Lattice Oxygen Species Research Articles

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.

Core-shell CoCuOx@MOx (M[dbnd]Nb, Ti and Ce) catalysts with outstanding durability and resistance to H2O for the catalytic combustion of o-dichlorobenzene

Configuring Co-based catalysts with excellent activity, durability, anti-H2O capability and superior chlorine resistance is an effective strategy for catalytic combustion of CVOCs. In this work, we elaborated a CoCuOx catalysts with the same core but different shell. The CoCuOx dodecahedron surface was successfully coated with shells of Nb2O5, TiO2, and CeO2 using a range of conventional synthesis methods. The prepared core-shell catalysts (CoCuOx@TiO2 and CoCuOx@Nb2O5) were found to generate plentiful acid sites and abundant lattice oxygen species, indicating a strong interaction between the core and shell layers that resulted in a significant enhancement of catalytic activity. Additionally, by-products generation was successfully controlled by acid sites and lattice oxygen species. More importantly, the core-shell structure design significantly improved the thermal stability and anti-H2O capability of the catalysts. Furthermore, the possible formation pathways and reaction mechanisms were proposed based on in-situ FTIR and selectivity analysis.

Understanding the mechanisms of catalytic enhancement of La-Sr-Co-Fe-O perovskite-type oxides for efficient toluene combustion

The merits of ABO3-type perovskite oxides as catalysts for volatile organic compounds (VOCs) combustion are that the redox capability of transition metal elements in their lattice structure can be well tailored through a facile doping strategy. In particular, La-Sr-Co-Fe-O perovskite-type oxides possess excellent tunable physicochemical properties, making them an ideal platform for promising prospects in VOCs combustion. This work synthesized a series of La1-xSrxCo1-yFeyO3 (x = 0, 0.3, 0.5, 0.8; y = 0, 0.2, 0.5) perovskites and analyzed their reaction kinetics on toluene combustion. Among all the catalysts, La0.5Sr0.5Co0.8Fe0.2O3-δ (LSCF) showed a remarkable catalytic activity towards the toluene oxidation with T90 of 270 °C at a weight hourly space velocity (WSHV) of 30000 mL·g−1·h−1 and apparent activation energy (Ea) of 44.76 kJ·mol−1 and obtained the superior stability. Based on the characterizations and analysis of in-situ DRIFTS, the outstanding catalytic activity of LSCF perovskite is mainly induced by the improvement of the redox ability, the enriched generation of oxygen vacancies, and the activation of the lattice oxygen species. The catalytic mechanism of toluene conversion over the LSCF perovskite was revealed to be consistent with Mars-van Krevelen (MVK) models. The knowledge obtained in this study provides helpful guidance for designing efficient heterogeneous catalysts of La-Sr-Co-Fe-O perovskite-type oxides toward efficient catalytic combustion for VOCs elimination.

Facile conversion of glycerol to 1,3-dihydroxyacetone by using mesoporous CuO–SnO2 composite oxide supported Au catalysts

Selective catalytic oxidation of polyols, e.g., the selective catalytic oxidation of the secondary –OH bond in glycerol, remains a considerable challenge. In this study, a series of mesoporous CuO–SnO2 composite oxides were prepared by a hard-template method and used to support Au catalysts for the selective oxidation of glycerol to 1,3-dihydroxyacetone (DHA) under base-free conditions. Catalysts with different Cu:Sn molar ratios gave different catalytic performances. A high conversion of glycerol (100%) and selectivity for DHA (94.7%) were obtained in 2 h at 80 °C and PO2 = 1 MPa over the Au/CuO–SnO2-3:1 catalyst. Further investigation indicated that the high catalytic activity of Au/CuO–SnO2-3:1 is related to the small size and high dispersion of Au nanoparticles (NPs), the interactions between the Au NPs and the support, the synergistic effect between CuO and SnO2, and the amount of surface lattice oxygen species. Various reaction parameters, namely the glycerol:Au molar ratio, the reaction temperature, the initial O2 pressure, the reaction time, and the support calcination temperature were studied. Although the conversion rate by the catalyst decreased after four cycles, the selectivity remained above 86%. Density functional theory calculations showed that the synergy between CuO and SnO2 improves the catalytic activity in glycerol oxidation to DHA. The results show that mesoporous composite oxide supports have a wide range of potential applications in the selective oxidation of glycerol to other high-value-added products.

