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For the first time, a nanosheet-state CoMnx mixed oxide with multifarious active regions was synthesized by oxidation-etching assembly of metal organic framework (MOF) precursor and applied for catalytic combustion of toluene at low temperatures. The obtained optimum catalyst denoted as CoMn6 showed excellent performance, which achieved 90% conversion of 1,000 ppm toluene under a weight hourly space velocity (WHSV) of 60,000 mL/(g·h) at 219 °C. While, it also exhibited long-term stability with strong water resistance property. The characterizations of physicochemical properties indicated that the oxidation-etching assembly process built an abundant mesoporous structure in the CoMnx catalyst, which greatly increased the specific surface area (SSA). Especially, potassium permanganate as oxidant and manganese source led to uniform dispersion and assembling of cobalt atoms, which caused the generation of low-crystallinity CoMnx mixed oxide with abundant dislocations, vacancies, phase interfaces and amorphous structures, resulting in excellent low-temperature reducibility, outstanding lattice oxygen mobility and abundant active species such as Mn

Volatile organic compounds (VOCs) are mainly derived from human activities, but they are harmful to the environment and our health. Catalytic oxidation is the most economical and efficient method to convert VOCs into harmless substances of water and carbon dioxide at relatively low temperatures among the existing techniques. Supporting noble metal and/or transition metal oxide catalysts on the porous materials and direct preparation of mesoporous catalysts are two efficient ways to obtain effective catalysts for the catalytic oxidation of VOCs. This review focuses on the preparation methods for noble-metal-based and transition-metal-oxide-based mesoporous catalysts, the reaction mechanisms of the catalytic oxidations of VOCs over them, the catalyst deactivation/regeneration, and the applications of such catalysts for VOCs removal. It is expected to provide guidance for the design, preparation and application of effective mesoporous catalysts with superior activity, high stability and low cost for the VOCs removal at lower temperatures.

In this article, two model order reduction (MOR) methods of Krylov subspace and Laguerre orthogonal polynomials were employed to the numerical simulation of heat transfer characteristics of ground ...

Conversion of CO2 into valuable chemicals via electrochemical CO2 reduction reaction (CO2RR) is a promising technology to alleviate the energy crisis and the greenhouse effect. Herein, low-cost woo...

Mn–Co mixed oxides were electrodeposited on Cu nanowires generated on Cu foam (CF) and used for effectively catalytic oxidation of toluene. The physical and chemical properties of the prepared catalysts were characterized by SEM, TEM, XRD, H2-TPR, O2-TPD and XPS. It is found that the Mn–Co mixed metal oxides were uniformly coated on the Cu nanowires by the electrochemical method, whose Mn/Co ratio can be tuned by adjusting the molar ratio of Mn/Co in the initial solution for the electrodeposition. The intimate contact between Mn and Co nanocrystals was found by HRTEM, which is important for realizing synergetic effects on improving catalytic activity. Meanwhile, the formation of the active surface oxygen species and the increase of the active species of Mn4+ and Co3+ were considered to make significant contribution to the catalytic oxidation of toluene. Mn–Co mixed metal oxide catalysts exhibited higher performance than the single metal oxide, and especially 0.10Mn–0.01Co/CF catalyst with the Mn/Co molar ratio of 10:1 in the initial solution for the electrodeposition achieved the highest catalytic activity with a low toluene conversion temperature (T90%) of 251 °C, and displayed excellent catalytic stability even in the presence of water vapor. It is expected that such a simply-electrodeposited mixed metal oxides based catalysts could be applied for the oxidation of volatile organic compounds (VOCs) in a practical process.

In this study, octahedral molecular sieve (OMS-2) is successfully delaminated by using trace holmium (Ho) via a facile redox co-precipitation route, which exhibits high performance for the total toluene oxidation at low temperature. High resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) analyses verify that abundant multi-phase interfaces and lattice dislocations are formed on the obtained delaminated OMS-2 by the Ho (Ho-OMS-2), which can induce more active oxygen species. In particular, the delaminated OMS-2 with a trace Ho amount has a high Oads/Olatt ratio with a balanced ratio of Mn3+ and Mn4+, demonstrating much higher activity (T100% of 228 °C even under 5 vol% H2O vapor over 0.5% Ho-OMS-2) than the parent OMS-2 (T100% of 261 °C) for the total toluene oxidation. Furthermore, the positive effect of the introduction of H2O on catalytic activity, especially the enhancement of the conversion of intermediates into CO2 and H2O, is verified by the in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS). Based on these results, the reaction mechanism for toluene oxidation over the OMS-2 based catalyst is proposed. It is expected to provide an effective preparation method to obtain high-performance catalysts for the VOCs oxidation at low temperatures.

