Adsorption Of NO Research Articles

Efficient adsorption of NO onto K, Na-embedded porous carbon material prepared by using zinc-bearing dust as activator

The increasingly generation of NO-containing flue gases and zinc-bearing dusts has posed huge pressure to the environment. A green process of integration of reduction of zinc-bearing dusts and preparation of porous carbon material with high NO adsorption capacity was developed and its mechanism was clarified in this paper. The reduced dusts with high content of iron (70.52 %) and low contents of harmful elements (0.017 % Zn, 0.015 % K and 0.026 % Na) could be used as high-quality raw material for ironmaking while the K, Na-embedded porous carbon material (APC) with surface area of 390.38 m2/g can be used as effective adsorbent for NO pollution control. The adsorption property and mechanism of NO on APC was investigated. It was found that the maximal removal rate of NO could reach 96.15 %, and the K, Na on porous carbon material could promote the chemisorption process of NO and increase the NO adsorption efficiency of APC. The hazardous waste was successfully utilized to treat the flue gas in this work.

Vacancy–assisted exposed Sn atoms enhancing NO2 room temperature sensing of SnSe2 nanoflowers

NO2 is a hazardous gas extremely harmful to the ecosystem and human health, so effective detection of NO2 is critical. SnSe2 is a promising candidate for gas sensors owing to its unique layered configuration that facilitates the diffusion of gas molecules. Here, ultrathin self–assembled nanoflowers F–SnSe2 rich in defects were synthesized by a simple solvothermal method. It exhibits excellent gas sensing performances for NO2 at room temperature (25 °C), with a high gas sensing response of 8.6 for 1 ppm NO2 and a lower detection limit as low as 200 ppb, capable of sensitively detecting ppb–level NO2. DFT calculations revealed that the presence of Se vacancies assists the central Sn atoms to break through the shielding effect of the surface Se atoms and become exposed active sites. The higher reactivity leads to more charge transfer and higher adsorption energy, which strongly promoted the adsorption of NO2. This work verifies the important role of vacancies for the exposed active sites and provides new guidance for defect engineering to modulate the gas sensing performances of SnSe2.

Unveiling the facet-dependent activity of Cu2O for enhanced selective electroreduction of nitric oxide to ammonia and Zn-NO batteries

The conversion of harmful industrial-emitted nitric oxide from emission into valuable NH3 through NO electrochemical reduction reaction (NORR) is a green and sustainable route, which can enable the nitrogen cycle. However, exploring efficient catalyst and unveiling relevant intrinsic mechanism remains a big challenge for improving the efficiency. Herein, we delve into the facet-dependent activity of Cu2O nanocrystal, unveiling for the superior performance of oxygen-vacancy-anchored Cu2O (111) with an unprecedented NH3 yield of 273.5 μmol h−1 cm−2 and a Faradaic efficiency of 96.9% at −0.4 V vs RHE, which is significantly higher than that of Cu2O (100) and Cu2O (100)&(111). Cu2O (111) with abundant oxygen vacancies and hydroxyl groups facilitated the adsorption of NO and suppressed the hydrogen evolution reaction (HER), insights supported by theoretical calculations and in-situ attenuated total reflectance-surface-enhanced IR absorption spectroscopy (ATR-SEIRAS). Further, leveraging Cu2O (111) as the cathode, a proof-of-concept Zn-NO battery delivered superior performance with a power density of 4.62 mW cm−2 and an NH3 yield of 308.0 μg h−1 cm−2. This work not only elucidates the facet-dependent catalytic behaviors but also sets a new benchmark for NH3 synthesis and Zn-NO battery development, presenting a significant advancement in the sustainable and efficient conversion of nitric oxide.

