Electrochemical Reduction Of Nitric Oxide Research Articles

Boron-embedded C3N nanosheets as efficient electrocatalysts for reduction of nitric oxide

The electrochemical reduction of nitric oxide (NO) is among the most efficient techniques for converting this poisonous gas into valuable compounds. This paper investigates the potential of boron (B)-doped C3N nanosheets for the catalytic reduction of NO molecules using density functional theory calculations. To achieve this goal, two unique B-doped C3N monolayers are investigated, namely, those in which the B atom is substituted with either a carbon (labeled as BC) or a nitrogen atom (labeled as BN). The findings reveal that the NO molecule might be sufficiently activated over both BC and BN electrocatalysts, with the successive reduction process producing NH3 at low coverages and N2 at high coverages. According to the Gibbs free energy diagrams, the BC nanosheet displays outstanding catalytic performance for NO reduction at normal temperature with no limiting potential. The strong coupling of the ∗HNO and NO species may result in the spontaneous formation of N2 at ambient temperature. The findings of this work might be used to develop metal-free electrocatalysts for removing hazardous NO molecules from the environment.

Electrochemical Reduction of Nitric Oxide with 1.7% Solar-to-Ammonia Efficiency Over Nanostructured Core-Shell Catalyst at Low Overpotentials.

Transition metals have been recognized as excellent and efficient catalysts for the electrochemical nitric oxide reduction reaction (NORR) to value‐added chemicals. In this work, a class of core–shell electrocatalysts that utilize nickel nanoparticles in the core and nitrogen‐doped porous carbon architecture in the shell (Ni@NC) for the efficient electroreduction of NO to ammonia (NH3) is reported. In Ni@NC, the NC prevents the dissolution of Ni nanoparticles and ensures the long‐term stability of the catalyst. The Ni nanoparticles involve in the catalytic reduction of NO to NH3 during electrolysis. As a result, the Ni@NC achieves a faradaic efficiency (FE) of 72.3% at 0.16 V RHE. The full‐cell electrolyzer is constructed by coupling Ni@NC as cathode for NORR and RuO2 as an anode for oxygen evolution reaction (OER), which delivers a stable performance over 20 cycles at 1.5 V. While integrating this setup with a PV‐electrolyzer cell, and it demonstrates an appreciable FE of >50%. Thus, the results exemplify that the core–shell catalyst based electrolyzer is a promising approach for the stable NO to NH3 electroconversion.

Cover Feature: Effect of Electrolyte and Electrode Configuration on Cu‐Catalyzed Nitric Oxide Reduction to Ammonia (ChemElectroChem 5/2022)

The Cover Feature illustrates the cross section of a Ti hollow fiber electrode modified with copper, enabling electrochemical reduction of nitric oxide to ammonia. The inside of the electrode is filled with NO, which is purged through the porous wall of the electrode to facilitate NO reduction at the gas-solid-liquid interface with high faradaic efficiency. More information can be found in the Article by P. M. Krzywda et al.

Selective electrochemical reduction of nitric oxide to hydroxylamine by atomically dispersed iron catalyst

Electrocatalytic conversion of nitrogen oxides to value-added chemicals is a promising strategy for mitigating the human-caused unbalance of the global nitrogen-cycle, but controlling product selectivity remains a great challenge. Here we show iron–nitrogen-doped carbon as an efficient and durable electrocatalyst for selective nitric oxide reduction into hydroxylamine. Using in operando spectroscopic techniques, the catalytic site is identified as isolated ferrous moieties, at which the rate for hydroxylamine production increases in a super-Nernstian way upon pH decrease. Computational multiscale modelling attributes the origin of unconventional pH dependence to the redox active (non-innocent) property of NO. This makes the rate-limiting NO adsorbate state more sensitive to surface charge which varies with the pH-dependent overpotential. Guided by these fundamental insights, we achieve a Faradaic efficiency of 71% and an unprecedented production rate of 215 μmol cm−2 h−1 at a short-circuit mode in a flow-type fuel cell without significant catalytic deactivation over 50 h operation.

