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Construction of heterojunctions is a normal and effective strategy to improve the photocatalytic performances of semiconductors, through which both the lifetime and the redox ability of electrons/holes can be improved, as compared to the respective component. On this basis, we constructed Z-scheme CdS/LaFeO3heterojunctions (CdS/LFO), by in-situgrowing different amounts of CdS on the surface of LaFeO3, for photocatalytic degradation of tetracycline hydrochloride (TC) in aqueous solution at room temperature. The crystal structure, surface morphology and optoelectronic properties of the CdS/LFO heterojunctions were systemically characterized to correlate the reaction activity. Photocatalytic tests indicate that the CdS/LFO heterojunctions exhibit promising activity for TC degradation under visible light irradiation (λ ≥ 420 nm), with 85% TC conversion obtained at reaction time of 45 min, which is 3.4 and 1.9 times higher than that of CdS and LaFeO3. The CdS/LFO heterojunctions are also stable in the reaction and can be reused for four cycles with no appreciable activity loss. The applicability of CdS/LFO to photocatalytic degradation of organic dyes, as well as the reaction mechanism, was also explored.

The surface reactivity of a metal can be modulated by placing a graphitic cover atop, and a concept of “Catalysis under Cover” has been suggested acting as a new route towards the modulation of surface reactions.

Transient absorption spectroscopy was used to directly observe the exciton relaxation process of an S-scheme heterojunction. Rapid interfacial charge transfer leads to high photocatalytic hydrogen production and organic transformation performance.

Low-dimensional hybrid nanocrystals are newly emerging active photocatalysts for separating electron-hole pairs, but the instability and low quantum efficiency caused by particle aggregation and hybrid structure relaxation remain great challenges. To this end, herein we constructed amorphous FeOx(A-FeOx) and crystalline LaFeO3hybrids by a sol-gel method. The amorphous-crystalline hybrids, A-FeOx/LaFeO3, not only improve the surface area and alter the band position, but also form numerous channels that are conducive to the transport of electrons and separation of electron–hole pairs, acting as microreactors. Photocatalytic tests show that the A-FeOx/LaFeO3is highly active for the degradation of various organic pollutants, with reaction rate constant of 1.19 × 10–2min–1for ciprofloxacin degradation, for example, which is 1.82 and 1.87 times higher than that of LaFeO3and Fe2O3/LaFeO3, respectively, owing to the formation of microreactors between A-FeOxand LaFeO3. Cycling tests show that the material has good stability in the reaction, and trapping experiments demonstrate that the photo-induced holes are the main reactive species of the reaction. This work provides a novel and feasible insight into the design of high performance low-dimensional hybrid nanocatalysts for photocatalysis.

Perovskite oxides LaCoO3prepared by templating, co-precipitation and sol-gel method with different complexants were systematically characterized and its catalytic performances for CO oxidation were investigated. The samples were characterized by X-ray diffraction, thermogravimetry analysis and differential scanning calorimetry, N2physisorption, transmission electron microscopy, temperature program reduction of hydrogen, temperature program desorption of oxygen and X-ray photoelectron spectroscopy measurement, results of which show that the properties of LaCoO3, such as surface morphology, surface area, surface compositions, redox capability, oxygen vacancy, as well as the calcination temperature and formation mechanism, depend intimately on the preparation method. Catalytic tests indicate that the sample prepared by carbon templating method shows the best activity for CO oxidation, with full CO conversion obtained at 135 °C. In particular, the catalyst can be activated and significant increase of activity can be obtained with the increase of reaction time. The cyclic and long-term stability of catalysts were discussed and compared.

