Electrocatalytic Reduction Of Nitric Oxide Research Articles

Cu@Co with Dilatation Strain for High-Performance Electrocatalytic Reduction of Low-Concentration Nitric Oxide.

Electrocatalytic reduction of nitric oxide (NO) to ammonia (NH3 ) is a clean and sustainable strategy to simultaneously remove NO and synthesize NH3 . However, the conversion of low concentration NO to NH3 is still a huge challenge. In this work, the dilatation strain between Cu and Co interface over Cu@Co catalyst is built up and investigated for electroreduction of low concentration NO (volume ratio of 1%) to NH3 . The catalyst shows a high NH3 yield of 627.20µg h-1 cm-2 and a Faradaic efficiency of 76.54%. Through the combination of spherical aberration-corrected transmission electron microscopy and geometric phase analyses, it shows that Co atoms occupy Cu lattice sites to form dilatation strain in the xy direction within Co region. Further density functional theory calculations and NO temperature-programmed desorption (NO-TPD) results show that the surface dilatation strain on Cu@Co is helpful to enhance the NO adsorption and reduce energy barrier of the rate-determining step (*NO to *NOH), thereby accelerating the catalytic reaction. To simultaneously realize NO exhaust gas removal, NH3 green synthesis, and electricity output, a Zn-NO battery with Cu@Co cathode is assembled with a power density of 3.08mW cm-2 and an NH3 yield of 273.37µg h-1 cm-2 .

An Amorphization-Engineered Catalyst for Electrocatalytic Reduction of Nitric Oxide to Ammonia.

Electrocatalytic NO-to-NH3 conversion (NORR) provides a fascinating route toward the eco-friendly and valuable production of NH3. In this study, amorphous FeS2 (a-FeS2) is first demonstrated as a high-efficiency catalyst for the NORR, showing a maximum FENH3 of 92.5% with a corresponding NH3 yield rate of 227.1 μmol h-1 cm-2, outperforming most NORR catalysts reported earlier. Experimental measurements combined with theoretical computations clarify that the exceptional NORR activity of a-FeS2 originates from the amorphization-induced upshift of the d-band center to promote the NO activation and NO-to-NH3 hydrogenation energetics.

Single and double transition metal atoms doped graphdiyne for highly efficient electrocatalytic reduction of nitric oxide to ammonia

The electrocatalytic conversion of nitric oxide (NORR) to ammonia (NH3) represents a pivotal approach for sustainable energy transformation and efficient waste utilization. Designing highly effective catalysts to facilitate the conversion of NO into NH3 remains a formidable challenge. In this work, the density functional theory (DFT) is used to design NORR catalysts based on single and double transition metal (TM:Fe, Co, Ni and Cu) atoms supported by graphdiyne (TM@GDY). Among eight catalysts, the Cu2@GDY is selected as a the most stable NORR catalyst with high NH3 activity and selectivity. A pivotal discovery underscores that the NORR mechanism is thermodynamically constrained on single atom catalysts (SACs), while being governed by electrochemical processes on double atom catalysts (DACs), a distinction arising from the different d-band centers of these catalysts. Therefore, this work not only introduces an efficient NORR catalyst but also provides crucial insights into the fundamental parameters influencing NORR performance.

Oxygen-Bridged Copper-Iron Atomic Pair as Dual-Metal Active Sites for Boosting Electrocatalytic NO Reduction.

Electrocatalytic reduction of nitric oxide (NO) to ammonia (NH3 ) is a promising approach to NH3 synthesis. However, due to the lack of efficient electrocatalysts, the performance of electrocatalytic NO reduction reaction (NORR) is far from satisfactory. Herein, it is reported that an atomic copper-iron dual-site electrocatalyst bridged by an axial oxygen atom (OFeN6 Cu) is anchored on nitrogen-doped carbon (CuFe DS/NC) for NORR. The CuFe DS/NC can significantly enhance the electrocatalytic NH3 synthesis performance (Faraday efficiency, 90%; yield rate, 112.52µmolcm-2 h-1 ) at -0.6V versus RHE, which is dramatically higher than the corresponding Cu single-atom, Fe single-atom and all NORR single-atom catalysts in the literature so far. Moreover, an assembled proof-of-concept Zn-NO battery using CuFe DS/NC as the cathode outputs a power density of 2.30mWcm-2 and an NH3 yield of 45.52µgh-1 mgcat -1 . The theoretical calculation result indicates that bimetallic sites can promote electrocatalytic NORR by changing the rate-determining step and accelerating the protonation process. This work provides a flexible strategy for efficient sustainable NH3 synthesis.