Fabricating PdCe/OMS-2 catalysts with boosted low-temperature activity for toluene deep degradation

Porous cryptomelane-type octahedral molecular sieve (OMS-2) with mixed Mn valence and abundant lattice oxygen species has attracted much attention in volatile organic compounds (VOC) catalytic elimination. However, complete conversion of arene over OMS-2 catalysts at relatively low temperature is still a challenge due to its limited crystal structure and inferior stability. Here, a series of PdCe/OMS-2 catalysts with different Pd/Ce molar ratios was fabricated by a facile impregnation method and the physicochemical properties of which were extensively characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), Brunauer–Emmett–Teller (BET) method, X-ray fluorescence (XRF), X-ray photoelectron spectroscopy (XPS), temperature programmed reduction of H2 (H2-TPR), Raman, In situ diffused reflectance infrared Fourier transform spectra (DRIFTS), and density functional theory (DFT) calculations. Results show that the total conversion of toluene can be achieved at 207 °C over PdCe2 with apparent activation energy as low as 62.6 kJ/mol. The strong synergistic effect between Pd and Ce remarkably boosts the catalytic activity of OMS-2, attributed to the abundant Mn3+–O bands and active surface oxygen species. DFT results reveal that oxygen vacancy can be formed over PdCe2 much easily than that of Pd/OMS-2 and Ce/OMS-2 with the oxygen vacancy formation energy of 2.42, 2.83 and 2.68 eV, respectively. Simply increasing the Pd content cannot promote the catalytic activity although PdO is a critical active center in toluene oxidation. Oxygen vacancy attributed to the integrative effect of Pd, Ce and Mn species plays a prominent role over prepared catalysts in toluene activation process. The findings reported in this work showed new insights into the designing of highly efficient OMS-2 catalysts for VOC deep oxidation by tuning oxygen vacancy concentration.

On the Role of Interfacial Water Dynamics for Electrochemical Stability of RuO2 and IrO2

AbstractBased on the coincident onsets of oxygen evolution reaction (OER) and metal dissolution for many metal‐oxide catalysts it was suggested that OER triggers dissolution. It is believed that both processes share common intermediates, yet exact mechanistic details remain largely unknown. For example, there is still no clear understanding as to why rutile IrO2 exhibits such an exquisite stability among water‐splitting electrocatalysts. Here, we employ density functional theory calculations to analyze interactions between water and the (110) surface of rutile RuO2 and IrO2 as a response to oxygen evolution involving lattice oxygen species. We observe that these oxides display qualitatively different interfacial behavior that should have important implications for their electrochemical stability. Specifically, it is found that IrO2(110) becomes further stabilized under OER conditions due to the tendency to form highly stable low oxidation state Ir(III) species. In contrast, Ru species at RuO2(110) are prone to facile reoxidation by solution water. This should facilitate the formation of high Ru oxidation state intermediates (>IV) accelerating surface restructuring and metal dissolution.

Design order macro-meso porous structure monolithic Co3O4/SiO2 catalyst via a novel 3D printing for the highly efficient catalytic combustion of toluene

The shortcomings of Co-based powder catalysts such as amorphous susceptibility to loss and high influence by pressure drop have become the key factors affecting their catalytic activity. In this paper, two methods were proposed to prepare novel monolithic Co3O4/SiO2 catalysts by 3D direct ink writing (DIW) technology: (1) one-step method of printing the active component with supports, (2) two-step method of printing the support first, and then loading the active components. The results showed that the monolithic catalyst prepared by the two-step method possessed more abundant Co3+ and lattice oxygen (Olatt) species than the one-step method, which jointly promoted the catalytic conversion of toluene. However, the catalyst printed by the one-step method had a stronger interaction between the active component and the support, showing better thermal stability and water resistance. In addition, the SiO2 support (the calcined product after SiO2 ink printing) enhances the activity, stability, compression resistance, while the N–SiO2 support (the calcined product after SiO2 precursor ink printing) can effectively prevent blockage of the pore structure by the binder and increase physical properties such as pore volume and specific surface area of Co3O4/SiO2 catalyst.

