Co3O4 Lattice Research Articles

Preparation of Mn-Doped Co3O4 Catalysts by an Eco-Friendly Solid-State Method for Catalytic Combustion of Low-Concentration Methane

Coalbed methane is a significant source of methane in the atmosphere, which is a potent greenhouse gas with a considerable contribution to global warming, thus it is of great importance to remove methane in coalbed gas before the emission. Exploring the economical non-noble metal catalysts for catalytic methane combustion (CMC) has been a wide concern to mitigate the greenhouse effect caused by the emitted low-concentration methane. Herein, a series of Mn-doped Co3O4 catalysts have been synthesized by the environmentally friendly solid-state method. As a result, the Mn0.05Co1 catalyst performed the best CMC activity (T90 = 370 °C) and good moisture tolerance (3 vol% steam). The introduction of an appropriate amount of manganese conduced Co3O4 lattice distortion and transformed Co3+ to Co2+, thus producing more active oxygen vacancies. Mn0.05Co1 exhibited better reducibility and oxygen mobility. In situ studies revealed that methane was adsorbed and oxidized much easier on Mn0.05Co1, which is the crucial reason for its superior catalytic performance.

Ir-doped Co3O4 as efficient electrocatalyst for acidic oxygen evolution reaction

Oxygen evolution reaction (OER) is an important bottleneck for large-scale acidic water splitting applications due to its sluggish reaction kinetics. Therefore, the development of highly active, stable, and inexpensive electrocatalysts for OER remains a challenge. Herein, we develop the iridium doped Co3O4 (Ir–Co3O4) with low Ir content of 2.88 wt% for efficient acidic OER. Considering systemic characterizations, it is probably concluded that Ir can be uniformly doped into the lattice of Co3O4 and induce a certain distortion. The electrochemical results reveal that Ir–Co3O4 nanoparticles demonstrate significantly enhanced electrocatalytic OER activity and stability in 0.5 M H2SO4 solution compared with pure Co3O4, in which the overpotential at the current density of 10 mA cm−2 decreases from 382 mV to 225 mV and the value of Tafel slope decreases from 101.7 mV dec−1 to 64.1 mV dec−1. Besides, Ir–Co3O4 exhibits excellent electrocatalytic durability for continuous 130 h's test without any activity attenuation. Moreover, this work provides a kind of high-performance acidic OER electrocatalyst for the development of hydrogen energy.

Enhanced and rapid photocatalytic degradation of toxic dyes by cobalt oxide and modified cobalt oxide under solar light irradiation

A solar light driven photo degradation approach for methylene blue (MB, model molecule of the thiazine dyes class) and malachite green (MG, model molecule of the triphenylmethane category) abatement by Co3O4 and Cr-Co3O4 spinel nanoparticles is reported. The effect of chromium load (5, 10 and 15%) in Co3O4 particles, synthesized by a simple co-precipitation process, was properly studied. The structural and morphological characteristics, chemical composition and optical properties of the materials were investigated by X-ray diffraction (XRD), Transmission Electron Microscopy(TEM), Field Emission Scanning Electron Microscopy – Energy Dispersive Spectroscopy (FE-SEM-EDS), FT-IR spectroscopy, UV–Vis diffuse reflectance spectroscopy (DRS),photoluminescence (PL) and BET surface area analysis. It was observed that properly tuning the initial pH, the initial dye concentration, the agitation time, and the photocatalyst dose, (10)Cr-Co3O4 exhibited an enhanced photocatalytic activity compared to that of pristine Co3O4, demonstrating the positive role of Cr doping In fact, the PL investigation showed that Cr doping in the Co3O4 lattice greatly increase the separation of electron-hole (e−/h+) pairs, whereas the UV DRS spectra and Tauc plot revealed a decrease in the band gap energy for Cr-Co3O4,. The investigations demonstrated that the MB dye degradation increases from 88% to 96% at pH = 11 after doping of Co3Oby 10% of Cr. Similarly, the Cr doping allowed to enhance the MG dye degradation from 85% to 92% at pH = 9. The photo degradation kinetics of both MB and MG dyes by Cr-Co3O4 and Co3O4 NPs were of pseudo-first-order mode. The active species involved in the photocatalytic process were properly identified using various scavengers by trapping holes and radicals. Finally, the photocatalysts showed good stability during recycling maintaining high performances after 5-time usage. .

