本研究利用眾所皆知的溶膠凝膠法(SG)製備高表面積且結晶性好的鉭酸鈉奈米顆粒(SG500)。與傳統固相法(SS)製備的低表面積觸媒(SS1200)相比，SG500可提供較多的活性座以利電子電洞對與水反應產生氫氣跟氧氣，此外，較小的結晶粒徑可縮短電子電洞傳遞的路徑，降低電子電洞對再結合的機率。本研究也探討氧化鎳共觸媒效應，使鉭酸鈉進一步提升光分解水的效率。於觸媒鑑定方面，主要利用TGA分析溶膠凝膠法製備鉭酸鈉的鍛燒過程，其結果顯示在低溫下 (550C) 即可得到純相的鉭酸鈉。由XRD鑑定得知SG和SS分別為兩種不同的結晶結構。我們同時以拉曼光譜佐證XRD的結果，並將XRD分析結果配合文獻所知利用電腦軟體模擬其原子排列結構，並經由第一原理的計算求得SG500與SS1200的電子能量狀態密度 (Density of state) 與電子能帶結構 (Band structure)。表面分析方面，由SEM觀察其表面結構得知，SS1200顆粒大小介於2-3 μm，並在顆粒表面發現奈米階梯狀的排列，層與層之間的距離大約10 nm；反觀SG500顆粒大小約為30-50 nm，且為不規則形狀。我們更利用HR-TEM分析其電子繞射圖譜並深入探討其結晶性。由UV-Vis吸收光譜分析得知SS1200和SG500的能隙大小分別為4.0 eV與4.1 eV。最後以懸浮法分解水測試觸媒的光催化活性，研究結果發現，不論在何種鍛燒溫度下，利用溶膠凝膠法製備之鉭酸鈉在光分解水的活性皆比SS1200高許多，由此可知光觸媒奈米化造成結晶結構的變化的確有助於提高光分解水效率。

A well-known sol-gel synthesis route was developed to prepare high surface area and fine crystalline Perovskite-type NaTaO3 nanoparticles (denoted as SG500). Compared to the NaTaO3 with low surface area that prepared from traditional solid-state method (denoted as SS1200), SG500 provides more active sites for electron-hole pair to react with water and evolve H2 and O2. Furthermore, the decreasing of crystalline size implies the reducing of the probability of electron-hole recombination. In present work, the effect of NiO cocatalyst is also discussed to promote the photocatalytic water-splitting efficiency of NaTaO3. For the characterization of these photocatalysts, TGA is employed to analyze the calcination process of the NaTaO3 synthesized from sol-gel method. The result shows that pure NaTaO3 powder could be obtained when the calcination temperature goes higher than 550C. SG and SS are two kinds of crystalline structure after XRD identification. This consequence is also proved by Raman spectrum. According to the result of XRD as well as reported papers, we are able to simulate the atoms arrangement in NaTaO3 by computer software and also calculate the DOS and band structures of SG500 and SS1200 by First-Principle Theory. From the surface morphology observed by SEM, the particle size of SS1200 is about 2-3 μm while SG500 with irregular shape is around 30-50 nm. Nanostep arrangement is found on the particle surface of SS1200 as well as the distant between layer and layer is about 10 nm. We also use HR-TEM to analyze the electron diffraction pattern and discuss its crystallography. The band gaps of SS1200 and SG500 are estimated to be 4.0 eV and 4.1 eV by UV-Vis diffuse reflectance spectra, respectively. Consequently, SGNaTaO3 exhibit higher photocatalytic activity in suspension water-splitting system than that of SS1200, especially SG500, owing to the synthesis of nanoparticles which indeed leads to the transformation of the crystalline structure.

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