Green rusts-derived iron oxide nanostructures catalyze NO reduction by CO

Green rusts with brucite-like layers of hydroxide intercalated with anions constitute a family of diverse precursors for the synthesis of iron oxides via dehydration,but precise structural control of the resulting oxides with respect to the size and shape at the nanometer level remains challenging due to the easy oxidation of the ferrous species.Herein,we report a new synthetic strategy for the facile preparation of fibrous-like green rusts by using appropriate balancing anions(CO_(3)^(2-)and SO_(4)^(2-))in ethylene glycol to regulate the morphology.Depending on the type of the intercalating anion,the green rusts were converted into hematite with fibrous-or plate-like shapes upon thermal activation.When evaluated in the reaction of NO reduction by CO,these iron oxides showed a prominent shape-dependent catalytic behavior.The fibrous-like Fe_(2)O_(3)was much more catalytically active and structurally robust than the plate-like analogue.Combined spectroscopic and microscopic characterizations on the nanostructured iron oxides revealed that the superior performance of the fibrous-like Fe_(2)O_(3)stemmed from a facile Fe_(2)O_(3)/Fe_(3)O_(4)redox cycle and a higher density of active sites for NO activation.

Characteristics of NO reduction with non-thermal plasma

As a new type of NO removal system, NO reduction in N_2-NO plasma was applied to solve the difficulties in the traditional methods, such as higher energy-consumption, larger equipment size and high cost, and so on. Using the experimental NO reduction system with single-pair electrode tip discharge structure, the NO reduction characteristics of N_2-NO system were revealed to guide the engineering practice; the results of NO reduction with single-pair electrode tip discharge plasma also have the same instructive meaning to the NO reduction with multi-pair electrode tip discharge plasma. The amount of both active N atom and NO removal rate increased with the distance l_g increasing between the two electrode tips and then dropped when the distance exceeded a certain value. The NO removal rate increased while the voltage between two electrode tips or the resident time of gas flow increased. The distance is a key geometrical variable factor that can determine the intensity of electric field between two electrode tips and the resident time of gas. In this paper, the effects of the dielectric features on NO reduction using dielectric-barrier discharge plasma system were also studied. The results of NO removal rate with different dielectrics such as Al_2O_3, CaO, MgO and glass showed that the electric field intensity is different with different dielectric, because it brings different energy to particles in discharge room and thus it causes different NO removal rate.

Mechanism of NO reduction with non-thermal plasma

Non-thermal plasma has been proved to be an effective and competitive technology for removing NO in flue gas since 1970. In this paper, the NO reduction mechanism of the non-thermal plasma reaction in NO/N_2/O_2 system was investigated using the method of spectral analysis and quantum chemistry. By the establishment of NO reduction and gas discharge plasma emission spectrum measuring system, the NO reduction results, gas discharge emission spectra of NO/N_2/O_2 and pure N_2 were obtained, and then the model of molecular orbit of N_2 either in ground state or its excited state was worked out using the method of molecular orbit Ab initio in Self-Consistent Field(SCF). It was found that NO reduction in NO/N_2 gas discharge plasma was achieved mainly through a series of fast elementary reactions and the N(E6) at excited state was the base for NO reduction.

Effects of Co-Firing Biomass and Pulverized Coal on NO Reduction in Cement Precalciner

With increased awareness of the large-scale CO_(2) emissions from the cement industry,there has been growing focus on greenhouse gas reduction strategies.Among all these strategies,fuel substitution using biomass fuel is extensively used to achieve CO_(2) zero-emission in cement production.Due to the avoidable high-temperature-generated thermal nitrogen oxides during cement production,research on the impact of biomass application on nitrogen oxide emissions shall be carried out.Three types of biomass fuel and bituminous coal were used to investigate the NO reduction characteristics under different O_(2) concentrations on experimental benches.It was found that the change in oxygen concentration from 9% to 1% increased the reaction time in the reactor from 555 s to 1425 s,which means the increase in oxygen concentration can lead to shorter reaction time,and correspondingly,the existing time of nitric oxide in the flue gas is also shortened,but the peak value of nitric oxide rises,during the process of O_(2) concentration changing from 1% to 9%,the peak NO concentration in the flue gas increased from 5.4×10^(-5) to 1.05×10^(-4).An increase in O_(2) concentration greatly reduces the total reduction of NO and the minimum change in NO concentration.The peak NO concentration during the combustion process of corn stalk is 4.56×10^(-4),which is approximately 7 times higher than that of coal,and it is caused by the high amount of N in corn stalk.The addition of raw meal has an inhibitory effect on the reduction of NO:after adding raw meal,the effective reduction time of NO by fuel decreased by about 20%,but adding raw meal raises CO_(2) concentration of fuel gas in the early stage of reaction.

