Adsorption state of NO on Ir(111) surfaces under excess O2 coexisting condition

Ikeda, Hideo; Koike, Yuna; Shiratori, Kunio; Ueda, Kohei; Shirahata, Naoki; Isegawa, Kazuhisa; Toyoshima, Ryo; Masuda, S.; Mase, Kenji; Nito, T.; Kondoh, Hiroshi

doi:10.1016/j.susc.2019.01.015

Cited by 7 publications

(5 citation statements)

References 25 publications

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“…It has been reported that the adsorption of NO and subsequent cleavage of the N−O bond are the determining factors in the CO+NO reaction [10,40–42] . Therefore, the adsorption and dissociation behaviors of NO on Ir/non‐m‐WO 3 , Ir 1 /m‐WO 3 , and Ir NPs/m‐WO 3 were further investigated using the NO‐TPD technique (Figure 9).…”

Section: Resultsmentioning

confidence: 99%

Single Ir Atoms Anchored on Ordered Mesoporous WO₃ Are Highly Efficient for the Selective Catalytic Reduction of NO with CO under Oxygen‐rich Conditions

Jiang

Liu

et al. 2021

ChemCatChem

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Under oxygen‐rich conditions, achieving a selective and efficient reduction of NO by CO is always challenging. Here, we report the synthesis of the catalyst consisting of single Ir atoms anchored on mesoporous WO3 (denoted as Ir1/m‐WO3) using a facile template method followed by wet impregnation. X‐ray diffraction and transmission electron microscope studies indicated that the Ir atoms were distributed uniformly on the internal surface of m‐WO3. When tested for the reduction of NO by CO, the Ir1/m‐WO3 catalyst with a low Ir loading of 0.28 wt % exhibited excellent catalytic performance in the presence of 2 vol % O2 (volume ratio of CO to O2 being 1 : 10), achieving a NO conversion of 73 % and N2 selectivity of 100 % at 350 °C. In particular, its turnover frequency (TOF) value reached 0.30 s−1 at 200 °C, which is six times higher than that of the catalyst with Ir nanoparticles supported on mesoporous WO3 (0.05 s−1). The superior catalytic performance of Ir1/m‐WO3 is attributed to the formation of the isolated Ir atoms and the more newly generated Ir‐WO3 interfaces that can promote the adsorption and activation of NO, and the presence of accessible mesopores in m‐WO3 that facilitates the mass transfer of NO and CO. This study brings a new fundamental understanding of active sites in Ir‐based catalysts for the CO+NO reaction and provides a new way to the design and synthesis of single‐atom catalysts, especially precious metal catalysts for emissions control.

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Section: Resultsmentioning

confidence: 99%

Single Ir Atoms Anchored on Ordered Mesoporous WO₃ Are Highly Efficient for the Selective Catalytic Reduction of NO with CO under Oxygen‐rich Conditions

Jiang

Liu

et al. 2021

ChemCatChem

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“…The peaks in the range of 1550–1650 cm –1 are assigned to the nitrate species adsorbed on the cation sites in ZSM-5. , Moreover, the peak at 1727 cm –1 could be assigned to the N 2 O 4 species . Notably, the peak at 1820 cm –1 was assigned to NO linearly adsorbed on the Ir 0 atop sites, which could not dissociate into N and O. ,, Previous reports have demonstrated that NO is mainly adsorbed on the atop sites and hollow sites of Ir. − NO adsorbed on the hollow sites could dissociate into N and O at low temperatures, whereas NO adsorbed on the atop sites is more stable than that on the hollow sites. ,, Thus, the peak of NO adsorbed on the Ir 0 hollow sites did not appear in this spectrum. Furthermore, the NO adsorption species in the presence of O 2 on different catalysts were also investigated (Figure S11).…”

Section: Resultsmentioning

confidence: 96%

“…Notably, only a small amount of N 2 O and NO 2 was formed during the reaction, demonstrating that the main products of this reaction in the absence of O 2 are N 2 and C 13 O 2 . Although a N 2 (28) signal was also detected by mass spectrometry, this signal cannot be attributed to the formation of N 2 through the CO-SCR reaction because of impurities in the inlet gas.…”

Section: Environmental Science and Technologymentioning

confidence: 98%

“…Typically, NO dissociation is an important process in the CO-SCR. Many in situ experiments have demonstrated that NO can be adsorbed on the atop and hollow sites of Ir crystals, and the dissociation of NO mainly occurs at the hollow sites to generate N and O species. − The dissociated N species can react with each other to generate N 2 (N ad + N ad → N 2 ). Moreover, the adsorption of NO on the atop sites can be inhibited by CO, and the ignition temperature of the NO ad + N ad reaction is highly dependent on the CO coverage .…”

Section: Introductionmentioning

confidence: 99%

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Insight into the Mechanism of Selective Catalytic Reduction of NO by CO over a Bimetallic IrRu/ZSM-5 Catalyst in the Absence/Presence of O₂ by Isotopic C¹³O Tracing Methods

Bai

Gao²,

Sun

et al. 2023

Environ. Sci. Technol.

