Evaluation of Pt,Rh, SnO2, (NH4)2Mo3S13, BaSO4 protection coatings on WSe2 photocathodes for solar hydrogen evolution

The stability of photoelectrodes is of prime importance, which determines the long-term efficiency of solar to hydrogen conversion. To this respect, the performances of Pt, Rh, SnO₂, (NH₄)₂Mo₃S₁₃ (ATM), BaSO₄ are compared as protection coatings for WSe₂ photocathodes. It is found that Pt and Rh catalysts, selectively photodeposited at the active edges of WSe₂ crystallites, are not able to sustain the maximum photocurrent densities for hydrogen evolution reaction due to surface oxidation. By comparison, the ATM layer effectively passivates the van der Waals planes of WSe₂, however, it is oxidized with further amorphization, thus decreasing the photocurrent density by 82% after 3 h 10 min of PEC testing. The SnO₂ layer on top of ATM/WSe₂ stabilizes the photocurrent to some extent, but limits the maximum photocurrent density. Solution deposition of BaSO₄ onto ATM/WSe₂ photocathodes did not compromise the photocurrent density and resulted in significant improvement of the PEC stability. Herein, the photocurrent density is decreased by 44% after 3 h 10 min of testing, which is rather less than that of bare ATM/WSe₂. The chemical states of all photocathodes are assessed by XPS analysis, before and after PEC testing, which identified that the BaSO₄ suppresses photo-corrosion of the ATM.     

Electrochemical reforming of methane using SrZr0.5Ce0.4Y0.1O3-δ proton-conductor cell combined with paper-structured catalyst

Reforming of hydrocarbon which is an important hydrogen production method proceeds in two steps, i.e. steam reforming and shift reaction. Due to different thermodynamics, the two reactions are conventionally conducted at different temperatures. This study examines one step methane reforming by use of proton-conducting electrochemical cell in combination with a reforming catalyst. Promotion of the reforming reaction was intended by extracting hydrogen via electrochemical hydrogen pumping with a proton conductor cell. In order to compensate for the slow kinetics of the steam reforming, a paper catalyst loaded with Ni was placed in front of the electrochemical cell. Electrolyte support cells were used to verify this concept, and the effect of the electrochemical hydrogen pump was investigated from the composition of the outlet gas. Electrode support cells using a thin film electrolyte was used to reduce overvoltage. It is demonstrated that the steam reforming reaction and the shift reaction take place in one electrochemical cell. Effective catalyst placement and energy efficiency is discussed.     

A new method to retrieve significant wave height from X-band marine radar image sequences

A new method is proposed to retrieve significant wave height (SWH) from X-band marine radar image sequences. To reduce the inhomogeneity of the nearshore wave field, the principal component (PC) of the radar image sequence is extracted by empirical orthogonal function (EOF) analysis. To measure the information contained in each PC, the Shannon entropy is introduced after the PC is normalized. Based on the information contained in the wave field, a linear relationship is established to retrieve the SWH from the Shannon entropy of the PC. The method is validated by comparison with measurements from in situ buoys: the root mean square error between the SWH measured by a buoy and the retrieved value is 0.22 m, while the corresponding bias and correlation coefficient are 0.01 m and 0.92, respectively. The physical meanings of different EOF modes decomposed from the wave field are also discussed.     

Effects of hydrogen atmosphere on pulsed-DC sputtered nanocrystalline Si:H films

Hydrogenated nanocrystalline silicon (nc-Si:H) films were prepared by a pulsed-DC magnetron sputtering method under an atmosphere of hydrogen/argon mixture. The effects of hydrogen concentration on the structural and electrical properties of the films were systematically investigated using grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy, and conductivity measurement. A threshold hydrogen concentration of about 70% was found necessary before any crystallinity was detectable. The deposition rate decreased monotonically with increasing hydrogen concentration, while the conductivity varied with crystallite size. The abnormally low conductivity level of these nc-Si:H films was due to the extraordinarily high defect density, which was attributed both to the enhanced ion bombardment from the pulsed-DC plasma and to the oxygen contamination from the target.     