Electrochemical NO reduction to NH3 on Cu single atom catalyst

Electrochemical NO reduction reaction(NORR)to generate NH_(3)emerges as a fascinating approach to achieve both NO pollution mitigation and sustainable NH_(3)synthesis.Herein,we demonstrate that single-atomic Cu anchored on MoS_(2)(Cu_(1)/MoS_(2))comprising Cu_(1)-S_(3)motifs can serve as a highly efficient NORR catalyst.Cu1/MoS_(2)exhibits an NH_(3)yield rate of 337.5μmol·h^(−1)·cm^(−2)with a Faradaic efficiency of 90.6%at−0.6 V vs.reversible hydrogen electrode(RHE).Combined experiments and theoretical calculations reveal that Cu1-S3 motifs enable the effective activation and hydrogenation of NO through a mixed pathway and simultaneously retard proton coverage,contributing to the high activity and selectivity of Cu1/MoS_(2)for the NORR.

Theoretical investigation on NO reduction electro-catalyzed by transition-metal-anchored SnOSe nanotubes

Electrochemical NO reduction reaction(NORR)to NH3 emerges as a fascinating approach to achieve both the migration of NO pollutant and the green synthesis of NH3.In this contribution,within the framework of computational hydrogen model and constant-potential implicit solvent model,the NORR electrocatalyzed by a novel transition-metal-anchored SnOSe armchair nanotube(TM@SnOSe_ANT)was investigated using density functional theory calculations.Through the checking in terms of stability,activity,and selectivity,Sc-and Y@SnOSe_ANTs were screened out from the twenty-five candidates.Considering the effects of pH,solvent environment,as well as applied potential,only Sc@SnOSe_ANT is found to be most promising.The predicted surface area normalized capacitance is 11.4μF/cm^(2),and the highest NORR performance can be achieved at the U_(RHE) of-0.58 V in the acid environment.The high activity originates from the mediate adsorption strength of OH.These findings add a new perspective that the nanotube can be served as a highly promising electrocatalyst towards NORR.

Morphology effects in MnCeO_(x)solid solution-catalyzed NO reduction with CO:Active sites,water tolerance,reaction pathway

Morphological effects of nanoparticles are crucial in many solid-catalyzed chemical transformations.We herein prepared two manganese-ceria solid solutions,well-defined MnCeO_(x)nanorods and MnCeO_(x)-nanocubes,exposing preferentially(111)and(100)facets of ceria,respectively.The incorporation of Mn dopant into ceria lattice strongly enhanced the catalytic performance in the NO reduction with CO.MnCeO_(x)(111)catalyst outperformed MnCeO_(x)(100)counterpart due to its higher population density of oxygen vacancy defects.In-situ infrared spectroscopy investigations indicated that the reaction pathway over MnCeO_(x)and pristine CeO_(2)is similar and that besides the direct pathway,an indirect pathway via adsorbed hyponitrite as an intermediate cannot be ruled out.X-ray photoelectron and Raman spectroscopies as well as first-principles density functional theory(DFT)calculations indicate that the enhanced catalytic performance of MnCeO_(x)can be traced back to its“Mn–OL(VÖ)–Mn–OL(VÖ)–Ce”connectivities.The Mn dopant strongly facilitates the formation of surface oxygen vacancies(VÖ)by liberating surface lattice oxygen(OL)via CO*+OL→CO_(2)*+VÖand promotes the reduction of NO,according to NO*+VÖ→N*+OL and 2N*→N_(2).The Mn dopant impact on both the adsorption of CO and activation of OL reveals that a balance between these two effects is critical for facilitating all reaction steps.