Generation of abundant oxygen vacancies in Fe doped δ-MnO2 by a facile interfacial synthesis strategy for highly efficient catalysis of VOCs oxidation

A series of homogenous Fe-Mn oxides with superior catalytic oxidation activity was developed via interfacial redox-precipitation method for eliminating VOCs from industrial waste gas. Among them, Fe1Mn5 oxide achieved the optimum catalytic performance for toluene oxidation with a T90 of 209 ℃. In addition, the catalyst demonstrated superior stability for long-time operation and great water resistance. By combining an array of analytical techniques with DFT calculations, the results revealed that Fe doping and interfacial redox-precipitation method synergistically resulted in high concentration of oxygen vacancy defect over Fe1Mn5 oxide, which improved lattice oxygen mobility and oxygen species activity, thus enhancing its low temperature reducibility. Meanwhile, in situ DRIFTS analysis revealed that both the adsorbed oxygen species and lattice oxygen with improved mobility could interact with adsorbed toluene, thus facilitating rapid dehydrogenation of methyl and demethylation of toluene and promoting the breakage of CC bond in the aromatic ring.

Effects of gas phase ion irradiation and vacuum annealing on the visible light photocatalytic properties of WO3

Oxygen vacancies were introduced into tungsten oxide (WO3) rods by irradiation with H2+, He+ or Ar+ ions and/or vacuum annealing. The surface chemical bonding states and visible light photocatalytic properties of these materials were subsequently assessed. Although the irradiated surfaces were contaminated with carbon and silicon species during ion irradiation, vacuum annealing at 500 °C decreased the extent of carbon contamination and increased the concentration of lattice oxygen species related to a surface WO3-x phase. The irradiated WO3-x rods exhibited low photocatalytic efficiencies during the degradation of rhodamine 6G compared with pristine WO3 rods, possibly due to the existence of contamination and oxygen vacancies. Vacuum-annealed WO3-x rods having a green coloration exhibited high photocatalytic efficiency as a result of enhanced visible light absorption and the low concentration of both surface contamination and vacancies.

Lattice distortion in Mn3O4/SmOx nanocomposite catalyst for enhanced carbon monoxide oxidation

Activation of lattice oxygen species in oxides is an important research topic for improving catalytic oxidation activity. Herein, we tuned the lattice distortion of Mn3O4 spinel oxide via interfacing with amorphous samarium oxides, which would facilitate the activation of lattice oxygen. The crystalline Mn3O4 dispersed uniformly on the amorphous SmOx with a large surface area, which builds abundant interfaces along with many active sites. The lattice distortion degree can be conveniently regulated by changing Sm amount and calcination temperature. The Sm0.3Mn (Sm/Mn molar ratio is 0.3, the calcination temperature is 400 °C) exhibited the optimal intrinsic activity for CO oxidation. Compared with the pristine Mn3O4, its TOFMn increased by 60%, and the reaction rate in wet conditions (10 vol% H2O) was fourfold faster, superior to most reported MnOx oxide catalysts. Integrating with the various characterizations, the improvement of the intrinsic activity fundamentally originates from the rich reactive oxygen species in the lattice-distorted Mn3O4. What’s more, the Sm0.3Mn exhibited better water resistance and SO2 tolerance. Electron characteristics and characterization results revealed that the full filling of the outer shell orbits of samarium protected the active sites at the interfaces from interacting with water. The weakened capacity for SO2 oxidation decelerated the accumulation of sulfate species. This work provides new insights into the rational modulation of reactive oxygen species and developed a practical catalyst with efficient catalytic CO oxidation activity, and excellent water resistance and SO2 tolerance.

The abundant oxygen vacancies of the Co–Ce mixed oxides towards catalytic combustion toluene

A series of catalysts (Co3O4/Beta-60, CeO2/Beta-60, CoCeOx/Beta-60) were prepared by constant volume impregnation method and were applied to the catalytic oxidation toluene. The characterization results showed that some Co ions were embedded into the lattice of CeO2 to form CoCeO2-δ solid solution that promoted the formation of a large number of oxygen vacancies and generation of active oxygen species for the deep oxidation of toluene. The mobility of active oxygen species and reducibility for CoCeOx/Beta-60 were both improved. Therefore, CoCeOx/Beta-60 showed the superior catalytic performance, the conversion of toluene was 90% when the temperature was 307 °C. The combination between the zeolite carrier and the active components endowed the supported catalyst with excellent stability. Additionally, the in situ DRIFTS results displayed that the oxidation of toluene over CoCeOx/Beta-60 followed the MvK mechanism and L-H mechanism. Adsorbed toluene could be oxidized by not only active adsorbed oxygen on oxygen vacancies but also the lattice oxygen species. However, gaseous oxygen was paramount importance for the total oxidation of toluene for the reason that the gaseous oxygen could be activated through the oxygen vacancies generated to fill the active oxygen species after the depletion of active adsorbed oxygen and lattice oxygen. The study systematically reviewed the data for the catalytic combustion of toluene, aiming to provide new avenues for the preparation and application of catalysts with excellent catalytic activity.