Tuning the sensing selectivity of mesoporous hierarchical Ti-doped Co3O4 to toluene and xylene via controlling the oxygen defects

Vast efforts have been made to develop high-performance gas sensing materials for the detection of harmful volatile organic compounds (VOCs) like toluene and xylene. However, it is challenging to selectively detect toluene and xylene simultaneously. Herein, the hierarchical Ti-doped cobalt layered hydroxides miscrospheres were synthesized first and sintered at high temperature consequently to prepare hierarchical Ti-doped Co3O4 miscrospheres. The incorporation of Ti into the lattice of Co3O4 decreased the crystal sizes and crystallinity, resulting in higher specific surface area and more oxygen defects. Interestingly, the 3 at.% Ti-doped Co3O4 miscrospheres sintered at 450 °C exhibited the highest response of 64.9 to 50 ppm of xylene at 210 °C, while the 1 at.% Ti-doped Co3O4 miscrospheres calcined at 500 °C displayed the highest response of 57.2 to 50 ppm of toluene at 240 °C, which were about 11.8 and 7.8 times higher in comparison with pristine Co3O4. The different selectivity of Ti-doped Co3O4 to toluene and xylene arises from the different amounts of oxygen vacancies and defect oxygen ions. The obtained Ti-doped Co3O4 microspheres also showed the merits of good selectivity, repeatability and long-term stability, indicating the promising applications of Ti-doped Co3O4 miscrospheres in the detection of toluene and xylene.

Strong Electronic Orbit Coupling between Cobalt and Single-Atom Praseodymium for Boosted Nitrous Oxide Decomposition on Co3O4 Catalyst.

Nitrous oxide (N2O) has gained increasing attention as an important noncarbon dioxide greenhouse gas, and catalytic decomposition is an effective method of reducing its emissions. Here, Co3O4 was synthesized by the sol-gel method and single-atom Pr was confined in its matrix to improve the N2O decomposition performance. It was observed that the reaction rate varied in a volcano-like pattern with the amount of doped Pr. A N2O decomposition reaction rate 5-7.5 times greater than that of pure Co3O4 is achieved on the catalyst with a Pr/Co molar ratio of 0.06:1, and further Pr doping reduced the activity due to PrOx cluster formation. Combined with X-ray photoelectron spectroscopy, X-ray absorption fine structure, density functional theory and in situ near-ambient pressure X-ray photoelectron spectroscopy, it was demonstrated that the single-atom doped Pr in Co3O4 generates the "Pr 4f-O 2p-Co 3d" network, which redistributes the electrons in Co3O4 lattice and increases the t2g electrons at the tetracoordinated Co2+ sites. This coupling between the Pr 4f orbit and Co2+ 3d orbit triggers the formation of a 4f-3d electronic ladder, which accelerates the electron transfer from Co2+ to the 3π* antibonding orbital of N2O, thus contributing to the N-O bond cleavage. Moreover, the energy barrier for each elementary reaction in the decomposition process of N2O is reduced, especially for O2 desorption. Our work provides a theoretical grounding and reference for designing atomically modified catalysts for N2O decomposition.