A novel hexagonal prism Copper (II) metal organic framework (Cu-BTC) was first synthesized by using a facile unipolar pulse electropolymerization method. It has been found that the morphology of Cu-BTC crystals can be changed from octahedron to hexagonal prism with the increase of pulse cycles. The XRD pattern confirms that the crystal structure of Cu-BTC was slightly affected by the change of the crystal morphology. Furthermore, the growth mechanism of hexagonal prism Cu-BTC crystals was proposed. This method provides valuable guidelines for the design of other MOFs and opens up new opportunities for exploring their application.

A novel electroactive polypyrrole (PPy)-threaded HKUST-1 metal-organic framework (MOF) composite film was constructed on an electrode. This was achieved by the in situ conversion of CuO in a PPy/CuO composite film to HKUST-1 MOF by a unipolar pulse electro-erosion (UPEE) and in situ coordination method for the recovery of lithium ions (Li+) with low concentrations in aqueous solutions. The obtained films were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis. A PPy/HKUST-1 composite film with HKUST-1 anchored in the PPy nanorod networks was successfully formed on the electrode. Extraction of various metal ions, Li+, K+, Na+, Mg2+, and Cu2+ with this film was investigated using the electrochemically switched ion exchange technique. The PPy/HKUST-1 composite film exhibited a high selective extraction ability for Li+ present in low concentrations. The Li+ adsorption capacity reached 37.55 mg/g with an adsorption equilibrium time of less than 25 min owing to the sieving function of the voids and excellent affinity of this film for the Li+ ions. It is expected that such an electroactive film can be applied to the separation and recovery of dilute Li resources from various aqueous solutions.

Molecular dynamics (MD) simulation was adopted to study the feed-membrane surface affinity and transport behavior of furfural molecules when a poly(ether block amide) (PEBA-2533) membrane was employed. The furfural molecules exhibited a stronger interaction with the PEBA-2533 membrane than the water molecules. Transport behavior analysis indicated that the self-diffusion selectivity in the membrane increased with an increase in feed furfural concentration and the cavity size of the membrane was crucial for the separation of larger molecules. Additionally, the fractional free volume, fractional accessible volume, and fractional cavity volume (FCV) of the PEBA-2533 membrane were analyzed to reveal the variation in membrane structure. Interestingly, the water flux was more sensitive to the variation in membrane thickness than the furfural flux. The permeate furfural concentration increased with an increase in membrane thickness and a membrane selectivity damping model was proposed to explain this phenomenon. The MD technique showed great potential as an approach to characterize the performance of the PEBA-2533 membrane during the pervaporation process.

Conversion of CO

With the rapid increase of various electronic products with lithium-ion batteries in our daily life, it is difficult to provide enough supplement to satisfy the growing demand of the market only through exploiting limited lithium resources on land. Consequently, lithium recovery from salt-lake brines, geothermal brines, wastewater from the treatment of wasted batteries, or even sea water has attracted great interest all around the world due to the abundant reserves and low price. Nowadays, various conventional technologies such as solar evaporation-precipitation way have been widely applied to extract lithium from the aqueous solution. Unfortunately, they are always time-consuming, uncontrollable with the secondary pollution generation. Recently, various electrochemical technologies have been received considerable attention for lithium recovery owing to their time-saving, little environmental impact as well as high efficiency. Herein, progresses for lithium recovery using the electrochemical technologies were outlined and discussed based on the previous studies reported in the literatures. The principles, advantages and challenges of electrochemical technologies were critically reviewed. Even though these methods are technically feasible, they are still limited by the poor technical maturity for the large-scale lithium recovery. Thence, more efforts should be made in the future development of electrochemical technologies for improving lithium selectivity as well as material stability, and simultaneously reducing some energy consumption and investing and operating costs. It could provide guidance on the development and design of more attractive electrochemical methods for lithium recovery from liquid resources, which will contribute to achieving the sustainable and renewable society.

