多种纳米结构Fe掺杂TiO2光热耦合水分解制氢研究

氧空位是材料缺陷工程的重要组成. 基于光生氧空位的直接热利用, 实现纯水分解制氢的光热耦合实验, 被认为是太阳能综合利用的有效途径. 以多种制备方法合成的TiO₂纳米材料为基础, 研究了多种形貌纳米TiO₂及其Fe掺杂改性材料的光热耦合反应能力. 通过高分辨透射电子显微镜(HRTEM)、 X射线衍射(XRD)和电子顺磁共振(EPR)对晶体特征进行表征, 利用漫反射光谱(DRS)、 光致发光(PL)和三电极测试法表征了材料的性能, 并结合密度泛函理论(DFT)计算了产氢反应路径. 研究结果表明, 溶胶-凝胶法制备的纳米颗粒相比水热法制备的纳米片及纳米线, 体相内缺陷较多, 载流子强度高, 光热耦合产氢效果较差. Fe掺杂改性扩展了光响应, 增强了载流子分离和寿命, 降低了电子传输阻抗, 利于光反应过程中光生氧空位的形成, 克服了制氢反应中的关键能垒. 同时, 纳米材料中的缺陷促进了Fe离子的有效掺杂, Fe掺杂TiO₂纳米颗粒的光热耦合平均产氢量为9.73 μmol/g, 性能提升达13倍.     

Bifurcations and chaotic threshold for a nonlinear system with an irrational restoring force

Nonlinear dynamical systems with an irrational restoring force often occur in both science and engineering, and always lead to a barrier for conventional nonlinear techniques. In this paper, we have investigated the global bifurcations and the chaos directly for a nonlinear system with irrational nonlinearity avoiding the conventional Taylor's expansion to retain the natural characteristics of the system. A series of transformations are proposed to convert the homoclinic orbits of the unperturbed system to the heteroclinic orbits in the new coordinate, which can be transformed back to the analytical expressions of the homoclinic orbits. Melnikov's method is employed to obtain the criteria for chaotic motion, which implies that the existence of homoclinic orbits to chaos arose from the breaking of homoclinic orbits under the perturbation of damping and external forcing. The efficiency of the criteria for chaotic motion obtained in this paper is verified via bifurcation diagrams, Lyapunov exponents, and numerical simulations. It is worthwhile noting that our study is an attempt to make a step toward the solution of the problem proposed by Cao Q J et al. (Cao Q J, Wiercigroch M, Pavlovskaia E E, Thompson J M T and Grebogi C 2008 Phil. Trans. R. Soc. A 366 635).     

介绍一个富有创意的自制气体发生装置

该自制发生装置的器材全部采用废弃物组装而成,若算成本只不过0.3元左右,然而却能够极为方便的运用于反应物状态为固-液、液-液,并不需要加热制取气体的实验。该装置的组装及使用,对于增强师生变废为宝的意识,对于增强师生的创新理念,对于节省实验经费,对于经费短缺的我国西部农村中学实验室建设等,将起到很好的促进作用。