Efficient Catalyst For CO Oxidation Research Articles

The confined surface C2N/Pt(111) as a highly efficient catalyst for CO oxidation.

The problem of poisoning on the surface of catalysts used in CO oxidation reactions, such as Pt, needs to be solved. In this work, we constructed lattice-matched C2N/Pt(111) catalysts with different configurations (top/fcc/hcp) and found that, within the confined space between the cover and the substrate, the adsorption energy of CO is reduced by 0.35 eV to 0.43 eV, while the adsorption of other reactants O/O2 is strengthened and the adsorption energy of the product CO2 is positive, indicating that the constraint effect produced by C2N and Pt(111) is beneficial to CO oxidation, when compared to the pure Pt(111). Our work suggests that the C2N cover not only protects the Pt surface under harsh conditions but also allows gaseous molecules CO and O2 to approach the Pt surface through a facile intercalation process, with enhanced surface reactivity for CO oxidation and reduced catalyst poisoning.

Tunable Single-Atom Catalysis of CO Oxidation on a Transition Metal-Anchored Defective In2Se3 Monolayer

Single-atom catalysts (SACs) have attracted extensive attention owing to their high atom efficiency and catalytic activity. However, their superior catalytic properties can hardly be manipulated without a suitable substrate. Here, based on first-principles calculations, we demonstrated that a two-dimensional (2D) defective In2Se3 monolayer with Se vacancy could be used as a proper substrate for various single atoms of transition metals including Zn, Rh, Ru, Pd, Ag, Ir, Pt, and Au. Moreover, the energy barrier of the rate-determining step can be effectively regulated by polarization switching of monolayer In2Se3, which is much lower in M|VSe-In2Se3 (M = Pt, Pd, Ag, and Au) with upward polarization. Especially, Ag|VSe-In2Se3 with upward polarization is identified as a highly efficient catalyst for CO oxidation due to the fairly low energy barrier (0.547 eV).

A theoretical study of the Pd10Sb3 single-atom alloy cluster for CO oxidations

Inspired by the experimental synthesis of Pd-based single-atom alloy (SAA) catalysts which display high performance for reactions in the chemical industry. In this work, we have designed a Pd10Sb3 SAA alloy cluster as an efficient catalyst for CO oxidation. It is stable at 400 K for 3 ps under the ab-initio molecular dynamic simulation. Compared with Pd13, the Sb atom transfers electrons to the neighbour Pd atom, which induces its 4d states near the fermi level reduced much more. As a result, Pd10Sb3 show much weaker adsorptions of CO and O2. In addition, CO and O2 prefer to be adsorbed on the Pd site rather than on the Sb site. Thus, we have considered the full path for CO oxidation on the pure Pd site on Pd13 and Pd10Sb3 clusters. Compared with Pd13, on Pd10Sb3 the barrier of the rate-limiting step, that is the peroxide-like OO-CO intermediate formation, decreases by 0.54 eV which indicates Pd10Sb3 can be a potential catalyst for CO oxidation.

CeO2-Supported TiO2-Pt Nanorod Composites as Efficient Catalysts for CO Oxidation.

Supported Pt-based catalysts have been identified as highly selective catalysts for CO oxidation, but their potential for applications has been hampered by the high cost and scarcity of Pt metals as well as aggregation problems at relatively high temperatures. In this work, nanorod structured (TiO2-Pt)/CeO2 catalysts with the addition of 0.3 at% Pt and different atomic ratios of Ti were prepared through a combined dealloying and calcination method. XRD, XPS, SEM, TEM, and STEM measurements were used to confirm the phase composition, surface morphology, and structure of synthesized samples. After calcination treatment, Pt nanoparticles were semi-inlayed on the surface of the CeO2 nanorod, and TiO2 was highly dispersed into the catalyst system, resulting in the formation of (TiO2-Pt)/CeO2 with high specific surface area and large pore volume. The unique structure can provide more reaction path and active sites for catalytic CO oxidation, thus contributing to the generation of catalysts with high catalytic activity. The outstanding catalytic performance is ascribed to the stable structure and proper TiO2 doping as well as the combined effect of Pt, TiO2, and CeO2. The research results are of importance for further development of high catalytic performance nanoporous catalytic materials.

