Hydrothermal synthesis, characterization, and photocatalytic performances of Cr incorporated, and Cr and Ti co-incorporated MCM-41 as visible light photocatalysts for water splitting

A series of Cr incorporated, and Cr and Ti co-incorporated MCM-41 photocatalysts were synthesized by hydrothermal method. X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (UV–vis), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence analysis (XRF), N₂ adsorption–desorption isotherms and Raman spectra were used to investigate the effects of the incorporated elements on the structure of MCM-41. The experimental results for photocatalytic water splitting under visible light irradiation (λ > 430 nm) demonstrated that the photocatalytic activities of Cr-MCM-41 and Cr-Ti-MCM-41 catalysts for hydrogen production decreased with an increase in the amount of Cr incorporated. Compared with the Cr-MCM-41 which had the same amount of incorporated Cr, the Cr-Ti-MCM-41 exhibited much higher hydrogen evolution activities.     

水平矩形管内气液两相流界面波特性

<正>气液两相流中界面波的存在对传热、传质、阻力特性及稳定性都有很大影响。前人有关界面波的研究大多偏重于两相流中界面波的类型及其转变,而对其特征参数变化规律(如振幅、波长、频率和速度等)的研究则很少。但界面波对气液两相流流动阻力和流动结构影响机理的深入研究必须以了解界面波的各特性参数为前提,同时界面波有关特性参数的深入研究也可为气液两相流的数学理论化提供实验基础。 本文以气、水为工质,系统研究了水平矩形管内气液两相流的界面波特性。根据界面波在时域、幅域内的不同特征区别出了各种类型的波并给出了相应的波形和流型图。着重研究了界面波各特征量随气液两相流量变化的变化规律。     

Preparation and photocatalytic activity of PANI-CdS composites for hydrogen evolution

In this paper, a series of PANI-CdS (PANI is the abbreviation of Polyaniline) composites were synthesized by changing the mass of PANI (molar ratio of PANI and CdS : 0.5, 0.7, 1, 1.5, 2). The PANI-CdS composites were characterized by XRD patterns, IR spectra and elemental analysis. The activities of as-prepared composites were also tested with regard to hydrogen evolution. It was found that PANI-CdS composites showed good activity for hydrogen evolution. With increment of PANI, the activity for hydrogen evolution of PANI-CdS reduced. But compared with pure CdS, PANI-CdS had a much higher activity for hydrogen evolution.     

Study on photocatalytic performance for hydrogen evolution over CdS/M-MCM-41 (M = Zr, Ti) composite photocatalysts under visible light illumination

A series of CdS/M(x)-MCM-41 (M = Zr, Ti, x stands for molar ratio of M/Si) photocatalysts were preprared by hydrotherm, ion-exchange and sulfidation process. The catalysts were characterized by X-ray diffraction, UV-vis spectra and N₂ adsorption-desorption isotherm et al. The characterization results shown that Zr or Ti was successfully doped into the mesoporous of MCM-41, and CdS was also successfully incorporated into such modified mesoporous. The results of photocatalytic performance for hydrogen production shown that CdS/Zr(0.005)-MCM-41 and CdS/Ti(0.02)-MCM-41 had the highest hydrogen evolution activity in triethanolamine aqueous solution under visible light (λ > 430 nm) irradiation, which can be explained by the diffusion velocity of the reactants and resultants and the protection which MCM-41 provided for CdS.     

A newly isolated Rhodobacter sphaeroides HY01 with high hydrogen production performance

A newly isolated strain, HY01, was identified to be Rhodobacter sphaeroides by phylogenetic analysis. Some DNA sequence data indicate that it is highly similar to R. sphaeroides ATCC 17029. The effects of initial pH values, nitrogen sources and carbon sources on hydrogen production were studied. The results showed that pH 7.25 is optimum for its hydrogen production. Among the nitrogen sources of glutamic acid, yeast extract, glycine, ethanolamine and l-aspartic acid, the maximum hydrogen production rate of 98.0 ± 6.2 mL/(Lh) using 10 mM glutamic acid and maximum hydrogen yield of 7012.5 ± 150 mL/L using 5 mM glutamic acid was obtained. Maximum hydrogen production rates of 148.7 ± 4.6 mL/(Lh) and 94.8 mL/(Lh) were obtained under 10 klux and 5 klux light intensity using 7 mM glutamic acid as nitrogen source, respectively. Compared with the reported data, it shows high hydrogen production performance and is a good candidate for further study.     