Activity performance and kinetics for glycerol carbonylation with urea over Zn‐Co mixed metal oxide catalyst

AbstractEfficient carbonylation of glycerol using urea with Zn‐Co mixed metal oxide (MMO) catalyst has been achieved. Various methods of catalyst preparation were explored for glycerol carbonate (GC) synthesis. The optimized method of catalyst preparation was found to be co‐precipitation (CP) with a Zn:Co ratio of 70:30, achieving 81% glycerol conversion with 97% GC selectivity. X‐ray diffraction (XRD) studies revealed the formation of ZnO, Co3 O4, and spinel ZnCo2O4 phases. Thermal treatment given to the catalyst allows insertion of Zn cations into Co3O4 lattice forming ZnCo2O4 phase which was also evidenced in X‐ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Herein, for the first time, reaction kinetics was studied to propose the rate equation, based on which a plausible reaction pathway is proposed involving two‐site adsorption of glycerol (basic site) and urea (acidic site), which undergo carbonylation followed by cyclization into GC. A recycle study and hot filtration test have proven the reusability of the catalyst.

Co2.8Mg0.2O4 as a promising thermochemical energy storage material with lower reduction onset temperature and higher energy density

Co-based oxides have been considered as one of the most promising materials for thermochemical energy storage (TCES) systems, however, the high operation temperature limits their applications. Specially, when Co3O4-based materials are used in concentrated solar power (CSP) system, a large mirror field area is required to meet the high endothermic temperature, which significantly increases the cost of a CSP system. In addition, the high cost of Co-based materials also limits its application. Improving the energy density can effectively reduce the use of the materials. Thus, in this work, to reduce the reduction onset temperature and increase the energy density of Co-based oxides, the TCES performance of Co3-xMgxO4 oxides is investigated. Co2.8Mg0.2O4 shows the best TCES performance. The reduction onset temperature of Co2.8Mg0.2O4 is ∼775.6 °C, which is 133.7 °C lower than that of the pure Co3O4 (∼909.3 °C). Mg-decoration can also improve the energy density of Co3O4 by 8.02 %. Furthermore, the in situ XRD spectra of the oxides indicate that precipitation of MgO from the Co3O4 lattice during the reduction reaction result in a metastable structure of the oxide, which is conducive to its reduction reaction. Density functional theory calculations indicate that Co2.8Mg0.2O4 possessed a higher defect formation energy and shorter chemical bonds than the pure cobalt oxide, which result in its lower reduction onset temperature and higher energy density. The cost-benefit analysis results showed that Mg-decoration could significantly reduce the area of mirror field and the use of energy storage material for a CSP system.

Gradually Fe-Doped Co3O4 Nanoparticles in 2-Propanol and Water Oxidation Catalysis with Single Laser Pulse Resolution

Controlling the surface composition of colloidal nanoparticles is still a challenging yet mandatory prerequisite in catalytic studies to investigate composition-activity trends, active sites, and reaction mechanisms without superposition of particle size or morphology effects. Laser post-processing of colloidal nanoparticles has been employed previously to create defects in oxide nanoparticles, while the possibility of laser-based cation doping of colloidal nanoparticles without affecting their size remains mostly unaccounted for. Consequently, at the example of doping iron into colloidal Co3O4 spinel nanoparticles, we developed a pulse-by-pulse laser cation doping method to provide a catalyst series with a gradually modified surface composition but maintained extrinsic properties such as phase, size, and surface area for catalytic studies. Laser pulse number-resolved doping series were prepared at a laser intensity chosen to selectively heat the Co3O4-NPs to roughly 1000 K and enable cation diffusion of surface-adsorbed Fe3+ into the Co3O4 lattice. The combination of bulk-sensitive X-ray fluorescence and surface-sensitive X-ray photoelectron spectroscopy was used to confirm the surface enrichment of the Fe-dopant. X-ray diffraction, magnetometry, and Mössbauer spectroscopy revealed an increasing interaction between Fe and the antiferromagnetic Co3O4 with arising number of applied laser pulses, in line with a herein proposed laser-induced surface doping of the colloidal Co3O4 nanoparticles with Fe. Using Fick’s second law, the thermal diffusion-related doping depth was estimated to be roughly 2 nm after 4 laser pulses. At the example of gas-phase 2-propanol oxidation and liquid-phase oxygen evolution reaction, the activity of the laser-doped catalysts is in good agreement with previous activity observations on binary iron-cobalt oxides. The catalytic activity was found to linearly increase with the calculated doping depth in both reactions, while only catalysts processed with at least one laser pulse were catalytically stable, highlighting the presented method in providing comparable, active, and stable gradual catalyst doping series for future catalytic studies.