Low Pt loaded CNTs as efficient catalysts for CO oxidation

CO oxidation on Pt/CNTs follows the ER mechanism. O2 is activated by adsorption on Pt nanoparticles to form a Pt NPs–O–O*–CO structure with CO. The structure then breaks down to yield CO2 and O*. Finally, O* reacts with CO to produce CO2.

Cu-doped fullerene: An efficient single-atom catalyst for CO oxidation under mild conditions

The catalytic CO oxidation under mild conditions attracts extensive interests. The exploration about the catalytic CO oxidation mechanism illustrates that the conversion from the triplet state to the singlet state takes place during the adsorption of O2, which is followed by CO adsorption. The barrier of the first CO oxidation, which corresponds to the rate-determining step, can be lowered distinctly by Cu-doping. A quartet-to-doublet spin crossing facilitates the CO oxidation by C59Cu. Significant electron transfer from the C59Cu dopant activates the O2 and CO molecules, then decreases the barrier and accelerates the reaction rate. The C59Cu dopant is an efficient catalyst for CO oxidation owing to the low-barrier (2.1 kcal/mol) CO oxidation reaction. It would be a potential material in solving the environmental protection problems and the purification of H2 for fuel cell applications

CeO2‐Supported Pt−Au Nanoparticles as Efficient Catalyst for CO Oxidation

AbstractThe nanorod shaped (Pt−Au)/CeO2 catalysts with varied Pt/Au ratio were achieved from Al91.7Ce8AuXPt0.15−X (X=0.05, 0.075, 0.1) precursor alloys through combined dealloying and calcination treatment. The surface morphology, microstructure as well as physicochemical features were characterized through XRD, SEM, TEM, XPS, Raman spectroscopy and N2 adsorption‐desorption tests. The catalytic measurement results imply that the (Pt0.075−Au0.075)/CeO2 catalyst displays optimal catalytic property with 50% and 99% reaction temperature as low as 37 °C, 80 °C, respectively. The (Pt0.075−Au0.075)/CeO2 was also stable after 60 h successive catalytic oxidation reaction. The outstanding catalytic performance is ascribed to the joint introduction of Pt and Au, which can suppress the agglomeration and growth of noble metal active phases during the catalytic process. What's more, the nanoscale interface formed between Pt&Au nanoparticles and CeO2 nanorods can also promote electron transfer rate, thus catalytic reaction efficiency is enhanced. The results will be of importance for design of novel nanoporous noble metal‐oxide‐based catalysts and application in exhaust treatment of fuel vehicles.

Crystal plane induced metal-support interaction in Pd/Pr-CeO2 catalyst boosts H2O-assisted CO oxidation

Catalytic oxidation is an effective method to remove CO in exhaust gas, yet it is challenging to enhance the H2O tolerance of catalysts at low temperature due to the strong competitive adsorption between H2O and reactants (CO and O2). Here, we report that the precise control of the metal-support interaction by regulating the support crystal plane of Pd/Pr-CeO2 catalysts leads to highly efficient CO oxidation catalysts under wet conditions. The addition of H2O inhibits the CO oxidation activity of Pr-CeO2 nano-cube and octahedron supported highly dispersed Pd catalysts, but enhances the CO oxidation activity over Pr-CeO2 nanorod supported highly dispersed Pd catalysts. After introduction of H2O in feed gas, the T99 (Temperature to achieve 99 % conversion of CO) decreases from 157 °C to 115 °C for Pd/Pr-CeO2-NRs (Nanorods) catalyst at a gas hourly space velocity of 70, 000 h−1 and remains stable for more than 2000 min in the presence of H2O. Systematic characterization reveals that the (110) crystal plane of Pr-CeO2 nanorod enhance the interaction between Pd species and support, resulting in the formation of abundant high dispersed Pd-oxygen vacancy (Ov) active sites. The kinetics study and in-situ DRIFTS characterization confirmed that CO oxidation Pd/Pr-CeO2-NRs mainly follows the H2O-mediated Langmuir-Hinshelwood mechanism in the presence of H2O. H2O promote the formation of active OH groups and accelerate CO oxidation through formate pathway at low temperature. In contrast, the CO oxidation follow traditional MvK mechanism in the absence of H2O.