Corrosion behaviour in concrete of three differently galvanized steel bars

The increasing use of galvanized steel reinforcements in concrete structures submitted to aggressive environments induces research into innovative zinc coatings with higher corrosion resistance. In this work, several cylindrical concrete specimens were manufactured with two cements of different alkalinity and reinforced with different hot-dip galvanized bars obtained from the “traditional” Zn–Pb bath and from two “modified baths”: Zn–Ni–Bi and Zn–Ni–Sn–Bi. The corrosion rate and corrosion potential of the bars were monitored during the air curing period and during wet–dry exposure both in tap water and in a 5% sodium chloride solution. The results showed that the coatings obtained from Zn–Ni–Sn–Bi bath have the highest corrosion rates, when the aggressiveness of the concrete matrix is determined mainly by its alkalinity. On the contrary, when the corrosion process is determined mainly by the penetration of chlorides (concrete manufactured with cement having a low alkali content) Zn–Ni–Sn–Bi was attacked only when the chloride concentration at the concrete cover depth reached the threshold of 4.02% (by weight of cement), which is higher than those necessary for the attack of the other coatings studied (1.36% for Zn–Ni–Bi, 1.73% for Zn–Pb).     

琼东南盆地南部深水凹陷生物礁及碳酸盐岩台地发育模式

生物礁及碳酸盐岩储层是一种典型的油气储层,具有巨大的油气勘探潜力。我国南海是西太平洋最大的边缘海,其在形成演化过程中出现了有利于生物礁及碳酸盐岩发育的环境。琼东南盆地南部深水凹陷远离物源,在构造演化过程中产生了较多的构造高点,在这些构造高点的周缘适合生物礁及碳酸盐岩台地的发育。通过地震资料的解释及海平面变化曲线与层序的对比发现,琼东南盆地南部深水凹陷发育有规模大小不等的生物礁和碳酸盐岩台地,而且这些生物礁和碳酸盐岩台地的发育与海平面变化曲线和构造演化的阶段可以对应起来,应具有较好的油气勘探潜力。     

琼东南盆地深水区多边形断层的发现及其油气意义

在高精度的三维地震资料基础上,利用层拉平和相干切片技术,在南海北部琼东南盆地首次发现多边形断层。多边形断层是一种非构造成因的断距微小的张性断层。琼东南盆地深水区的多边形断层长度为150～1500m,间距为150～3000m,断距为10～40m,倾角为50°～90°,发育在3个层位。琼东南盆地可以分为裂谷断陷期和裂后热沉降期两个演化阶段;裂后热沉降期构造断裂不发育,缺乏连接烃源岩和储层的通道,不利的油气疏导系统成为制约该期成藏最主要的因素之一。多边形断层的存在可以有效地解决这个问题,它可作为油气运移的疏导体系,使下部生油层中的油气向上运移成藏,对南海北部裂后热沉降期油气运聚具有重要的意义。     

地质样品中微量元素的高效测试方法

设计并加工了具有双内弧密封结构的防腐高效溶样罐,在消解地质样品时,加入内标¹⁰³Rh校正样品中元素的浓度,以内标¹⁸⁵Re校正分析信号的漂移,使用电感耦合等离子体质谱测定深海沉积物标准物质和国际地质标准物质中的34种微量元素浓度。与以往消解方法相比,该方法密封性好、酸消耗少,只需1.5 mL浓HF、0.5 mL浓HNO₃和0.25 mL HClO₄就可将40 mg地质样品在短时间内消解完全,消解效率高。前处理过程中加入内标¹⁰³Rh,样品稀释时无需准确定容,节省操作时间。方法检测下限为0.001~0.621 μg/g,精密度（RSD,n=10）小于5%,准确度小于6.5%（其中大多数元素小于3%）,适用于多种地质样品中多元素的分析。     

Efficacy of a Chitin-Based Water-Soluble Derivative in Inducing Purpureocillium lilacinum against Nematode Disease (Meloidogyne incognita)

Plant-parasitic nematodes cause severe economic losses annually which has been a persistent problem worldwide. As current nematicides are highly toxic, prone to drug resistance, and have poor stability, there is an urgent need to develop safe, efficient, and green strategies. Natural active polysaccharides such as chitin and chitosan with good biocompatibility and biodegradability and inducing plant disease resistance have attracted much attention, but their application is limited due to their poor solubility. Here, we prepared 6-oxychitin with good water solubility by introducing carboxylic acid groups based on retaining the original skeleton of chitin and evaluated its potential for nematode control. The results showed that 6-oxychitin is a better promoter of the nematicidal potential of Purpureocillium lilacinum than other water-soluble chitin derivatives. After treatment, the movement of J2s and egg hatching were obviously inhibited. Further plant experiments found that it can destroy the accumulation and invasion of nematodes, and has a growth-promoting effect. Therefore, 6-oxychitin has great application potential in the nematode control area.