单个液滴蒸发模型中不同质量传递公式的有效性分析

液滴蒸发是液体喷雾的重要物理过程,文献中使用了不同的模型计算液滴蒸发中的质量流率。依据质量传递驱动力HM的处理,可将这些模型归类于三种不同形式,即经典模型、质量类比模型和漂移流动模型。本文对这些模型的来源和假设作了分析和总结,发现漂移流动模型考虑了Stefan效应和质量迁移,应为正确的表述,而经典模型忽略了瞬态效应,质量类比模型忽略了Stefan流效应。最后以两种不同蒸发率条件下的液滴蒸发为例进行计算,研究了不同质量传递驱动力对液滴蒸发的影响, 发现经典模型和质量类比模型都对液滴的蒸发估计过低,且高蒸发率下三种模型对液滴蒸发特性的影响更显著。     

气液两相流界面波的双平行电导探针测量方法研究

使用双平行电导探针，通过测量气液两相瞬时液膜厚度，来反映气液两相流界面上的波动规律，对经测量系统进行了理论和实验研究，根据界面波的物理特性，设计出一种能够快速准确地测量液膜厚度的电导探针系统，并且提出了一种不受实验条件变化影响的探针标定方法。通过对水平管内空气－水气液两相流分层流界面厚度的测量，证明这种方法是切实可行的。     

Activating ZnO nanorod photoanodes in visible light by Cu ion implantation

Utilization of visible light is of crucial importance for exploiting efficient semiconductor catalysts for solar water splitting. In this study, an advanced ion implantation method was utilized to dope Cu ions into ZnO nanorod arrays for photoelectrochemical water splitting in visible light. X-ray diffraction （XRD） and X-ray photo-electron spectroscopy （XPS） results revealed that Cu^＋ together with a small amount of Cu^2＋ were highly dispersed within the ZnO nanorod arrays. The Cu ion doped ZnO nanorod arrays displayed extended optical absorption and enhanced photoelectrochemical performance under visible light illumination （A 〉 420 nm）. A considerable photocurrent density of 18 μA/cm^2 at 0.8 V （vs. a saturated calomel electrode） was achieved, which was about 11 times higher than that of undoped ZnO nanorod arrays. This study proposes that ion implantation could be an effective approach for developing novel visible-light-driven photocatalytic materials for water splitting.     

连续式超临界水中煤/CMC催化气化制氢

在向水煤浆中添加CMC（羧甲基纤维素钠），成功实现水煤浆高压均匀输送基础上，对超临界水中煤／CMC催化气化制氢性能进行了进一步研究。结果表明：在压力20～25MPa、停留时间15～30s、NaOH添加量0．1％、反应器外壁温650℃条件下，超临界水中煤/CMC催化气化制氢气体产物中H2摩尔含量远比常规气化高，主要气体产物是H2、CO2和CH4。增加物料中CMC的含量、升高压力均有利于提高气体产物中心的产量，延长停留时间虽有利于物料气化但不利于氢气的制取。     

Experimental research on catalysts and their catalytic mechanism for hydrogen production by gasification of peanut shell in supercritical water

Peanut shell, mixed with sodium carboxymethyl-cellulose, was gasified at a temperature of 450°C and a pressure range from 24 to 27 MPa with the presence of different catalysts, including K₂CO₃, ZnCl₂ and Raney-Ni. The experimental results show that different catalysts have greatly different effects on the reaction. Gasification efficiency (GE), hydrogen gasification efficiency (GHE), carbon gasification efficiency (GCE), yield of hydrogen production and potential yield of hydrogen production are applied to describe the catalytic efficiency. From the result of gaseous components, ZnCl₂ has the highest hydrogen selectivity, K₂CO₃ is lower, and Raney-Ni is the lowest, but Raney-Ni is the most favorable to gasify biomass among the three catalysts, and its G _E, G _HE, G _CE reach 126.84%, 185.71%, 94.24%, respectively. As expected, hydrogen selectivity increased and CH₄ reduced rapidly when the mixture of ZnCl₂ and Raney-Ni is used under the same condition. The optimization mixture appeared when 0.2 g of ZnCl₂ was added to 1 g of Raney-Ni, 43.56 g·kg⁻¹ of hydrogen production was obtained. In addition, the catalytic mechanisms of different catalysts were analyzed, and the possible reaction pathway was brought forward, which helped to explain the experiment phenomena and results correctly. __________ Translated from Journal of Xi’an Jiaotong University, 2006, 40(9): 1 263–1 267 [译自: 西安交通大学学报]