Catalytic Oxidation Of CO Research Articles

Pd Single-Atom Loaded Ce-Zr Solid Solution Catalysts Prepared by Flame Spray Pyrolysis for Efficient CO Catalytic Oxidation.

Single-atom catalysts (SACs) exhibit remarkable catalytic activity at each metal site. However, conventionally synthesized single-atom catalysts often possess low metal loading, thereby constraining their overall catalytic performance. Here, a flame spray pyrolysis (FSP) method for the synthesis of a single-atom catalyst with a high loading capacity of up to 1.4wt.% in practice is reported. CeZrO2 acts as a carrier and provides a large number of anchoring sites, which promotes the high-density generation of Pd, and the strong interaction between the metal and the support avoids atom aggregation. Pd-CeZrO2 series catalysts have excellent CO oxidation performance. When 0.97wt.% Pd is added, the catalytic activity is the highest, and the temperature can be reduced to 120°C. This work presented here demonstrates that FSP, as an inherently scalable technique, allows for elevating the single-atom loading to achieve an increase in its catalytic performance. The method presented here more options for the preparation of SACs.

Removal of CO in flue gas by catalytic oxidation: a review

Abstract Most coal-fired industrial flue gases contained low concentration CO. How to deal with it effectively was a research hotspot in recent years. Catalytic oxidation was considered as the most promising method in the 21st century for the removement of CO with the high efficiency, environmentally friendly, easy to operate and low cost. In this review, the reaction mechanisms of CO oxidation were described, which could provide ideas for the development of new catalysts. The effects of supports and preparation methods on catalysts activity was also reviewed systematically. In addition, some suggestions and outlooks were provided for future development of CO catalytic oxidation.

Single-and double transition metal atoms anchored C2N as a high-activity catalyst for CO oxidation: A first-principles study

The oxidation of CO has attracted great interest in recent years due to its important role in enhancing the catalyst durability in fuel cells and solving the growing environmental problems caused by CO emissions. Consequently, the catalytic oxidation of CO at double non-noble metal atoms anchored C2N is investigated using density functional theory (DFT) computations. All the screened Ti@C2N and Ti2@C2N are thermodynamically stable based on their binding energy calculations. The electronic characteristics, the natural bond orbital analyses (NBO), Frontier orbital, statistical thermodynamics, projected densities of states (PDOS) characteristics, non-covalent interactions (NCI), and quantum theory of atoms in molecules (QTAIM) descriptors of these systems have been examined to analyze the interaction process. Our comparative study suggested that the newly predicted double-atom catalyst (Ti2@C2N) is highly active for CO oxidation, which is a useful guideline for further development. The calculated static first-order hyperpolarizability (βo) illustrated that the double-atom catalyst under investigation can be considered a potential candidate for non-linear optical behavior and could be used for NLO applications. CO oxidation on Ti2@C2N along the Eley–Rideal (ER) mechanism with a low energy barrier of 0.16 eV, which is smaller than the maximum energy barrier (0.73 eV) of CO oxidation along the Langmuir–Hinshelwood (LH) mechanism. Consequently, the ER mechanism is more favorable both thermodynamically and dynamically. This work can provide useful insights and guidelines for future theoretical and experimental investigations to promote the design and development of highly effective and low-cost non-precious-metal Ti2@C2N nanocatalysts towards CO oxidation at ambient temperature.

Cooperation of Mn and P atoms in graphene for efficiently catalyzing CO oxidation at low temperature

Computational studies show that the co-doping of Mn and P atoms in graphene (MnP4-Gr) can provide high CO oxidation performance at room temperature. Results suggest that the configuration (CO+O2)* can be easily obtained due to the better adsorption of CO on the Mn atom and O2 on the P atom. (CO+O2)* is further found to undergo a fast Langmuir−Hinshelwood (LH) process and then left one atomic oxygen on P which is difficult to remove. Therefore, due to the more favorable adsorption of CO on the Mn atom and O2 on other P atoms, coupled with the speed of the LH process, the configuration (CO+4O)* of one atomic oxygen adsorbed on each P atom and CO on Mn atom is finally obtained. The whole reaction is determined by the atomic oxygen removal in (CO+4O)* with an energy barrier of 0.80 eV. It is predicted that the cooperation of Mn and P atoms is conducive to the fast LH process of MnP4-Gr and also the weaker binding between P and O in MnP4-Gr. Moreover, thermodynamic and kinetics analysis indicates that increasing temperature can accelerate CO oxidation and facilitate reaction in thermodynamics. Therefore, the insights reported in this paper will provide a new catalyst for low-temperature CO oxidation.