Ab Initio Investigation of the Adsorption and Dissociation of O2 on Cu-Skin Cu3Au(111) Surface

Surface adsorption and dissociation processes can have a decisive impact on the catalytic properties of metal alloys. We have used density functional theory to investigate the adsorption and dissociation of O2 on Cu-skin Cu3Au(111) surface. The calculated results show that the b-f(h)-b adsorption configuration is the most energetically favorable on the Cu-skin Cu3Au(111) surface. For O2 dissociation, there are two thermodynamically favorable dissociation paths. One path is from b-f-b to two O atoms in hcp sites, and the other path is from b-h-b to two O atoms in fcc sites. Moreover, the stability of O2 adsorption is higher and the dissociation energy barrier of the adsorbed O2 is lower as compared to those on the Cu(111) surface. This theoretical work provides valuable guidance for the practical application of Cu-Au alloys as highly efficient CO oxidation catalysts.

Cobalt oxide confined in mesoporous SiO2 as effective catalyst for CO oxidation

Ordered mesoporous SiO 2 samples (SBA-15) with different pore sizes were prepared as carriers, and a series of catalysts (CoO x @SBA-15( X )) were synthesized to confine CoO x in SBA-15 through the solid-state grinding method for CO oxidation. The characterization results showed that the aggregation of CoO x in the pores of the carrier SBA-15 was effectively inhibited by the confinement effect, which further facilitated the formation of the main catalytic site Co(III) species. The results of the density-functional theory calculations further confirmed that Co(III) was the important catalytic site for CO oxidation. Compared with the catalyst prepared through the impregnation method, catalysts CoO x @SBA-15( X ) exhibited a lower CO conversion temperature and activation energy for CO oxidation. In addition, the pore size of the carrier SBA-15 had a significant impact on the catalytic activity of CoO x , and the catalyst prepared with a larger pore size SBA-15 as carrier exhibited a higher catalytic activity. This result was mainly attributed to the fact that the confinement effect could effectively enhance the defect formation in metal oxides. Furthermore, the catalyst with a larger pore size SBA-15 as a carrier presented a higher content of Co(III) species, which significantly enhanced the catalytic activity of CoO x for CO oxidation. The results demonstrated that the pore structure of SBA-15 could affect the formation of the metal oxide (CoO x ) species, which further significantly affected the catalytic activity of CoO x for CO oxidation. The results are expected to provide a strategy to synthesize efficient catalysts for CO oxidation by using ordered mesoporous materials. • Solid state grinding method is an effective way to confine CoO x in SBA-15 pores. • Confinement effect could enhance the catalytic activity of catalysts for CO oxidation. • SBA-15 with larger pore size was more favorable for the formation of Co(III) species.

A low cost bimetallic AuCu3 tetramer on Ti2CO2 MXene as an efficient catalyst for CO oxidation: a theoretical prediction.