Mn-incorporated Co3O4 bifunctional electrocatalysts for zinc-air battery application: An experimental and DFT study

Manganese-incorporated Co3O4 catalysts were prepared via thermal pyrolysis of ZIF-67, and the effect of manganese incorporation and annealing temperature on their catalytic performances for oxygen reduction and evolution reactions (ORR, OER) were investigated. Notable crystalline distortion was induced by manganese insertion into Co3O4 lattice, resulting in smaller crystallite size, more abundant Co2+ and considerable oxygen vacancies. All these properties were regarded as the crucial origins for electrocatalytic activity elevation. The catalyst annealed at 450 °C (denoted as Mn/Co-450) exhibited the optimal catalytic activity with an ultra-low potential gap (0.83 V). Using Mn/Co-450 as an air cathode, the zinc-air battery delivered high power density (115.5 mW cm−2), competitive specific capacity (783.4 mAh g−1) and good cycling stability. The theoretical overpotentials of ORR and OER were respectively decreased by 0.18 V and 0.05 V by DFT calculation due to the weakened interaction between Co and OH group and the strengthened Co-OOH interaction.

Lattice doping of Zn boosts oxygen vacancies in Co3O4 Nanocages: Improving persulfate activation via forming Surface-Activated complex

The presence of oxygen vacancies (OVs) promotes persulfate activation. However, rational modulation of OVs without compromising the inherent structure of catalysts is challenging. Herein, novel OVs-enriched hollow ZnCo2O4 nanocages are synthesized based on a bimetallic ZIF-67@ZIF-8 precursor for efficient peroxydisulfate (PDS) activation. The incorporation of Zn into the lattice of Co3O4 boosts the number of OVs in the catalysts while preserving the morphology of Co3O4 nanocages derived from metal-organic framework (MOFs) templates. As a result, the degradation rate of organic pollutants such as bisphenol A is improved by over 20 times in the developed PDS activation system. OVs promote the formation of a surface-activated complex from PDS onto the catalyst surface, which can subsequently deprive electrons from pollutants. The developed PDS activation system is resistant to Cl−, NO3− and humic acid at environmental concentrations. This system adapts to selectively degrade organic pollutants with low ionic potential, and shows applicable potential in practical packaging wastewater treatment. The decreased catalytic performance of catalysts during utilization can be recovered with a facile thermal treatment. Our work constructs OV active sites on Co3O4 nanocages while preserving their original structural superiorities, providing a new strategy to functionalize MOF-derived materials.

Manganese-doped cobalt tetroxide for formaldehyde oxidation

Cobalt-based oxides are appealing but less-well investigated catalytic materials for formaldehyde (HCHO) oxidation. We herein report a careful study of carbon-supported Co3−xMnxO4 catalyst, with special focuses on the incorporation of Mn ions into Co3O4 lattice and its effect on the catalytic activity for HCHO oxidation. The Co3−xMnxO4/C catalysts were fabricated using a co-precipitation method followed by annealing treatment. A combination of phase structure/chemical structure analyses and control experiments confirmed the substitutional doping of Mn ions in Co3O4 lattice, which resulted in increment of oxygen vacancy concentration. Benefiting from Mn-doping and the dispersion effect of carbon, the Co2.7Mn0.3O4/C catalyst prepared under optimal conditions exhibited an impressively high activity for HCHO oxidation, fairly good stability and excellent moisture tolerance. For instance, it enabled a 100% HCHO conversion at 90 °C with a ten-fold higher mass-specific activity compared to Co3O4/C. A possible mechanism describing the HCHO oxidation over Co3−xMnxO4/C catalyst was proposed based on the in situ diffused reflectance infrared spectroscopy results.

