不同有機和無機水污染物從不同行業排出，有來自紡織工廠的染料汙染，有從皮革、電鍍、鋼鐵製造、染色和木材防腐產業所釋放具有高毒性的六價鉻。除非有效處理這些有機和無機有毒化學品，否則健康和環境問題將會惡化。光催化劑有潛力以還原或氧化反應來降解毒化學物質成毒性較小或無毒的化合物。
論文第一部分，主要探討金屬氧化物/g-C3N4複合光催化劑，提出光催化劑表面缺陷所促進的氧吸附於光催化染料降解的研究。研究中，使用水熱法製備具氧缺陷的Sn-WO3固溶體，再將Sn-WO3和g-C3N4混合粉末在450oC空氣熱處理，實現具有吸附氧的Sn-WO3/g-C3N4光催化劑。實驗中，以不同的材料檢測技術分析，也採用陰離子型甲基橙(MO)和陽離子型羅丹B (RhB)染料的降解，來檢測可見光照射下其光催化劑活性。在所有複合光催化劑中，8-SnWg催化劑在照射時間2小時內，獲得1.42×10-2min-1的降解率，達87％MO降解。在可見光照射50分鐘內，8-SnWg催化劑有8.44×10-2 min-1的RhB降解速率，達99％RhB降解。X射線光電子能譜(XPS)分析顯示，分子氧吸附在所製備的複合光催化劑表面上。具有Sn：W比為1：2的Sn-WO3固溶體中，錫的引入以及與石墨化的氮化碳(g-C3N4)的異質界面構造對於光催化活性的增強有著至關重要的作用，係藉由通過吸附氧的活化與染料分子反應達到染料降解。
論文第二部分，藉由電子-電洞分離的控制、氧空位形成、光催化劑的粒徑和形態等，對提高光催化劑的催化活性進行探討。研究中，BiOCl光催化劑係通過在KCl飽和水溶液中，於UV光照射的處理下，使用簡單水解方法製備沿著具反應性的(001)面成長與合成BiOCl粉體。實驗中，以不同的材料檢測技術分析，並以降解不同種類的有機染料來評價其光催化活性。實驗結果顯示，用20mmolKCl製備的20-BiOCl，在可見光照射10分鐘
內，可降解99.9%的RhB。根據動力學數據，UV光處理的20-BiOCl分別比未UV光處理的20-BiOCl和不飽和合成的5-BiOCl，其降解RhB染料速率分別高過7倍和3倍。此外，20-BiOCl催化劑在UV光照射下進行染料降解時，幾乎可完全降解RhB、MO和MB三種染料。在可見光照射下，超氧化物(O2.-)和羥基(·OH)自由基被認為是RhB染料降解的主要活性物質。重要結論是合成BiOCl催化劑時，KCl飽和度和UV光處理二者，都對光催化劑的光催化活性起著至關重要的作用。
論文第三部分，利用低帶隙可見光響應光催化劑與紫外光響應光催化劑結合所形成的異質結構造，可使UV光活化材料也具有可見光染料降解能力。此工作中，我們使用簡單的反應攜出法合成具異質接面結構的Bi2(O,S)3/Zn(O,S)光催化劑。實驗中，以不同的材料檢測技術分析與重金屬Cr(VI)去汙研究。所合成的複合光催化劑，在整個可見光譜中皆顯示出高的光吸收能力。通過Cr(VI)還原來評價光催化劑的還原催化活性。雖然純Zn(O,S)催化劑沒有出顯著的Cr(VI)還原能力，但在用Bi2(O,S)3的異質結構造複合之後，表現出比單個組分更高的光催化活性。 Bi/Zn摩爾百分比為20%的20-BiZnOS催化劑，在可見光照射12min內，Cr(VI)還原率達99.5％，是複合材料中表現出最佳的光催化活性。20-BiZnOS複合催化劑其Bi2(O,S)3和Zn(O,S)納米粒子之間的異質結構形成、Cr(VI)的選擇性吸附和Cr(III)的表面脫附，是複合光催化劑具有增強的光催化活性主要原因。

Organic and inorganic water contaminants are discharged from different industries. Dyes from textile factories make their way mostly to water bodies. Highly toxic, water soluble, hexavalent chromium are also released to the environment from leather, electroplating, steel manufacturing, dyeing, and wood preservation industries. Unless there is effective way of treating these organic and inorganic toxic chemicals, the health and environmental problems are expected to be catastrophic. Photocatalysts are employed in either reduction or oxidation of these toxic chemicals to less toxic or nontoxic substances. In the first work, defect-mediated oxygen adsorption on metal oxide/g-C3N4 composites was proposed for photocatalytic dye degradation processes. Thus, oxygen deficient Sn-WO3 solid solution was first prepared using solvothermal method. Oxygen adsorbed Sn-WO3/g-C3N4 composites synthesis was experimentally achieved by annealing the mixture of Sn-WO3 and g-C3N4 powders at 450 oC under atmospheric oxygen. The materials were characterized with different techniques and photocatalytic activities were examined by the degradation of anionic methyl orange (MO) and cationic Rhodamine B (RhB) dyes under visible light. Among all the composites, the highest rate of 1.42×10-2 min-1 with 87% MO degradation was obtained by 8-SnWg catalyst within two hours of irradiation time. RhB dye removal with a rate of 8.44×10-2 min-1 and 99% degradation was also achieved within 50 minutes of visible light illumination. X-ray photoelectron spectroscopy (XPS) analysis reveals molecular oxygen adsorption on the surface of the as-prepared composite material. The introduction of tin in Sn-WO3 solid solution with a high atomic Sn:W ratio of 1:2 and the construction of interfacial heterojunction with graphitic carbon nitride (g-C3N4) plays a vital role to the enhanced