Expression of concern: Palladium supported on mixed-metal-organic framework (Co-Mn-MOF-74) for efficient catalytic oxidation of CO.

Expression of Concern for 'Palladium supported on mixed-metal-organic framework (Co-Mn-MOF-74) for efficient catalytic oxidation of CO' by Reda S. Salama et al., RSC Adv., 2021, 11, 4318-4326, https://doi.org/10.1039/D0RA09970H.

Correction and removal of expression of concern: Palladium supported on mixed-metal-organic framework (Co-Mn-MOF-74) for efficient catalytic oxidation of CO.

[This corrects the article DOI: 10.1039/D0RA09970H.].

Engineering Grain Boundary and Surface Sites of Binary Cu-Mn Catalysts to Boost CO Oxidation

The catalytic oxidation of CO over Cu-based catalysts has garnered significant interest due to their promising potential in addressing environmental pollution and enhancing industrial processes. Herein, we report a dual-stimuli...

Enhanced CO oxidation in porous metal-oxide nanoparticles derived from MOFs

Porous nanoparticles of Co3O4, Fe2O3 and Fe3O4 were successfully developed. Among them, the porous Co3O4 nanoparticles greatly improved the catalytic CO oxidation performance due to their large specific surface area and excellent Co active sites.

Microalgae-derived Co3O4 nanomaterials for catalytic CO oxidation.

Efficient carbon monoxide oxidation is important to reduce its impacts on both human health and the environment. Following a sustainable synthesis route toward new catalysts, nanosized Co3O4 was synthesized based on extracts of microalgae: Spirulina platensis, Chlorella vulgaris, and Haematococcus pluvialis. Using the metabolites in the extract and applying different calcination temperatures (450, 650, 800 °C) led to Co3O4 catalysts with distinctly different properties. The obtained Co3O4 nanomaterials exhibited octahedral, nanosheet, and spherical morphologies with structural defects and surface segregation of phosphorous and potassium, originating from the extracts. The presence of P and K in the oxide nanostructures significantly improved their catalytic CO oxidation activity. When normalized by the specific surface area, the microalgae-derived catalysts exceeded a commercial benchmark catalyst. In situ studies revealed differences in oxygen mobility and carbonate formation during the reaction. The obtained insights may facilitate the development of new synthesis strategies for manufacturing highly active Co3O4 nanocatalysts.

Mechanochemical transformation of spent ternary lithium-ion battery electrode material to perovskite oxides for catalytic CO oxidation

This study introduces a mechanochemical approach to convert lithium-removed cathode material from spent ternary LIBs into perovskite oxides for catalyzing CO oxidation.

Spin-polarized p-block antimony/bismuth single-atom catalysts on defect-free rutile TiO2(110) substrate for highly efficient CO oxidation.

Developing high-loading spin-polarized p-block-element-based single-atom catalysts (p-SACs) upon defect-free substrates for various chemical reactions wherein spin selection matters is generally considered a formidable challenge because of the difficulty of creating high densities of underpinning stable defects and the delocalized electronic features of p-block elements. Here our first-principles calculations establish that the defect-free rutile TiO2(110) wide-bandgap semiconducting anchoring support can stabilize and localize the wavefunctions of p-block metal elements (Sb and Bi) via strong ionic bonding, forming spin-polarized p-SACs. Cooperated by the underlying d-block Ti atoms via a delicate spin donation-back-donation mechanism, the p-block single-atom reactive center Sb(Bi) exhibits excellent catalysis for spin-triplet O2 activation and CO oxidation in alignment with Wigner's spin selection rule, with a low rate-limiting reaction barrier of ∼0.6 eV. This work is crucial in establishing high-loading reactive centers of high-performance p-SACs for various important physical processes and chemical reactions, especially wherein the spin degree of freedom matters, i.e., spin catalysis.