Monoatomic oxygen fueled by oxygen vacancies governs the photothermocatalytic deep oxidation of toluene on Na-doped Co3O4

Reported herein is a study of oxygen vacancies (OVs) provoking the complete mineralization of toluene with Na-doped Co3O4 as a photothermal catalyst. Doping Na+ into Co3O4 leads to distortion and charge disequilibrium in the Co3O4 lattice, which generates abundant OVs. OVs work as specific centers to convert the absorbed O2 molecules to the active oxygen species O-. Abundant O- radicals boost the outermost decomposition of toluene. Comparing the optimal Na-doped Co3O4 (3%Na-Co3O4) with the pristine Co3O4, despite almost the same removal efficiency (100%) on them, the 3%Na-Co3O4 significantly outperforms Co3O4 concerning the CO2 yield in the photothermocatalytic oxidation of toluene under full-spectrum light irradiation (425 mW/cm2; equilibrium temperature of 218 °C). A mineralization degree of 89.8% is achieved on 3%Na-Co3O4, which is 7-fold higher than that over Co3O4. The OVs also help render the high sustainability of 3%Na-Co3O4, which maintains its outstanding performance even after 10 successive runs.

Fe-doped porous Co3O4 nanosheets with highly efficient catalytic performance for soot oxidation

A series of CoxFe1-x-PNS materials were synthesized at room temperature through the one-pot MgO-mediated method and were then used as catalysts for soot oxidation. Of all the catalyst samples prepared, the porous Co0.8Fe0.2-PNS nanosheets exhibited the highest catalytic performance for soot oxidation under both loose and tight contact modes. The 2D nanosheets provided a larger external surface area for contact between the catalyst and soot, and the porous structure was beneficial to the adsorption and diffusion of reactant gas. It was found that Fe was successfully doped in the lattice of Co3O4, and the mechanism regarding how Fe doping enhances intrinsic activity was investigated by a series characterization and DFT calculations. The results indicated that Fe doping made it easier to form oxygen vacancies and adsorb gaseous O2, which effectively improved the catalytic activity of soot oxidation. Hence, it is believed that the synergy between the well-defined porous nanosheets morphology and the properties induced by the doping of Fe resulted in better catalytic activity. This study also provided insight into the design of 2D transition metal oxides nanosheets as catalysts for soot oxidation.

Oxygen vacancies induced by charge compensation tailoring Ni-doped Co3O4 nanoflakes for efficient hydrogen evolution

The electronic structure modulation of the catalysts shows great significance towards hydrogen evolution reaction (HER). A charge compensation was realized by doping octahedral Ni2+ ions into the Co3O4 lattice, where the oxygen vacancies generate to maintain the electric neutrality. The oxygen vacancies lead to the local lattice distortion of Co3O4, trigger the concomitant electron redistribution, as well as optimize the d-band center of Ni-Co3O4. Then, the accelerated charge transfer and matter conversion boost the HER kinetics of Ni-Co3O4. As expected, the obtained Ni-Co3O4 catalyst exhibits the brilliant HER catalytic performance with a low overpotential of only 47 mV at 10 mA cm−2, and a Tafel slope of 46 mV dec−1. The density function theory calculations verify that this charge compensation strategy could efficiently promote the water dissociation and hydrogen transformation kinetics. Our work paves an effective avenue for rationally contriving high-efficiency catalysts towards HER.

Metal-organic frameworks-derived Mn-doped Co3O4 porous nanosheets and enhanced CO sensing performance

