热动力学方法的研究Ⅰ. 反应速率常数、活化能的量热法测定

用流动型微量量热法测定了在不同温度下乙酸和甲醇及乙醇的酯化反应的速率常数, 并籍助于阿累尼鸟斯公式测定了这些反应的活化能。为了检验此方法的可靠性, 测定了乙酸甲酯和乙酸乙酯水解反应(酯化反应的逆反应)的速率常数, 这一实验结果与根据酯化反应实验数据计算得到的结果相一致。     

3D Nitrogen-Doped Graphene Encapsulated Metallic Nickel–Iron Alloy Nanoparticles for Efficient Bifunctional Oxygen Electrocatalysis

It is extremely desirable to explore high-efficient, affordable and robust oxygen electrocatalysts toward rechargeable Zn–air batteries (ZABs). A 3D porous nitrogen-doped graphene encapsulated metallic Ni₃Fe alloy nanoparticles aerogel (Ni₃Fe-GA₁) was constructed through a facile hydrothermal assembly and calcination process. Benefiting from 3D porous configuration with great accessibility, high electrical conductivity, abundant active sites, optimal nitrogen content and strong electronic interactions at the Ni₃Fe/N-doped graphene heterointerface, the obtained aerogel showed outstanding catalytic performance toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Specifically, it exhibited an overpotential of 239 mV to attain 10 mA cm⁻² for OER, simultaneously providing a positive onset potential of 0.93 V within a half-wave potential of 0.8 V for ORR. Accordingly, when employed in the aqueous ZABs, Ni₃Fe-GA₁ achieved higher power density and superior reversibility than Pt/C−IrO₂ catalyst, making it a potential candidate for rechargeable ZABs.     

Low Temperature Studies on the Grain-Size Effect on the Electro-optical Properties of ZnO Luminophores

The electroluminescence and photoluminescence of the self-activated ZnO luminophores exhibit three prominent bands in the green, yellow and Yellow-orange regions. With the reduction in grain size, these bands shift towards lower energy side and their energies are enhanced. The bands shift towards lower energy side with decreasing temperature of the luminophores. Both the electroluminescence and photoluminescence have maximum overall brightness for 33 micron grain size. One additional peak at 120 °K is found during the brightness studies of electroluminescence and photoluminescence of the luminophores. The appearence of such an additional peak is also confirmed from the studies of the brightness waves. The effects of grain size on the electro-optical properties of the self-activated ZnO luminophores are discussed on the basis of the existing ideas about photo- and electroluminescence.