Catalyst For CO Oxidation Reaction Research Articles

Enhancing the Performance of BaxMnO3 (x = 1, 0.9, 0.8 and 0.7) Perovskites as Catalysts for CO Oxidation by Decreasing the Ba Content.

Mixed oxides featuring perovskite-type structures (ABO3) offer promising catalytic properties for applications focused on the control of atmospheric pollution. In this work, a series of BaxMnO3 (x = 1, 0.9, 0.8 and 0.7) samples have been synthesized, characterized and tested as catalysts for CO oxidation reaction in conditions close to that found in the exhausts of last-generation automotive internal combustion engines. All samples were observed to be active as catalysts for CO oxidation during CO-TPRe tests, with Ba0.7MnO3 (B0.7M) being the most active one, as it presents the highest amount of oxygen vacancies (which act as active sites for CO oxidation) and Mn (IV), which features the highest levels of reducibility and the best redox properties. B0.7M has also showcased a high stability during reactions at 300 °C, even though a slightly lower CO conversion is achieved during the second consecutive reaction cycle. This performance appears to be related to the decrease in the Mn (IV)/Mn (III) ratio.

Revealing pretreatment-induced structure evolution of LaFeO3 supported Au catalyst for CO oxidation reaction

Heterogeneous catalysts play a pivotal role in the chemical industry. Pretreatments in reducing or oxidizing atmospheres have been widely utilized to alter the structure of heterogeneous catalysts, with the aim of enhancing their catalytic performance. However, the pretreatment atmosphere can, at times, trigger unexpected structural changes in catalysts and even lead to catalytic degradation. Hence, the selection of an appropriate pretreatment atmosphere for heterogeneous catalysts is critical and requires a clear understanding of their corresponding dynamic evolution to improve their performance in a targeted manner, particularly relying on in situ observation. In this study, a promising CO oxidation catalyst, LaFeO3 supported Au nanoparticles (Au/LFO) is selected, and the influence of the pretreatments in different atmospheres on Au/LFO is explored by using in situ transmission electron microscopy (TEM) and density functional theory (DFT) calculation. Our findings reveal that the commonly used reducing pretreatment for noble-metal catalysts triggered strong metal-support interactions in Au/LFO, suppressing its CO adsorption performance. In contrast, the oxidizing pretreatment preserves the metallic Au and the metal/support interface as efficient active sites to promote CO oxidation activity and stability simultaneously. This work discloses the structure evolution at the interface between noble metals and perovskite oxide supports in response to different gas phase treatments and clarifies their structure-property relationships.

Fe@χ3-borophene as a promising catalyst for CO oxidation reaction: A first-principles study.

A novel single-atom catalyst of Fe adsorbed on χ3-borophene has been proposed as a potential catalyst for CO oxidation reaction (COOR). Quantitative pictures have been provided of both the stability of Fe@χ3-borophene and various kinetic reaction pathways using first-principles calculations. Strong adsorption energy of -3.19 eV and large diffusion potential of 3.51 eV indicates that Fe@χ3-borophene is highly stable. By exploring reaction mechanisms for COOR, both Eley-Ridel (E-R) and trimolecule E-R (TER) were identified as possible reaction paths. Low reaction barriers with 0.49 eV of E-R and 0.57 eV of TER suggest that Fe@χ3-borophene is a very promising catalyst for COOR. Charge transfer between the χ3-borophene and CO, O2 and CO2 gas molecules plays a key role in lowering the energy barrier during the reactions. Our results propose that Fe@χ3-borophene can be a good candidate of single-atom catalyst for COOR with both high stability and catalytic activity.

NaCl-Templated Ultrathin 2D-Yttria Nanosheets Supported Pt Nanoparticles for Enhancing CO Oxidation Reaction.

Morphology of support is of fundamental significance to the fabrication of highly efficient catalysts for CO oxidation reaction. Many methods for the construction of supports with specific morphology and structures greatly rely on controlling general physical and chemical synthesis conditions such as temperature or pH. In this paper, we report a facile route to prepare yttria nanosheet using NaCl as template to support platinum nanoparticles exhibiting higher CO oxidation activity than that of the normally prepared Pt/Y2O3. With the help of TEM and SEM, we found that Pt NPs evenly distributed on the surface of NaCl modified 2D-nanosheets with smaller size. The combination of XAFS and TEM characterizations demonstrated that the nano-size Pt species with PtxOy structure played an essential role in the conversion of CO and kept steady during the CO oxidation process. Moreover, the Pt nanoparticles supported on the NaCl templated Y2O3 nanosheets could be more easily reduced and thus exposed more Pt sites to adsorb CO molecules for CO oxidation according to XPS and DRIFTS results. This work offers a unique and general method for the preparation of potential non-cerium oxide rare earth element oxide supported nanocatalysts.

