalocyanine catalysed electroreduction of nitrate and nitrite ions in alkaline media

The electrochemical reduction of nitrite and nitrate in alkaline solution has been studied on glassy carbon electrodes modified with phthalocyanine complexes of Mn, Fe, Co, Ni, Cu and Zn (MnPc, FePc, CoPc, NiPc, CuPc and ZnPc, respectively, and Pc(-2) is phthalocyanine dianion). Voltammetry shows that the reduction of nitrite occurs at potentials slightly less negative than for nitrate reduction. The MPc complexes lower the overpotential for the reduction of nitrite and nitrate as follows: CuPc > FePc > NiPc > CoPc > MnPc > ZnPc > glassy carbon electrode. The main product for the reduction of nitrite and nitrate is ammonia, with high yields of ammonia being obtained, depending on the choices of the electrolysis potential and MPc complex.

In Situ Fourier Transform Infrared Spectroscopic Studies of Nitrite Reduction on Platinum Electrodes in Perchloric Acid

Nitrous oxide generated by the electrochemical reduction of nitrite on a polycrystalline platinum electrode in aqueous 0.1 M HClO4 was monitored by in situ potential difference Fourier transform infrared reflection absorption spectroscopy. An analysis of the intensity of the N2O asymmetric stretch band at 2231 cm-1, A(N2O), monitored during a slow linear potential (E) sweep in the range 0.8 > E > −0.32 V vs SCE, indicated that N2O begins to form at E ∼0.5 V vs SCE, reaches a maximum at E ∼0.05 V, and disappears completely for E < −0.1 V. These observations are in agreement with those made by on-line mass spectrometry (MS) using high-area Pt electrodes in acid electrolytes reported in the literature. In addition, a plot of A(N2O) vs E was found to be directly correlated with that of the integral of the N2O generation rate, as measured by on-line dynamic differential electrochemical MS (DEMS) by Nishimura et al. (Electrochim. Acta 1991, 36, 877) in sulfuric acid solutions.

Electrochemical reduction of nitrite and nitric oxide catalyzed by an iron-alizarin complexone adsorbed on a graphite electrode

The ligand alizarin complexone, [((3,4-dihydroxy-2-anthraquinolyl)methyl)imino]diacetic acid is strongly and irreversibly adsorbed on graphite electrode surfaces and binds ferric ions to form surface-bound metal complexes. Upon reduction, the adsorbed complex is an active electrocatalyst for the reduction of both nitrite reduction. The main products of this electrocatalytic nitrite reduction are believed to be NH[sub 2]OH and NH[sub 3]. Adducts formed between substrate and adsorbed catalyst are formed in the initial steps of the reduction on the basis of surface cyclic voltammetric behavior. The possible application of this electrocatalytic reduction in the analysis of nitrite and nitric oxide is also discussed. Four other ligands, xylenol orange, methylthymol blue, fluorexon, and thymolphthalein complexone, which have the same coordination structure of a (methylimino)diacetate group and adjacent aromatic hydroxyl group, were also electrocatalysts for nitrite reduction.

Electrochemical Reduction of Nitrate and Nitrite in Concentrated Sodium Hydroxide at Platinum and Nickel Electrodes

The electrochemical reduction of nitrite and nitrate in concentrated sodium hydroxide solution has been studied as a function of electrode material, temperature, and solution composition. Electrolysis of in , at 80°C using platinized nickel cathodes resulted in high current efficiency for the overall electrode reaction, a five‐electron reduction to dinitrogen. Ammonia is formed in constant current electrolyses at high current densities. The presence of oxygen in the cathode compartment was shown to increase the rate of nitrate reduction under these conditions. Nonideal cyclic voltammetric behavior was observed indicative of complex electrode processes.

ChemInform Abstract: THE ELECTROCATALYTIC REDUCTION OF NITROGEN COMPOUNDS. PART II‐ THE INFLUENCE OF THE ELECTRODE MATERIAL ON THE ELECTROCHEMICAL REDUCTION OF NITRITE

AbstractDie elektrochemische Reduktion von N0; an Pt‐, Ir‐, Rh‐, Nb‐, Ta‐ und Pb‐Elektroden in 7.5 M H2SO4 ‐Lösungen wird durch Aufnahme der Strom‐Spannungs‐Kurven untersucht.

The electrocatalytic reduction of nitrogen compounds. Part II: The influence of the electrode material on the electrochemical reduction of nitrite

AbstractThe electrochemical reduction of nitrite was studied at several electrode materials in 7.5 M sulfuric acid solutions. The thin oxide films on the noble metals, Pt, Ir and Rh, did not interfere with the reduction process. A thick oxide layer, as on Nb and Ta, however, did shift positively the reducing potential by several hundreds of mV.In these solutions, the protecting layer on a lead electrode (lead sulfate) behaved in the same manner. From the decrease in the current in repeated cyclic experiments, it could be concluded that poisoning of the active surface sites of the electrodes by oxygen did change the reduction mechanism of nitrite.