Degradation of aqueous phenol by combined ultraviolet and electrochemical oxidation treatment

The industrial wastewater containing phenol is characterized by its elevated toxicity, resistance to biodegradation, and pronounced bioaccumulation. Traditional treatment methods frequently fall short in effectively removing phenol. In this study, a UV photoelectrochemical synergistic catalytic oxidation process was employed for the efficient elimination of phenol. The investigation systematically assessed the impact of various factors, including electrolyte type, concentration, current density, and initial pH, on phenol degradation. Furthermore, the degradation products were analyzed using high-performance liquid chromatography and gas chromatography-mass spectrometry. The results indicate that the oxidation and degradation of phenol in the UV photoelectrochemical synergistic catalytic system adhere to a first-order kinetic equation. Moreover, the combined UV and electrochemical catalytic degradation process demonstrated a synergistic effect, significantly enhancing the efficiency of phenol degradation. This study aimed to elucidate the mechanism of UV combined electrochemical catalytic degradation of phenol and provide reasonable speculation on the degradation pathway of phenol under UV electrochemical co-catalytic oxidation.

Tailoring Au-CuO interfaces for enhanced activity in CO oxidation

Tailoring metal-oxide interfaces with controllable structures are challenging due to the complexity of interfacial structures involving multiple influence factors. Herein, both Au-CuO/Cu2O catalysts with different Au-CuO interfaces tuned by altering original Cu2O morphologies were prepared via a colloid-deposition method followed by restructuring in 1 %CO/Air atmosphere at 240 °C. Strong morphology dependence on original Cu2O nanocrystals was observed. The Au-CuO interactions over Au-CuO/c-Cu2O (cubes) catalyst are stronger than those over Au-CuO/o-Cu2O (octahedra), resulting in less electron-rich Au species formed. Catalytic performance of different Au-CuO interfaces in CO oxidation follows an order of Au-CuO/c-Cu2O > Au-CuO/o-Cu2O. Kinetic results together with in situ DRIFTS spectra demonstrate that a Langmuir-Hinshelwood (LH) mechanism was proceeded over Au-CuO/c-Cu2O catalyst, whose excellent activity could arise from the fleet desorption of adsorbed surface carbonate species to produce CO2, while Au-CuO/o-Cu2O catalyzing CO oxidation was involved with both LH and Mars-van-Krevelen mechanisms. These results greatly deepen the fundamental understanding of Au-CuO interfacial catalysis in CO oxidation and broaden the concept of morphology engineering strategy in developing efficient heterogeneous catalysts.

(Invited) Understanding the Effects of Metal Nanoparticle Exsolution from La0.3Ca0.7Fe0.7Cr0.3O3-δ Perovskites on CO2-CO Electrocatalysis

