Fabrication of hierarchical SrTiO3@MoS2 heterostructure nanofibers as efficient and low-cost electrocatalysts for hydrogen-evolution reactions.

The construction of low-cost, high-performance electrocatalysts instead of platinum catalysts is critical to solving the energy crisis. Here, using simple electrospinning and hydrothermal methods, new MoS2 nanosheets on SrTiO3 nanofibers (NFs) and 2D SrTiO3@MoS2 heterostructure NFs are synthesized. In addition, SrTiO3@MoS2 heterostructure NFs are compared with bare SrTiO3 NFs and MoS2 nanosheets. Importantly, the prepared SrTiO3@MoS2 heterostructure shows better hydrogen-evolution reaction performance than other MoS2-based electrocatalysts with an overpotential of 165 mV at 10 mA cm-2, a Tafel slope of 81.41 mV dec-1, and long-term electrochemical durability of 3000 cycles. Therefore, the present work strongly demonstrates the positive synergy between SrTiO3 NFs and layered MoS2, and also provides a strategy for preparing low-cost and high-activity water-decomposition electrocatalysts.

Construction of cellulose acetate-based composite nanofiber films with effective antibacterial and filtration properties.

In recent years, the safety of public health has attracted more and more attention. In order to avoid the spread of bacteria and reduce the diseases caused by their invasion of the human body, novel filtration and antibacterial materials have attracted more and more attention. In this work, the antibacterial agents silver nanoparticles (AgNPs) and cetylpyridine bromide (CPB) were introduced into a cellulose acetate (CA) nanofiber film by electrospinning technology to prepare CA-based composite films with good antibacterial and filtration properties. The results of the antibacterial test of the composite nanofiber films showed that AgNPs and CPB had synergistic antibacterial effects and exhibited good antibacterial properties against a variety of bacteria. In addition, in vitro cytotoxicity, skin irritation and skin sensitization experiments proved that the CA/AgNPs, CA/CPB and CA/CPB/AgNPs films produced no skin irritation or sensitization in the short term. These are expected to become potential materials for the preparation of new antibacterial masks. This work provides a new idea for developing materials with good antibacterial properties for enhancing protection via filtration masks.

Recent developments in the application of membrane separation technology and its challenges in oil-water separation: A review.

In the development and production process of domestic and foreign oil fields, large amounts of oil-bearing wastewater with complex compositions containing toxic and harmful pollutants are generated. These oil-bearing wastewaters will cause serious environmental pollution if they are not effectively treated before discharge. Among these wastewaters, the oily sewage produced in the process of oilfield exploitation has the largest content of oil-water emulsion. In order to solve the problem of oil-water separation of oily sewage, the paper summarizes the research of many scholars in many aspects, such as the use of physical and chemical methods such as air flotation and flocculation, or the use of mechanical methods such as centrifuges and oil booms for sewage treatment. Comprehensive analysis shows that among these oil-water separation methods, membrane separation technology has higher separation efficiency in the separation of general oil-water emulsions than other methods and also exhibits a better separation effect for stable emulsions, which has a broader application prospect for future developments. To present the characteristics of different types of membranes more intuitively, this paper describes the applicable conditions and characteristics of various types of membranes in detail, summarizes the shortcomings of existing membrane separation technologies, and offers prospects for future research directions.

Proper Orthogonal Decomposition-Based Method for Predicting Flow and Heat Transfer of Oil and Water in Reservoir.

Calculation process of some reservoir engineering problems involves several passes of full-order numerical reservoir simulations, and this makes it a time-consuming process. In this study, a fast method based on proper orthogonal decomposition (POD) was developed to predict flow and heat transfer of oil and water in a reservoir. The reduced order model for flow and heat transfer of oil and water in the hot water-drive reservoir was generated. Then, POD was used to extract a reduced set of POD basis functions from a series of "snapshots" obtained by a finite difference method (FDM), and these POD basis functions most efficiently represent the dynamic characteristics of the original physical system. After injection and production parameters are changed constantly, the POD basis functions combined with the reduced order model were used to predict the new physical fields. The POD-based method was approved on a two-dimensional hot water-drive reservoir model. For the example of this paper, compared with FDM, the prediction error of water saturation and temperature fields were less than 1.3% and 1.5%, respectively; what is more, it was quite fast, where the increase in calculation speed was more than 70 times.

Facile Synthesis of Ag/Pd Nanoparticle-Loaded Poly(ethylene imine) Composite Hydrogels with Highly Efficient Catalytic Reduction of 4-Nitrophenol.

Poly(ethylene imine) (PEI) has abundant amino groups in a macromolecular chain and can be used as a graft source for metal nanocomposites, which shows excellent ability to form stable complexes with heavy metal ions. In this work, a simple and convenient method was used to make PEI into a stable hydrogel with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide-N-hydroxysuccinimide and subsequently coprecipitate with silver nitrate solution or palladium chloride solution to form metal-loaded composite hydrogels. In addition, the characterizations of composite hydrogels were investigated by scanning electron microscopy, specific surface area tests (Brunauer-Emmett-Teller), X-ray photoelectron spectroscopy, and ultraviolet spectroscopy. The properties of composite hydrogels on the catalytic reduction of 4-nitrophenol were studied. The results showed that the composite hydrogels could be easily separated from the water environment, which indicated the large-scale potential application in organic catalytic degradation and wastewater treatment.

Correction of torque transfer lag in magnetic coupling rheological test system.

In this study, a mathematical model for the magnetic coupling transmission process was set up to solve the problem of torque transfer lag in magnetic-coupled rheological testing systems. This model was developed on the basis of torque balance in a magnetic coupling rotatory rheometer test system, which considered friction loss for the jewel bearing, as well as the inertia of both the motor and fixture. Taking the HAAKE-MARS60 high-pressure rheometer as an example, the rheological properties of Newtonian fluid at the initial measuring stage under controlling constant stress conditions were tested to verify the accuracy of the model and using the model to modify the rheological test results. The results show that the load torque mainly influences the alternating frequency of the rotational speed and the hysteresis degree of the inner and outer magnetic rings, the larger the load torque, the greater the deviation of the magnetic coupling test results of the rotational rheometer. The results of the apparent viscosity test are modified under different loading conditions, and the rheological curves of the initial shear phase of the Newtonian fluid are coincident with the steady-state test results, showing the true viscosity of the Newtonian fluid, which conforms to the cognition of Newtonian fluid rheology being independent of time. The results of the initial start test of gelling crude oil were modified, the yield stress and yield time were reduced, and the lower the test temperature and the higher the shear rate, the more obvious the correction effect was. Under different shear rate conditions, the yield strain corresponding to the modified yield stress was close and the yield strain was approximately not changed with the shear rate. The results can provide a basis for understanding the rheological properties of materials in the start-up transient process under high pressure conditions.