Carbon Monoxide Oxidation on Model Planar Titania Supported Platinum Nanoparticles Catalyst

A high-throughput (parallel) thermographic screening methodology was developed to enable the measurements of the particle size and support influence on heterogeneous catalysts. A high throughput screening chip has been used to establish the catalytic activity of titania supported platinum nanoparticles catalyst for CO oxidation reaction. The catalytic activity of Pt nanoparticles between 1.3 to 7.8 nm has been investigated for CO conversion at a pressure of 0.11 and 1.1 mbar with O2:CO ratio of 1:1 at 80 °C and 0.6, 1.1 and 2.4 mbar at O2:CO ratio of 1:1 at 240 °C. At these experimental conditions, there was an increase in the TOF with decreasing particle size for instance, at 80 °C and O2:CO ratio of 1:1, total pressure of 0.11 and 1.1 mbar, the TOF increased from 0.01 s–1 to 0.171 s–1 with decreasing Pt particle size from 7.8 to 1.3 nm, respectively. However, Pt nanoparticles catalyst displayed higher activity at higher temperature, for example, the TOF increased from 3.312 s–1 to 4.355 s–1 at O2:CO ratio of 1:1, total pressure of 0.6 and 1.1 mbar, respectively, for Pt particle size of 1.3 nm in agreement with the previous reports. Results show that CO oxidation on titania supported Pt nanoparticles catalyst is particle size dependent. On the other hand, findings from XPS measurements show no major change in the particle size after the reaction thus, reflecting the stability of Pt particles. While there is no apparent consensus in the literature reports on the activity trend with particle size for this system, these findings are consistent with most of the previously reported findings.
 Keywords: platinum; titania; nanoparticles; thermography; CO oxidation.

Comparative activity of Platinum and Gold nanoparticles catalysts for Carbon monoxide oxidation

The activity of Pt and Au nanoparticles catalysts over titania support for carbon monoxide oxidation was investigated. Pt and Au catalysts were synthesised by a high-throughput physical vapour deposition methodology (HT-PVD). A parallel thermographic screening methodology, which enabled the quantification of the activity of Pt and Au catalysts for CO oxidation reaction, was applied. A particle size effect in the catalytic activity of Pt and Au was observed, with the smallest particles exhibiting the highest activity. The activity of Pt and Au catalysts increased with temperature. Au catalyst displayed high activity at 80 ℃, while Pt catalyst had higher activity at 170 ℃. Although CO oxidation on Pt and Au catalysts is particle size-dependent, results show that Au nanoparticles catalyst exhibits the strongest particles size dependence as compared to Pt catalyst.

Synthesis of CuO‐Loaded Ceria Hollow Spheres for Catalytic CO Oxidation

AbstractCopper‐ceria has been widely investigated as an active heterogeneous catalyst for CO oxidation reaction. Herein we report a reliable synthesis of CuO loaded ceria hollow spheres (CHS‐CuO) which show an outstanding performance of 6.1712 μmolCO⋅gcat−1⋅s−1 CO consumption rate at 120 °C over other reported ceria‐based catalysts for the CO oxidation reaction. The performance is superior to CuO loaded ceria nanoparticles (CNP‐CuO) and ceria hollow spheres (CHS), due to hollow structure, large surface area, more adsorptive oxygen and subsequent lower activation energy. TEM images reveal CuO nanoparticles are uniformly dispersed on the surface of ceria hollow spheres. XPS investigation shows that Cu2+ is the dominant copper species in CHS‐CuO. The synthesis reliability is demonstrated with the case of Ag loaded CHS fabrication. The reported strategy enables the fabrication of similar bimetal hollow spheres, holding good promise for various heterogeneous catalysis.