Enhancement of photocatalytic NO oxidation by Ag-sulfide on TiO2 mixed with Na-ZSM-5

Enhancing NO oxidation performance is pivotal for integrating photocatalysts with wet scrubbers in continuous flow systems. Despite the recent development of various catalysts, such as MOFs, our goal was to simplify the composition by using photocatalyst + zeolite catalyst, bringing us closer to a catalyst that can be practically applied. In this study, we have utilized Ag2S doping and Na-ZSM-5 mixing to improve the photocatalytic NO oxidation performance. Results showed that Ag2S doping improved visible light absorbance and NO oxidation, despite the observed fluctuations in NO conversion being attributable to mass transfer limitations. Mixing with Na-ZSM-5 compensated for the mass transfer limitations and improved its average NO conversion from 19 to 34 %. The Na-ZSM-5 increased the NO adsorption capacity considerably to 0.67 mmol g−1, which reduced the fluctuations in the catalytic performance; subsequently, the diffusion of NO led to its oxidation. Detailed analyses using NO-TPD and DRIFTS further elucidated these improvements, highlighting the significance of optimizing both oxidation reaction and mass transfer rates in the photocatalytic process. We believed that the composite of Ag2S-TiO2 + Na-ZSM-5 could simplify the ways to improve the photocatalytic NO oxidation performance and make it closer to practical applications.

Amplified sensing of nitrogen dioxide with a phosphate-doped reduced graphene oxide powder

Surface chemistry plays an essential role in gas-sensing applications, enabling significant improvements in the sensing performance. This study investigates the influence of the graphene oxide (GO) synthesis route on the sensitivity to NO2 gas at room temperature (25 °C) and 100 °C in a dry and humid atmosphere. GO powders were synthesized using both the classical Hummers' method (HGO), and an improved version of the Hummers' method (IGO) using a mixture of phosphoric and sulfuric acids. The subsequent reduction (resulting in rHGO and rIGO, respectively) aimed to enhance the electrical properties and procure nanomaterials sensitive to surface adsorbates. In contrast to the HGO, both IGO and rIGO samples exhibited a transient sensor response and an outstanding recovery performance, which was attributed to the existence of phosphate groups in the latter samples. Notably, the rIGO sample achieved a 23-fold increase in response to NO2 compared to rHGO. Additionally, the limit of detection (LOD) was calculated to be 0.98 ppb at 100 °C. Computational studies considering models of GO and of GO with phosphorus-containing species demonstrate that the presence of the latter, either at the surface or below the surface, leads to a four-fold increase in the NO2 adsorption energies, hence accounting for the significant enhancement in the sensing performance observed experimentally. This underscores the importance of tailoring the structure and chemical properties of GO/rGO materials for optimal performance in gas sensing applications.

Activity of CuCoCe layered double hydroxides catalysts and mechanism for C3H6-SCR

CuxCoyCez-LDH prepared with layered double hydroxides (LDHs) as precursors was calcined to form CuxCoyCezO catalysts which were experimentally investigated for the selective catalytic reduction of NO by C3H6 (C3H6-SCR) in a fixed bed micro-reactor in the presence of O2. The physical–chemical properties of the catalysts were characterized and analyzed with respect to the SCR reactivity. In situ DRIFTS study was conducted to investigate the intermediate species during the SCR reaction. Results showed that NO conversion was as high as 95 % at 225 °C over Cu0.21Co0.48Ce0.31O catalyst. The excellent activity of the catalyst could be attributed to the synergistic effect between Cu, Co, and Ce. The XRD results showed that the synergistic effect between the metals was because of the formation of the solid solution between Cu, Co, and Ce, which promoted the interaction and dispersion of the three active components. EDS mapping further proved this point. According to the XPS data, Cu and Co had a redox reaction that increased the number of oxygen vacancies favorable for NO adsorption and dissociation. The redox properties between Cu and Co was further confirmed to improve the catalytic activity by H2-TPR. Additionally, the results of BET and NH3-TPD demonstrated that the SCR catalytic activity was promoted by the right quantity of acidic sites and the specific surface area. In situ DRIFTS experiments provided a mechanism for the C3H6-SCR reaction on the catalyst and confirmed the formation of reaction intermediates such as bidentate and monodentate nitrate, formate, and acetate.