Preparation of a transition metal-supported TiO2 catalyst and the catalytic oxidative degradation of toluene

The synthesis of supported transition metal oxides with satisfactory low-temperature catalytic performance and application potential is still a challenge for the complete degradation of VOCs. Ni-Cu-loaded TiO2 catalysts were prepared by an impregnation method. The lattice defect and oxygen vacancy concentrations of the prepared materials could be tuned by controlling the Ni/Cu molar ratio and the mass proportion of the TiO2 support. 5Ni-Cu/TiO2 exhibited the best catalytic activity and showed superior catalytic stability during complete toluene oxidation. The obtained catalysts were fully characterized by XRD, FT-IR, TEM, N2 adsorption analysis, XPS, H2-TPR, O2-TPD, TPD analysis, and XPS. The 5Ni-Cu/TiO2 catalyst had improved pore sizes and specific surface area, had more oxygen vacancies on its surface, had increased concentrations of adsorbed and lattice oxygen species, and had good redox properties; these characteristics were favorable for low-temperature catalytic performance and catalytic stability. Cyclic transformations of metal valence states between Cu+ and Cu and between Ni and Ni2+ were observed in the catalytic system. A potential catalytic reaction process based on the M-vK mechanism was proposed. This work serves as a reference for the application of supported transition metal catalysts for the degradation of VOCs.

Boosting catalytic stability for VOCs removal by constructing PtCu alloy structure with superior oxygen activation behavior

The elimination of volatile organic compounds (VOCs) emitted from the process of industry production is of great significance to improve the atmospheric environment. Herein the catalytic oxidation of the toluene and iso-hexane mixture, as the typical components from furniture paint industry, and the enhancement in the catalytic stability for toluene oxidation were investigated in detail. The formation rate of active oxygen species was very important for the development of the catalyst with high catalytic stability. Compared with the Pt/M catalyst, the Pt-Cu/M catalyst owned stronger ability of VOCs adsorption and gaseous oxygen activation by introducing additional sites for activating O2. The Langmuir–Hinshelwood (adsorbed oxygen) and Mars–van Krevelen (lattice oxygen) mechanism existed in toluene oxidation over the present Pt/M and Pt-Cu/M catalysts, respectively. The change in the involved active oxygen species during toluene oxidation was resulted from the Pt-Cu alloy structure. In addition to the adsorption of O2, a part of active lattice oxygen species can also be replenished by the migration of bulk lattice oxygen over Pt-Cu/M. With a rise in the reaction temperature, weakly adsorbed iso-hexane could be timely reacted with the more active lattice oxygen species to keep the catalytic stability over the Pt/M and Pt-Cu/M catalysts. Generally, we not only prepared a promising material for the catalytic removal of VOCs from the furniture paint industry, but also provided a new strategy for the generation of active oxygen species, making the catalyst exhibit high catalytic oxidation stability.

Active sites and deactivation of room temperature CO oxidation on Co3O4 catalysts: combined experimental and computational investigations

Co3O4 is a well-known low temperature CO oxidation catalyst, but it often suffers from deactivation. We have thus examined room temperature (RT) CO oxidation on Co3O4 catalysts by operando DSC, TGA and MS measurements, as well as by pulsed chemisorption to differentiate the contributions of CO adsorption and reaction to CO2. Catalysts pretreated in oxygen at 400 °C are most active, with the initial interaction of CO and Co3O4 being strongly exothermic and with maximum amounts of CO adsorption and reaction. The initially high RT activity then levels-off, suggesting that the oxidative pretreatment creates an oxygen-rich reactive Co3O4 surface that upon reaction onset loses its most active oxygen. This specific active oxygen is not reestablished by gas phase O2 during the RT reaction. When the reaction temperature is increased to 150 °C, full conversion can be maintained for 100 h, and even after cooling back to RT. Apparently, deactivating species are avoided this way, whereas exposing the active surface even briefly to pure CO leads to immediate deactivation. Computational modeling using DFT helped to identify the CO adsorption sites, determine oxygen vacancy formation energies and the origin of deactivation. A new species of CO bonded to oxygen vacancies at RT was identified, which may block a vacancy site from further reaction unless CO is removed at higher temperature. The interaction between oxygen vacancies was found to be small, so that in the active state several lattice oxygen species are available for reaction in parallel.