Abatement of CO, due to its poisonous nature, is an extensively researched topic. Oxidation to CO2 is one of the strategies deployed and finds application in automobiles and fuel cells. Gold nanoparticles on an oxide support is a pioneering catalyst in this field, but need improvement in cost, stability, and O2 activation. Doping with Cu can open up avenues for improvement in these attributes. In the present investigation, we have explored the possibility of using bimetallic AunCum (n + m = 4) clusters supported on Ti2CO2 MXene. We find that AuCu3 is the most stable cluster on the support. The complete CO oxidation cycle on this supported cluster proceeds through a mix of Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms. Our calculations predict that the first cycle is expected to proceed only via the LH mechanism due to kinetic and thermodynamic limitations ascribed to ER and Mars van Krevelen (MvK) mechanisms, respectively. The second cycle, however, prefers ER over the LH mechanism. Overall, with the highest barrier of 0.56 eV, this low cost novel catalyst performs better in terms of stability and/or activity in comparison with many of the catalysts reported in the literature.

New insights into the single-atom-decorated Zr2CO2 (MXene) as an efficient catalyst for CO oxidation in incomplete combustion gas

To design novel non-noble metal nano-catalysts for CO oxidation at low temperature and further understand the mechanism of CO oxidation in incomplete combustion gas (mainly containing CO, N2, CO2, and O2) with MXene-based materials, CO oxidation on Zr2CO2 with surface decoration by transition metal atoms was investigated by density functional theory (DFT) calculations. Sc and Ti atoms were preliminarily proven to be stably anchored on Zr2CO2 monolayer but O2 is easier to be dissociated into two O atoms on Ti/Zr2CO2. For CO, N2, and CO2, they are easy to automatically desorbe from the catalysts in presence of O2, what is beneficial for the CO oxidation reaction and preventing catalyst poisoning. On Sc/Zr2CO2, CO is difficult to be catalytically oxidized into CO2 with high reaction barriers. For Ti/Zr2CO2, the energy barrier to form the first CO2 in the ER mechanism is 0.58 eV, lower than that of the LH mechanism (0.7 eV) although their rate-determining barriers are same (0.8 eV). Furthermore, Ti/Zr2CO2 is also capable of resisting CO2 poison to enhance the reusability of the catalyst. Therefore, Ti/Zr2CO2 is a promising catalyst for CO oxidation at low temperature for incomplete combustion gas treatment.

Heat-resistant TiO2 nanocomposites with anatase phase as carriers for highly efficient CO oxidation catalysts

Thermally stable nanocomposites TiO2 with anatase structure doped with ceria or yttria have been synthesized by impregnation method with using a special precursor of titania. All dopants used in this research increase the temperature of anatase to rutile transition and stabilize anatase phase up to 900 °C. In obtained composites calcined at 300-600 °C, microstructural analysis revealed the formation of nanocristalline TiO2 structure consisting of intergrown incoherently 3–8 nm fine anatase particles with the formation of inrerblock boundaries between them. In the region of interblock boundaries the anatase structure is disordered and dopants are localized there in near atomic state. Under the heating at high temperatures, all composites have the rather high surface area and uniform pore diameter. The ceria doped composite was used as support for preparation of 2% Pt/Ce-TiO2 catalyst for CO oxidation. The obtained catalyst demonstrates a high catalytic activity at rather low temperature.

Rh/CeO2 composites prepared by combining dealloying with calcination as an efficient catalyst for CO oxidation and CH4 combustion

In this paper, a series of Rh/CeO2 catalysts with three-dimensional porous nanorod frameworks and large specific surface area were prepared by chemical dealloying Al–Ce–Rh precursor alloys and then calcining in pure O2. The effects of the Rh content and calcination temperature on CO oxidation and CH4 combustion were studied, and the results reveal that the Rh/CeO2 catalysts produced by dealloying melt-spun Al91.3Ce8Rh0.7 alloy ribbons and then calcining at 500 °C exhibit the best catalytic activity, the reaction temperatures for the complete conversion of CO and CH4 are as low as 90 and 400 °C, respectively. Furthermore, after 150 h of continuous testing at high concentrations of H2O and CO2, the nature of the catalyst is not irreversibly destroyed and can still return to its initial level of activity. This excellent catalytic activity is attributed to a portion of Rh being uniformly distributed on the CeO2 nanorod surface in the form of nanoparticles, forming strong Rh–CeO2 interfacial synergy. Another portion of Rh permeated into the CeO2 lattice, which results in a significant increase in the number of oxygen vacancies in CeO2, thus allowing more surface active oxygen to be adsorbed and converted from the gas phase. Moreover, the catalytic reaction can proceed even in an oxygen-free environment due to the excellent oxygen storage performance of the Rh/CeO2 catalyst.