The remarkable effect of divalent transition metal ions on the electrochemical performance of transition metal-based layered double hydroxides (LDHs) was systematically investigated via computational and experimental approaches. Ni3−xCoxAl-LDHs (x = 0, 1, 2, and 3) were synthesized on carbon paper by a unipolar pulse electrodeposition (UPED) method and used as electrodes in energy storage systems. The structures were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Their electrochemical performance was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The mechanism of different electrochemical performances with various divalent transition metal ions was investigated by the density functional theory (DFT) plus U method and molecular dynamics (MD) simulations. The computational and experimental data demonstrated that the electronic and ionic conductivity and deprotonation of NiAl-LDHs were improved by doping Co species, and the incorporation of Co and Ni cations enabled LDHs to exhibit a larger interlayer spacing which can facilitate the diffusion of OH− ions, indicating that NiCo2Al-LDHs had the highest specific capacitance.

The utilization of lignin as a source of phenolic compounds requires highly efficient and selective depolymerization catalysts. Herein, lignin depolymerization was investigated over Ni2P catalysts supported on nitrogen-doped activated carbon (Ni2P/AC_N). The catalysts were prepared by an incipient wetness co-impregnation method followed by reduction with H2 gas. The presence of nitrogen-containing functional groups on the activated carbon surface resulted in the dispersion of Ni2P particles. The good distribution and small crystal size of Ni2P significantly increased the active surface area, which enhanced both the catalytic activity and phenol selectivity. Investigations of the catalytic activity at different reaction temperatures and lignin-to-catalyst ratios using pyrolysis–gas chromatography/mass spectrometry revealed that the highest phenol selectivity of 80% was achieved using the Ni2P/AC_N25% catalyst. The proposed reaction mechanism involves lignin depolymerization via C–O and C–C cleavage with subsequent phenol formation by demethoxylation. Owing to its high phenol selectivity, the Ni2P/AC_N catalyst has good potential for the transformation of lignin to phenol.

The oriented coral-like polyaniline (PANI) nano-arrays for the all-solid-state supercapacitor was successfully synthesized by using a three-step galvanostatic technology in the absence template. The average diameter and length of PANI nano-rod after 6 h growing were about 30 nm and 400 nm, respectively. The formation mechanism of vertically oriented coral-like PANI nano-arrays was proposed based on the electrostatic potential surface. Compared with SO42− ions, ClO4− ions resulted in more regular surface charge distribution, which remarkably improved the order degree of coral-like PANI nano-arrays. The specific capacitance of supercapacitor made of this nano-arrays reached about 537 F/g at a current density of 3 A/g and retained about 84.8% of their initial value even in a 120° bending state, and the symmetrical all-solid-state supercapacitor device using polyvinyl alcohol (PVA/H2SO4) as solid electrolyte retained 93.9% of its initial value even in a 120° bending state. It indicates that such a PANI nano-arrays should be promising materials for the flexible and portable energy storage device.

Cyber-Physical System (CPS) is a typical intelligent system composed of agents. It has an important feature of spatial temporal constraints. To describe the constraints on agents, Chen proposed the spatial-temporal consistency language (STeC) in 2012 and the hybrid clock system in 2014. In this paper we will set up the hybrid clock logic systems (HCL) to specify the spatial temporal constraint property of agents in CPS. After giving the syntax and semantics of HCL, we consider the satisfaction relationship between a STeC design and HCL specification of a CPS agent. Some case studies show this satisfaction relationship is reasonable. We also introduce a model-checking algorithm for HCL.

A facile agar-gel method was successfully applied to prepare a series of homogenous Mn-Co mixed oxides with different Mn/Co molar ratios for highly efficient catalysis of total toluene oxidation. The obtained Mn2Co1 mixed oxide exhibited a high catalytic activity with excellent durability as well as high tolerability even under 20 vol.% water vapor environment. Characterizations by XRF, XRD, N2 adsorption-desorption, SEM, TEM, H2-TPR, O2-TPD, XPS measurements with density functional theory (DFT) calculations indicated that the obtained optimum Mn-Co mixed oxide had high specific surface area, large amounts of Co3+, Mn3+, and Mn4+ species, abundant adsorbed oxygen species, rich lattice defects, high reducibility at low temperature, and excellent O2 adsorption ability. Meanwhile, in situ DRIFTS spectra measurements confirmed the generated intermediates at different environments during the toluene oxidation and revealed that both adsorbed oxygen and lattice oxygen species could simultaneously participate in the toluene adsorption-oxidation process, especially the rate-controlling step should be the C=C breakage of aromatic ring. It is expected that the present agar-gel method with low cost and convenient operation could be widely applied for the designing of novel mixed metal oxides catalysts for VOCs oxidation.