Exploring the Micropore Functional Mechanism of N2O Adsorption by the Eucalyptus Bark-based Porous Carbon.

Nitrous oxide (N2O), recognized as a significant greenhouse gas, has received insufficient research attention in the past. In view of their low energy consumption and cost-effectiveness, the application of porous materials in adsorption is increasingly regarded as a potent strategy to reduce N2O pollution. In this study, a series of microporous porous carbons with a preeminent specific surface area (244.54-2018.08 m2 g-1), which are derived from the fast-growing eucalyptus bark, were synthesized by KOH activation at high temperatures. The obtained materials demonstrated a relatively fine N2O capture capability (0.19-0.68 mmol g-1) at normal temperature and pressure. More importantly, the optimal pore size affecting N2O adsorption (0.8 and 1.0 nm) has been detected, which is a meaningful view that has never been put forward in previous studies. The rationality of the N2O adsorption mechanism was also validated by combining the experimental analysis and Grand Canonical Monte Carlo (GCMC) simulation. The calculated results showed that 0.8 and 1.0 nm of the porous carbon were the preferred pore sizes for N2O adsorption, and the interaction force between N2O and the pore wall decreased with the increase of distance. This study provides a significant theoretical basis for the preparation of biomass porous carbon with excellent N2O adsorption performance and practical adsorption application.

DFT studies of the structural and electronic properties of PdGe n (n = 1–11) clusters and adsorption capacity for some gas molecules

Density functional theory calculations have been employed for the theoretical studies of the geometric structures and electronic characteristics of PdGe n (n = 1−11) clusters. An analysis of the second- order energy differences indicates that PdGe7 and PdGe10 clusters possess superior thermodynamic stability. PdGe10 displays the highest chemical stability and the lowest chemical activity, due to its largest energy gap value (E g). Vertical ionization potential and vertical electron affinity exhibit the decreasing and increasing trends, respectively, with the increase of the number n of Ge atoms. PdGe10 presents the highest electronegativity among these clusters. The analysis on the adsorption properties of PdGe n (n = 7,10) clusters for gas molecules (e.g. CO, NO, NO2, NH3, SO2 and H2S) yields the adsorption structures, adsorption energies, Mulliken charge transfer and the changes in the electronic properties. All the listed gas molecules chemically adsorb onto PdGe7. PdGe10 has a better adsorption performance for NO2, while its adsorption ability for CO is poorer. The potentiality of PdGe n (n = 7, 10) clusters as gas sensors is also evaluated and reveals that NO adsorption significantly affects the electronic properties, especially conductivity, of the systems. PdGe10 has an appropriate NO adsorption capacity and significant charge transfer, with the adsorption energy of −0.278 eV and the recovery time of about 10−9s, indicating its fast response and hence good potentiality as the NO sensor. In contrast, PdGe7 has a higher adsorption capability towards NO with a lower adsorption energy of −1.16 eV, leading to the difficulty in desorption and a longer recovery time of over 12 h.

Adsorption of small gas molecules onto boron nitride nanotubes and their Al-, Ga-, Cr- and Fe-doping derivatives for gas sensing, storage, and catalytic properties: Periodic DFT study