Optimalization of ceramic-based noble metal-free catalysts for CO oxidation reactions

Optimalization of ceramic-based noble metal-free catalysts for CO oxidation reactions

Reactivity and characteristics of Pd/MOF and Pd/calcinated-MOF catalysts for CO oxidation reaction: Effect of oxygen and hydrogen

For the first time, the effect of calcination process on characteristics and catalytic performances of Pd supported on different MOFs (MIL-101(Cr), NH2-MIL-101(Cr), and HKUST-1) was evaluated. Besides, the various orders of calcination process and reduction one on Pd/MOF and Pd/calcinated-MOF were studied, and their performances in CO oxidation reaction were presented to find the effect of H2 and O2. Results showed that the effect of calcination and reduction processes on the catalytic activities and characteristics strongly depends on the nature of MOF. Among MIL-based catalysts, the catalyst with no calcination treatment showed the best activity. Among MNH2-based catalysts, high activity was obtained for Pd/MNH2, Pd/MNH2-C, and Pd/MNH2(RC) samples and Pd/calcinated-MNH2was the best. Catalytic activities of HKUST-1-based catalysts decreased with calcination due to high changes in their structures. The results are useful for predicting the performance of MOFs in oxidation processes, especially reactions in which high oxygen concentrations are involved.

N-Coordinated Dual-Metal Single-Site Catalyst for Low-Temperature CO Oxidation

Catalysts for CO oxidation reaction are mainly based on oxide/hydroxide materials with multicomponent active sites. Here, we report a nonoxide/hydroxide material, atomically dispersed dual-metal single sites (Fe–Co sites) on N-doped carbon support, as a highly active catalyst for CO oxidation. It can greatly lower the temperature for complete CO conversion as low as −73 °C with a turnover frequency of 0.096 s–1. X-ray absorption near-edge structure spectra, pulse-adsorption microcalorimetry, and density functional theory studies show that the Fe–Co sites synergistically catalyze CO oxidation facilely following the Langmuir–Hinshelwood (L-H) mechanism with CO preferentially adsorbing at the Co sites and O2 adsorbing at the Fe sites. These results, for the first time, reveal that the dual-metal single site on N-doped carbon can efficiency catalyze low-temperature CO oxidation reaction without the involvement of supports, such as oxygen vacancies and surface hydroxyl groups.

Insights into facet-dependent reactivity of CuO–CeO2 nanocubes and nanorods as catalysts for CO oxidation reaction

Copper–ceria (CuO–CeO2) catalysts have been known to be very effective for the oxidation of CO, and their chemical behavior has been extensively studied during the last decades. However, the effect of different CeO2 crystal surfaces on the catalytic activity of CuO–CeO2 for the oxidation of CO is still unclear and should be further elucidated. In this study, we deposited 1 wt% Cu on mostly {100}-exposed CeO2 nanocubes (1CuCe NC) and mostly {110}-exposed CeO2 nanorods (1CuCe NR), respectively. Both 1CuCe NC and 1CuCe NR have been used as catalysts for the oxidation of CO and achieved 100% and 50% CO conversion at 130 °C, respectively. The differences in the catalytic activity of 1CuCe NC and 1CuCe NR were analyzed using temperature-programmed reduction of H2 and temperature-programmed desorption of CO techniques. The results confirmed the excellent reducibility of the 1CuCe NC catalyst, which was attributed to the weak interactions between Cu and the CeO2 support. Moreover, in situ diffuse reflectance infrared Fourier-transform spectroscopy studies indicated that the {100} planes of 1CuCe NC facilitated the generation of active Cu(I) sites, which resulted in the formation of highly reactive Cu(I)-CO species during the oxidation of CO. Both the excellent redox properties and effective CO adsorption capacity of the 1CuCe NC catalyst increased its catalytic reactivity.

Effect of tungsten oxide on ceria nanorods to support copper species as CO oxidation catalysts

In this work, tungsten oxide with different concentrations (0, 0.4 at%, 2.0 at% and 3.2 at%) was introduced to the ceria nanorods via a deposition-precipitation (DP) approach, and copper species of ca. 10 at% were sequentially anchored onto the modified ceria support by a similar DP route. The aim of the study was to investigate the effect of the amount of tungsten oxide (0, 0.4 at%, 2.0 at%, and 3.2 at%) modifier on the copper-ceria catalysts for CO oxidation reaction and shed light on the structure-activity relationship. By the aids of multiple characterization techniques including N2 adsorption, high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), and temperature-programmed reduction by hydrogen (H2-TPR) in combination with the catalytic performance for CO oxidation reaction, it is found that the copper-ceria samples maintain the crystal structure of the fluorite fcc CeO2 phase with the same nanorod-like morphology with the introduction of tungsten oxide, while the textural properties (the surface area, pore volume and pore size) of ceria support and copper-ceria catalysts are changed, and the oxidation states of copper and tungsten are kept the same as Cu2+ and W6+ before and after the reaction, but the introduction of tungsten oxide (WO3) significantly changes the metal-support interaction (transfer the CuOx clusters to Cu-[Ox]-Ce species), which delivers to impair the catalytic activity of copper-ceria catalysts for CO oxidation reaction.