Cerium (Ce) modified cobalt (Co)-based (Co-Ce) mixed oxide catalysts were electrodeposited on nickel foam (NF) with different Co/Ce molar ratios and directly used for the catalytic oxidation of toluene. Physicochemical properties of the obtained Co-Ce/NF catalysts were obtained by SEM, XRD, TEM, H2-TPR, O2-TPD and XPS techniques. It was found that the Co-Ce mixed oxide with a well nanosheet structure could be uniformly deposited on NF by adjusting the Co/Ce molar ratio in the initial solution for electrodeposition. H2-TPR analysis indicated that Ce doping improved the reducibility of Co-Ce/NF catalyst due to the synergistic effect between Co and Ce. In the toluene catalytic oxidation, the 10Co-Ce/NF catalyst prepared with a molar ratio of Co/Ce at 10 in the initial solution achieved the best catalytic performance among all the catalysts with a complete toluene conversion temperature of 268 °C and CO2 selectivity of 100 %. This can be contributed to the superior physiochemical properties of uniform nanosheet structure, rich surface and lattice active oxygen species at low temperatures, high content of Co3+ active species with high oxygen vacancies and Ce4+/Ce3+ redox couples in the catalyst. In addition, the 10Co-Ce/NF catalyst exhibited long-term stability in the presence of water vapor. It is expected that such a time-saving electrodeposition method could provide a promising way to prepare highly active and stable transition metal based catalysts for the oxidation of VOCs.

A series of samarium (Sm) doped cerium oxide (x% Sm/CeO2) catalysts were prepared by pyrolysis of Sm containing Ce-based metal organic framework (Sm/Ce-MOF) precursor and applied for catalytic oxidation of toluene. The obtained catalysts were characterized by SEM, TEM, XRD, BET, Raman, XPS, H2-TPR, O2-TPD, and their catalytic activities were evaluated by oxidation of toluene over them. It was found that doping of Sm increased the concentration of oxygen vacancy as well as the low temperature reducibility, thereby improved the catalytic performance. Moreover, among the prepared Sm doped CeO2 catalysts, the 1% Sm/CeO2 catalyst showed the best performance for the oxidation of toluene with conversions of 50 % and 100 % at temperatures of 194 and 222 °C respectively under a WHSV of 60,000 mL/(g·h). In addition, the 1% Sm/CeO2 catalyst also exhibited excellent stability and high toleration to the moisture.

To improve operability as well as the removal efficiency for cesium ions in the wastewater treatment, a novel electrochemically switched ion exchange (ESIX) technique by using electroactive Prussian-blue(PB)-based magnetic microparticles (PB@Fe3O4 microparticle) with different uniform particle sizes in the range of 300–900 nm as the adsorption materials was developed. The obtained PB@Fe3O4 microparticle were characterized by Scanning electron microscopy (SEM), Transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and Thermogravimetric analysis (TGA). It is found that the PB can be well coated on the surface of Fe3O4 microsphere, which can be easily adsorbed on the magnetic electrode substrate for the electrochemical adsorption of Cs+ ions. Electrochemical adsorption of 97% Cs+ on PB/Fe3O4 was achieved in less than 10 min, and the maximum adsorption capacity was 16.13 mg/g, and the distribution coefficient (KD) of Cs+ ions reached as high as 3938. In addition, the electrochemical adsorption behavior of PB@Fe3O4 microparticle fitted well with the Freundlich adsorption isotherm and the Pseudo-second-order kinetic models. It is expected that such an ESIX technique using PB@Fe3O4 microparticle can be applied for the separation and recovery of dilute Cs+ ions from cesium-contaminated solution in a practical process.

A novel catalyst with special three-dimensional structure was prepared for the catalytic oxidation of toluene using a three-step electrochemical process, in which copper nanowires (CNWs) were generated on the surface of three-dimensional Cu foam (CF) by an electro-oxidization process at first and then, CeO2 was uniformly coated on the CNWs by a unipolar pulse electro-deposition (UPED) method and finally highly dispersed Ag nanoparticles were embedded on the surface of CeO2 using a constant voltage electrodeposition method. It is found that the suitable Ag loading amount effectively enhanced the low-temperature reducibility, the generation of oxygen vacancies, and distribution of surface acid sites, which are favorable to the catalytic oxidation of toluene. Especially, the obtained 80Ag-CeO2@CNWs/CF catalyst with an electrodeposition time of 80 s for Ag loading exhibited the best catalytic activity with the T10, T50 and T90 of toluene conversion at 222, 240 and 256 °C, respectively. Long-term stability tests with and without water vapor further indicated that the 80Ag-CeO2@CNWs/CF catalyst had good stability and water resistance ability during the catalytic oxidation of toluene. It is expected that the present electrodeposition method could be a promising way to prepare high-performance catalysts for the catalytic oxidation of VOCs.