Single transition metal anchored C9N4 sheets as an efficient catalyst for CO oxidation: a first-principles study.

Single-atom catalysts (SACs) often exhibit superb catalytic activity due to their high atom utilization. By comparing the adsorption energies of O2 and CO adsorbed on TM@C9N4, we expect that Co and Ni anchored at the cavity of C9N4 exhibit a higher catalytic activity for CO oxidation. For the entire reaction, the Eley-Rideal, New Eley-Rideal, Ter-molecular Eley-Rideal and Langmuir-Hinshelwood mechanisms are all taken into account. Depending on the reaction mechanisms, the catalysts Co@C9N4 and Ni@C9N4 show excellent activity, with a kinetic energy barrier ranging from 0.19 eV to 0.54 eV for the former, while the corresponding energy barrier is 0.26 eV to 0.44 eV for the latter. The superior stability and activity of Co/Ni@C9N4 can efficiently oxidize the large amounts of CO caused by inadequate combustion of coal and natural gas resources.

Theoretical Calculation of Different Reaction Mechanisms for CO Oxidation on MnN3-Doped Graphene.

In recent decades, great expectation has always been placed on catalysts that can convert toxic CO into CO2 under mild conditions. The catalytic mechanism of CO oxidation by Mn-coordinated N-doped graphene with a single vacancy (MnN3-SV) and a double vacancy (MnN3-DV) was studied by density functional theory (DFT) calculations. Molecular dynamics simulations showed that CO2 on MnN3-SV could not be desorbed from the substrate and MnN3-SV was not suitable for use as a CO oxidation catalyst. MnN3-DV was more suitable for CO oxidation (COOR) and from the electronic structure it was found that the Mn atom was the main active site, which was the reaction site for CO oxidation. At temperatures of 0 and 298.15 K, CO oxidation on MnN3-DV via the Langmuir–Hinshelwood (LH) mechanism was the best reaction pathway. The rate-determining step using MnN3-DV as the catalyst for CO oxidation through the LH mechanism was O2 + CO → OOCO, and the energy barrier was 0.861 eV at 298.15 K. MnN3-DV was suitable as a catalyst for CO oxidation in terms of both thermodynamics and kinetics. This study provides a comprehensive understanding of the various reaction mechanisms of CO oxidation on MnN3-DV, which is conducive to guiding the development and design of efficient catalysts for CO oxidation.

C20 fullerene and its boron- and nitrogen-doped counterparts as an efficient catalyst for CO oxidation

DFT calculations are utilised to investigate the CO oxidation on the C20, BC19, and NC19 clusters. For CO oxidation over considered clusters, two continuous steps are proposed that in each step one CO2 molecule is released from clusters surface. The calculations demonstrate that in the case of the C20 cluster, the first step of CO oxidation takes place through the ER mechanism on two routes with a barrier height of 1.06 eV and 2.57 eV for the rate-limiting step. Also, in the cases of BC19 and NC19 clusters, both reaction paths occur via the ER mechanism. The activation energy of the first reaction step is about 0.53 and 0.46 eV, while it is negligible for the second step that is 0.04 and 0.18 eV for BC19 and NC19 clusters, respectively. Based on the present theoretical results, the catalytic activity of BC19 and NC19 clusters toward the CO oxidation is more than that of the C20 cluster. These results show that the BC19 and NC19 clusters can be recommended as an efficient and metal-free catalyst for CO oxidation at near ambient temperatures. Research Highlights CO oxidation over C20 fullerene has been investigated. The effect of N/B-doing on the CO oxidation reaction is also studied. The N/B-doping increases the catalytic activity of C20 fullerene. Boron/Nitrogen-doped C20 fullerene can be applied as an efficient catalyst for CO oxidation.