Solid Oxide Fuel Cells (SOFCs) and Solid Oxide Electrolysis Cells (SOECs) are highly useful devices, capable of generating and storing large amounts of energy, respectively.1 They can do this by catalyzing CO oxidation at a SOFC anode and CO2 reduction (CO2RR) at a SOEC cathode, while the other electrode catalyzes oxygen reduction or evolution. The conduction of oxide ions through the electrolyte completes the circuit, making Solid Oxide Cells (SOCs) an excellent choice for clean energy production and use since there are no undesired byproducts.1 While traditional SOC electrodes are composed of oxide-conducting ceramics mixed with electronically conducting metals,1 a newer category of catalysts are Mixed Ionic Electronic Conductors (MIECs), with one example being the perovskite La0.3M0.7Fe0.7Cr0.3O3-δ (M = Sr, Ca) (LMFCr), investigated heavily by our group.2,3,4 As an MIEC, the full surface of LMFCr is electrochemically active, giving excellent activity at both the cathode and anode, including for CO2RR and CO oxidation.2,3 However, efforts are being made to further improve the CO2RR-CO oxidation kinetics and durability, with the Ca analogue having a better chemical match with standard electrolytes.4 One approach used recently to improve MIEC oxide performance is B-site doping with transition metals (TMs) while also creating an A-site deficiency, resulting in nanoparticle (NP) formation (exsolution) when the perovskite is subjected to reducing conditions.2 For instance, Fe-Ni NPs of a ~20 nm average size can be exsolved from (La0.3Ca0.7)0.95Fe0.7Cr0.25Ni0.05O3-δ(LCFCrNi), even at 600 °C in 70CO2:30CO (pO2 ~10-18 atm). Furthermore, NP features can easily be tailored by changing the reducing conditions or dopant used.2 In general, higher temperatures and lower pO2 lead to larger NPs over time, and more easily reducible metals tend to exsolve first under less harshly reducing conditions.2 Recent studies have suggested that NP formation enhances electrocatalytic activity by creating additional sites of reactivity, suggesting that strong NP-substrate interactions are important to catalysis.5 However, there is no clear understanding of the role played by exsolved NPs in catalyzing SOC reactions. To gain further insights, detailed electrochemical studies of LCFCrNi electrodes were done on 1-inch diameter cells constructed using Samarium-Doped Ceria buffered Scandia-Stabilized Zirconia electrolyte substrates. LCFCrNi was made into an ink and tape-cast on 0.5 cm2 on one side (working electrode, WE) and 1 cm2 on the other (counter electrode, CE) on each substrate. The cells were sintered at 1100 °C for 2 h, coated with Au ink, and sintered at 850 °C for 1 h. Electrochemical Impedance Spectroscopy (EIS) was performed at 600 °C with 70CO2:30CO at the WE and air at the CE, followed by exsolution in 5H2:95N2 at a higher temperature, and then EIS was repeated multiple times under the same conditions at 600 °C. Cells were imaged via Scanning Electron Microscopy (SEM) after ramping down to room temperature in N2 to determine the size and distribution of the NPs for each set of exsolution conditions.Under all conditions employed, the polarization resistance (Rp) was found to be stable before exsolution occurred, but started decreasing once the NPs formed, especially via a shrinking of the low frequency resistance. The low frequency resistance has been associated with CO oxidation,2 so the fact that it improves with exsolution is an indication that the increased electrode area serves to improve CO oxidation more than CO2RR. When exsolution was carried out at 800 °C for 25 h, Rp decreased more rapidly than after exsolution at 800 °C for 14 h. Exsolution at 800 °C for 25 h also showed a more rapid decrease in Rp compared to 700 °C exsolution for 25 h. These results argue that the initial formation of larger NPs (formed after longer time or at a higher temperature) results in a faster increase in the active surface area of the electrode at the lower 600 °C temperature. Further experiments are being carried out to better understand whether it is the growth of NPs or new NP formation after higher temperature exsolution that is the reason behind this observation. The results of operando synchrotron studies in CO2/CO environments before and after exsolving, as well as the use of different transition metal dopants, are also being investigated for this purpose.

Hydrogen Spillover Induced PtCo/CoOx Interfaces with Enhanced Catalytic Activity for CO Oxidation at Low Temperatures in Humid Conditions.

The development of catalysts with abundant active interfaces for superior low-temperature catalytic CO oxidation is critical to meet increasingly rigorous emission requirements, yet still challenging. Herein, this work reports a PtCo/CoOx/Al2O3 catalyst with PtCo clusters and enriched Pt─O─Co interfaces induced by hydrogen spillover from the Pt sites and self-oxidation process in air, exhibiting excellent performance for CO oxidation at low temperatures and humid conditions. The combination of structural characterizations and in situ Fourier transform infrared spectroscopy reveals that the PtCo cluster effectively prevents CO saturation/poisoning on the Pt surface. Additionally, the presence of Pt─O─Co interfaces in the PtCo/CoOx/Al2O3 catalyst provides a significant number of active sites for oxygen activation and ─OH formation. This facilitates efficient generation of CO2 at ambient temperature by coupling with nearby adsorbed CO molecules, resulting in superior low-temperature activity and long-term stability for CO oxidation under humid conditions. This work provides a facile route toward rationalizing the design of catalysts with more active interfaces for superior low-temperature CO oxidation under humid conditions for practical applications.