Production of hydrogen by electrochemical water splitting is considered as one of the most promising ways for sustainable energy storage and hydrogen society realization in the future. However, the key for the large-scale application of this technique is to develop highly efficient electrocatalysts with low-cost to replace the noble-metal-based ones. To date, a series of transition-metal-based bifunctional electrocatalysts for both anode and cathode have been already developed for the overall water splitting. Herein, the characteristics of hydrogen and oxygen evolution reactions on the electrodes of water electrolysis cell and the basic methods for the evaluation of the performance of electrocatalysts are introduced at first and then, the prospects of various earth-abundant transition-metal-based bifunctional electrocatalysts are critically reviewed. Finally, the challenges in the development of earth-abundant transition-metal-based bifunctional electrocatalysts are discussed. It is expected to provide a guidance for the design and fabrication of the novel bifunctional electrocatalysts with high performance in a practical water splitting process.

The remarkable effect of divalent transition metal ions on the electrochemical performance of transition metal-based layered double hydroxides (LDHs) was systematically investigated via computational and experimental approaches. Ni3-xCoxAl-LDHs (x = 0, 1, 2, and 3) were synthesized on carbon paper by a unipolar pulse electrodeposition (UPED) method and used as electrodes in energy storage systems. The structures were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Their electrochemical performance was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The mechanism of different electrochemical performances with various divalent transition metal ions was investigated by the density functional theory (DFT) plus U method and molecular dynamics (MD) simulations. The computational and experimental data demonstrated that the electronic and ionic conductivity and deprotonation of NiAl-LDHs were improved by doping Co species, and the incorporation of Co and Ni cations enabled LDHs to exhibit a larger interlayer spacing which can facilitate the diffusion of OH- ions, indicating that NiCo2Al-LDHs had the highest specific capacitance.

This study is concerned with the level of antibiotic resistance of extended-spectrum β- lactamase (ESBL)-producing Klebsiella pneumoniae, isolated in Shantou, China, and its mechanism. Seventy- four non-repetitive clinical isolates of K. pneumoniae producing ESBLs were isolated over a period of 2 years. Antibiotic susceptibility, carried out by Epsilometer test, showed that most of the isolates were multiresistant. Polymerase chain reaction showed that, among the several types of β-lactamases, SHV was the most prevalent, TEM was the second most prevalent, and CTX-M was the least prevalent. Sixty-nine isolates were positive for integrase gene IntI1, but no IntI2 or IntI3 genes were found. The variable region of class 1 integrons were amplified and further identified by sequencing. Thirteen different gene cassettes and 11 different cassette combinations were detected. Dfr and aadA cassettes were predominant and cassette combinations dfrA12, orfF and aadA2 were most frequently found. No gene cassettes encoding ESBLs were found. Integrons were prevalent and played an important role in multidrug resistance in ESBL-producing K. pneumoniae.

This study is concerned with the level of antibiotic resistance of extended-spectrum beta-lactamase (ESBL)-producing Klebsiella pneumoniae, isolated in Shantou, China, and its mechanism. Seventy-four non-repetitive clinical isolates of K. pneumoniae producing ESBLs were isolated over a period of 2 years. Antibiotic susceptibility, carried out by Epsilometer test, showed that most of the isolates were multiresistant. Polymerase chain reaction showed that, among the several types of beta-lactamases, SHV was the most prevalent, TEM was the second most prevalent, and CTX-M was the least prevalent. Sixty-nine isolates were positive for integrase gene IntI1, but no IntI2 or IntI3 genes were found. The variable region of class 1 integrons were amplified and further identified by sequencing. Thirteen different gene cassettes and 11 different cassette combinations were detected. Dfr and aadA cassettes were predominant and cassette combinations dfrA12, orfF and aadA2 were most frequently found. No gene cassettes encoding ESBLs were found. Integrons were prevalent and played an important role in multidrug resistance in ESBL-producing K. pneumoniae.