摘要
以采用改进的气相沉积法制备的具有规整{1010}晶面的氧化锌纳米线为载体,合成了氧化锌纳米线负载钯催化剂,考察了还原温度和负载量对催化剂表面形成Pd Zn合金过程的影响,并通过适当的后处理过程制备了氧化锌纳米线外延生长Pd Zn纳米粒子催化体系.结果表明,当金属钯负载量较低(质量分数约为2%)时,经400℃还原后的催化剂表面会形成PdxZny(x>y)合金,从而影响催化剂的CO选择性;提高钯负载量或还原温度有利于将PdxZny(x>y)合金转化为Pd Zn合金,降低CO选择性.负载Pd Zn合金纳米粒子与氧化锌纳米线载体之间外延生长的界面关系使其在甲醇水蒸气重整反应中显示出优异的反应稳定性.
Zn O nanowires（ NWs） supported Pd catalysts were prepared by modified deposition-precipitation method and characterized by X-ray diffraction（ XRD）,X-ray photoelectron spectra（ XPS）,transmission electron microscopy（ TEM） and high angle annular dark field scanning transmission electron microscope（ HAADF-STEM）. The effects of Pd loading and reduction temperature on the formation of Pd Zn were investigated. The results showed that the high CO selectivity of 2. 1% Pd / Zn O NW catalyst after reduced at 400 ℃ is due to the formation of PdxZny（ xy） alloy. Increasing of Pd loading or reduction temperature is favorable for the transformation of PdxZny（ xy） to Pd Zn alloy which can inhibit CO formation. By a modified wet chemistry method and apt post-synthesis treatment,we have been able to grow Pd Zn alloy nanoparticles epitaxially onto the { 1010} nanofacets of the Zn O NWs. It showed better stability than Pd Zn supported on commercial Zn O powders in long term reaction. The methanol conversion at 300 ℃ over Pd / Zn O NW remained constant for about 40 h without obviously deactivation. On the contrary,the methanol conversion over Pd / Zn O powders catalyst gradually decreased with time on stream by more than 30%. The better stability of Pd / Zn O NW catalysts is due to the highly stable Zn O NWs primarily enclosed by the low-energy { 1010} surfaces and the epitaxial relationships between Pd Zn nanoparticles and Zn O NWs support.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
2016年第7期1372-1379,共8页
Chemical Journal of Chinese Universities
基金
国家留学基金委(CSC)项目资助~~