A theoretical study into the performance of DACs loaded on MgO utilized in CO oxidation

Single-atom catalysts (SACs) have garnered significant attention due to their unique combination of advantages from both heterogeneous and homogeneous catalysts. However, SACs composed of just one metal cannot adequately meet the various catalytic requirements. Thus, this study focused on the addition of a second metal atom to M1/MgO systems (M = Au, Ag and Cu) to create dual-atom catalysts (DACs) supported on different di-vacancy types on MgO(100) surfaces. Homogeneous (Au2, Ag2, Cu2) and multiphase (Au1Ag2, Au1Cu2 and Ag1Cu2) were analyzed for their selectivity in CO oxidation by Langmuir-Hinshaw (LH) and Eley-Rideal (ER) mechanisms using density functional theory (DFT) method. The results indicated that the tri-molecules ER pathway had the highest selectivity, and the multiphase DACs had better CO catalytic oxidation activity compared to homogeneous DACs. Among all multiphase DACs in the tri-molecules ER pathway, alloy DACs of Au1Ag2/MgO(Fc-Fc) and Au1Cu2/MgO(Fc-Vc) had the lowest energy barrier for CO oxidation, and the addition of a second metal atom improved stability compared to SAC of Au1/MgO(Fc). DFT calculations combined with microkinetic simulations revealed that under reaction conditions, Au1Cu2/MgO(Fc-Vc) had a remarkably high TOF of CO2, making it a promising DAC for practical applications. This study provides valuable insights into the development of efficient and low-cost atomic-scale catalysts.

Ultrasmall Pd Clusters in FER Zeolite Alleviate CO Poisoning for Effective Low-Temperature Carbon Monoxide Oxidation.

Ultrasmall Pd4 clusters form in the micropores of FER zeolite during low-temperature treatment (100 °C) in the presence of humid CO gas. They effectively catalyze CO oxidation below 100 °C, whereas Pd nanoparticles are not active as they are poisoned by CO. Using catalytic measurements, infrared (IR) spectroscopy, X-ray absorption spectroscopy (EXAFS), microscopy, and density functional theory calculations, we provide the molecular-level insight into this previously unreported phenomenon. Pd nanoparticles get covered with CO at low temperatures, which effectively blocks O2 activation until CO desorption occurs. Small Pd clusters in zeolites, in contrast, demonstrate fluxional behavior in the presence of CO, which significantly increases the affinity for binding O2. Our study provides a pathway to achieve low-temperature CO oxidation activity on the basis of a well-defined Pd/zeolite system.

Dynamic Behavior of Tin at Platinum Surfaces during Catalytic CO Oxidation

Dynamic Behavior of Tin at Platinum Surfaces during Catalytic CO Oxidation

Catalytic Oxidation of CO over LaNi1/3Sb5/3O6 Synthesized by Different Methods

Methods for the synthesis of LaNi1/3Sb5/3O6 with a rosiaite structure have been developed using citrate method and coprecipitation followed by annealing. The influence of synthesis conditions on the morphology of the samples has been demonstrated. A comparative analysis of the catalytic properties of LaNi1/3Sb5/3O6 synthesized by various methods, in the reaction of CO oxidation has been carried out. The catalyst synthesized by the citrate method demonstrated the greatest efficiency and stability (the temperature of 90% CO conversion was T90 = 336°C). The LaNi1/3Sb5/3O6 surface was studied before and after catalysis by in situ diffuse reflectance IR spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed O2 desorption. It has been shown that the catalytic oxidation of CO on the LaNi1/3Sb5/3O6 surface proceeds according to the Mars–van Krevelen mechanism and is accompanied by redox Sb3+ ↔ Sb5+ processes. It has been established that no contamination of the sample surface occurs during the catalysis process.

Catalytic Oxidation of CO over LaNi1/3Sb5/3O6 Synthesized by Different Methods

Catalytic Oxidation of CO over LaNi1/3Sb5/3O6 Synthesized by Different Methods