Shunt Pt/FeOx‑Al2O3 Catalystsfor SO2‑TolerantCO Oxidation

Understanding the intrinsic catalytic properties of perovskite materials can accelerate the development of highly active and abundant complex oxide catalysts. Here, we performed a first-principles density functional theory study combined with a microkinetics analysis to comprehensively investigate the influence of defects on catalytic CO oxidation of LaFeO3 catalysts containing single atoms of Rh, Pd, and Pt. La defects and subsurface O vacancies considerably affect the local electronic structure of these single atoms adsorbed at the surface or replacing Fe in the surface of the perovskite. As a consequence, not only the stability of the introduced single atoms is enhanced but also the CO and O2 adsorption energies are modified. This also affects the barriers for CO oxidation. Uniquely, we find that the presence of La defects results in a much higher CO oxidation rate for the doped perovskite surface. A linear correlation between the activation barrier for CO oxidation and the surface O vacancy formation energy for these models is identified. Additionally, the presence of subsurface O vacancies only slightly promotes CO oxidation on the LaFeO3 surface with an adsorbed Rh atom. Our findings suggest that the introduction of La defects in LaFeO3-based environmental catalysts could be a promising strategy toward improved oxidation performance. The insights revealed herein guide the design of the perovskite-based three-way catalyst through compositional variation.

Promotion effect of Au single-atom support graphene for CO oxidation

In this study, Ag/γ-Al2O3 catalysts were synthesized by an Ar dielectric barrier discharge plasma using silver nitrate as the Ag source and γ-alumina (γ-Al2O3) as the support. It is revealed that plasma can reduce silver ions to generate crystalline silver nanoparticles (AgNPs) of good dispersion and uniformity on the alumina surface, leading to the formation of Ag/γ-Al2O3 catalysts in a green manner without traditional chemical reductants. Ag/γ-Al2O3 exhibited good catalytic activity and stability in CO oxidation reactions, and the activity increased with increase in the Ag content. For catalysts with more than 2 wt% Ag, 100% CO conversion can be achieved at 300 °C. The catalytic activity of the Ag/γ-Al2O3 catalysts is also closely related to the size of the γ-alumina, where Ag/nano-γ-Al2O3 catalysts demonstrate better performance than Ag/micro-γ-Al2O3 catalysts with the same Ag content. In addition, the catalytic properties of plasma-generated Ag/nano-γ-Al2O3 (Ag/γ-Al2O3-P) catalysts were compared with those of Ag/nano-γ-Al2O3 catalysts prepared by the traditional calcination approach (Ag/γ-Al2O3-C), with the plasma-generated samples demonstrating better overall performance. This simple, rapid and green plasma process is considered to be applicable for the synthesis of diverse noble metal-based catalysts.

Effect of cobalt on CeO2 nanorod supported Pt catalyst: Structure, performance, kinetics and reaction mechanism in CO oxidation