The efficient electrocatalytic and photocatalytic reduction of nitric oxide into ammonia over 0D/3D g-C3N4 quantum dots/3DOMM-TiO2-x heterojunction

An appealing strategy for air pollution treatment is the conversion of NOx in flue gas to valuable chemicals in ambient conditions. The electrocatalytic reduction of nitric oxide has been demonstrated to be a very effective process, however, the photocatalytic reduction of nitric oxide hasn't received much research attention. Herein, we developed a novel 0D/3D g-C3N4 QDs/3DOMM-TiO2-x catalyst, and investigated its performances in both electro- and photocatalytic reduction of nitric oxide to ammonia through experimental analysis and theoretical computation. In the electrocatalytic reduction of NO, the NH3 yield of g-C3N4 QDs/3DOMM-TiO2-x is up to 3841.5 μg h−1 mg−1, which is 15.15, 3.14, and 1.15 times that of TiO2 (P25), 3DOMM-TiO2 and g-C3N4 QDs/3DOMM-TiO2, respectively. The best reaction pathway is *NO → *HNO → *HNOH → *NH→ *NH2 → *NH3 → *NH4+, and the potential determining step is *NH → *NH2. Furthermore, the NH3 yield is estimated to be 95.07 μg h−1 mg−1 in the photocatalytic reduction of NO, using g-C3N4 QDs/3DOMM-TiO2-x as single photoelectrode. The NO molecules are reduced to NH3 on the CB of the g-C3N4 QDs by the accumulated photoelectrons, and charge migration occurs according to the S-scheme in the g-C3N4 QDs/3DOMM-TiO2-x photocatalyst. The results pave a new route for producing ammonia from NO under ambient conditions using electricity and solar energy.

The in situ decoration of Ti3C2 quantum dots on Cu nanowires for highly efficient electrocatalytic reduction of nitric oxide to ammonia

An efficient and stable electrocatalyst (Ti3C2 QDs/Cu NWs) with greatly improved NO conversion performances were developed for NORR, which is regarded as a promising alternative for the traditional Haber–Bosch process.

Single Transition Metal Atoms Anchored on Defective MoS2 Monolayers for the Electrocatalytic Reduction of Nitric Oxide into Ammonia and Hydroxylamine.

Ammonia (NH3) and hydroxylamine (NH2OH) are important feedstocks in the chemical industry. Electrocatalytic reduction of nitric oxide (eNORR) to these chemical feedstocks is desirable for green energy conversion and waste utilization. In this work, by means of density functional theory (DFT) calculations, the eNORR activity of defective single-layer MoS2 catalysts decorated with transition metal atoms (TM@MoS2) is systematically studied. Sulfur defects innately generated during the preparation of MoS2 monolayers are natural hosting sites for TM atoms. Out of the 27 considered TM@MoS2 (3d to 5d period) catalysts, 19 are thermodynamically stable and experimentally feasible. Among these 19 candidates, 13 exhibit a high eNORR activity toward NH3, while six prefer the production of NH2OH. Then, their abilities to inhibit hydrogen evolution reaction (HER) and byproducts (N2O/N2) are evaluated. Eventually, five TM@MoS2 catalysts (TM = Ni, V, Cr, Nb, Ti) are found to be promising for affording NH3 with very low limiting potentials (UL = -0.18 to 0 V). Two TM@MoS2 catalysts (TM = Ag and Pt) are screened out for generating NH2OH, with UL of 0 V. The adsorption of NO is a good descriptor for eNORR's activity and product selectivity. Thus, the TM@MoS2 catalysts may open a new avenue for electrochemical NH3/NH2OH synthesis and NO removal.