Based on the toxic gases and their conversion to non-toxic gases on the high potentials doping derivatives of boron nitride nanotubes (BNNTs), adsorption abilities of (5,5) and (10,0) BNNTs doped by selected dopants (Al, Ga, Cr and Fe) on small gas molecules was explored. Adsorption of small gas molecules, H2O, H2S, SO2, CO2, CO, NH3, N2O, and NO onto the pristine (5,5) and (10,0) BNNTs, their doping derivatives (Al-, Ga-, Cr- and Fe-doped (5,5) and (10,0) BNNTs) were investigated using periodic DFT method. Strong adsorptions of N2O (-4.26 eV) and SO2 (-2.56 eV) on the Cr-(5,5) and Cr-(10,0) BNNTs were found. Furthermore, the Cr-(5,5) and Cr-(10,0) BNNTs as the catalysts for N2O conversion to N2 and O2 were found. The Al- and Ga-(5,5) BNNTs, Al- and Ga-(10,0) BNNTs are suggested as the NO sensing materials and NH3 storage materials. All the suggested materials such Cr-(5,5), Cr-(10,0), Al-(5,5), Ga-(5,5), Al-(10,0) and Ga-(10,0) BNNTs could be experimentally tested for conversion, sensitivity, and storage of mentioned toxic gases in the future.

High switching characteristics and sensing-performance improvement of two-dimensional MN4 (M = Be, Mg, Ga) monolayer based nanodevices

Beryllium tetrazolium nitride (BeN4) has recently been synthesized under high pressure by laserheated diamond anvil electrodes as a new class of two-dimensional layered materials. Inspired by this, we perform first-principles calculations to investigate the electronic transport properties of MN4 (M = Be, Mg and Ga) monolayers and their gas sensing properties towards nitride-gases (NH3, NO2, NO). The obtained results show that BeN4 exhibits semi-metallic properties, MgN4 is a semiconductor with a bandgap of 0.13 eV, and the GaN4 monolayer presents strong metallic properties. Interestingly, the BeN4 and MgN4 monolayers are found to have anisotropic Dirac cones. The MN4-based 2D devices all exhibit excellent conductance as well as strong anisotropic transport, with maximum switching ratios of 107 and 104 for MgN4 and BeN4, respectively. The adsorption properties indicate that the adsorption of NH3, NO2, and NO molecules on MN4 monolayers are all chemisorptions, with the system owning much larger adsorption energies and bader charge transfers of the NO2 and NO molecules than those for the NH3 molecules, suggesting the MN4 monolayer has strong selective adsorption and responsiveness to NO2 and NO molecules. The designed gas sensor based on MgN4 show good response characteristics for NO molecules, as evidenced by the maximum current changes before and after adsorption of 30.31 µA, respectively. In summary, MN4 (M = Be, Mg and Ga) monolayers can be important candidates for high switching ratio devices and for the detection and trapping of toxic gas molecules NO.

Transition metals vs. chalcogens: The impact on NOx adsorption on MoS2, MoSe2 and WS2 transition-metal dichalcogenides

The widely developed industry of today generates significant amounts of harmful gases, which prompts the search for modern materials allowing for their efficient and reliable detection. Transition-metal dichalcogenides (TMD) constitute well-known example of such, with particularly high potential for excellent sensing of NO2. It is known, that the adsorption of this hazardous molecule varies on the TMD composition, however the importance of transition metal and chalcogen types were never previously contrasted. Moreover, the other NOx compounds, namely NO and N2, interact much less with TMD sheets, the reason for which is not yet well understood. This work utilizes density functional theory (DFT) approach to untangle these problems by examining the adsorption processes of NO2, NO, and N2 on the monolayers of WS2, MoS2, and MoSe2. The calculations allowed to establish two important conclusions: (i) the chalcogen is significantly more important than transition metal, allowing for much greater increase in adsorption of NO2 on MoSe2 than on WS2, as compared to that on MoS2, (ii) only molecules acting as an acceptor with respect to the TMD sheet can benefit from the enhancement coming from the composition of the latter. The gained insight can likely contribute to the informed design of devices allowing selective detection, the lack of which is a recognized problem among semiconductor sensors.