Defect engineering over Co3O4 catalyst for surface lattice oxygen activation and boosted propane total oxidation

Developing efficient and stable catalyst is crucial for the catalytic removal of volatile organic compounds (VOCs). Herein, we report an effective and versatile surface defect engineering for regulation of surface lattice oxygen species in Co3O4 catalyst by alkaline-earth metal doping-etching strategy. The as-synthesized Ca-Co3O4-Ac exhibited remarkable catalytic activity and stability in propane oxidation, with high propane oxidation rate (5.65 × 10−7 mol g−1 s−1) and turnover frequency (TOF, 2.12 × 10−3 s−1) at 210 °C. Simultaneously, the doping-etching strategy could increase the specific surface area, low-temperature reducibility, and oxygen mobility of Co3O4 catalyst. In addition, in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS), density function theory (DFT) calculation, and propane temperature-programmed desorption/surface reaction (C3H8-TPD/TPSR) further revealed that active lattice oxygen species induced by doping-etching strategy promoted the propane activation on the catalyst surface. This work offers a deeper understanding of the reactive oxygen species and provides a feasible strategy for the design of efficient catalysts for practical VOCs removal.

Insight into the selective oxidation of isobutene to methacrolein over Ce-accelerated Mo-Bi-Fe-Co-K-O catalyst

Understanding the mechanism of multi-component metal oxide catalyst for the selective oxidation of isobutene to methacrolein has long been challenging for its complexity. Herein, the key role of Ce on the Mo-Bi-Fe-Co-K-O catalysts for accelerating the selectivity of methacrolein was revealed. It was suggested that the Ce addition could replace the Bi3+ and then generate defects which changed the transformation of electron and the migration mobility of ions: Ⅰ. the production of Ce3+/Ce4+ and Co2+/Co3+ redox couples regulated the catalytic redox ability; and Ⅱ. the interaction effect between Ce and Co enhanced the storage capacity and mobility of oxygen which could benefit the adsorption and activation ability for isobutene molecules. Interestingly, it was found that adding appropriate amount of Ce adjusted the molar ratio of the catalytically active lattice oxygen and defect oxygen species. Therefore, proper amount of Ce addition to the catalyst significantly accelerated the methacrolein selectivity from 47.9% to 70.6%.

Mn-doped Ca2Fe2O5 oxygen carrier for chemical looping gasification of biogas residue: Effect of oxygen uncoupling

Anaerobic digestion is an important approach to treat and utilize kitchen waste, while kitchen waste derived biogas residue (BR) disposal remains a serious problem in this process. This study investigated the feasibility of chemical looping gasification (CLG) as an efficient way to treat and generate syngas from BR. Besides, Mn-doped Ca2Fe2O5 (MCF) as a novel oxygen carrier with mild oxygen uncoupling capability was developed, and its performance against traditional Ca2Fe2O5 (CF) oxygen carrier was compared. Results indicated that, significant oxygen release capability was observed on the prepared MCF oxygen carrier. In the gasification tests, CLG with MCF at 800 ℃ showed optimal total gas yield, carbon conversion, and cold gas efficiency, which increased 0.08 Nm3/kg, 17.22%, and 13.37% compared to CF, respectively. According to the XPS, H2-TPR and XRD characterization results, the optimal performance of MCF could be attributed to the oxygen uncoupling characteristic brought by Mn addition. The formation of the oxygen uncoupling capability of MCF could be explained by three reasons: (1) Mn in MCF mainly existed in form of Mn3+ and Mn4+, which resulted in the extremely strong oxidability at a temperature as low as 250 ℃. (2) The higher Fe3+/Fe2+ ratio of 1.55 in MCF than CF caused by Mn addition led to greater oxidability of Fe ions. (3) MCF had a higher lattice oxygen amount than CF at about 3.86%, and the lattice oxygen in its crystal structure had been transformed into active lattice oxygen species, which were between lattice oxygen (O2–) and atomic adsorbed oxygen (O−). As a result, this paper investigated the potential of CLG to treat and utilized BR, and the superiority of CLG with oxygen uncoupling (CLGOU) on MCF was highlighted. It’s hoped that this study could provide a fundamental knowledge on CLG and CLGOU of BR, and benefit to better downstream process design of anaerobic digestion industry.

