Epitaxial hetero-structure of CdSe/TiO2 nanotube arrays with PEDOT as hole transfer layer for photoelectrochemical hydrogen evolution

The photocatalytic decomposition of water is believed to be able to help mitigate the crisis of fossil fuel depletion. However, the photocatalytic hydrogen production remains challenge to obtain high and stable photoconversion efficiency. Here we report an epitaxial hetero-structure of CdSe/TiO2 nanotube arrays as efficient photo-anodes via simple room-temperature, low-cost electrochemical deposition. With the help of the similar d spacing with TiO2, CdSe sensitization layer is epitaxially grown on the tube wall of the TiO2 nanotubes, resulting in an ideal coherent grain boundary and single crystal growth. The resultant photo-anode produces 30% more photocurrent than those samples without coherent grain boundary. Notably, the especial epitaxial hetero-structure is beneficial to decrease the recombination site and accelerate the separation of photogenerated electron-hole pairs. Furthermore, an ultrathin PEDOT surface layer was developed on the epitaxial hetero-structure of CdSe/TiO2 nano-tube arrays in which it functions as both a physical passivation barrier and a hole transfer layer. As a result, significantly enhanced photocurrent density and substantially better stability have been achieved. This methodology may be providing a new pathway of epitaxial growth for preparing the heterogeneous junction materials which have similar d spacing

Influence of diameter of empty hole on the fragmentation effect of parallel cut blasting under confining pressure

Cut blasting is the key technology for roadway blasting excavation. High confining pressure has obvious inhibition effect on cut blasting effect, while empty hole is of great significance to improve cut blasting efficiency, but the relevant research is not sufficient so far. To study the crushing effect of the cut blasting with different empty hole diameters under the confining pressure, cubic cement mortar test blocks whose side length was 600 mm were made with sand cement ratio of 2:1. The test blocks were subjected to equal bi-axial confining pressure through an electro-hydraulic servo loading system, and the parallel cut blasting cement mortar physical model test was carried out. After the blasting fragmentation was screened and statistically analyzed, the fragmentation distribution and average particle size of model fragments under different empty hole diameters were analyzed and investigated. With fractal features of fragments characterized by fractal dimension, the fragmentation degree was quantitatively analyzed. ANSYS/LS–DYNA software was used to establish numerical models based on the parameters of the test model, and the stress contour at different times with different hole diameters was analyzed. The research result shows that, when two empty holes are charged with different charge of 2 g and 3 g, respectively, the maximum fractal dimension of the model fragment can be attained with empty holes in diameter of 24 mm and 16 mm, respectively, with the particle size of the fragment mainly concentrated in the middle segment between 19 to 75 mm, and the largest total mass of the fragment is 3.128 kg and 3.615 kg, respectively; When the sizes of empty holes are different, the stress concentration effect and the reflected tensile wave produced near the empty hole are also different, which brings the difference of cut blasting fragmentation effect and can effectively benefit from the empty hole effect. The peak value and action range of stress wave near the empty hole are bigger, with a long action time, suggesting a better crushing effect; the diameter of the empty hole is too small, the stress around the empty hole is small. An oversized empty hole will lead to the overflow of the stress wave from the hole. The compressive stress is small after the superposition of stress concentration, and the action area of tensile stress is also small. The proportion of large rock pieces will be high with extremely large or small empty hole. When charged with 3 g, the fractal dimension difference between empty hole model fragments of 32 mm and 16 mm is greater than the difference of model fragments between 16 mm and without empty hole, indicating that the influence on the fragmentation of rock is greater when the empty hole diameter is too large. When the empty hole diameter is the same as 16 mm, the average particle size of the fragments in the model charged with 3 g is less than that in the model charged with 2 g, with the greater fractal dimension and total mass of the fragments than that in the test model charged with 2 g. This shows that an increased charge can contribute to rock fragmentation and the volume of the cut cavity with the same diameter of empty holes

Qishen Yiqi dripping pills for chronic ischaemic heart failure:results of the CACT-IHF randomized clinical trial