Tandem Electrocatalytic Reduction of Nitrite to Ammonia on Rhodium–Copper Single Atom Alloys

AbstractElectrocatalytic reduction of NO2− to NH3 (NO2RR) presents a fascinating approach for simultaneously migrating NO2− pollutants and producing valuable NH3. In this study, single‐atom Rh‐alloyed copper (CuRh1) is explored as a highly active and selective catalyst toward the NO2RR. Combined theoretical calculations and in situ FTIR/EPR spectroscopic experiments uncover the synergistic effect of Rh1 and Cu to promote the NO2RR energetics of CuRh1 through a tandem catalysis pathway, in which Rh1 activates the preliminary adsorption and hydrogenation of NO2− (NO2− → *NO2 → *NOOH → *NO), while the generated *NO on Rh1 is then transferred on Cu substrate which promotes the rate‐determining step of *NO → *NHO toward the NH3 synthesis. As a result, CuRh1 equipped in a flow cell presents an unprecedented NH3 yield rate of 2191.6 µmol h−1 cm−2 and NH3‐Faradaic efficiency of 98.9% at a high current density of 322.5 mA cm−2, as well as long‐term stability for 100 h electrolysis.

High-Efficiency Electrocatalytic Reduction of N2O with Single-Atom Cu Supported on Nitrogen-Doped Carbon.

Nitrous oxide (N2O) is a potent greenhouse gas with a high global warming potential, emphasizing the critical need to develop efficient elimination methods. Electrocatalytic N2O reduction reaction (N2ORR) stands out as a promising approach, offering room temperature conversion of N2O to N2 without the production of NOx byproducts. In this study, we present the synthesis of a copper-based single-atom catalyst featuring atomic Cu on nitrogen-doped carbon black (Cu1-NCB). Attributed to the highly dispersed single-atom Cu sites and the effective suppression of the hydrogen evolution reaction, Cu1-NCB demonstrated an optimal N2 faradaic efficiency (82.1%) and yield rate (3.53 mmol h-1 mgmetal-1) at -0.2 and -0.5 V vs RHE, respectively, outperforming previously reported N2ORR electrocatalysts. Further, a gas diffusion electrode cell was employed to improve mass transfer and achieved a 28.6% conversion rate of 30% N2O with only a 14 s residence time, demonstrating the potential for practical application. Density functional theory calculations identified Cu-N4 as the crucial active site for N2ORR, highlighting the significance of the unsaturated coordination and metal-support electronic structure. O-terminal adsorption of N2O was favored, and the dissociative adsorption (*ON2 → *O + N2) was the rate-determining step. These findings reveal the broad prospects of N2O decomposition via electrocatalysis.

Unraveling the impact of phosphate doping on surface properties and catalytic activity of gold supported on mixed iron-niobium oxide in gas phase methanol oxidation

In recent decades, there has been notable interest in understanding the influence of the support composition on the reactivity of gold species in oxidation processes. This study fits in with this scientific trend and investigates the effects of incorporating phosphate ions into Au catalysts supported on mixed iron-niobium oxides in methanol oxidation. All materials were thoroughly characterized using XRD, ICP-OES, DR-UV-Vis, N2 physisorption, HRTEM, HAADF-STEM, SEM-EDX, XPS, TPD-NH3, TPD-CO2, and in situ FTIR combined with adsorption of NO. Activity of the catalysts was evaluated using a fixed-bed flow reactor combined with gas chromatography and operando FTIR-MS system. It was observed that the phosphate-doped catalyst supported on mixed Fe-Nb oxide exhibited significantly higher activity than phosphate-free sample. This improvement resulted from increased electron mobility, enhanced acidity, and optimized distribution of gold nanoparticles on the former catalyst. Knowledge resulting from this work can lead to the development of more efficient gold catalysts.