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The development of efficient catalysts for the selective catalytic reduction of NO by CO (CO-SCR) in the presence of O 2 is highly desirable for controlling the emission of toxic gases from tailpipes. Here, a bimetallic IrRu/ZSM-5 catalyst was prepared for the selective catalytic reduction of NO by CO in the presence of O 2 (5%) for the low-temperature treatment of exhaust gas. IrRu/ZSM-5 afforded 90% NO x conversion in the range of 225−250 °C and maintained 90% NO x conversion after 12 h of reaction. Ru addition inhibited agglomeration of the Ir particles during the reduction process and provided more active sites for NO adsorption. Isotopic C 13 O tracing and in situ diffuse reflectance infrared Fouriertransform spectroscopy experiments were used to elucidate the CO-SCR mechanism in the absence or presence of O 2 . NCO could easily form on the surface of catalysts in the absence of O 2 , whereas NCO formation has been inhibited owing to the quick consumption of CO in the presence of O 2 . Moreover, some byproducts such as N 2 O and NO 2 are generated in the presence of O 2 . Finally, a possible mechanism for CO-SCR under different conditions was proposed based on in situ experiments and physicochemical analyses.

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“…The experimental observations indicate that a structural transformation follows a h-BN–BO x –h-BN path. O 2 molecules are readily dissociated into active atomic oxygen catalyzed by Ir(111) surfaces. , The suggested oxidation mechanism is that O atoms actively embedded into the h-BN lattice replace N atoms, generating solid B 2 O 3 structures adsorbed on the surface, and NO gases desorbed due to the difference in their volatility . In the transition from B 2 O 3 to h-BN, H atoms from the NH 3 -dehydrogenated reaction on the Ir(111) surface combine with O atoms to form H 2 O, accompanying incorporation of N atoms into the lattice.…”

Section: Resultsmentioning

confidence: 99%

An Ammonization-Based Transformation of Hexagonal Boron Nitride on Ir(111) from Surface to Near-Surface Regions

et al. 2021

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Epitaxial growth of thin films on solid substrates significantly depends on the surface structure, including outmost and near-surface reconstruction. Here, using in situ surface measurements, we show an ammonization-based hexagonal boron nitride (h-BN) transformation on the Ir(111) substrate, from surface to near-surface regions. Near-surface B dopants are driven to segregate onto the surface induced by N atoms from NH 3 dehydrogenation; thus, B species react with N species to form h-BN overlayers on the surface, i.e., the ammonization growth route. Further, growth dynamics in near-surface-dependent ammonization and normal chemical vapor deposition growth are systematically investigated. The activation energy of the former is 0.53 eV higher than the latter. The difference in growth barriers is attributed to the diffusion of B species from nearsurface to surface regions, causing the growth mechanism changes from reaction-limited aggregation to diffusion-limited aggregation. In addition, h-BN overlayers are converted into boron oxide (B 2 O 3 ) in an O 2 atmosphere and reverse back to h-BN by reacting with NH 3 on the surface; thus, a reversible structural transformation on the surface was achieved by successive oxidation and ammonization. This work gains a deep understanding of the h-BN conversion from surface to near-surface regions and provides valuable insights into their evolution dynamics.

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Adsorption state of NO on Ir(111) surfaces under excess O2 coexisting condition

Cited by 7 publications

References 25 publications

Single Ir Atoms Anchored on Ordered Mesoporous WO₃ Are Highly Efficient for the Selective Catalytic Reduction of NO with CO under Oxygen‐rich Conditions

Single Ir Atoms Anchored on Ordered Mesoporous WO₃ Are Highly Efficient for the Selective Catalytic Reduction of NO with CO under Oxygen‐rich Conditions

Insight into the Mechanism of Selective Catalytic Reduction of NO by CO over a Bimetallic IrRu/ZSM-5 Catalyst in the Absence/Presence of O₂ by Isotopic C¹³O Tracing Methods

An Ammonization-Based Transformation of Hexagonal Boron Nitride on Ir(111) from Surface to Near-Surface Regions

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Adsorption state of NO on Ir(111) surfaces under excess O2 coexisting condition

Cited by 7 publications

References 25 publications

Single Ir Atoms Anchored on Ordered Mesoporous WO3 Are Highly Efficient for the Selective Catalytic Reduction of NO with CO under Oxygen‐rich Conditions

Single Ir Atoms Anchored on Ordered Mesoporous WO3 Are Highly Efficient for the Selective Catalytic Reduction of NO with CO under Oxygen‐rich Conditions

Insight into the Mechanism of Selective Catalytic Reduction of NO by CO over a Bimetallic IrRu/ZSM-5 Catalyst in the Absence/Presence of O2 by Isotopic C13O Tracing Methods

An Ammonization-Based Transformation of Hexagonal Boron Nitride on Ir(111) from Surface to Near-Surface Regions

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Single Ir Atoms Anchored on Ordered Mesoporous WO₃ Are Highly Efficient for the Selective Catalytic Reduction of NO with CO under Oxygen‐rich Conditions

Single Ir Atoms Anchored on Ordered Mesoporous WO₃ Are Highly Efficient for the Selective Catalytic Reduction of NO with CO under Oxygen‐rich Conditions

Insight into the Mechanism of Selective Catalytic Reduction of NO by CO over a Bimetallic IrRu/ZSM-5 Catalyst in the Absence/Presence of O₂ by Isotopic C¹³O Tracing Methods