ZnO microstructures and nanostructures with control ed-morphology were synthesized by the hydrothermal method. Al samples were prepared using precursors at different pH values and then annealed at 500 ° C 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. Al 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)42-was generated via coordination with Zn2+, 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 photocatalytical y reduce CO2 under il umination. 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.%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°C退火2 h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(Cl－)抑制了ZnO在锌极性面({Zn2+}crystal surface)的生长，水热反应产物为片状Zn5(OH)8Cl2∙H2O，退火后得到微孔片状ZnO；当溶液中添加氢氧根(OH－)后，锌离子(Zn2+)被络合为四羟基锌络合离子(Zn(OH)42－)，该络离子促进了ZnO在{Zn2+}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。
展开▼
