O2 TPD Research Articles

Sources of the active substances in microwave catalytic redox processes induced by iron-based carbon materials: The key role of B doping

Organic and heavy metal water pollutants is an urgent environmental problem to be solved. Herein, a B-doped iron-based carbon material (FC-B) was synthesized and used in a microwave field for the degradation of sulfamethoxazole (SMX) and the reduction of Cr(VI). Under a low power of microwave irradiation (240 W), FC-B rapidly degraded SMX (99.8 %, 12 min) and reduced Cr(VI) (100.0 %, 14 min) without adding any oxidizing and reducing agents. SEM, XRD, XPS, and FTIR verified the successful synthesis of FC-B. And the “temperature visualization test” verified the existence of “hot spots”. The presence of O2− in the MW/FC-B system but not in the MW/FC system was verified by quenching experiments, electron paramagnetic resonance (EPR) experiments and nitro blue tetrazolium chloride (NBT) quantitative experiments, and then the conversion of microwave-generated electrons (e−) to O2− was elaborated using N2 blowing experiments, temperature-programmed desorption of O2 (O2-TPD), density functional theory (DFT) calculations and electrochemical tests. Subsequently, cycling experiments showed that FC-B has good reusability. Finally, the practical application of the MW/FC-B system was verified with antibiotic-containing farm wastewater. This study not only proposed a new technology for water pollution treatment, but also provided a pioneering explanation of the production of oxidizing substances in microwave-induced catalytic reactions.

Enhanced Catalytic Soot Oxidation over Co-Based Metal Oxides: Effects of Transition Metal Doping.

A series of Co-M (M = Fe, Cr, and Mn) catalysts were synthesized by the sol-gel method for soot oxidation in a loose contact mode. The Co-Fe catalyst exhibited the best catalytic activity among the tested samples, with the characteristic temperatures (T10, T50, and T90) of 470 °C, 557 °C, and 602 °C, respectively, which were 57 °C, 51 °C, and 51 °C lower than those of the CoOx catalyst. Catalyst characterizations of N2 adsorption-desorption, X-ray diffraction (XRD), X-ray photo-electron spectrometry (XPS), and the temperature programmed desorption of O2 (O2-TPD) were performed to gain insights into the relationships between the activity of catalytic soot oxidation and the catalyst properties. The content of Co2+ (68.6%) increased due to the interactions between Co and Fe, while the redox properties and the relative concentration of surface oxygen adsorption (51.7%) were all improved, which could significantly boost the activity of catalytic soot oxidation. The effects of NO and contact mode on soot oxidation were investigated over the Co-Fe catalyst. The addition of 1000 ppm of NO led to significant reductions in T10, T50, and T90 by 92 °C, 106 °C, and 104 °C, respectively, compared to the case without the NO addition. In the tight contact mode, the soot oxidation was accelerated over the Co-Fe catalyst, resulting in 46 °C, 50 °C, and 50 °C reductions in T10, T50, and T90 compared to the loose contact mode. The comparison between real soot and model Printex-U showed that the T50 value of real soot (455 °C) was 102 °C lower than the model Printex-U soot.

MnO2 shape dependent catalytic activity in vapour phase benzyl alcohol (BnOH) oxidation in presence of air

Understanding the relationship between the structure and the activity of the catalyst relies on the shape–controlled synthesis of nanostructures is crucial importance. The vapor phase oxidation of benzyl alcohol (BnOH) process over morphologically designed shape–selective manganese oxide nanorods (MnO2NR) and nanospheres (MnO2NS) catalysts are studied. The key catalytic properties are determined and demonstrated by various characterisation techniques such as P–XRD, BET, H2–TPR, O2–TPD, and Raman analysis. In addition, EDX and STEM–HRTEM microscopic analysis were carried out in better understanding the surface morphology, shape, and structure of the nanocatalysts. The prepared nanoporous MnO2NS catalyst enabled to generate more crystal defects, high surface area, strong reducing capacity, enhanced oxygen vacancies (Ov), and increased reactive surface oxygen species compared to nanorod shaped–MnO2NR catalyst. Significantly the rate of benzaldehyde (BnZA) formation in BnOH oxidation reaction over MnO2NS catalyst is ∼ 1.55 times higher than that of MnO2NR. Over MnO2NS creation of abundant O vacancies considerably improved the capacity of oxygen activation and redox ability.Thus, as a result, there are more active oxygen species which are mobile and reactive in accelerating the BnOH oxidation process.