Ultrafine Cu nanoparticles decorated porous TiO2 for high-efficient electrocatalytic reduction of NO to synthesize NH3

Low-temperature electrocatalytic reduction of nitric oxide (NORR) is promising for the low-cost, high-efficiency removal and utilization of nitric oxide (NO), which couples the two crucial industrial processes of denitration and synthetic ammonia. We reported a binary catalyst of Cu/P–TiO2 for NORR process, which took advantages of the Cu electrocatalysts and porous TiO2. The increase of surface areas and channels can improve the adsorption of NO molecules. The decoration of the ultrafine Cu nanoparticles on the porous TiO2 may prevent the agglomeration of ultrafine Cu nanoparticles. The as-prepared Cu/P–TiO2 electrode exhibits excellent electrocatalytic activity with a Faraday efficiency of 86.49% and NH3 yield of 3520.80 μg·h−1·mg−1 in 0.1 M K2SO4 at −0.3 V vs. RHE. The mechanism of the NORR reaction process with Cu/P–TiO2 catalysts was also discussed. This research may broaden the application areas of TiO2-based materials in the electrocatalysis and provide a new sight in the treatment of NO pollutants.

NiFe layered double hydroxide nanosheet array for high-efficiency electrocatalytic reduction of nitric oxide to ammonia.

Here, we demonstrate that under ambient conditions, a nickel-iron layered double hydroxide nanosheet array can exhibit a promising NORR performance, delivering a maximal faradaic efficiency of 82% and a corresponding yield rate of 112 μmol h-1 cm-2, along with high stability for over 30 h. This superior performance is further confirmed as a proof-of-concept for a Zn-NO battery, in which a peak power density of 1.8 mW cm-2 and a large NH3 yield rate of 32 μmol h-1 cm-2 are observed. Theoretical analyses indicate that NiFe-LDH exhibits effective NO activation capacity and slow hydrogen evolution kinetics.

Element table of TM-substituted polyoxotungstates for direct electrocatalytic reduction of nitric oxide to ammonia: a DFT guideline for experiments

We screened out NiII, CoII, CuII, PdII, PtII, and AgI substituted heteropolytungstates as promising electrocatalysts for nitric oxide to ammonia with high activity and high selectivity.

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.

A selective nitric oxide nanocomposite biosensor based on direct electron transfer of microperoxidase: Removal of interferences by co-immobilized enzymes

A highly selective nitric oxide (NO) biosensor was developed by immobilizing microperoxidase (MP) onto the MWCNT-poly-5,2′:5′,2″-terthiophene-3′-carboxylic acid (PTTCA) nanocomposite. Catalase (CAS) and superoxide dismutase (SOD) co-immobilized on the probe successfully protected the interferences of H 2O 2 and O 2 − during NO detection. The nanocomposite layer showed the direct electron transfer processes of the immobilized CAS, SOD, and MP simultaneously at −0.11/+0.04, −0.33/−0.27, and −0.47/−0.40 V vs. Ag/AgCl. Au nanoparticles (AuNPs) were electrodeposited on a glassy carbon surface to enhance the sensitivity of the sensor probe. The layers of CAS/SOD/MP/MWCNT-PTTCA/AuNPs were characterized using SEM, XPS, and QCM. The CAS/SOD/MP/MWCNT-PTTCA/AuNPs probe showed an excellent performance in the electrocatalytic reduction of NO which was attributed to the heme group of MP. Experimental conditions affecting the sensitivity of the biosensor were optimized in terms of pH, temperature, and applied potential. The dynamic range of NO analysis was from 1.0 to 40 μM with the detection limit of 4.3 ± 0.2 nM. The reliability of biosensor was examined for the determination of NO released from the real samples of rat liver, stomach (AGS), and intestinal (HT-29) cancer cells.

Electrocatalytic reduction of nitric oxide on Pt nanocrystals of different shape in sulfuric acid solutions