Improving the gas-sensing performances of p-type oxide semiconductors is an important research issue. Here, we reported the simple fabrication of bare Co3O4 and Mn-doped Co3O4 porous nanosheets by annealing the Co-based metal-organic frameworks (MOFs) nanosheets precursors synthesized from the ion-assisted solvothermal treatment. Different characterization techniques were adopted to verify the physical and chemical morphologies of the as-prepared samples. The results demonstrate that Mn cations have been successfully doped into the lattice of Co3O4. Besides, these prepared samples were used for detection of carbon monoxide (CO). Results show that 3 mol% Mn-doped Co3O4 nanosheets present enhanced CO-sensing properties [(Rg − Ra)/Ra = 280% to 40 ppm at 125 °C] compared with bare Co3O4 nanosheets. The response reported here for the detection of CO even exceeds those of some n-type oxides under the same conditions. We speculate that the enhanced CO-sensing properties are probably due to the high specific surface area, abundant oxygen vacancies generated by Mn doping, and the relatively high Co3+/Co2+ ratio. The Mn-doped Co3O4 sensor has a huge potential advantage in detecting low concentrations of CO.

Total oxidation of propane over Co3O4-based catalysts: Elucidating the influence of Zr dopant

A series of Zr-doped Co3O4 catalysts (x% Zr-Co3O4), prepared by citrate sol-gel method with a low doping amount of zirconium, was applied in the catalytic oxidation of 1000 ppm propane at a weight hourly space velocity of 40,000 mL g−1 h−1. Different techniques were used to characterize the catalysts. The results showed that the physicochemical properties and catalytic performances of the x% Zr-Co3O4 catalysts were significantly influenced by the addition of zirconium. Only a small part of Zr could be doped into the Co3O4 lattice and the spare Zr would prefer to aggregate on the surface to form zirconium oxide. In the x% Zr-Co3O4 catalysts, Zr disordered Co3O4 spinel is formed by entering into the Co3O4 lattice and forming Co-O-Zr species, resulting in smaller Co3O4 crystallite size, larger specific surface area, better low-temperature reducibility, higher surface Co2+ concentration, and higher content of surface oxygen vacancies and active oxygen species. The best performance was achieved on 1% Zr-Co3O4 for propane oxidation, with 90% propane conversion at 241 °C. The most active catalyst showed excellent performance in toluene and propene oxidation as well. Propane reaction tests, carried out without oxygen in the gas stream, indicated the promoting effect of the low amount of Zr on the oxygen mobility of x% Zr-Co3O4 catalysts. Durability tests of propane oxidation showed that stable conversion could be achieved over 1% Zr-Co3O4, thus being a potential active catalyst for practical application.

Metal-Organic frameworks-derived 2D spindle-like sn-doped Co3O4 porous nanosheets as efficient materials for TEA detection

Abstract Rational construction of two-dimensional (2D) metal-organic frameworks (MOFs) nanomaterials attracts researcher’s much attention due to their unique structural merits. Herein, 2D spindle-like pure and Sn-doped Co3O4 porous nanosheets have been synthesized using 1, 4-dicarboxybenzene (H2BDC) as a ligand acid, and via a simple solvothermal method and following thermal treatment. The structure, morphology and composition of the as-obtained samples are characterized by XRD, FESEM, TEM, XPS, ICP, AFM, UV–vis-NIR, UPS and nitrogen adsorption-desorption measurement. The results show that Sn4+ has been successfully doped into the lattice of Co3O4. The gas sensing properties of pure and Sn-doped Co3O4 porous nanosheets have been systematically analyzed. The 5 at% Sn-doped Co3O4 sample shows high responses of 70.7–100 ppm triethylamine (TEA) at a relatively low working temperature of 180 °C, which are about 11 times than that of pure Co3O4 (6.4). In addition, the 5 at% Sn-doped Co3O4 exhibits rapid response/recovery time (1 s/17 s), excellent anti-humidity properties, good gas selectivity and repeatability as well as superior long-term stability.

Improved Oxygen Activation over a Carbon/Co3O4 Nanocomposite for Efficient Catalytic Oxidation of Formaldehyde at Room Temperature.