CO oxidation over CuOx/TiO2 catalyst: The importance of oxygen vacancies and Cu+ species

It is well documented that the existence of oxygen vacancies and active Cu species can improve CO oxidation activity over TiO2 substrate. Herein, TiO2-supported copper catalysts (CuOx/TiO2) with different ratio of oxygen vacancies (Ov) and Cu+ has been synthesized. The existence and amount of Ov and Cu+ species were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectrum (EPR). The synergetic effect between Cu+ and oxygen vacancies was investigated in terms of O2 temperature-programmed desorption (O2–TPD), H2 temperature-programmed reduction (H2–TPR) and in situ DRIFTS spectra. Cu+ is the adsorption site for CO molecules, the abundant Ov can significantly activate molecular oxygen, which effectively oxidize the adsorbed CO molecules. The most suitable ratio between Cu+ and Ov has been confirmed. The CuOx/TiO2(Cu+ rich) catalyst (51% Cu+, 26.3% Ov) shows superior CO oxidation activity (T90 = 136 °C) compared to CuOx/TiO2(Ov rich) catalyst (39% Cu+, 28.5% Ov, T90 > 350 °C). This work provides comprehensive investigation of the role for abundant oxygen vacancies and Cu+ in CO oxidation reactions.

Ozone catalytic oxidation of low-concentration formaldehyde over ternary Mn-Ce-Ni oxide catalysts modified with FeOx.

Manganese oxide-based catalysts have attracted extensive attention due to their relatively low cost and remarkable performance for removing VOCs. In this research, we used the Pechini method to synthesize manganese-cerium-nickel ternary oxide catalysts (MCN) and evaluated the effectiveness of catalytic destruction of formaldehyde (HCHO) and ozone at room temperature. FeOx prepared by the impregnation method was applied to modify the catalyst. After FeOx treatment, the catalyst represented the best performance on both HCHO destruction and ozone decomposition under dry conditions and exhibited excellent water vapor resistance.The as-prepared catalystswere next characterized via H2-temperature programmed reduction (H2-TPR), temperature programmed desorption of O2 (O2-TPD), and X-ray photoelectron spectroscopy (XPS), and the results demonstrated that addition of FeOx increased Mn3+ and Ce3+ concentrations, oxygen vacancies and surface lattice oxygen species, facilitated adsorption, and redox properties. Based on the results of in situ diffuse reflectance infrared Fourier transform spectrometry (DRIFTS), possible mechanisms of ozone catalytic oxidation of HCHO were proposed. Overall, the ternary mixed-oxide catalyst developed in this study holds great promise for HCHO and ozone decomposition in the indoor environment.

Lewis acid Fe3+ in TiO2 ultra-thin nanosheet boosts oxygen species activation

Breaking the bottleneck of the light absorption, photocarriers transmission and separation (PTS), and surface reactions efficiency of photocatalysis is hot topic. For this, the Fe3+ acted as Lewis acid site is successfully built in TiO2 ultra-thin nanosheet (FT) through hydrothermal method. The detailed effect of Lewis acid site is systematically studied. Based on DFT, in-situ XPS, O2 TPD, CV, hole transfer efficiency (ηtrans) and ESR, Lewis acid of Fe3+ acts as a photo-generated electron trapped site, and the imbalance of charge by the construction of Lewis acid, which makes the O2 reduction process more easily occurs on Ti4+ (adjacent to the Lewis acid site) as well as Lewis acid site itself. Meanwhile, the oxygen defect (OD) near Lewis acid site promotes the adsorption, activation and oxidation of H2O. The photo-redox reaction is simultaneously accomplished around the Lewis acid site, which is the PTS driving force of photocarriers. The photocurrent density of 5% FT is 4 to 5 times higher than intrinsic one (T), and Lewis acid site of Fe3+ leads to the reduction of interfacial resistance due to lower the activation energy of redox process. As result, FT displays higher photocatalytic activity than T.