Fe-containing carbon nitrides (Fe–CN) prepared with various CN precursors, including dicyandiamide, melamine, guanidine hydrochloride and urea, were characterized by X-ray diffraction, thermal gravimetric analysis, N2physisorption, transmission electron microscopy, X-ray photoelectron spectroscopy and atomic emission spectrometer measurements, and used as catalysts to catalyze the rhodamine B oxidation with H2O2as oxidant. Characteristic results showed that Fe–CN exhibits different compositions, properties and catalytic performances if different CN precursors are used. The Fe–CN prepared from dicyandiamide contains mainly CN phase and certain amounts of surface Fe2O3phase, exhibits the best activity; while that prepared from urea contains mainly Fe2O3phase and few amounts of CN phase, exhibits the worst activity. Contrasting experiments conducted under light irradiation, with a supported Fe/CN_D catalyst, and that using a washed catalyst, suggested that the surface Fe2O3is the active site of the reaction.

Catalytic transfer hydrogenation is an attractive route for the synthesis of biomass-derived chemicals. However, development of efficient, low-cost, and stable catalysts for that reaction is still a challenge. Here, we report on the preparation and testing of a non-noble perovskite oxide (LaFeO3) catalyst synthesized by an in situ carbon templating method. We show that our catalyst is quite active and selective toward the hydrogenation of unsaturated organics. Compared to an analogous LaFeO3catalyst prepared by a more traditional method, using citric acid, the new LaFeO3exhibited a more porous structure, a La-enriched surface composition, and abundant oxygen vacancies, all characteristics that improve contact with the reactants. In the case of the conversion of furfural to furfuryl alcohol (FOL) using iso-propanol as hydrogen donor, the new LaFeO3showed a furfural conversion of 90% and a selectivity to FOL of 94%, significantly higher than with the reference LaFeO3prepared by the traditional sol–gel method (60 and 91%, respectively). Moreover, our new LaFeO3catalyst can be recovered after a calcination treatment, with no appreciable changes in its structure or activity, a test that we repeated six times, and can promote the hydrogenation of other carbonyl compounds containing electron-withdrawing groups. A reaction mechanism is proposed in which metal cations are the adsorption sites for iso-propanol and oxygen vacancies are the adsorption sites for furfural, and where the conversion proceeds following an acid–base mechanism. We believe that the novel use of perovskites as catalysts for hydrogenation reactions reported here may be easily extendable to other processes, and that our carbon-templating synthetic approach offers a way to synthesize viable perovskite catalysts with high surface areas for optimized activity.

This work aims to study the effect of redox property and surface morphology of perovskite oxides on the catalytic activity of CO oxidation and CO+NO reduction, with the redox property being tuned by doping Fe at the Co site of La0.8Sr0.2Co1‒xFexO3and the surface morphology being modified by supporting La0.8Sr0.2CoO3on various me-soporous silicas(i.e., SBA-16, SBA-15, MCF). Characteristic results show that the Fe doping improves the match of redox potentials, and SBA-16 is the best support of La0.8Sr0.2CoO3when referring to the oxidation ability(e.g., the Co3+/Co2+molar ratio). A mechanism for oxygen desorption from perovskite oxides is proposed based on O2-TPD experiments, showing the evolution process of oxygen released from oxygen vacancy and lattice framework. Cata-lytic tests indicate that La0.8Sr0.2CoO3is the best for CO oxidation, and La0.8Sr0.2FeO3is the best for CO+NO reduc-tion. The mechanism of CO+NO reduction changes as the reaction temperature increases, with XNO/XCOvalue de-creases from 2.4 at 250 °C to 1.0 at 400 °C. As for the surface morphology, La0.8Sr0.2CoO3supported on SBA-16 possesses the highest surface Co3+/Co2+molar ratio as compared to the other two, and shows the best activity for CO oxidation.