Oxygen activation is a key step in the catalytic oxidation of formaldehyde (HCHO) at room temperature. In this study, we synthesized a carbon/Co3O4 nanocomposite (C-Co3O4) as a solution to the insufficient capability of pristine Co3O4 (P-Co3O4) to activate oxygen for the first time. Oxygen activation was improved via carbon preventing the agglomeration of Co3O4 nanoparticles, resulting in small particles (approximately 7.7 nm) and more exposed active sites (oxygen vacancies and Co3+). The removal efficiency of C-Co3O4 for 1 ppm of HCHO remained above 90%, whereas P-Co3O4 was rapidly deactivated. In static tests, the CO2 selectivity of C-Co3O4 was close to 100%, far exceeding that of P-Co3O4 (42%). Various microscopic analyses indicated the formation and interaction of a composite structure between the C and Co3O4 interface. The carbon composite caused a disorder on the surface lattice of Co3O4, constructing more oxygen vacancies than P-Co3O4. Consequently, the surface reducibility of C-Co3O4 was improved, as was its ability to continuously activate oxygen and H2O into reactive oxygen species (ROS). We speculate that accelerated production of ROS helped rapidly degrade intermediates such as dioxymethylene, formate, and carbonate into CO2. In contrast, carbonate accumulation on P-Co3O4 surfaces containing less ROS may have caused P-Co3O4 inactivation. Compared with noble nanoparticles, this study provides a transition metal-based nanocomposite for HCHO oxidation with high efficiency, high selectivity, and low cost, which is meaningful for indoor air purification.

Engineering Cationic Sulfur-Doped Co3O4 Architectures with Exposing High-Reactive (112) Facets for Photoelectrocatalytic Water Purification.

Promoting the generation of intermediate active species (superoxide radical (•O2-)) is an important and challenging task for water purification by photoelectrocatalytic (PEC) oxidation. Herein, we have constructed hierarchical cationic sulfur-doped Co3O4 architectures with controllable morphology and highly exposed reactive facets by introducing l-cysteine as a capping reagent and sulfur resource via a one-step hydrothermal reaction. The as-obtained cationic sulfur (1.8 mmol l-cysteine) source doped Co3O4 (SC-1.8) architectures with highly exposed (112) facets exhibited superior PEC activities and long-term stability (∼25,000 s) in 1.0 mol·L-1 sulfuric acid for an accelerated reactive brilliant blue KN-R degradation test. Our experimental and theoretical results confirmed that the superior PEC performance of the SC-1.8 architectures could be ascribed the following factors: (1) the highly exposed reactive (112) facets of SC-1.8 promoted carrier transport and diffusion during the PEC process and facilitated separating the electron/hole pairs and producing the predominant active species (•O2-) compared with currently used other electrodes. (2) Cationic sulfur doped on the lattice of Co3O4 can narrow the band gap to extend the photoadsorption range and improve the lifetime of •O2- to enhance the PEC efficiency. This work not only proves that the SC-1.8 architectures with highly exposed (112) facets are a promising PEC catalyst due to increasing the electron transport and the lifetime of active species but also presents a new strategy for constructing an active PEC catalyst.

Effect of Cr doping in promoting the catalytic oxidation of dichloromethane (CH2Cl2) over Cr-Co@Z catalysts

A core–shell catalyst which consists of a Co3O4 core and ZSM-5 shell, was prepared by microwave hydrothermal method and subjected for dichloromethane (DCM) oxidation. Chromium, cerium, niobium, and manganese species were separately introduced into the core-shell catalyst using the wet precipitation method and denoted as M-Co@Z (M = Cr, Ce, Nb, Mn). The catalytic activity of the Cr-Co@Z catalyst was significantly increased due to the interaction between Cr2O3 and Co3O4. The results of Raman spectra indicated the incorporation of chromium into the Co3O4 lattice and revealed the existence of the interaction between Cr2O3 and Co3O4. The synergistic effect between Cr2O3 and Co3O4 might be conducive to the generation of highly defective structure and increase the ratio of Co3+/Co2+ of the sample, leading to its better oxygen mobility. The dechlorination ability of Cr-Co@Z was also promoted due to the enhanced mobility of lattice oxygen. Based on in situ DRIFT studies, a possible reaction route of CH2Cl2 oxidation over Cr-Co@Z catalyst was proposed.