Electrochemical Performance of Ba0.5Sr0.5Co0.8Fe0.2O3−δ in Symmetric Cells With Sm0.2Ce0.8O1.9 Electrolyte for Nitric Oxide Reduction Reaction

The emission of nitric oxide from the combustion process of fossil fuels causes air pollution problems. In addition to traditional removal methods, nitric oxide can be removed by the electrochemical reduction method. In this study, Ba0.5Sr0.5Co0.8Fe0.2O3−δ powders were synthesized using a solid-state reaction method. Symmetrical cells, with Sm0.2Ce0.8O1.9 as the electrolyte and Ba0.5Sr0.5Co0.8Fe0.2O3−δ as the electrodes, were prepared as the electrochemical reactor for nitric oxide reduction. In the process of electrochemical reduction, nitric oxide reduction occurs at the cathode and oxygen evolution occurs at the anode. To study the nitric oxide reduction performance of the electrode, impedances of the symmetrical cell in different atmospheres were analyzed. For the nitric oxide conversion in symmetric cells, two different modes, dual chamber and single chamber, were applied. Results demonstrated that the denitrification performance of the double chamber was better but the single chamber mode had other advantages in its simple structure. Presliminary stability results of the single chamber symmetric cell show that the electrochemical reduction of nitric oxide in symmetric cells with BSCF performed most reliably.

Electrochemical reduction of nitric oxide in different carbon-driven solid state cells

A novelty of nitric oxide (NO) abatement technology in a solid state cell has been developed firstly, in which solid carbonaceous materials instead of gas (eg., H2 or CH4 etc.) work as reductant and fuel. The configuration of anode-supported nickel-yttrial stablized zirconia (Ni-YSZ), YSZ (yttrial stablized zirconia) electrolyte, LSM-YSZ (lanthanum strontium manganite-yttrial stablized zirconia) cathode, was fabricated into tubular cell with 13 mm in length and inner diameters 5 mm. Three carbonaceous materials, including activated carbon (AC), carbon black (BC) and graphite (GC), were investigated with regard to specific area, functional group, thermal activity and morphology by means of N2-BET, FT-IR, TG and SEM, respectively. NO conversion efficiency in excess of 85% can be achieved in the solid state cells driven by AC at 800 °C, higher than cells by BC and GC. BC is one of cheaper carbonaceous material substituting for AC in NO electrochemical reduction, due to its comparable performance. Higher specific area (1745 m2 g−1) and higher content of oxygen-containing functional groups assigned to AC contributes to the better electrochemical behaviours evidenced by AC impedance spectra. Similar thermal activities can be observed both for AC and BC. This novel configuration offers a low-risk, inexpensive and highly-efficient option applicable to purification of exhausts from diesel or gasoline engine.

Electrochemical reduction of NO by solid electrolyte cells with La0.8Sr0.2MnO3-Ce0.8Sm0.2O1.9 composite cathodes

Solid electrolyte cells with La0.8Sr0.2MnO3-Ce0.8Sm0.2O1.9 (LSM-SDC) composite cathodes are fabricated for nitric oxide (NO) reduction. The effects of SDC content, inlet NO flow rate and concentration, operating temperature, cathodic polarization, additional gas compositions on NO conversion are investigated systematically. Various characterization methods such as XRD, TEM, SEM, BET, I-V curve, electrochemical impedance spectra (EIS), Raman spectra, XPS, and in situ DRIFT spectra are performed. It is found that the moderate SDC addition expands the three phase boundaries (TPBs) and oxygen vacancies at cathodes, thereby decreasing the polarization resistance and facilitating the gas adsorption. The cathode containing 35 wt% SDC has the highest NO conversion of 67.22% and the lowest polarization resistance of 75.24 Ω cm2 at 700 °C. The high flow rate and low temperature have the negative effects on NO conversion but the high concentration even improves the electrochemical performance of cells. The cathodic voltage promotes the cell performance because of the reduction of Mn ions and the generation of more oxygen vacancies at cathode. The cells show the relatively good tolerance for CO2 and great reversible inhibition effect on SO2, but the excess O2 can degrade the NO conversion evidently due to the competitive effect. The reaction mechanism is proposed in the end that NO2 is the possible intermediate and NO3− is the major adsorption species on cathode surfaces.