Effect of doped strontium on catalytic properties of La1‒xSrxMnO3 for rhodamine B degradation

A series of La1‒xSrxMnO3 samples were prepared by sol–gel method and used to degrade rhodamine B (RhB) in water. All samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption, temperature-programmed reduction of H2 (H2-TPR) and temperature-programmed desorption of O2 (O2-TPD). The results show that the degradation of RhB is highly dependent on the initial pH value of solution. Sr doping enhances the degradation ability of LaMnO3 for RhB in the time range of 0–40 min under a strong acidic environment, but all samples exhibit similar degradation rate from 40 to 60 min. In La0.7Sr0.3MnO3–RhB reaction system, there are two different degradation pathways, including N-de-ethylation, chromophore cleavage, ring-opening and mineralization. La1‒xSrxMnO3 (x ≤ 0.3) has the perovskite structure of La–Mn oxides, while La0.6Sr0.4MnO3 exhibits a Sr0.4MnLa0.6O2.98 perovskite phase. Sr doping leads to distortion of rhombohedral crystal structure and increases the relative content of Mn4+. The perovskite structure is stable in strong acidic environment during RhB degradation, but the relative content of Mn4+ and Mn3+ on the material surface changes. Sr doped LaMnO3 achieves specific surface area of 58.8 m2/g and total pore volume of 0.152 cm3/g. Furthermore, Sr2+ doping improves redox properties of La–Mn oxides, and the presence of defects makes oxygen diffusion easier compared with the undoped samples.

Comparative study of Co3O4-ZSM-5 catalysts synthesized by different hydrothermal methods for the catalytic oxidation of dichloromethane

In this work, various Co3O4-ZSM-5 catalysts were prepared by the microwave hydrothermal method (MH-Co3O4@ZSM-5), dynamic hydrothermal method (DH-Co3O4@ZSM-5), and conventional hydrothermal method (CH-Co3O4/ZSM-5). Their catalytic oxidation of dichloromethane (DCM) was analyzed. Detailed characterizations such as X-ray diffractometer (XRD), scanning microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), H2 temperature-programmed reduction (H2-TPR), temperature-programmed desorption of O2 (O2-TPD), temperature-programmed desorption of NH3 (NH3-TPD), diffuse reflectance infrared Fourier-transform spectra with NH3 molecules (NH3-DRIFT), and temperature-programmed surface reaction (TPSR) were performed. Results showed that with the assistance of microwave, MH-Co3O4@ZSM-5 formed a uniform core-shell structure, while the other two samples did not. MH-Co3O4@ZSM-5 possessed rich surface adsorbed oxygen species, higher ratio of Co3+/Co2+, strong acidity, high reducibility, and oxygen mobility among the three Co3O4-ZSM-5 catalysts, which was beneficial for the improvement of DCM oxidation. In the oxidation of dichloromethane, MH-Co3O4@ZSM-5 presented the best activity and mineralization, which was consistent with the characterizations results. Meanwhile, according to the TPSR test, HCl or Cl2 removal from the catalyst surface was also promoted in MH-Co3O4@ZSM-5 by their abundant Brønsted acid sites and the promotion of Deacon reaction by Co3O4 or the synergistic effect of Co3O4 and ZSM-5. According to the results of in situ DRIFT studies, a possible reaction pathway of DCM oxidation was proposed over the MH-Co3O4@ZSM-5 catalysts.

Catalytic combustion of vinyl chloride emissions over Co3O4 catalysts with different crystallite sizes

A series of Co3O4 catalysts was prepared by ammonia (Co-AP) and oxalate (Co-OP) precipitation, sol–gel (Co-SG), and urea hydrothermal (Co-UH) methods, and their physicochemical properties were characterised by numerous techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen sorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction of H2 (H2-TPR), temperature-programmed desorption of O2 (O2-TPD), and temperature-programmed desorption of NH3 (NH3-TPD). The catalytic activity of each catalyst was estimated for the catalytic combustion of vinyl chloride (VC) emissions. The crystallite size of the Co3O4 catalyst was found to be well correlated with the amounts of surface-adsorbed oxygen species and number of acid sites on the catalyst surface, and consequently, determined several physicochemical properties of the catalyst. Of the catalysts studied here, the Co-AP catalyst exhibits the smallest crystallite size, which increases the specific surface area and the concentration of Co2+ on the catalyst surface. This, in turn, enhances the redox property, oxygen mobility, and the number of acid sites associated with the Co-AP catalyst. In fact, the Co-AP catalyst exhibits the best catalytic activity for VC combustion at 360 °C and does not produce any chlorinated by-products.