Durable ruthenium oxide/ceria catalyst with ultralarge mesopores for low-temperature CO oxidation

With more stringent CO emission limits, the development of efficient and durable catalysts for low-temperature (<200 °C) CO oxidation is crucial for the automotive industry. Here we report significant improvement in catalytic activity by incorporation of RuO2 into the CeO2 lattice. The Ru0.15Ce0.85O2-y demonstrates the highest catalytic activity with T100 value of 165 °C (rCO = 3.65 × 10−5 mol gcat−1 s−1), corresponding to activation energy of 49.8 kJ mol−1. The TOF of Ru0.15Ce0.85O2-y (48.6 × 10−3 s−1) is approximately 20 times higher than that of Ru0.015Ce0.975O2-y (2.48 × 10−3 s−1) and Ru0.3Ce0.7O2-y (2.72 × 10−3 s−1) catalysts at 160 °C. The catalyst remained stable after 70 h continuous operation under high GHSV (150000 ml g−1 h−1) without any noticeable compositional and structural changes. The necessity of using CO-TPR instead of commonly used H2-TPR analysis is presented to assess the surface reducibility of the catalysts for CO oxidation reaction. Based on the structural characterizations combined with kinetic studies, we find the catalyst surface reducibility by CO determines the activity in CO oxidation.

Catalytic Oxidation of CO over Nanocrystalline La1–xCexNiO3 Perovskite‐Type Oxides

AbstractNanocrystalline La1–xCexNiO3 (x = 0.1, 0.3, 0.5, 0.7, 0.9) perovskite‐type oxide catalysts prepared by the Pechini method were employed in catalytic CO oxidation and the effect of substitution of La by Ce on CO conversion was evaluated. The results indicated the remarkable effect of La substitution with Ce on the catalytic performance at low temperatures. The reaction temperature had a significant influence on the stability of the catalysts. The La0.1Ce0.9NiO3 sample exhibited the highest activity among the prepared catalysts in CO oxidation reaction. In addition, the influence of different parameters including pretreatment condition, feed ratio, and gas hourly space velocity (GHSV) on the catalytic performance was examined. The optimum catalyst proved high stability under severe reaction conditions in the presence of water vapor and CO2 in the feed stream.

First principles investigation of atomic gold dispersed g-C3 N4 as an active catalyst for CO oxidation reaction

First principles investigation of atomic gold dispersed g-C3 N4 as an active catalyst for CO oxidation reaction

Copper-promoted ceria catalysts for CO oxidation reaction

Abstract A hydrothermal method employing citric acid as the chelating agent and sodium hydroxide as the precipitating agent, and different copper precursors (nitrate salt and metallic ring) has been applied in this work for the synthesis of atomically dispersed copper-ceria catalysts. These catalysts were evaluated in CO oxidation reaction. Copper ions were finely and atomically dispersed in both catalysts and strong interaction between copper supported species and ceria resulted in a remarkable promotion of the activity, thus playing a crucial role in the achievement of higher performance in contrary to other physicochemical properties such as specific surface area and defects concentrations, which seem to play a minor role.

Kilogram-scale fabrication of 3D CeO2 active catalytic support with tailored 12 nm spherical mesopores via colloidal solution combustion synthesis

Abstract Synthetic methods that enable low-cost, large-scale, and reliable production of oxides with ultralarge mesoporous structure are imperative for broad commercial adoption. In this study, for the first time, a kilogram-scale economical synthesis of three-dimensional CeO2 nanostructure with uniform ultralarge 12 nm spherical mesopores, 2–5 nm crystal size, large specific surface area (190 m2/g) and large pore volume (0.48 ml/g) is reported via a colloidal solution combustion synthesis method. Depending on the amount of colloids used in the initial precursor mixture the textural properties such as porosity, specific surface area and pore volume of oxide produced can be precisely tuned. As the catalyst for CO oxidation reaction, 3D mesoporous CeO2 demonstrates excellent activity achieving complete conversion of CO at 315 °C, which is 80 °C lower than that of commercial non-porous ceria catalyst.