10.1002/ehf2.12980ESC Heart Failure763881-389

Improvement of photocatalytic hydrogen generation from CdSe/CdS/TiO2 nanotube-array coaxial heterogeneous structure

The fabrication and characterization of CdSe/CdS/TiO2 nanotube-array coaxial heterogeneous structure that has potential applications in photocatalytic water splitting and toxic pollutants degradation are investigated. CdSe(top)/CdS(under) double-layer is conformally deposited onto TiO2 nanotubes by successive ionic layer adsorption and reaction (SILAR) and electrochemical atomic layer deposition (ECALD), respectively, for the CdS under layer and the CdSe top layer. Such double sensitized TiO2 nanotubular photoelectrode exhibits significant enhancements in photoconversion efficiency, visible light response, and efficient hydrogen generation. The detailed synthesis process and the surface morphology, phase structure, elemental analysis, and photoelectrochemical properties of the resulting films with the CdSe/CdS/TiO2 nanotube-array coaxial heterogeneous structure are discussed. The photoconversion efficiency of 9.47% and hydrogen generation rate of 10.24 ml h?1 cm?2 were observed. Both values are a 7-fold enhancement compared with that of the pure TiO2 nanotube. The as-prepared photoelectrode presents potential application for industrialized photocatalytic hydrogen generation in the future

Piperazine polypyrophosphat-halloysite nanotubes-melamine cyanurate synergistic flame retardant epoxy resin

By improving the existing preparation methods, a piperazine polypyrophosphat (PAPP) with high thermal stability was synthesized. It was compounded with halloysite nanotube (HNTs) and melamine cyanurate (MCA) to form P-N-Si intumescent flame retardant, and was used in synergistic flame retardant epoxy resin (EP). The effect of intumescent flame retardant on the flame retardancy of EP was investigated by means of limiting oxygen index, vertical combustion, cone calorimeter and SEM etc. The results show that the introduction of the compound flame retardant forms a dense and continuous intumescent carbon layer, which improves the flame retardant efficiency of the epoxy resin in the condensed phase and the gas phase. It reduces the heat release and heat release rate of epoxy resin and the toxic gases release effectively. When the PAPP/HNTs/MCA ratio is 7∶1∶2, the limiting oxygen index of flame retardant resin reaches 34.3%, the UL-94 vertical combustion test reaches V-0 level. Compared with pure EP, the amount of residual carbon is increased significantly, the peak heat release rate (HRR) is decreased by 60.56%, and the total heat release (THR) and toxic gas emissions are reduced significantly for modified EP. In addition, the thermogravimetric analysis results suggest that the initial decomposition temperature of flame retardant modified EP is decreased by 4.4% (ΔT), and the modified EP still has high thermal stability

Study on the Development of High-Performance P-Mo-V Catalyst and the Influence of Aldehyde Impurities on Catalytic Performance in Selective Oxidation of Methacrolein to Methacrylic Acid

A series of KxH1.1-xCu0.2Cs1(NH4)1.5PVMo11O40 (KxCuCsNH4PVA) catalysts with different x values were synthesized to catalyze the selective oxidation of methacrolein (MAL) to methacrylic acid (MAA). The effects of potassium (K) ions on both the structure and catalytic activity were studied in detail. The optimum K0.6CuCsNH4PVA exhibited a large surface area, more acid sites, and abundant active species (V4+/VO2+) in the secondary structure of the Keggin structure, consequently offering good catalytic performance. Furthermore, K ions increased the MAA selectivity at the expense of carbon monoxide and carbon dioxide (together defined as COX). Additionally, several process parameters for MAL oxidation were evaluated in the processing experiments. The effects of aldehyde impurities (formaldehyde and propanal) on the catalytic performance were investigated. Possible detrimental effects (catalyst poisoning and structural damage) of aldehyde impurities were excluded. A light decrease in MAL conversion could be attributed to the competitive adsorption of aldehyde impurities and MAL on the catalyst. Hopefully, this work contributes to the design of stable and feasible catalysts for the industrial production of MAA