Evaluation of LaBO3 (B=Mn, Cr, Mn0.5Cr0.5) perovskites in catalytic oxidation of trichloroethylene

In this study, La–Mn–Cr perovskite-type catalysts were synthesized as LaMnO3,LaCrO3, and LaMn0.5Cr0.5O3 by a microwave-assisted gel-combustion method. They were then calcined at 600oC for 5h in air. X-ray diffraction (XRD) analysis indicated that the crystalline perovskite phase is the dominant phase formed in all the synthesized samples. The scanning electron microscopy (SEM) analysis showed that the perovskites have a full spongy and porous structure. The specific surface area (BET) analysis showed a specific surface area of about 12.4-26.8 m2/g, and the highest specific surface area belonged to the LaMn0.5Cr0.5O3 perovskite. Moreover, the highest oxygen mobility revealed by the temperature-programmed desorption of oxygen (O2–TPD) analysis was related to the LaMn0.5Cr0.5O3 sample. The catalytic activity of the synthesized perovskites in catalytic oxidation of 1000 ppm trichloroethylene (TCE) in air was investigated at different temperatures. The substituted perovskite (LaMn0.5Cr0.5O3) with the highest BET specific surface area and the highest oxygen mobility yielded the best catalytic performance among the probed perovskites.

Preparation and Evaluation of Copper–Manganese Oxide as a High-Efficiency Catalyst for CO Oxidation and NO Reduction by CO

In this work, highly efficient Cux–Mn composite catalysts (0 ≤ x ≤ 0.20) were synthesized by an improved hydrothermal–citrate complex method and tested in the catalytic total oxidation of CO and the removal of NO by CO. The influence of Cu on manganese oxide materials was characterized by several techniques, including FESEM, HRTEM, XRD, BET analysis, H2 TPR, O2 TPD, XPS, and DRIFTS. Possible reaction mechanisms for the NO + CO model reaction and CO oxidation were also tentatively proposed. The Cu-modified manganese oxide materials showed higher catalytic activity in CO oxidation and the selective catalytic reduction (SCR) of NO with CO than pure MnOx materials. The improved catalytic activity in CO oxidation observed for the copper–manganese oxide catalyst was associated with a greater amount of adsorbed oxygen species and high lattice oxygen mobility due to the formation of a Cu1.5Mn1.5O4 spinel active phase (Cux2+–Mnx3+–[O(y–z)⊙z] species). Furthermore, in terms of the CO-SCR model reaction, the surface...

Structurally defined SnO2 substrates, nanostructured Au/SnO2 interfaces, and their distinctive behavior in benzene and methanol oxidation

SnO2 crystallites of regular morphology [rhombic dodecahedra (r.d-SnO2), elongated octahedra (e.o-SnO2), and octahedra (o-SnO2)], together with low-dimensional rod-clusters (r.c-SnO2) and plates (p-SnO2), were controllably synthesized. Based on (HR)TEM, SEM, and SEAD characterizations, the SnO2 facets were identified as {111}, {110}, and {101}. Au nanoparticles of 2.2–2.4nm with narrow particle size deviation (±0.6–0.7nm) were monodispersed on the SnO2 substrates. Au/SnO2 interfacial structures with structurally defined oxide substrate and comparable Au particle size and morphology were accomplished. The systems achieved made it possible to study the distinct interfaces in catalytic benzene combustion and methanol oxidation. H2 TPR, O2 TPD, and XPS characterizations revealed that the specific Au–SnO2 interaction has a strong effect on the reactivity of surface and bulk lattice oxygen, the oxidation state of surface Sn atoms, and the sort and relative concentration of surface oxygen adspecies. The Au/SnO2{110} and Au/SnO2{101} interfaces favor selective oxidation of methanol, whereas Au/SnO2{111} enhances total oxidation of both benzene and methanol. These interfacial structures were rather stable in both reactions. Through structural analysis of SnO2 facets, the evolution of active oxygen species and the possible reaction pathways of benzene combustion have been proposed. The involved reaction pathways are notably influenced by the specific Au/SnO2 interfacial structure and the nature of the reactant molecule, as well as the reaction temperature. The current study gained insight into the significance of specific Au/SnO2 facets determining the catalytic activity of benzene and methanol oxidation.

금속이온이 치환된 Y형 제올라이트에서 벤젠의 촉매연소반응

Catalytic combustion of benzene over various metal cation-exchanged zeolites has been investigated. Y(4.8)-type zeolite showed the highest activity among the used zeolites and Cu/Y(4.8) catalyst also showed the highest activity among metal cation/ Y(4.8) zeolites. The catalytic activity increased according to the amount of adsorbed oxygen acquired from O2 TPD results. The catalytic activity also increased with an increase of Cu cation concentration on Cu/Y(4.8) catalysts. The conversion of benzene on the combustion reaction depended on not benzene concentration but the oxygen concentration. In addition, the introduction of water into reactants decreased the catalytic activity.