N-doped carbon xerogel (N-CX) is synthesized and used for adsorption removal of microcystin-LR (MC-LR) from aqueous solution. Characterizations including N2physisorption, TEM and XPS indicate that N atoms are doped into the N-CX and the material has porous structure. Adsorption tests show that the N-CX is efficient for MC-LR adsorption, with adsorption capacity of 1916.2 μg g−1, which is higher than that of commercial activated carbon (1034.13 μg g−1) and graphene oxide (1700 μg g−1). The material is recyclable after desorption treatment by washing with NaOH solution, with no loss of uptake within five cycles. Effect of initial MC-LR concentration, temperature, and pH on the adsorption behavior is further investigated, to realize the adsorption process, showing that the adsorption process obeys the Langmuir isotherm and pseudo-second-order equation. Thermodynamical calculation indicates that the adsorption of MC-LR onto N-CX is a spontaneous and exothermic process, with the Gibbs free energy (ΔG) of −16.1 kJ mol−1and enthalpy (ΔH) of −18.45 kJ mol−1.

Graphitic carbon nitride, g-C3N4, is a polymeric material consisting of C, N, and some impurity H, connected via tris-triazine-based patterns. Compared with the majority of carbon materials, it has electron-rich properties, basic surface functionalities and H-bonding motifs due to the presence of N and H atoms. It is thus regarded as a potential candidate to complement carbon in material applications. In this review, a brief introduction to g-C3N4is given, the methods used for synthesizing this material with different textural structures and surface morphologies are described, and its physicochemical properties are referred. In addition, four aspects of the applications of g-C3N4in catalysis are discussed: (1) as a base metal-free catalyst for NO decomposition, (2) as a reference material in differentiating oxygen activation sites for oxidation reactions over supported catalysts, (3) as a functional material to synthesize nanosized metal particles, and (4) as a metal-free catalyst for photocatalysis. The reasons for the use of g-C3N4for such applications are also given, and we expect that this paper will inspire readers to search for further new applications for this material in catalysis and in other fields.

Ce-incorporated SBA-15 was prepared and used as support for Co3O4in CO oxidation reaction, showing that Ce incorporation can improve the activity and the optimum Ce content is at a Ce/Si molar ratio of 0.02. Detailed studies indicated that Ce incorporation activates the surface chemical properties of SBA-15 and influences the physicochemical properties of Co3O4. Thus, the CO oxidation reaction can be conducted on two different active sites, thereby improving the activity.In addition to act as a support of Co3O4, Ce-SBA-15 can influence the catalytic performances of Co3O4through interacting with the Co atoms and participate in the CO oxidation reaction as an active site by providing oxygen vacancies for oxygen activation, due to the Ce incorporation, leading to improved CO oxidation activity.

Energy crisis is one of the most urgent tasks of today, and the utilization of solar power is regarded as one powerful way to solve this problem. In this aspect, titanium dioxide (TiO2) is especially interesting as it is an efficient material that can convert solar power into energies that can be directly used in our daily life. Consequently, various studies and patents relating to the preparation and modification of TiO2 have been reported and issued, to accelerate its practical application. In this work, we synthesized nano-sized TiO2 particles by hydrothermal method under different conditions and investigated its photocatalytic performances for degradation of ethane. Results indicated that for solvents neutral water, acidic water and ethanol, only use neutral water could the product possesses mesoporous structure. Further studies indicated that the particle size increases and the surface area decreases with increasing the calcination temperature. The TiO2 hydrolyzed at 100 °C and calcined at 500 °C showed average particle size of 13.5 nm and surface area of 73 m2/g. No obvious change in the textural properties was observed, but an increase in the surface hydroxyl groups was found for TiO2 hydrolyzed at different temperatures. Photocatalytic tests on C2H4 degradation reaction (C2H4 ? CO2) indicated that the TiO2 synthesized in this work is more active than the standard Degussa P25 TiO2, in particular for the one hydrolyzed at high temperature (i.e. 120 °C), which possesses the largest amount of surface hydroxyl groups.