Perovskite Oxides La0.8Sr0.2Co1-xFexO3 for CO Oxidation and CO＋NO Reduction： Effect of Redox Property and Surface Morphology

This work aims to study the effect of redox property and surface morphology of perovskite oxides on the catalytic activity of CO oxidation and CO＋NO reduction, with the redox property being tuned by doping Fe at the Co site of La0.8Sr0.2Co1-xFexO3 and the surface morphology being modified by supporting La0.8Sr0.2CoO3 on various mesoporous silicas（i.e., SBA-16, SBA-15, MCF）. Characteristic results show that the Fe doping improves the match of redox potentials, and SBA-16 is the best support of La0.8Sr0.2CoO3 when referring to the oxidation ability（e.g., the Co^3＋/Co^2＋ molar ratio）. A mechanism for oxygen desorption from perovskite oxides is proposed based on O2-TPD experiments, showing the evolution process of oxygen released from oxygen vacancy and lattice framework. Catalytic tests indicate that La0.8Sr0.2CoO3 is the best for CO oxidation, and La0.8Sr0.2FeO3 is the best for CO＋NO reduction. The mechanism of CO＋NO reduction changes as the reaction temperature increases, with XNO/XCO value decreases from 2.4 at 250℃ to 1.0 at 400℃. As for the surface morphology, La0. Sr0.2CoO3 supported on SBA-16 possesses the highest surface Co^3＋/Co^2＋ molar ratio as compared to the other two, and shows the best activity for CO oxidation.

Defect engineering for high-selection-performance of NO reduction to NH3 over CeO_(2)(111)surface:A DFT study

To reduce the greenhouse effect caused by the surgery of nitrogen-oxides concentration in the atmosphere and develop a future energy carrier of renewables,it is very critical to develop more efficient,controllable,and highly sensitive catalytic materials.In our work,we proposed that nitric oxide(NO),as a supplement to N_(2) for the synthesis of ammonia,which is equipped with a lower barrier.And the study highlighted the potential of CeO_(2)(111)nanosheets with La doping and oxygen vacancy(OV)as a high-performance,controllable material for NO capture at the site of Vo site,and separation the process of hydrogenation.We also reported that the E_(ads) of-1.12 eV with horizontal adsorption and the Bader charge of N increasing of 0.53|e|and O increasing of 0.17|e|at the most active site of reduction-OV predicted.It is worth noting thatΔG of NORR(NO reduction reaction)shows good performance(thermodynamically spontaneous reaction)to synthesize ammonia and water at room temperature in the theoretical calculation.

High-efficiency electrocatalytic NO reduction to NH_(3) by nanoporous VN

Electrocatalytic NO reduction reaction to generate NH_(3)under ambient conditions offers an attractive alternative to the energy-extensive Haber-Bosch route;however,the challenge still lies in the development of cost-effective and high-performance electrocatalysts.Herein,nanoporous VN film is first designed as a highly selective and stable electrocatalyst for catalyzing reduction of NO to NH_(3)with a maximal Faradaic efficiency of 85%and a peak yield rate of 1.05×10^(-7)mol·cm^(-2)·s^(-1)(corresponding to 5,140.8mg·h^(-1)·mg_(cat).^(-1))at-0.6 V vs.reversible hydrogen electrode in acid medium.Meanwhile,this catalyst maintains an excellent activity with negligible current density and NH_(3)yield rate decays over 40 h.Moreover,as a proof-of-concept of Zn-NO battery,it delivers a high power density of 2.0 mW·cm^(-2)and a large NH_(3)yield rate of 0.22×10^(-7)mol·cm^(-2)·s^(-1)(corresponding to 1,077.1mg·h^(-1)·mg_(cat).^(-1)),both of which are comparable to the best-reported results.Theoretical analyses confirm that the VN surface favors the activation and hydrogenation of NO by suppressing the hydrogen evolution.This work highlights that the electrochemical NO reduction is an eco-friendly and energy-efficient strategy to produce NH_(3).

Bi nanoparticles/carbon nanosheet composite:A high-efficiency electrocatalyst for NO reduction to NH_(3)

Electrochemical reduction of NO offers us an attractive alternative to traditional selective catalytic reduction process for harmful NO removal and simultaneous NH_(3)production,but it requires efficient electrocatalyst to enable the NO reduction reaction with high selectivity.Here,we report on the development of Bi nanoparticles/carbon nanosheet composite(Bi@C)for highly effective NO reduction electrocatalysis toward selective NH_(3)formation.Such Bi@C catalyst attains an impressive NH_(3)yield of 1,592.5μg·h^(−1)·mgcat.^(−1)and a high Faradaic efficiency as high as 93%in 0.1 M Na_(2)SO_(4)electrolyte.Additionally,it can be applied as efficient cathode materials for Zn–NO battery to reduce NO to NH_(3)with high electricity generation.

