以負載銀、銅之改質二氧化鈦結合MCM-41 進行光催化產氫之研究

Abstract

利用二氧化鈦產氫之研究已相當廣泛，為提升光催化產氫效率，本研究將金屬銅及銀以光沉積法負載於二氧化鈦表面，並結合中孔洞分子篩MCM-41，製備金屬負載二氧化鈦結合MCM-41之奈米複合材，以SEM、TEM、XRD、BET、UV-Vis 光譜及ESCA等不同鑑定方法分析光觸媒之表面型態、結構與特性。再利用不同操作參數進行光催化產氫之實驗，探討產氫效率以尋求最適操作條件。 研究結果顯示，當銅與銀金屬劑量分別為4.75 wt%及2.36 wt%，及光觸媒與MCM-41之比例為1:2時，有較佳之產氫效率。探討不同光觸媒對於產氫效率之影響，負載銅與銀金屬後TiO2之產氫量提升約3.1-3.3倍，推測金屬能有效抑制電子電洞對再結合。而光觸媒結合MCM-41後，產氫量亦可再增加2.1-2.9倍。探討其機制，MCM-41不僅提供高比表面積，增加甲醇與光觸媒表面接觸機會，同時延遲電子回復，進而增加產氫效率；另外，由氧氣產生速率顯示，產氫來源應以甲醇重組居多。

Hydrogen production over TiO2 catalysts composited with Ag/Cu metals and MCM-41 to form metal/TiO2-MCM41 nanocomposite materials has been studied. The photocatalytic H2 production rates were compared with those of pure TiO2 and metal/TiO2 photocatalysts. The surface and crystal structure analyses of photocatalysts were characterized by SEM, TEM, XRD, BET, UV/VIS and ESCA analyses. To effectively increase the hydrogen production, the optimization parameters were also investigated in this study. The results showed that the loading amount of Cu and Ag was 4.75 wt% and 2.36 wt% respectively, and the optimum ratio of photocatalysts and MCM-41 was 1:2 for maximizing the hydrogen yield rate. The amount of hydrogen generation was triply enhanced over metal loaded TiO2 as compared to the pure TiO2, which may be due to the presence of metal which suppressed e-/h+ recombination. And further supported the metal/TiO2 on MCM-41 led to about 2.1-2.9 times higher than metal/TiO2. The MCM-41 functioned as electron acceptor and as support matrix, it increased the contact probability between photocatalysts and methanol solution. According to the oxygen production rate, it showed that methanol was the major source for the hydrogen production.