Pressure behaviour of the UV and green emission bands in ZnO micro-rods

The pressure behavior of the ultraviolet (UV) and green emission bands in ZnO tetrapod-like micro-rods has been investigated at 300 and 70 K, respectively. The pressure coefficient of the UV band at 300 K is 24.5 meV/GPa, consistent with that of the band gap of bulk ZnO. However, the pressure coefficient of the green band is 25 meV/GPa, far larger than previous literature reports. The green band in this work originates from Cu-related emission, as confirmed by the fine structure observed in the spectra at 10 K. The pressure coefficients of four phonon replicas of the free exciton emission (FX) at 70 K are 21.0, 20.2, 19.8, and 19.3 meV/GPa, respectively. The energy shift rate of the FX emission and the LO phonon energies is then determined to be 21.4 and 0.55 meV/GPa. The pressure coefficient of the neutral donor bound exciton ((DX)-X-0) transition is 20.5 meV/GPa, only 4% smaller than that of FX. This confirms that the (DX)-X-0 emission corresponds to excitons bound to neutral shallow donors. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Temperature and pressure dependences of the copper-related green emission in ZnO microrods

We have investigated the temperature and pressure dependences of the copper-related green emission, which show fine structure at low temperature, from tetrapodlike ZnO microrods. The temperature dependence of the green emission energy follows the changes in the band gap from 10-200 K, but deviates from this behavior above 200 K. The pressure dependence of the copper-related green band (25 +/- 5 meV/GPa) is similar to that of the band gap of ZnO, and is larger than that reported previously for defect-related green emission in ZnO. (c) 2006 American Institute of Physics.

The role of CeO2-ZrO2 as support in the ZnO-ZnCr2O4 catalysts for autothermal reforming of methanol

Autothermal reforming of methanol for hydrogen production was investigated over ZnO-ZnCr2O4 supported on a series of metal oxides (Al2O3, CeO2, ZrO2 and CeO2-ZrO2)CeO2-ZrO2 mixed oxides with Ce /Zr molar ratio of 4/1 was found to be the optimal support which showed significant effect on the catalytic activity and selectivity. The ZnO-ZnCr2O4/CeO2-ZrO2 and ZnO-ZnCr2O4 catalysts were characterized by XRD, TEM, H-2-TPR and XPS. The results show that CeO2-ZrO2 mixed oxides have significant effect on the catalytic performance and the supported catalyst shows more uniform temperature distribution in the catalyst bed which was mainly due to its reasonable redox properties.

贵金属改性的Cu/ZrO2基合成甲醇催化剂及其制备方法和应用

一种贵金属改性的Ｃｕ／ＺｒＯ↓［２］基合成甲醇催化剂重量组成为Ｃｕ：９－２４％，Ｚｒ７５－９０％，Ｐｄ或Ａｇ０．１－１．０％。用硝酸铜和氧氯化锆的混合溶液，在６０－９０℃下与碳酸钠溶液搅拌状态共沉淀，保持ｐＨ值在９－１１，沉淀经蒸馏水洗涤至无氯离子检出为止，经干燥后在３５０－５５０℃下焙烧，自然冷却至室温后，压片成型，破筛至４０－６０目。用浸渍法引入钯或银助剂，以硝酸盐的形式加入，浸渍时间为１２－２４小时，经红外灯照射烘干后制得催化剂。本发明具有催化剂机械强度好，性能重复性好，制备方法简单，易于操作的优点。