酸碱度调控氧化锌纳米材料形貌及其光催化还原CO_2研究  

Controllable Modulation of Morphology and Photocatalytic Performance of ZnO Nanomaterials via pH Adjustment

作　　者：胡海峰[1,2] 贺涛[1] 

机构地区：[1]国家纳米科学中心中国科学院纳米系统与多级次制造重点实验室,北京100190 [2]中国科学院大学,北京100049

出　　处：《物理化学学报》2016年第2期543-550,共8页Acta Physico-Chimica Sinica

基　　金：国家科技部国际合作司(2015DFG62610)资助项目~~

摘　　要：利用水热法合成了形貌可控的氧化锌(ZnO)微纳材料。利用X射线衍射(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM),紫外-可见(UV-Vis)分光光谱和比表面积分析(BET)等技术对所制备的ZnO材料进行了表征。不同酸碱度(pH值)条件下,经过500℃退火2h制备的ZnO均为纤锌矿结构。随着前驱液pH值的增加,所得ZnO从片状晶体变为棒状晶体。片状ZnO主要暴露极性晶面,棒状ZnO主要暴露非极性晶面。从生长角度考虑,在溶液为弱酸性条件下(pH 6.5),溶液中游离的氯离子(CI^-)抑制了ZnO在锌极性面({Zn^(2+)}_(crystal surface))的生长,水热反应产物为片状Zn_5(OH)_8Cl_2·H_2O,退火后得到微孔片状ZnO;当溶液中添加氢氧根(OH^-)后,锌离子(Zn^(2+))被络合为四羟基锌络合离子(Zn(OH)_4^(2-)),该络离子促进了ZnO在Zn^(2+)}_(crystal surface)的生长,从而得到棒状晶体。利用上述催化剂,在氙灯照射下进行光催化还原二氧化碳实验,发现极性面较多的片状ZnO具有更高的光催化性能。ZnO microstructures and nanostructures with controlled-morphology were synthesized by the hydrothermal method.All samples were prepared using precursors at different pH values and then annealed at 500 ℃ for 2 h.The samples were characterized by X-ray diffraction（XRD） patterns,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,ultraviolet-visible spectroscopy（UV-Vis）,and BET specific surface area measurement.All samples were confirmed by XRD to be wurtzite ZnO.As the pH value of the precursor increased,sheet-like ZnO disappeared and rod-like ZnO was produced.The major surfaces of sheet-like and rod-like ZnO were polar and nonpolar crystal faces,respectively.At pH 6.5,Cl- was adsorbed onto the（002） polar face and inhibited the growth along the polar crystal face（{Zn2＋}（crystal surface））.A microporous sheet ZnO was formed by annealing the obtained sheet-like Zn5（OH）8Cl2·H2O.When OH^- was added into the precursor,Zn（OH）4^（2-） was generated via coordination with Zn^（2＋）,which was adsorbed onto the（002） polar face and promoted growth along the polar crystal face.Rod-like ZnO was thus produced.The obtained ZnO could photocatalytically reduce CO2 under illumination.Sheet-like ZnO exhibited better photocatalytic performance than rod-like ZnO.This may be because the polar crystal face shows better photocatalytic activity than the unpolar crystal face.

关 键 词：ZNO PH值 水热法 形貌 光催化CO2 

分 类 号：O643.36[理学—物理化学] TB383.1[理学—化学]