Stepwise electrocatalytic reduction of nitric oxide by cationic picket-fence porphyrin in an ultrathin phospholipid film

The electrochemical reduction of nitric oxide (NO) catalyzed by metal porphyrins as enzyme mimics provides a promising way to understand its roles in biological denitrification. Here, a stepwise electrocatalytic reduction of NO was demonstrated by a cationic picket-fence porphyrin incorporated in an ultrathin phospholipid film. The mass transport-corrected Tafel slopes demonstrated −117 mV/dec and −60 mV/dec for the first and second reduction of NO at physiological pH (pH 7.0), respectively, suggesting a distinguish mechanism for the two-step reduction of NO. More significantly, the potential of the first reduction is constant at −0.37 V vs. NHE while the second potential shifted positively with decreasing pH, giving pH dependence with a slope of −43 mV/pH. A kinetic mechanism of electrocatalytic NO reduction is thus proposed, and provides a promising hint for decoding the functions of the various enzymes.

Activation/Deactivation Phenomena in the Electrochemical Reduction of Nitric oxide and Oxygen on LSM perovskites

Activation/Deactivation Phenomena in the Electrochemical Reduction of Nitric oxide and Oxygen on LSM perovskites

Electron transfer of Pseudomonas aeruginosa CP1 in electrochemical reduction of nitric oxide

This study reports catalytic electro-chemical reduction of nitric oxide (NO) enhanced by Pseudomonas aeruginosa strain CP1. The current generated in the presence of bacteria was 4.36times that in the absence of the bacteria. The strain was able to catalyze electro-chemical reduction of NO via indirect electron transfer with an electrode, revealed by a series of cyclic voltammetry experiments. Soluble electron shuttles secreted into solution by live bacteria were responsible for the catalytic effects. The enhancement of NO reduction was also confirmed by detection of nitrous oxide; the level of this intermediate was 46.4% higher in the presence of bacteria than in controls, illustrated that the electron transfer pathway did not directly reduce nitric oxide to N2. The findings of this study may offer a new model for bioelectrochemical research in the field of NO removal by biocatalysts.

Insights into Ferrocene-Mediated Nitric Oxide Sensing – Elucidation of Mechanism and Isolation of Intermediate

An amperometric nitric oxide (NO) sensor based on a ferrocene methanol functionalized electrode was fabricated. The sensor could work at low over potential with a detection limit of 50nM. The sensor exhibited excellent analytical performance, including a NO sensitivity of 6μAnM−1cm−2. The surface coverage of ferrocence on the modified electrode was calculated to be 2.06×10−10molcm−2. The heterogeneous rate constant calculated for ferrocene mediated NO reduction was found to be 3.5×105cm3mol−1s−1. Further, the blue colored intermediate (Ferrocene hyponitrite) obtained during chemical and electrochemical reduction of NO mediated by ferrocene was isolated and characterized spectroscopically. Nitrous oxide (N2O), the final product of electrochemical reduction of NO was characterized using GC-MS. The mechanism of ferrocene-mediated nitric oxide reduction was found to be similar to biological NO reduction exhibited by the enzymes.

The role of ceria in LSM-GDC composite cathode for electrochemical reduction of nitric oxide