δ-MnO2 decorated layered double oxides in-situ grown on nickel foam towards electrothermal catalysis of n-heptane

Energy-saving and efficient monolithic catalysts are hotspots of catalytic purification of industrial gaseous pollutants. Here, we have developed an electrothermal catalytic mode, in which the ignition temperature required for the reaction is provided by Joule heat generated when the current flows through the catalyst. In this paper, Mn/NiAl/NF, Mn/NiFe/NF and Mn/NF metal-based monolithic catalysts were prepared using nickel foam (NF) as the carrier for thermal and electrothermal catalysis of n-heptane. The results indicated that Mn-based monolithic catalysts exhibit high activity in thermal and electrothermal catalysis. Mn/NiFe/NF achieve conversion of n-heptane more than 99% in electrothermal catalysis under a direct-current (DC) power of 6 W, and energy-saving is 54% compared with thermal catalysis. In addition, the results indicated that the introduction of NiAl (or NiFe) greatly enhanced the catalytic activity of Mn/NF, which attributed to the higher specific surface area, Mn3+/Mn4+, Ni3+/Ni2+, adsorbed oxygen species (Oads)/lattice oxygen species (Olatt), redox performance of the catalyst. Electrothermal catalytic activity was significantly higher than thermal catalytic activity before complete conversion, which may be related to electronic effects. Besides, Mn/NiFe/NF has good cyclic and long-term stability in electrothermal catalysis. This paper provided a theoretical basis for applying electrothermal catalysis in the field of VOCs elimination.

Evolution behavior and active oxygen quantification of reaction mechanism on cube Cu2O for CO self-sustained catalytic combustion and chemical-looping combustion

Catalytic combustion (CC) and chemical looping combustion (CLC) are promising technologies for energy saving and emission reduction of CO2 in treatment of steelmaking off-gas. This work firstly reports and compares the evolution behavior and quantitative reaction mechanisms of cube Cu2O model catalyst for CC and CLC reactions. The Cu2O-CC exhibited the higher activity and stability than Cu2O-CLC. The typical characterization results suggested that the only surface unstable Cu2O was oxidized to CuO, and the excellent synergistic effect of metal-oxide interface (100) between Cu+/Cu2+ and active lattice oxygen species for Cu2O-CC reaction. But, for CLC reaction, Cu2O structure was collapsed, which caused the agglomeration of CuOx species and gradual decrease of reaction stability. Three different active oxygen species (surface cycle lattice oxygen, bulk lattice oxygen, and adsorbed oxygen) and the detailed reaction pathways were proposed by the in situ IR spectroscopy, isotopic (18O2) transient exchange experiments and DFT simulation. The intrinsic activity of surface cycle lattice oxygen was higher in terms of TOF (13.5 × 10−3 s−1) and facile formation of C16O18O on the cubic interface of Cu2O-CC through adsorbed CO during CC process. The contribution degrees of Mars-van-Krevelen (M-K) and Langmuir–Hinshelwood (L-H) mechanisms for CC and CLC reactions were 76.6% and 23.4% for CC, and 89.7% and 10.3% for CLC on Cu2O catalyst, respectively.

Introduced oxygen vacancies in cadmium ferrite anode materials via Zn2+ incorporation for high performance lithium-ion batteries

Cationic substitution strategy was recognized as an effective approach to create a defective structure and increase the oxygen vacancies in the crystal structure for improving the electrochemical performance of Li-ion batteries components. In this study, ZnxCd1-xFe2O4 nanoparticles were synthesized via a facile inexpensive process at low temperature. The collected XRD data confirmed the formation of cubic structure with Fd3m space group. HR-TEM investigations showed the size enlargement of spherical-like crystals with increasing the concentration of doping Zn2+ ion. FESEM and BET measurements indicated the conversion of micropores in pure CdFe2O4 into mesopores and macropores in Zn-doped CdFe2O4 samples. XPS results of O1s spectra elucidated that Zn-doped CdFe2O4 samples have higher conductivity due to the created lattice defects and oxygen species. Zn-doped CdFe2O4 anodes exhibit great improvement in their initial discharge capacities ∼1618 and 1880 mAhg−1 upon substitution of Cd with 5% and 10% Zn, respectively. Furthermore, 10% Zn-doped CdFe2O4 anode displayed the highest Li-ions diffusion coefficient and exchange current density due to the enhanced Li+ ions mobility. The increase in zinc content (0.0–0.1) led to a decrease in the DC activation energy from 0.11 to 0.09 eV.