Pt tetrahexahedral (Pt-THH) nanocrystals enclosed with 24 { h k 0} facets, Pt nanothorns (Pt-Thorn) with a high surface density of atomic steps, and congeries of Pt nanoparticles (Pt-NP) were prepared and served as catalysts to study the electrocatalytic reduction of both adsorbed and solution nitric oxide. The structure sensitivity for the reduction of a saturated NO adlayer on the Pt nanocrystals (NCs) of different shape was studied by cyclic voltammetry (CV) and in situ FTIR spectroscopy in sulphuric acid solutions. The results revealed that two types of NO adsorbates can be reduced independently at separated potentials, i.e. the reduction of linear bonded NO (NO L) on the Pt-NP electrode gives rise to a current peak at −0.01 V (vs. SCE), while the bridge adsorbed NO (NO B) yields a current peak at −0.08 V. The in situ SNIFTIRS results confirmed the assignment of NO adsorbates, i.e. the NO B species yielding a IR absorption bipolar band with its negative-going peak at 1636 cm −1 and positive-going peak around 1610 cm −1, and the NO L species giving rise to a bipolar band with its negative-going peak at 1809 cm −1 and positive-going peak around 1720 cm −1. It has determined that the NO L species can be preferentially formed on the Pt NCs with open surface structure, i.e. the more open the surface structure of the Pt NCs, the larger the relative quantity of NO L versus NO B. It has also revealed that the Pt NCs with a high surface density of atomic steps exhibit superior electrocatalytic activity for the reduction of solution NO species. The steady-state current density of NO reduction on Pt-THH NCs is 7.5–12 times as large as that on Pt-NP, and that on Pt-Thorn is 2.5–4 times of that on Pt-NP in the reduction potential region of electrochemical dynamic control.

Electrochemical and electrocatalytic behaviors of Safranin O/Nafion film deposited on the glassy carbon electrode

The glassy carbon (GC) electrode modified with Nafion and Safranin O (SFO) was prepared and its electrochemical properties were investigated. The SFO molecules were strongly and irreversibly adsorbed on the Nafion — modified GC surface. The electrochemical behavior and mechanism for interactions of the SFO molecules with the Nafion film were investigated through cyclic voltammetric method. The electrocatalytic reduction of nitric oxide was performed at this modified electrode by cyclic voltammetric and hydrodynamic amperometric techniques. The Nafion membrane played a duel role as a matrix for the SFO immobilization and also helped to partition the nitric oxide from the solution phase. The diffusion coefficient of NO at the SFO/Nafion/GC modified electrode was calculated using chronoamperometry. The dependence of response currents on the concentration of NO was examined and was linear in the range of 0.05–1.9 mM of NO.

Metallo Protoporphyrin Functionalized Microelectrodes for Electrocatalytic Sensing of Nitric Oxide

Nitric oxide (NO) has been considered as an important bio-regulatory molecule in the physiological process. All the existing methods often employed for NO measurement are mainly indirect and not suitable for in vivo conditions. In this paper, we report a systematic study of electrocatalytic NO reduction by comparing the redox properties of NO at carbon microelectrodes functionalized by Fe, Mn and Co protoporphyrins. The mechanisms of electrocatalytic reduction of NO by different metalloporphyrins have been proposed and compared. In addition, by varying the metallic cores of the metalloporphyrins, NO exhibits voltammograms in which the cathodic peak current occur at different potential. A comparative study on the electrochemical behavior of each of these metalloporphyrin (as a result of varying the metallic core) has been performed and a possible mechanism for the observed behavior is proposed. The results confirmed the potential applicability of using metalloporphyrins modified electrodes for voltammetric NO detection.

Noncovalent nanoassembly of porphyrin on single-walled carbon nanotubes for electrocatalytic reduction of nitric oxide and oxygen

Water-soluble iron(III) meso-tetrakis( N-methylpyridinum-4-yl)porphyrin (FeTMPyP) was successfully immobilized on single-walled carbon nanotubes (SWNTs) via 1-pyrenebutyric acid (PBA). The formed SWNTs/PBA/FeTMPyP film showed an enhanced electrocatalytic peak at −0.70 V and −0.17 V towards reduction of nitric oxide and oxygen, respectively. SWNTs accelerated the electron transfer between FeTMPyP and electrode, and increased the amount of FeTMPyP adsorbed. FeTMPyP acted as a catalyst to decrease the reduction potential, exhibiting a synergy in electrocatalysis. The excellent electrocatalytic behaviors made SWNTs/porphyrin nanocomposite have a promising potential in fabricating new type of biosensors.