Electrochemical reduction of nitric oxide (NO) in a solid state cell reactor (SSCR) is conducted at intermediate-temperature (500–550°C) using three (La0.85Sr0.15)0.9MnO3 (LSM)- Ce0.8Gd0.2O2 (GDC) composite cathodes (LSM:GDC=3:1, 2:2 and 1:3wt.%, denoted respectively as LSM-GDC31, LSM-GDC22, and LSM-GDC13). GDC-free LSM cathode is compared as blank sample. The NO conversion and current generation are evaluated. In the absence of oxygen, NO apparent conversion at the closed circuit state at 550°C is almost 60%, and the corresponding current density at 0.3V is 17mAcm−2 with LSM-GDC22. NO apparent conversion and current produced are greatly enhanced up to 80% and 66.7mAcm−2 in 2000ppm NO-10% O2 at 500°C due to the electrochemical promotion of catalysis (EPOC). The combined electrochemical impedance spectra, in-situ diffuse reflectance infrared fourier transform spectra, scanning electron microscope and Raman spectra are applied and prove that the oxygen-storage properties of ceria improves the selectivity towards NO electrochemical reduction in oxygen-rich atmosphere. In addition, the introduction of GDC enhances the electrode activities due to the increased three phase boundary (TPB) for oxygen reduction reaction.

Electrochemical Reduction of Oxygen and Nitric Oxide at Low Temperature on La1−x Sr x FeO3−δ Cathodes

A series of six strontium-substituted lanthanum ferrites (La1−x Sr x FeO3−δ, x = 0.00, 0.05, 0.15, 0.25, 0.35, and 0.50) were synthesized using the glycine-nitrate process and evaluated as cathodes for the electrochemical reduction of oxygen and nitric oxide in the temperature range 200 to 400 °C, using cone-shaped electrodes and cyclic voltammetry. It was shown that the ferrites had a higher activity towards the electrochemical reduction of nitric oxide than towards the electrochemical reduction of oxygen, in the investigated temperature range. The highest activity towards the electrochemical reduction of nitric oxide was found for La0.95Sr0.05FeO3−δ at 400 °C. This compound also showed the highest activity towards the electrochemical reduction of oxygen at 400 °C. The highest apparent selectivity was found for the compound LaFeO3 at 200 °C. The materials showed ability to oxidize nitric oxide to nitrogen dioxide.

Direct electrochemistry of hemoglobin immobilized on the water-soluble phosphonate functionalized multi-walled carbon nanotubes and its application to nitric oxide biosensing

The direct electron transfer and electrocatalysis of hemoglobin (Hb) immobilized on the phosphonate functionalized multi-walled carbon nanotubes (MWCNTs) are investigated. Fourier transform infrared (FT-IR) spectra, UV–vis spectra and cyclic voltammetry (CV) analyses reveal that the phosphonate functionalized MWCNTs have good biocompatibility for Hb immobilization, and promote the electron communication between Hb and electrode. The immobilized Hb shows a pair of redox peak with a formal potential of −406±10mV (vs. SCE) and the electrochemical behavior of Hb was a surface-controlled process in a pH 7.0 phosphate buffer solution. And the immobilized Hb can act in an electrocatalytic manner in the electrochemical reduction of nitric oxide (NO). Accordingly, an unmediated NO electrochemical biosensor is constructed. Under optimized experimental conditions, the NO electrochemical biosensor shows the fast response (less than 3s), the wide linear range (1.5×10−7 to 2.7×10−4M) and the low detection limit (1.5×10−8M), which is attributed to the good mass transport, the large Hb loading per unit area and the fast electron transfer rate of Hb.

Electrochemical reactors for NO decomposition. Basic aspects and a future

The electrochemical reduction of nitric oxide in the presence of the excess oxygen was reviewed. It was shown that the selectivity and activity of the cathodes is strongly dependent on the composition and on the microstructure of the cathode material. A concept of electrochemical reactor with multilayer electro-catalytic electrode was proposed and successfully designed in Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya, Japan. The typical values of current efficiency in such electrochemical reactors are of the order of 10–20% at gas composition: 1,000 ppm NO and 2% O2 balanced in He and at gas flow rate 50 ml/min. The value of current efficiency depends on the functional multi-layer electrode composition, structure, and operating temperature. Such electrochemical reactors show the value of NO/O2 selectivity (ν sel) higher than 5 (ν sel > 5) at intermediate temperature and up to ν sel = 25 at low temperature operation. It was shown that multilayer electro-catalytic electrode should consist at list from three main functional layers: cathode, electro-catalytic electrode, covering layer, in order to operate as an electrode with high selectivity.