High Efficiency CeCu Composite Oxide Catalysts Improved via Preparation Methods for Propyl Acetate Catalytic Combustion in Air

Abstract A famous hard-template method (HT), coprecipitation method (PC), and complex method (CA) were used to prepare CeCu composite oxide catalysts. The prepared catalysts were characterized via XRD, BET, Raman, XPS, FI–IR, and O2–TPD, and their catalytic activity and stability were evaluated for the propyl acetate catalytic combustion. The results showed that the CeCu oxide solid solution and oxygen vacancies were formed in the prepared CeCu oxide catalysts, even for CeCu–PC and CeCu–CA having a specific amount of isolated crystalline or amorphous CuO species. Comparing with the CeCu–PC and CeCu–CA of low porosity, CeCu–HT developed a mesoporous structure with a much larger specific surface area through a negative replica on the structure of KIT-6, and in it, CuO was completely dissolved in the CeO2 lattice to form more CeCu oxide solid solution and a large amount of oxygen vacancies. As a result, the CeCu–HT catalyst has more surface-adsorbed oxygen species, more –OH group which can also change into surface-adsorbed oxygen species at relatively high temperatures, higher oxygen desorption ability, and higher oxygen mobility than CeCu–PC and CeCu–CA. The CeCu–HT catalyst shows high and stable propyl acetate catalytic combustion performance at 190 °C. The propyl acetate catalytic combustion activity on the prepared CeCu oxide catalysts can be ranked as: CeCu–HT > CeCu–PC > CeCu–CA, which follows the orders of CeCu oxide solid solution content, surface-active oxygen content, and oxygen desorption and mobility of the CeCu composite oxide catalysts.

Investigation of the Facet-Dependent Catalytic Performance of Fe2O3/CeO2 for the Selective Catalytic Reduction of NO with NH3

The facet-dependent catalytic performance of Fe2O3/CeO2 catalysts for the selective catalytic reduction of NO with NH3 (NH3–SCR) has been investigated using combined experimental and density functional theory (DFT) methods. The structure and surface characteristics of the synthesized samples were characterized by XRD, XPS, TEM, ICP–AES, N2 sorption isotherms, Raman spectra, photoluminescence spectra, H2–TPR, NH3–TPD and NO + O2–TPD. It is found that the CeO2 nanorods and Fe2O3/CeO2 nanorods predominately exposed {110} and {100} facets rather than the stable {111} facets on CeO2 nanopolyhedra and Fe2O3/CeO2 nanopolyhedra. The influence of the micromorphologies and surface properties of CeO2 supports on the NO conversion and N2 selectivity has been compared. The Fe2O3/CeO2 nanorods achieve higher catalytic activity than the Fe2O3/CeO2 nanopolyhedra for NH3–SCR of NO. The synergetic effect between CeO2 supports and Fe2O3 species has been demonstrated. The insight into molecular facet dependence by the DFT me...

Enhanced CO oxidation activity of CuO/CeO2 catalyst prepared by surfactant-assisted impregnation method

A modified CuO/CeO2 catalyst was prepared by surfactant-assisted impregnation method and showed better catalytic activity for low temperature CO oxidation than that from conventional impregnation method. The physicochemical properties of different CuO/CeO2 catalysts were characterized by thermogravimetric and differential scanning calorimetric measurements (TG-DSC), X-ray diffraction (XRD), N2 adsorption-desorption, Raman spectroscopy, H2 temperature-programmed reduction (H2-TPR), temperature-programmed desorption of O2 (O2-TPD), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results suggested that the addition of hexadecyl trimethyl ammonium bromide (CTAB) into the impregnation solution could improve the dispersion of CuO species, which could facilitate Cu2+ incorporating into CeO2 lattice and strengthened the synergistic effects between CuO and CeO2, making the lattice oxygen more active, and eventually resulting in enhanced activity for CO oxidation.

