Photocatalytic H2 evolution activity of CuO/ZrO2 composite catalyst under simulated sunlight irradiation

Zirconia-supported CuO (CuO/ZrO₂) composite photocatalysts were successfully synthesized via citric acid-assisted sol-gel technique. For comparison, CuO/ZrO₂ materials were also prepared by solid state reaction and co-precipitation method. The as-prepared powders were characterized by X-ray diffractometry (XRD), transmission electron microscopy (TEM), and thermogravimetric-differential thermal analysis (TG-DTA). The photocatalytic activity of CuO/ZrO₂ catalyst was investigated based on the H₂ evolution from oxalic acid solution under simulated sunlight irradiation. The effects of molar ratio of CuO to ZrO₂, preparation method, phase change with the calcination temperature and the durability on the photocatalytic activity of the photocatalyst were investigated in detail. It is found that the optimal activity of photocatalytic H₂ evolution (2.41 mmol·h⁻¹μ⁻¹) can be obtained when CuO/ZrO₂ composite photocatalyst is synthesized by sol-gel technique and the mole ratio of CuO to ZrO₂ is 40%. The activity of copper oxide supported on monoclinic ZrO₂ calcined at higher temperature is much higher than that on tetragonal ZrO₂ calcined at lower temperature, and the best calcination temperature is 900 °C.     

添加VN颗粒的铸态AZ91镁合金在NaCl溶液中的腐蚀行为（英文）

采用光学显微镜(OM)、X射线衍射(XRD)、扫描电子显微镜(SEM)技术和电化学实验研究铸态AZ91-xVN(x=0,0.25,0.5,1，质量分数，%)合金的显微组织和腐蚀行为。结果表明，VN对AZ91合金显微组织具有明显的细化和改性作用。随着VN颗粒的加入，AZ91合金的耐腐蚀性能先提高后降低。铸态AZ91-0.25VN合金具有最佳的耐腐蚀性能，其腐蚀速率最低(P_W=(1.47±0.06)mm/a)，这主要归因于其具有更多可作为腐蚀屏障的晶界。随着VN含量的进一步增加，合金中片状β-Mg₁₇Al₁₂析出相的量增加，由于β相与α-Mg基体易发生电偶腐蚀，合金的耐蚀性能逐渐降低。