使用鹼性礦化劑進行水熱法合成高結晶性奈米氧化鋅錫特性之研究

Abstract

光觸媒產業近年來掀起一股熱潮，以二氧化鈦材料為主的光觸媒研究與開發已經有一段時間，除了本身具有快速帶電電荷之再結合和較低的界面間電荷遷移等缺點仍需改善，且對於其他光觸媒材料的發展並不成熟，因此在光觸媒材料的研發上更需要朝多元的方向來突破。氧化鋅錫(Zn2SnO4，ZTO)材料不僅具有很好的光電特性，而且其熱穩定性與化學穩定性佳，因此在光觸媒產業與半導體產業中甚具開創性，然而相關研究非常有限，而水熱法長晶可以有效將氧化鋅錫材料奈米化，使之在奈米尺寸下能夠呈現更好的光觸媒及光電特性。 本研究利用水熱法，將含有鋅和錫離子之水溶液與鹼性礦化劑(NaOH、Na2CO3)，混合於密封壓力釜中，在低溫與高壓下使水溶液達到超臨界狀態，讓鋅與錫粒子間可以充分交互作用，並形成高結晶性奈米級氧化鋅錫粉末。在不同水熱處理下控制長晶條件，實驗結果發現，經過250oC、48h之水熱條件下可達到結晶性最佳的奈米顆粒，由拉曼光譜得知ZTO屬於尖晶石結構(spinel structure)，其中Na2CO3礦化劑系統之ZTO為略小於50nm之不規則顆粒狀，對於紫外光光吸收與光觸媒實驗效果良好，與商用P25 TiO2 十分接近。

Due to the wide applications of green technology, photocatalysts has become popular in recent years. Although much attentions of TiO2 has been paid since ever, TiO2 still has some disadvantages (e.g., fast charge-carrier recombination and low interfacial charge-transfer rate) needed to be improved. Due to this, to develop other photocatalysts for myriads of applications is a priority issue to industry. Recent findings indicated that ZTO has significant potential to be used for applications in photocatalysts and semiconductor due to its attractive optical and electric properties, and good thermal and chemical stability. However, related studies for these characteristics were seldom to be mentioned. As ZTO can be effectively scale down in nano level by hydrothermal method, it could express better photoelectric property than conventional materials. Here, we used a hydrothermal method applied under high pressure to combine zinc ion and tin ion solution with mineralizers (NaOH, Na2CO3) into a sealed autoclave. After that, the solution was heated to supercritical condition to form high nano-crystalline ZTO powder via interactions with zinc and tin particles. By different hydrothermal treatment, our findings showed that high-crystalline ZTO nanoparticles could be formed at 250oC for 48 hours. According to Raman analysis, this ZTO belongs to spinel structure. The UV-Visible absorption spectrum and photocatalytic investigations exhibited that in the Na2CO3 system ZTO was shown in particle size less than 50 nm and express an excellent performance of photocatalytic activity in comparison to commercial P25 TiO2.