A kinetic model for sulfur poisoning and regeneration of Cu/SSZ-13 used for NH3-SCR

In this study, we have developed a multi-site kinetic model that describes the sulfur poisoning and gradual sulfur removal over Cu/SSZ-13 used for NH3-SCR. Sulfur poisoning was conducted under SCR conditions and thereafter, repeated SCR experiments were conducted to examine the effect of such poisoning and the subsequent gradual removal of sulfur. In addition, the effect of sulfur poisoning was examined on NH3 TPD and ammonia oxidation experiments. The following sites were used in the kinetic model: copper in the six-membered rings as described by S1Cu, copper in the larger cages with S2 and S3 as a site where physisorbed ammonia can attach. Further, ammonia was also adsorbed on the Brönsted sites, represented by S1Brön in the model, but in order not to further complicate the model, small amounts of ammonia storage on Brönsted sites were also lumped into S2. In the model, SO2 was adsorbed on the sites containing copper, which are S1Cu and S2. It should be noted that S1Cu and S2 represents hydrated copper sites. Interestingly, we observed experimentally that ammonia storage was larger after sulfur poisoning compared to before, which is why we added ammonia storage and desorption to the S1Cu–SO2 and S2–SO2 sites. However, ammonia was already adsorbing on the copper site; thus, these steps did not result in increased storage. Consequently, reaction steps were added where additional ammonia was adsorbed to form S1Cu–SO2–(NH3)2 and S2–SO2–(NH3)2 species, which could be interpreted as precursors to ammonium sulfates. Another aspect that must be addressed in the model is the observation in the literature that SO2 is more easily desorbed in SO2+NH3+O2 TPD than SO2+O2 TPD. Reversible reaction steps were therefore added whereby the S1Cu–SO2–NH3 and S2–SO2-NH3 species were decomposed to form SO2. A final reaction step was incorporated into the model to describe the SCR reaction with ammonia attached to the sulfur sites. The developed model could well describe the sulfur poisoning and gradual regeneration during repeated SCR experiments. In addition, the model well described the NH3 TPD and NH3 oxidation before and after sulfur poisoning.

The behaviors of ultra-low-gold-loaded catalysts (Au/CeO2) for CO oxidation in the presence of water on the catalysts

The catalytic behavior of ultra-low-gold-loaded Au/CeO2 during CO oxidation was studied using HRTEM, TGA, in-situ FTIR, CO–TPD, O2–TPD, and O2–TPO. Herein, water, which facilitates CO oxidation, is present on the catalyst rather than obtained from the reactant gas. The experimental results show that the presence of water on the catalyst enhances the adsorption and activation of O2 to produce Oact on the catalyst surface, resulting in excellent catalytic activity. Different reaction pathways for CO oxidation over Au/CeO2 may be present; however, the dominant pathway is influenced by the species on the catalyst surface.

Sodium-promoted Pd/TiO2 for catalytic oxidation of formaldehyde at ambient temperature.

Catalytic oxidation of formaldehyde (HCHO) to CO2 at ambient conditions is of great interest for indoor HCHO purification. Here, we report that sodium-doped Pd/TiO2 is a highly effective catalyst for the catalytic oxidation of HCHO at room temperature. It was observed that Na doping has a dramatic promotion effect on the Pd/TiO2 catalyst and that nearly 100% HCHO conversion could be achieved over the 2Na-Pd/TiO2 catalyst at a GHSV of 95000 h(-1) and HCHO inlet concentration of 140 ppm at 25 °C. The mechanism of the Na-promotion effect was investigated by using Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), CO chemisorption, Temperature-programmed reduction by H2 (H2-TPR), X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption of O2 (O2-TPD) methods. The results showed that Na species addition can induce and further stabilize a negatively charged and well-dispersed Pd species, which then facilitates the activation of H2O and chemisorbed oxygen, therefore resulting in the high performance of the 2Na-Pd/TiO2 catalyst for the ambient HCHO destruction.

Development of Ternary Cathodes Using MyCe1–x–yMnxO2–δ (M = La, Gd) as Catalysts for Oxygen Reduction Reactions

AbstractMyCe1–x–yMnxO2–δ (M = La, Gd) oxides have been investigated as oxygen reduction catalysts for LSM–YSZ based ternary cathodes. MyCe1–x–yMnxO2–δ samples are characterized by X‐ray diffraction (XRD), temperature programmed reduction of H2 (H2‐TPR), and temperature programmed desorption of O2 (O2‐TPD). The results show that the incorporation of M (M = La, Gd) ions increases the solution limit of Mn in the solid solutions, which increases the amount of oxygen vacancies and promotes oxygen adsorption and dissociation processes. The ternary cathodes show much higher electrochemical performance than LSM–YSZ binary cathode, and greatly accelerate oxygen dissociative adsorption and diffusion of oxygen species. The MyCe1–x–yMnxO2–δ catalysts exhibit greatly high activity for oxygen reduction at intermediate temperature. The ternary cathodes have high stability and high resistance to CO2 at 600 °C.