Mesoporous Co‐Al oxide nanosheets as highly efficient catalysts for CO oxidation

AbstractWe report mesoporous Co‐Al oxide nanosheets (CoxAl‐Ns, where x denotes the Co/Al ratio in the samples) prepared by calcination of CoAl‐hydrotalcite and subsequent alkaline treatment. X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy measurements show that the prepared Co‐Al oxide nanosheets (CoxAl‐Ns) are very thin (10–15 nm) and exhibit high mesoporosity (3–5 nm). Catalytic CO oxidation tests reveal that the CoxAl‐Ns exhibit excellent catalytic performances at relatively low temperatures: for example, the Co2.5Al‐Ns catalyst could achieve 99% CO conversion at −98°C. Kinetic studies and experimental investigations indicate that the high activity of the Co2.5Al‐Ns sample is strongly related to the abundance of active sites associated with the large Brunauer–Emmett–Teller surface area. The Co2.5Al‐Ns catalyst also achieves full conversion of CO in tests performed with a gas mixture simulating automobile exhaust gas at 200°C. After loading the Co2.5Al‐Ns on a porous ceramic substrate, the obtained Co2.5Al‐Ns/PC shows high activity and stability in CO oxidation process. These features are potentially important for future industrial applications of these catalysts.

Low-Temperature Catalytic CO Oxidation Over Non-Noble, Efficient Chromia in Reduced Graphene Oxide and Graphene Oxide Nanocomposites

Herein, bare chromia nanoparticles (Cr2O3 NPs) and chromia supported on reduced graphene oxide (rGO) and graphene oxide (GO) hybrids were synthesized, followed by characterization by means of FESEM, Raman spectroscopy, TGA, XRD, TEM/HRTEM, XPS and N2 sorptiometry. The investigated bare Cr2O3 and the hybrids (Cr2O3/rGO and Cr2O3/GO) were employed as catalysts for low-temperature CO oxidation. Compared with the other catalysts, the results revealed efficient catalytic activity using Cr2O3/GO, which was attributed to its higher surface area together with the mixed oxidation state of chromium (Cr3+ and Cr>3+). These are important oxidation sites that facilitate the electron mobility essential for CO oxidation. Moreover, the presence of carbon vacancy defects and functional groups facilitate the stabilizing of Cr2O3 NPs on its surface, forming a thermally stable hybrid material, which assists the CO oxidation process. The Cr2O3/GO hybrid is a promising low-cost and efficient catalyst for CO oxidation at low temperatures. The higher activity of graphene oxide supported Cr2O3 NPs can provide an efficient and cost-effective solution to a prominent environmental problem.

Metal-organic framework templated Pd/CeO2@N-doped carbon for low-temperature CO oxidation.

A new Pd/Ce based metal–organic framework is designed and synthesized as a self-sacrificial template for fabrication of an efficient catalyst for CO oxidation. The catalyst obtained by thermal annealing at 700 °C (Pd/CeO2@NC-700) is composed of N-doped carbon with embedded Pd and CeO2 nanoparticles, which are highly dispersed and closely connected in the N-doped carbon; the high Pd loading (33.7 wt%) and the coupling between Pd and the CeO2 phase synergistically boost the CO oxidation performance. The Pd/CeO2@NC-700 catalyst exhibits a 100% conversion temperature of 89 °C and excellent long-term stability. By combining structural characterization with density functional theory calculations, two possible CO oxidation pathways of TPB and TOP are revealed, in which the adsorbed O2 directly dissociates to O* atoms and activates CO* molecules. The transfer of O* between Pd and Ce (TPB) or Pd and Pd (TOP) facilitates the formation of intermediates and finally results in the production of CO2. This work provides a new insight into the development of novel efficient catalysts for CO oxidation based on metal–organic frameworks.