Electrochemical DeNOx in Solid Electrolyte Cells — An Overview

AbstractFor Abstract see ChemInform Abstract in Full Text.

Electrochemical Reduction of NO by Hemin Adsorbed at Pyrolitic Graphite

The mechanism of the electrochemical reduction of nitric oxide (NO) by hemin adsorbed at pyrolitic graphite was investigated. The selectivity of NO reduction was probed by combining the rotating ring disk electrode (RRDE) technique with a newly developed technique called on-line electrochemical mass spectroscopy (OLEMS). These techniques show that NO reduction by adsorbed heme groups results in production of hydroxylamine (NH(2)OH) with almost 100% selectivity at low potentials. Small amounts of nitrous oxide (N(2)O) were only observed at higher potentials. The rate-determining step in NO reduction most likely consists of an electrochemical equilibrium involving a proton transfer, as can be derived from the Tafel slope value of 62 mV/dec and the pH dependence of -42 mV/pH. The almost 100% selectivity toward NH(2)OH distinguishes this system both from NO reduction on bare metal electrodes, which often yields NH(3), and from biological NO reduction in cytochrome P450nor, which yields N(2)O exclusively.

A Nitric Oxide Biosensor Based on Myoglobin Adsorbed on Multi‐Walled Carbon Nanotubes

AbstractMyoglobin (Myb) of horse heart is incorporated on multi‐walled carbon nanotubes (MWNTs) and immobilized at a glassy carbon (GC) electrode surface. Its electrochemical behavior and enzyme activity are characterized by employing electrochemical methods. The results indicate that MWNTs can obviously promote the direct electron transfer between Myb and electrode, and that the Myb on MWNTs behaves as an enzyme‐like activity towards the electrochemical reduction of nitric oxide (NO). Accordingly, an unmediated NO biosensor is constructed. Experimental results reveal that the peak current related to NO is linearly proportional to its concentration in the range of 2.0×10−7–4.0×10−5 mol/L. The detection limit is estimated to be 8.0×10−8 mol/L. Considering a relative standard deviation of 2.1% in seven independent determinations of 1.0×10−5 mol/L NO, this biosensor shows a good reproducibility. The biosensor based on Myb/MWNTs modified electrode can be used for the rapid determination of trace NO in aqueous solution with a good stability, nice selectivity and easy construction.

Multi-step reduction of nitric oxide by cytochrome c entrapped in phosphatidylcholine films

By entrapping cytochrome c (Cyt c) in phosphatidylcholine (PC) film, we have obtained the direct electrochemistry of the protein. Meanwhile, the catalytic reduction of nitric oxide (NO) has been investigated. Besides the pair of peaks corresponding to the redox reactions of Cyt c, two new cathodic peaks can be observed after the addition of NO into the test solution. One, located at −0.510 V, is proposed to come from the formation of hydroxylamine. The other, at −0.690 V, is assigned to the electrochemical reduction of NO. These observations are very different from the previous reports, because only one peak can be obtained for the other studies. The difference is related to the electron transfer rate and the escape rate of the products in the NO reduction process. This study might bring clearer insight into the reduction mechanism of NO.

Electrochemical DeNOx in solid electrolyte cells—an overview

The investigations in the field of electrochemical reduction of nitric oxide are reviewed. Using a cell based on an oxide ionic conductor it is shown that the selectivity and activity of the cathodes is strongly dependent on the temperature and of the composition of the cathode material. In general the selectivity is highest at the lowest temperatures. Cathode materials with a high redox capacity are shown to have the highest performance towards the reduction of nitric oxide. Different approaches using a protonic conductor are also reviewed. In the end a few examples of the electrochemical promotion of the reduction of nitric oxide with a reducing agent are given. Literature reveals that electrochemical promotion of the reduction of nitric oxide with a reducing agent is possible also under lean conditions. The electrochemical promotion is accompanied by an increase in the selectivity towards the formation of nitrogen.