Effects of Cu species in Cu-SSZ-13 zeolites on the performance of NOx reduction reactions

In diesel vehicle exhaust after-treatment systems, high silica Cu-SSZ-13 has received increasing attention as a commercialized catalyst owing to its high efficiency in selective catalytic reduction reactions with NH3 (NH3-SCR). However, research on the regulation of Cu2+ species within metal active centers in the pore structure of chabazite (CHA)-type zeolite to improve catalytic performance lacks sufficient depth. Herein, SSZ-13 zeolite with various Al distributions was prepared by adjusting the proportion of N,N,N-Trimethyl-1-adamantanaminiumhydroxide (TMAdaOH) and Na in the initial gel. Moreover, three representative Cu-SSZ-13 catalysts with different Cu2+ species were synthesized via an ion exchange method. 23Na MAS NMR and NO adsorption infrared spectroscopy results revealed that with increasing Na content and decreasing TMAdaOH concentration in the initial gel, the number of paired Al in the CHA framework gradually increased. Consequently, this increased the number of Cu2+-2Z sites near six-membered ring (MR) and reduced the amount of [Cu(OH)]+-Z sites near eight-MR. The fresh Cu-SSZ-13 catalyst, with a moderate amount of Cu2+-2Z and [Cu(OH)]+-Z, exhibited optimal catalytic performance across the entire temperature window. After hydrothermal aging, Cu-SSZ-13 with a higher concentration of Cu2+-2Z species featured optimal performance among all Cu-SSZ-13 catalysts above 400 °C. These findings indicated the significance of balancing the amount of both Cu2+-2Z and [Cu(OH)]+-Z in the Cu-SSZ-13 zeolite. Additionally, the results elucidated the reaction intermediates involved in the NH3-SCR process catalyzed by Cu-SSZ-13 with various Cu species.

Surface fluorinated anatase TiO2 nanosheets for NO deep oxidation in O3/H2O2 system: Enhanced mechanism and oxidation characteristics

O3 technology has exhibited promise in removing NO at low-temperature. However, challenges of high NO2 concentration that are difficult to absorb due to insufficient O3 oxidizing capacity remains. Herein, we reported an efficient strategy to generate oxygen-containing radicals for NO deep oxidation via fluorine and {001} facets modulated anatase TiO2 triggering highly activity sites that catalyzed O3/H2O2 to address the above issue. The strong electron withdrawing effect of F sites enhanced the deprotonation of H2O2, while Ti5c on {001} surface exhibited strong Lewis acid to activate O3, thermal stabilization treatment of the catalyst strengthened the synergistic effect of F and Ti5c, resulting in a 97 % NO deep oxidation efficiency at 100 °C with 3 % water vapor content. Additionally, the oxidation characteristics of the radicals was carefully discussed by occupying NO adsorption sites on TiO2 surface, the result revealed that radicals could remarkably react with gas-phase NO. Finally, the synergistic effect and oxidation properties would possess guiding significance for improving NO oxidation and applications.

Steady-State and transient kinetic investigations of the oxidation of NO over Pt/SiO2

The reaction mechanism of the oxidation of NO under conditions of high NO concentration over a 2 wt% Pt/SiO2 was studied using both kinetic and transient isotopic tracing experiments. The reaction mechanism was found to involve both NO adsorption and oxygen adsorption, contrary to the situation under low NO concentration where NO reacts from the gas phase. The kinetic rate data could be fitted to the Langmuir-Hinshelwood model permitting the estimation of rate and equilibrium constants of elementary steps. These steps were investigated using transient responses following independent reactant gas isotopic switches for tracing the nitrogen path and the oxygen path during NO oxidation. These transients could be sufficiently described by a microkinetic model based on two pools of NO intermediates, one pool each for the adsorbed molecular oxygen and atomically adsorbed oxygen. Surface atomic oxygen was found to be formed by two different routes: via a direct dissociation of molecularly adsorbed oxygen and also via an assisted pathway that leads to NO2 formation. The latter surface reaction between adsorbed NO and adsorbed molecular oxygen comprised the kinetically relevant step. Insights from the two experimental and model approaches were in good agreement and provided a coherent reaction mechanism for NO oxidation under high NO reactant concentration.

