站在变换的高度系统地研究函数图象变换

1.问题提出 复习课的目标之一就是帮助学生系统归纳整理所学知识,及各知识点的联系与区别.由于高三数学复习的内容多,时间紧,不少教师为了加大容量,提高效率,往往省略使知识连贯起来,完成知识由厚到薄转化的过程,而是采用快速直接呈现知识网络结构,紧接着讲解例题,然后提供相应习练习.     

Dramatically Enhanced Visible-light-responsive H_2 Evolution of Cd_(1-x)Zn_xS via the Synergistic Effect of Ni_2P and 1T/2H MoS_2 Cocatalysts

Photocatalytic hydrogen generation from water-splitting holds huge promise for resolving the current energy shortage and environmental issues.Nevertheless,it is still challenging so far to develop non-noble-metal photocatalysts which are efficient toward solar-powered hydrogen evolution reaction(HER).In this work,through an ultrasonic water-bath strategy combined with solvothermal and electrostatic assembly processes,we obtain homogeneous Cd_1-xZn_xS–Ni₂P–MoS₂ hybrid nano-spheres consisting of Cd_1-xZn_xS solid solutions decorated by Ni₂P and 1 T/2 H MoS₂ cocatalysts,which demonstrate excellent activity and stability for visible-light-responsive(λ>420 nm)H₂ production.Specifically,the Cd_1-xZn_xS-Ni₂P-MoS₂ nano-spheres with 2 wt%Ni₂P and 0.2 wt%MoS₂(CZ_0.7S–2 N–0.2 M)exhibit the optimal HER activity of 55.77 mmol·g^-1·h^-1,about 47 and 32 times more than that of CZ_0.7S and Pt–CZ_0.7S,respectively.The outstanding HER performance of Cd_1-xZn_xS–Ni₂P–MoS₂ can be ascribed to the presence of abundant HER active sites in Ni2 P nanoparticles and 1 T/2 H MoS₂ nanosheets as well as the effective transfer and separation of charge carriers.Moreover,the coupling sequence of cocatalysts in Cd_1-xZn_xS–Ni₂P–MoS₂ is found to be critical in the regulation of charge transfer pathways and thus the resultant photocatalytic efficiency.The results displayed here could facilitate the engineering of high-performance photocatalysts employing multi-component cocatalysts for sustainable solar-to-fuel conversion.     

SO2气体对质子交换膜燃料电池阴极性能的影响

将5×10-8~3.2×10-6(空气中的体积含量)的SO2通入质子交换膜燃料电池(PEMFC)单电池阴极, 研究了SO2对PEMFC性能的影响. 实验得到的电压-时间(V-t)曲线和极化(V-I)曲线表明, 空气中SO2含量达到5×10-7时, 将对PEMFC的性能产生显著的和不可逆的影响, 且SO2浓度越大电池性能的下降幅度越大. 对SO2影响前后的电化学交流阻抗谱(EIS)的解析表明, 电池电荷传递阻抗(Rct)的变化可逆, 而阴极的表面状态发生了不完全可逆的变化. 循环伏安(CV)实验数据进一步证明, SO2毒化后阴极的活性电化学表面积(EAS)缩小.     

电镜用双层支持膜的制备及应用

本文综合了Formvar膜强度大和火棉胶膜分散性好的优点,制备出了Formvar-火棉胶双层支持膜。Formvar膜在下层增大了膜的强度,火棉胶膜在上层改善了膜的分散性。根据电镜对支持膜的特殊要求,摸索出了制备双层支持膜的原料溶液的浓度范围及浓度配比范围,并且通过红外光谱(IR)证实了双层支持膜结构的存在。通过实际应用,发现双层支持膜具有高分辨率、强电子束照射下膜保持稳定不破损等优点,双层支持膜比以前传统使用的单层支持膜在许多方面都取得了较大的改善,尤其适用于纳米材料的电镜观察,因此,值得进一步推广应用。     

环状磷酸催化合成2-取代苯并咪唑

以邻苯二胺和醛为原料,四氢呋喃为溶剂,在环状磷酸催化下,室温下合成了一系列2-取代苯并咪唑化合物.考察了催化剂种类、用量和溶剂对反应的影响,确定了最优反应条件,提出了可能的反应机理.该反应具有操作简单,条件温和,产率高及环境友好等优点.