Catalytic performances and the reaction mechanism of Co3O4/AC (AC=activated carbon) for aerobic oxidation of alcohols carried out in the liquid phase were investigated. Co3O4/AC shows a high activity for aerobic oxidation of benzyl alcohol, comparable to noble metal catalysts (e.g., Au/AC) even in the absence of additives or promoters (e.g., NaOH). Changing preparation conditions, such as treatment temperature and/or time, can affect the catalytic performances of Co3O4/AC, due to decomposition of surface groups of the carbon support. Careful studies show that low alcohol conversions are obtained with either Co3O4or AC alone, which indicates that the high conversion observed over the Co3O4/AC is due to a synergistic effect between Co3O4and AC. Parallel experiments using a high‐surface‐area covalent triazine framework or oxygen‐inert carbon nitride as support for the Co3O4catalyst also show lower conversions, which suggest that the ability of AC (in Co3O4/AC) to activate molecular oxygen is essential for the reaction. FTIR and XPS spectra taken from catalysts before and after the reaction confirm that oxygen activation proceeds mainly on the carbon support. As a result, it can be assumed that the alcohol dehydrogenation step proceeds on the metal oxide, whereas the oxygen activation step occurs mainly on the carbon support.

Active site structure for NO decomposition carried out on perovskite-like oxides were discussed based on the N2yield measured from LaSrNi1-xAlxO4with different B-site cations and from La2-ySryCuO4with different crystal phases. Results show that the active site contains two oxygen vacancies, two transition metals, and one lattice-oxygen, with the oxygen vacancy locating on the apex of MO6octahedron, and the lattice oxygen locating between the two transition metals (i.e., M-O-M plane). Density functional theory (DFT) analysis to the structure shows that this new active site is the most active structure for NO adsorbing, and hence, for NO decomposition. The similar trend of the relative energies that are required for the formation of oxygen vacancies with fform (calculated from DFT), the amount of oxygen vacancies, and the activities (N2yield) certifies this result further.

Catalytic reactions with different oxidation process were investigated and correlated to the electrochemical properties of the catalysts. The activity of suprafacial reaction is closely related to the area of redox peak, while that of the intrafacial one is to the match of redox potentials. Accordingly, it is supposed that cyclic voltammetry (CV) measurement could be a means for predicting the oxidation process in heterogeneous catalysis.

Correlations between the catalytic performance and the electrochemical properties in heterogeneous catalysis were observed, using perovskite-like oxides La2−xSrxMO4(x= 0.0, 0.5, 1.0, M = Cu, Ni) as the model catalysts and CO oxidation as the probe reaction. For a reaction that contains reducing agent in the feed gas, the activity depends mainly on the area of redox peak in the CV curves, while has no much relation to the symmetry of the redox potentials. The irreversible cycle in the first CV curves of LaSrCuO4suggested that the first step of the reaction is adsorption, corresponding to Mn+(Cu2+) to M(n+1)+(Cu3+).

Ce involved perovskite-like oxides (La1−xCexSrNiO4, x ≤ 0.3) show high activity for NO decomposition even in the presence of excess oxygen, which might be mainly ascribed to the new active site formed in the catalyst due to the entry of Ce to the La site of LaSrNiO4.

As one of the key parts of rotary machine, the fault diagnosis and running condition monitoring of rolling bearings are of great importance for normal working and safe production of rotary machine. However, the traditional diagnosis approaches merely count on artificial feature extraction and domain expertise. Meanwhile, the existing convolutional neural networks (CNNs) have the problem of low fault recognition rates. This paper proposes a novel convolutional neural network with one-dimensional structure (ODCNN) for the automatical fault diagnosis of rolling bearings, which adopts six sets of convolutional and max-pooling layers to extract signal features and applies a flattening convolutional layer followed by two fully-connected layers for feature classification. The architectures of one-dimensional LeNet-5, AlexNet, and the proposed ODCNN are illustrated in detail, followed by the obtaining of training and testing samples, which is pre-processed by overlapping the vibration signals of rolling bearings. Finally, the classification experiment is carried out. The experimental results show that the ODCNN has higher fault diagnosis rates and can achieve high accuracy with load variant. Additionally, the extracted features of three CNNs are visualized, which illustrate that the new CNN has a better classification capacity.

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