Dendritic copper oxide catalyst engineering weak-polarity Cu-O bond for high-efficiency nitrate electroreduction

Nitrate reduction reaction (NO3RR) is deemed a promising pathway for both ammonia synthesis and water purification. Developing a high-efficiency catalyst with excellent NH3 selectivity and catalytic stability is desirable but remains challenging. In this work, a dendritic copper oxide catalyst (Cu-B2) has been developed to efficiently catalyze NO3RR for ammonia production, the Cu-B2 exhibits excellent catalytic performance, achieving an NH3 Faradaic efficiency as high as 94 % and an NH3 yield of 16.9 mg h−1 cm−2 with a current density of 192.3 mA cm−2 at − 0.6 V (vs. RHE, reversible hydrogen electrode). During NO3RR testing, the Cu-B2 catalysts are reduced in situ to form highly active Cu0/Cu+ sites, while retaining its dendritic morphology. Compared with other catalysts, the Cu-O bond in Cu-B2 catalyst has weaker polarity, resulting in Cu0/Cu+ sites in lower oxidation states. In situ attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) studies reveal the Cu-B2 catalyst exhibits a potential-independent capability for *NO3- adsorption and high conversion efficiency of NO2- intermediate into ammonia, DFT calculations reveal that Cu-B2 exhibts higher NO3- adsorption energy and lower NO3- adsorption energy barrier than Cu-B1, thus endowing it with a remarkably improved catalytic activity and durability.

Computational investigation on adsorption and activation of atmospheric pollutants CO, NO and SO on small cobalt clusters

The adsorption of CO, NO and SO on cobalt clusters (Co2-7) were investigated using density functional theory. The adsorption energy supports efficient chemisorption of greenhouse gases on the cobalt clusters, with CO and NO forming one to three CoC and CoN bonds, respectively, the first being the most stable. The SO formed bidentate complexes with CoS and CoO bonds in ConSO structures, displaying notably high adsorption energy. The interactions between Con clusters and gas molecules (G) result in weakened bonds of CO, NO, and SO, evident through increased bond lengths, red-shifted frequencies, and lowered local vibrational force constants in ConG complexes. The results with bond weakening and charge transfer from metal to gas molecules suggest strong catalytic potential for small cobalt clusters in activating gas molecules. The current research findings hold significance in the quest for efficient catalytic processes to capture and recycle gaseous pollutants, contributing to a sustainable future.

High-temperature resistant BaO-Y2O3 catalysts with different morphologies for NO decomposition and mechanism study

The high-temperature reaction is a common phenomenon in combustion society, and its catalytic response remain a tremendous challenge hampered by the activity and resistance of the catalyst to high temperatures exceeding 1000 ℃. Three distinct forms of BaO-Y2O3 catalysts—nanosphere, nanorod, and rod—were created using a hydrothermal method and high-temperature annealing to enable direct decomposition of NO. To gather reaction-relevant structural and property information for BaO-Y2O3, we combined reactor activity measurements, chemisorption and DFT studies to elucidate NO high-temperature decomposition process and pinpoint the critical role of oxygen vacancy. We have systematically clarified the increasing favorability of NO decomposition on the nano-catalysts (nanospheres and nanorods) at high temperatures is through stable lattice structure, large specific surface areas, high porosity, and active Ba–O–Y bond. Due to the attraction of electrons gathering in vacancies to NO molecules, oxygen vacancies created in situ at high temperatures, as validated by O2-TPD and density functional theory (DFT) calculations, are advantageous for NO adsorption and decomposition. Moreover, N2 formation pathway over Ba-Y2O3(111) structure is revealed by DFT calculations that NO molecules are apt to be caught by active sites, the region of Ba–O–Y, resulting in the production of N2O2 intermediate and its subsequent bond breaking to N2O as well as N2. In situ DRIFTS experiment further confirms the reaction mechanism via the detected adsorbed species, and clarify the significance of NO2− to O2 formation. In a nutshell, the synthetic combustion catalysts are effective in high-temperature environments that contribute to de-NOx combustion, and the insights into the adsorption configurations of reactant and intermediates unlock fundamental understanding for emissions gas chemistry.