Bioinspired electrocatalytic reduction of nitric oxide by immobilized heme groups

Abstract This paper discusses our work on the reduction of nitric oxide (NO) by heme groups immobilized on electrode surfaces, which has been conducted in search for selective NO reduction catalysts. Results show two reduction pathways, one leading to the formation of N2O and another leading to the formation of NH2OH. By changing the conditions (pH, potential, NO concentration and immobilization method), 100% selectivity toward either N2O or NH2OH can be obtained. A difference compared to NO reducing enzymes and metals is that immobilized heme groups do not reduce NH2OH further to NH3. Apparently, binding to an isolated heme group is insufficient to break the N–O bond.

Mechanism of Electrocatalytic Reduction of Nitric Oxide on Pt(100)

The mechanism of electrocatalytic reduction of nitric oxide on Pt(100)-(1 x 1) in acidic media has been studied using voltammetry, in-situ infrared spectroscopy, and on-line mass spectroscopy, considering the effect of surface defects, NO coverage, and the nature of the supporting electrolyte (sulfate vs perchlorate). Related mechanistic aspects of hydroxylamine (HAM) transformations on the same surface have been also examined. The adsorption of nitric oxide on Pt(100) results in the formation of an adlayer with a structure similar to that formed under ultrahigh vacuum (UHV) conditions. Ammonia was shown to be the main product of NOads reduction on Pt(100). The saturation coverage of NO adsorbate on Pt(100) was found to be around 0.5 ML, in agreement with previous UHV and electrochemical studies. Two features observed in the voltammetric profile for the electrocatalytic reduction of saturated and subsaturated NO adlayers were tentatively ascribed to reactions of NO species having different reactivity. The Tafel slope analysis of these voltammetric features gives values of ca. 60 mV decade(-1). This value was interpreted in terms of an EC mechanism, in which the first electron/proton transfer is at equilibrium, resulted in formation of HNOads intermediate, while the second reaction step is a chemical rate-determining step. This chemical step is assumed to involve the N-O bond breaking in HNOads intermediate, which most probably requires a free neighboring site. From a comparison with NOads reduction on Pt(111) and Pt(110), it follows that (i) the reaction mechanism is structure sensitive and (ii) Pt(100) is the most active surface for breaking the N-O bond, which is in agreement with the trend observed under UHV conditions. As suggested in our previous studies, the electrocatalytic reduction of HAM is likely to proceed through its partial dehydrogenation. In this study, we further develop this idea, and, based on the mechanism for NOads reduction proposed here, we suggest HNOads to be the intermediate appearing both in HAM reduction/oxidation and in NOads reduction.

Electrocatalytic reduction of nitric oxide and other substrates on hydrogel triblock copolymer Pluronic films containing hemoglobin or myoglobin based on protein direct electrochemistry

Protein-Pluronic film modified electrodes were constructed by casting the mixture of hemoglobin (Hb) or myoglobin (Mb) and triblock copolymer poly(ethylene oxide) 100–poly(propylene oxide) 65–poly(ethylene oxide) 100 (Pluronic) solutions onto the surface of pyrolytic graphite (PG) electrodes. A pair of well-defined and nearly reversible CV peaks at about −0.35 V versus SCE in pH 7.0 buffers was observed for protein-Pluronic films, characteristic of the protein heme Fe(III)/Fe(II) redox couples. The films were characterized by scanning electron microscopy (SEM), UV–vis and IR spectroscopy, as well as electrochemistry. The heme proteins were quite stable and retained their near-native structure in Pluronic films. Oxygen, hydrogen peroxide, nitrite and nitric oxide were electrochemically catalyzed by protein-Pluronic films with significant lowering of reduction overpotential. Both nitrite and hydrogen peroxide underwent dismutation in electrocatalysis. The reduction of NO 2 − and H 2O 2 on protein-Pluronic films was actually the catalytic reduction of their disproportionation products, NO and O 2, respectively. The biocatalytic mechanism of these substrates at protein-Pluronic film electrodes were discussed and speculated.

Electrocatalytic Reduction of Nitric Oxide by Cytochrome P450-modified Gold Electrodes

Department of Microbial Engineering and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, KoreaReceived October 29, 2003Key Words : Cytochrome P450, NO reduction, Modified electrodes, ImpedanceDetection of NO has drawn much attention as NO playsimportant roles in physiological processes such as neuro-transmission, muscle relaxation and immune system medi-ation.