新穎Cu 氧化物奈米結構之合成、X 光繞射模擬分析及其異質接面光觸媒之應用

Abstract

本論文主要利用化學還原法，製備各式新穎p-type之Cu2O及CuO奈米結構、n-type之ZnO奈米結構、及其混合之p-n異質接面奈米結構，並探討此些奈米結構對光觸媒特性之影響。 在p-type之Cu2O及CuO奈米結構合成方面，Cu2O係利用典型Cu金屬奈米粒子製程於水中自然氧化所得，其形貌為圓球形，尺寸約為5 nm。其後再藉由各種氧化參數之改變，在液相水介質之中，將製備所得之零維Cu2O奈米粒子，轉變成為各式一維、二維之CuO奈米結構，包含鹿角狀、線形與片狀等等形貌，其長約100 ~350 nm，寬約15~120 nm不等。其中，並發現一維短柱狀Cu(OH)2奈米結構之存在，其長約數μm，寬約70 nm。 在n-type之ZnO奈米結構合成方面，藉由製程參數之調控，製備出一維單晶柱、八面體結構及三維花形結構。並利用懸浮零維Cu2O奈米粒子作為基材，使ZnO奈米結構直接成長於其上，合成出CuO/ZnO之 p-n 異質接面結構。實驗結果證實，透過ZnO與CuO的結合，可延長其受光激發電子與電洞的分離時間，使其光催化效果較單純混合ZnO與CuO奈米結構為佳，以線形CuO/花形ZnO複合材料為例，當使用Rhodamine B (Rh-B)作為染料時，其光催化效能可比直接混合兩材料提昇45%左右。在此些CuO/ZnO異質接面奈米結構中，以線形CuO/柱狀ZnO複合材料的光催化效果為最佳。 由於奈米粒子經常與其本身塊材之形貌有所不同，故本論文針對一些常見的奈米粒子形貌，進行XRD繞射光譜的理論模擬，在金屬奈米粒子方面包括球形、方形、十面體與二十面體奈米粒子，在氧化物方面則包含球形、方形與線形。從模擬數據與實驗數據的分析比對，歸納出由XRD繞射峰的強度比快速得知奈米粒子形貌之方法。

This thesis contains two main topics: heterojunction nano-structures and photocatalysts. First, a series of novel p-type Cu2O and CuO, n-tpye ZnO, and their mixed p-n heterojunction nano-structures were newly prepared mainly by chemical reduction method. Second, the nano-structures obtained were applied as photocatalysts and the nano-structural influence on photocatalytic performance was compared and discussed. Cu2O was prepared by spontaneous oxidation of spherical Cu nano-particles (~5 nm in diameter) in water at room temperature. Several novel CuO nano-structures were then simply synthesized by the further oxidation of the prepared Cu2O nano-particles in aqueous solutions. Accompanying with the oxidation process, a distinct morphological transformations from zero-dimensional (Cu2O) to one-dimensional or two-dimensional (CuO) was found and its mechanism is considered as the key point to produce such a variety of CuO nanostructures including buckhorn-like rods, short rods, and flakes, in this work. In addition, one-dimensional Cu(OH)2 nano-structures (~100 nm long and 15 nm in width) can also be found under some oxidation conditions. ZnO nano-structures including one-dimensional single crystal rods, octahedra and three-dimensional flower-like assemblies were synthesized. In addition, using suspended Cu2O nano-particles as substrates, ZnO nano-structures could directly grow on Cu2O to form a p-n heterojunction ZnO/CuO composite. Our photocatalytic experiment has proved that the p-n heterojunction ZnO/CuO composite prepared indeed presents at least 45% enhancement of the degradation efficiency of organic dye, Rhodamine B, comparing with the simple mixture of CuO and ZnO nano-structures. Nano-structures generally demonstrate a variety of morphologies in comparison with bulk materials. In this thesis, we illustrated a series of XRD analysis with theoretical calculations to distinguish some frequently observed morphologies of nano-particles, including cube, sphere, decahedron and icosahedron for metals and sphere, cube and rod for oxides.