Synthesis of Nd_(2-x)Sr_xCoO_(4±λ)(x=0.4～1.2) and Catalytic Properties in Reduction of NO

The mixed oxides, Nd2-xSrxCoO4±λ（0.4 ≤ x≤ 1.2）, with K2NiF4 structure were synthesized by the polyglycol gel method. The composition and structure of the catalysts were characterized by means of IR, TPD, TPR, chemical analysis and so on. The catalytic performance for NO reduction was investigated. The results show that the mixed oxides have K2NiF4 structure. Other phases are found when x = 1.2. The amount of Co^3＋ and the lattice oxygen over Nd2-xSrxCoO4±λ increase with the increase of x. It is found that the catalytic activity for NO reduction is closely correlated with the concentration of oxygen vacancies and the amount of Co^3＋ .

Preparation, Characterization of Solid Solution La_4BaCu_(5- x)Mn_xO_(13+λ)(x= 0—5) and ItsCatalytic Activity in the Reduction of NO by CO

A series of layered mixed oxides La 4BaCu 5-x Mn x O 13+λ ( x =0—5) was prepared, characterized and used as catalysts for NO+CO reaction. It was found that all the samples were single phase having a structure with five layered perovskite. La 4BaCu 2Mn 3O 13+λ showed the highest activity in the title reaction, this could be attributed to the synergetic effect between Cu and Mn. The results of TPR, TPD and excess oxygen investigations confirmed that the Cu ion would be the active center. The displacement of the Cu ion by Mn caused the Cu ion to be more easily reducible and more content of excess oxygen, and it was beneficial to the activity of the catalyst. The reaction mechanism was also proposed.

Promotional effect for SCR of NO with CO over MnO_(x)-doped Fe_(3)O_(4) nanoparticles derived from metal-organic frameworks

MnO_(x)-Fe_(3)O_(4) nanomaterials were fabricated by using the innovative scheme of pyrolyzing manganesedoped iron-based metal organic framework in inert atmosphere and exhibited extraordinary performance of NO reduction by CO(CO-SCR).Multi-technology characterizations were conducted to ascertain the properties of fabricated materials(e.g.,TGA,XRD,SEM,FT-IR,XPS,BET,H_(2)-TPR and O_(2)-TPD).Moreover,the interaction between reactants and catalysts was ascertained by in situ FT-IR.Experimental results demonstrated that Mn was an ideal promoter for iron oxides,resulting in decrease of crystallite size,improve reducibility property,enhance the mobility and the amount of lattice O^(2-) species,as well as strength the adsorption ability of active NO and CO to form multiple species(e.g.,nitrate and carbonate).The unprecedented enhancement of CO-SCR activity over Mn-Fe nanomaterials follows the Eley-Rideal(E-R)and Langmuir-Hinshelwood(L-H)reaction pathway.

Promotional effect of CO pretreatment on CuO/CeO_2 catalyst for catalytic reduction of NO by CO

The CuO/CeO2 catalysts were investigated by means of X-ray diffraction （XRD）, laser Raman spectroscopy （LRS）, X-ray photoelectronic spectroscopy （XPS）, temperature-programmed reduction （TPR）, in situ Fourier transform infrared spectroscopy （FTIR） and NO＋CO reaction. The results revealed that the low temperature （〈150℃） catalytic performances were enhanced for CO pretreated samples. During CO pretreatment, the surface Cu＋/Cu0 and oxygen vacancies on ceria surface were present. The low va- lence copper species activated the adsorbed CO and surface oxygen vacancies facilitated the NO dissociation. These effects in turn led to higher activities of CuO/CeO2 for NO reduction. The current study provided helpful understandings of active sites and reaction mechanism in NO＋CO reaction.