Metal- and Nonmetal-Atom-Modified Graphene as Efficient Catalysts for CO Oxidation Reactions

This study explores the metal Co- and nonmetal-atom-codoped graphene (CoNMx-graphene, x = 1–3 and NM = N, Si, P) as substrates for CO oxidation reactions. By density functional theory calculations, we show the formation mechanism of CoNM3-graphene configurations and their corresponding electronic structures and magnetic properties. On the CoNM3-graphene sheets, the adsorbed O2 is more stable than that of the CO molecule and serves as the reactive species. Besides, the coadsorption of CO/O2 (or 2CO) has larger adsorption energies than those of the isolated O2 and CO molecules, which would be used as an initial state for the CO oxidation reactions. Furthermore, the possible reaction mechanisms for CO oxidation on CoNM3-graphene are investigated in detail. It is found that the Eley–Rideal (ER) mechanism (CO + O2 → CO2 + Oads) on CoN3-graphene sheets has a smaller energy barrier than that of another initial state (CO + O2 → CO3), which is energetically more favorable than the Langmuir–Hinshelwood and new term...

Promotion of Pt/CeO2 catalyst by hydrogen treatment for low-temperature CO oxidation.

Low temperature CO oxidation reaction is known to be facilitated over platinum supported on a reducible cerium oxide. Pt species act as binding sites for reactant CO molecules, and oxygen vacancies on surface of cerium oxide atomically activate the reactant O2 molecules. However, the impacts of size of Pt species and concentration of oxygen vacancy at the surface of cerium oxide on the CO oxidation reaction have not been clearly distinguished, thereby various diverse approaches have been suggested to date. Here using the co-precipitation method we have prepared pure ceria support and infiltrated it with Pt solution to obtain 0.5 atomic% Pt supported on cerium oxide catalyst, and then systematically varied the size of Pt from single atom to ∼1.7 nm sized nanoparticles and oxygen vacancy concentration at surface of cerium oxide by controlling the heat-treatment conditions, which are temperature and oxygen partial pressure. It is found that Pt nanoparticles in range of 1–1.7 nm achieve 100% of CO oxidation reaction at ∼100 °C lower temperature compared to Pt single atom owing to the facile adsorption of CO but weaker binding strength between Pt and CO molecules, and the oxygen vacancy in the vicinity of Pt accelerates CO oxidation below 150 °C. Based on this understanding, we show that a simple hydrogen reduction at 550 °C for the single atom Pt supported on CeO2 catalyst induces the formation of highly dispersed Pt nanoparticles with size of 1.7 ± 0.2 nm and the higher concentration of surface oxygen vacancies simultaneously, enabling 100% conversion from CO to CO2 at 200 °C as well as 16% conversion even at 150 °C owing to the synergistic effects of Pt nanoparticles and oxygen vacancies.

Hollow‐Co3O4@Co3O4@SiO2 Multi‐Yolk‐Double‐Shell Nanoreactors for Highly Efficient CO Oxidation

AbstractThe engineering of highly active, stable, and inexpensive catalysts for CO oxidation reaction through the modulations of morphology and structure is desirable but remains a great challenge. Herein, we reported the rational design of novel hollow‐Co3O4@Co3O4@SiO2 multi‐yolk‐double‐shell nanoreactors by using a two‐step annealing recipe employing core‐shelled ZIF‐67@SiO2 as a precursor. The unique structures of the multi‐yolk‐double‐shell and hollow interior of Co3O4 endowed the materials with promising properties of sufficient active interfacial sites, porous structures, efficient oxygen delivery capacity, and more oxygen vacancies, which were beneficial for CO oxidation. Consequently, the H−Co3O4@Co3O4@SiO2(35)‐250 nanoreactor exhibited outstanding catalytic performance, achieving complete CO conversion at 100 °C, which was far exceeding that of hollow Co3O4 NPs derived from pure ZIF‐67 and also solid Co3O4@SiO2(35)‐250 with a complete conversion of CO at 190 and 230 °C, respectively, and even outperformed most of the reported Co3O4‐based catalysts. Moreover, H−Co3O4@Co3O4@SiO2(35)‐250 could continuously work for 28 h without any deactivation and maintain 93 % CO conversion within 34 h at 100 °C. The proposed strategy of designing and fabricating novel structures offers great opportunities in developing highly active hollow metal oxide‐based nanoreactors for a variety of advanced applications.