In situ infrared study of catalytic CO oxidation over Au/TiO2 shows that the catalyst prepared from AuCl3 exhibits higher activity than those prepared from HAuCl4. The high activity of Au appears to be related to the presence of reduced and oxidized Au sites as well as carbonate/carboxylate intermediates during CO oxidation. Addition of H2O2 further promotes the oxidation reaction on Au/TiO2 catalysts. Introduction Supported Au catalysts have been extensively studied because of their unique activities for the low temperature oxidation of CO and epoxidation of propylene (15). The activity and selectivity of Au catalysts have been found to be very sensitive to the methods of catalyst preparation (i.e., choice of precursors and support materials, impregnation versus precipitation, calcination temperature, and reduction conditions) as well as reaction conditions (temperature, reactant concentration, pressure). (6-8) High CO oxidation activity was observed on Au crystallites with 2-4 nm in diameter supported on oxides prepared from precipitation-deposition. (9) A number of studies have revealed that Au0 and Au+3 play an important role in the low temperature CO oxidation. (3, 10) While Au0 is essential for the catalyst activity, the Au0 alone is not active for the reaction. The mechanism of CO oxidation on supported Au continues to be a subject of extensive interest to the catalysis community. The reaction pathway, reactivity of the active sites, and the nature of adsorbed intermediates constitute the catalytic reaction mechanism. Our study has been focused on the investigation of the nature of adsorbed intermediates under reaction conditions. We report the results of in situ infrared study of CO and ethanol oxidation on Au/TiO2 catalysts. This study revealed the high activity of Au/TiO2 is related to the presence of reduced Au and oxidized Au sites which may promote the formation of carbonate/carboxylate intermediates during CO oxidation. Experimental Section Two 1% Au/TiO2 catalysts, designated as HAuCl4 and AuCl3 were prepared by deposition-precipitation of HAuCl4 (Aldrich) and AuCl3 (Alfa Asar) onto Degussa-P25 TiO2, respectively (16, 17). The specific procedure involves (i) adding NaOH solution in an appropriated amount of aqueous solution (150ml) of AuCl3 or HAuCl4-4H2O with 2 g TiO2 at 343 K to adjust the mixture to pH = 7, (ii) washing the resulting solid five times with warm distilled water, (iii) centrifuging to remove Na+ and Cl-ions, (iv) drying the sample at 353 K for 12 h, and then (v) calcining the sample at 673 K for 5 h. The experimental apparatus is explained elsewhere (18) but briefly described here. The experimental apparatus consists of (i) a gas flow system with a four port and six port valve, (ii) a DRIFTS (Diffuse Reflectance Infrared Spectroscopy) reactor, (iii) an analysis section with Mass Spectrometer (MS). The CO oxidation was performed from 298 K to 523 K. The reactor temperature was varied at a rate of 10 K/min. The gas species consists of He/CO (90/10 Vol%), He/CO/O2 (72/14/14 Vol%), He/CO/H2O2/O2 (72/13.3/13.3/1.4 Vol%), He/O2 (86/14 Vol%), He/H2O2/O2 (84/2/14 Vol%), He/CH3CH2OH (83/17 Vol%), and He/CH3CH2OH/O2 (72/14/14 Vol%), He/CH3CH2OH/H2O2/O2 (75/8/2/15 Vol%) at a total flow rate of 35 cm3/min; it takes 13 s for the gases to reach the DRIFTS reactor and 27 s to reach the MS from the four port valve. CH3CH2OH and H2O2 species added by flowing He through a saturator. Transient IR Spectra were collected by a Digilab FTS4000 FT-IR. The effluent gases of the DRIFTS reactor were monitored by a Pfeiffer OmnistarTM Mass Spectrometer. Results and Discussion Fig. 1(a) shows both Au catalysts give very similar XRD patterns; Fig. 1(b) shows both catalysts exhibit a UV peak in the 500-600 nm region; the Au particle size was determined to be 88 nm for HAuCl4 and 86 nm for AuCl3 by XRD.

Highly dispersed boron-nitride/CuOx-supported Au nanoparticles for catalytic CO oxidation at low temperatures

Selective phase transformation of layered double hydroxides into mixed metal oxides for catalytic CO oxidation

Mechanistic insight into the catalytic CO oxidation and SO2 resistance over Mo-decorated Pt/TiO2 catalyst: The essential role of Mo

Identifying Key Descriptors for the Single-Atom Catalyzed CO Oxidation

Influence of CuO x additives on CO oxidation activity and related surface and bulk behaviours of Mn 2O 3, Cr 2O 3 and WO 3 catalysts

Catalytic oxidation of CO over Pt/TiO2 with low Pt loading: The effect of H2O and SO2

Theoretical studies of CO oxidation with lattice oxygen on Co3O4 surfaces

Effect of temperature on the catalytic oxidation of CO over nano-sized iron oxide

Shape-regulation: An effective way to control CO oxidation activity over noble metal catalysts

Dynamic structural changes of perovskite-supported metal catalysts during cyclic redox treatments and effect on catalytic CO oxidation