FeP nanorod array:A high-efficiency catalyst for electroreduction of NO to NH3 under ambient conditions

Sustainable mitigation of the continuously rising concentration of NO contaminants is among the most urgent issues of this century.Ambient electrocatalytic conversion of NO into useful NH_(3)offers an attractive path toward achieving sustainable NO abatement and NH_(3)production simultaneously.However,its efficiency is challenged by the intense competition from hydrogen evolution reaction and relatively high energy barriers of NO activation.It is thus highly desirable to explore active electrocatalyst for NO reduction reaction and investigate the mechanisms on relevant surfaces.Herein,we introduce an FeP nanorod array on carbon cloth as a high-efficiency catalyst for NO electroreduction to NH3.In 0.2 M phosphate-buffered solution,this catalyst exhibits a low onset potential of-0.014 V.Moreover,it achieves a remarkable Faradaic efficiency of 88.49%and a large NH_(3)yield of 85.62μmol·h^(-1)cm^(-2),with durability for stable NO conversion over 12 h of electrolysis.The catalytic mechanism on FeP is investigated further by theoretical calculations.

Ce-Ti catalysts modified with copper and vanadium to effectively remove slip NH_(3) and NO_x from coal-fired plants

In this work,V/Ce-Ti catalysts were modified with different kinds of transition metals(Cu,Fe,Co,Mn) by sol-gel and impregnation methods.The NH_(3) oxidation performance of them was tested to select the most active catalyst in NH_(3)-selective catalytic oxidation(NH_(3)-SCO).The effect of NO,SO_(2) and H_(2)O was also investigated.The experimental results indicate that 1% Cu-V/Ce-Ti catalyst exhibits the most significant ability to remove slip ammonia discharged from coal-fired plants and its NH_(3) conversion efficiency reaches90% at 300℃.In additio n,97% NO_x can be removed when NO is introduced in the gas.Cu-V/Ce-Ti catalyst also obtains good resistance to H_(2)O and SO_(2).Based on the characterization experiment,the introduced Cu and V are highly dispersed on Ce-Ti catalyst and they can increase the redox properties and the number of acidic sites.Besides,the redox cycles among Cu,V and Ce species on Cu-V/Ce-Ti catalyst surface are conducive to generating more active oxygen and promoting the oxidation capacity of the catalyst.

Catalytic reduction of NO_x by CO on hydro-talcites-derived mixed oxides Co AIM and MgAlM (M = Cr, Mn, Fe, Co, Ni, Cu)

Two series of mixed oxides, CoAlM and MgAlM (M= Cr, Mn, Fe, Co, Ni, Cu) , were prepared by calcining their corresponding hydrotalcite-like compounds (HTLc) . The ratio of Mg: Al: M (or Co: Al: M) was 3:1:1. The catalytic activity of all samples for the reaction of NO + CO was investigated. The results showed that the activity of CoAlM was much higher than that of MgAlM. The structure and the property of redox were characterized by XRD and H2-TPR. The results indicated that only MgO phase was observed after calcining MgAlM hydrotalcites, and the transition metals became more stable. The spinel-like phase appeared in all of CoAlM samples after the calcination, and the transition metals were changed to be more active, and easily reduced . The activities of three series of mixed oxides CoAlCu obtained from different preparation methods, different ratio of Co:Al:Cu and at different calcination temperatures, were studied in detail for proposing the mechanism of reaction. The ability of adsorption of NO and CO were investigated respectively for supporting the mecha-

Nitric oxide removal by wastewater bacteria in a biotrickling filter

Nitric oxide （NO） is one of the most important air pollutants in atmosphere mainly emitted from combustion source. A biotriclding filter was designed and operated to remove NO from an air stream using bacteria extracted from the sewage sludge of a municipal sewage treatment plant. To obtain the best operation conditions for the biotrickling filter, orthogonal experiments （L9（34）） were designed. Inlet oxygen concentration was found to be the most significant factor of the biotrickling filter and has a significant negative effect on the system. The optimal conditions of the biotrickling filter occurred at a temperature of 40℃, a pH of 8.0 and a chemical oxygen demand of 165 mg/L in the recycled water with no oxygen in the system. The bacteria sample was detected by DNA sequencing technology and showed 93%-98% similarity to Pseudomonas mendocina. Moreover, a full gene sequencing results indicated the bacterium was a brand new strain and named as P. mendocina DLHK. This strain can transfer nitrate to organic nitrogen. The result suggested the assimilation nitrogen process in this system. Through the isotope experimental analysis, two intermediate products （^15NO and ^15N2O） were found. The results indicated the denitrification function and capability of the biotrickling filter in removing NO.