II
photocatalytic activity of the as-prepared composites by activating oxygen to react with dye molecules.
On the second work, we considered the control of electron-hole separation, oxygen vacancy formation, particle size, and morphology together is supposed to boost the catalytic activity of the materials. Hence, BiOCl photocatalysts were synthesized by a systematic control of particle growth along reactive (001) plane using simple hydrolysis method in KCl saturated aqueous solution with simultaneous UV light treatment. The materials were characterized using different techniques and the photocatalytic activities were evaluated for degradation of different kinds of organic dyes. 20-BiOCl prepared with 20 mmol KCl showed 99.9% RhB degradation within 10 minutes of visible light irradiation. From kinetics data, 20-BiOCl showed 7 and 3 times higher rates on RhB dye degradation than untreated 20-BiOCl and unsaturated 5-BiOCl, respectively. Furthermore, 20-BiOCl catalyst also exhibited almost complete degradation of RhB, MO, and MB dyes under UV light irradiation. Supper oxide (O2.-) and hydroxyl (·OH) radicals are identified as the main active species on the degradation of RhB dye under visible light irradiation. Both KCl saturation and UV light treatment during synthesis of BiOCl catalysts play a crucial role to the exhibited extraordinary photocatlytic activities.
Heterojunction construction with low band gap materials is another effective way of utilizing UV light active materials under visible light irradiation. On the last work, we report the synthesis of Bi2(O,S)3/Zn(O,S) hetrostructure using simple solvothermal method without surfactant. The catalysts were investigated with different characterization techniques. All the composite catalysts showed high light absorption capacity in the whole visible light spectrum. The catalytic activity of the catalysts was evaluated by Cr(VI) reduction. While pure Zn(O,S) catalyst showed no significant Cr(VI) reduction, higher photocatalytic activity than individual components were
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exhibited after heterojunction construction with Bi2(O,S)3. 20-BiZnOS catalyst with Bi/Zn molar percentage of 20% showed the best photocatalytic activity among the composites with 99.5% Cr(VI) reduction within 12 min under visible light irradiation. Heterojunction formation between Bi2(O,S)3 and Zn(O,S) nanoparticle, selective adsorption of Cr(VI) and desorption of Cr(III) on the surface of 20-BiZnOS composite catalyst were ascribed to the enhanced photocatalytic activity of the composite catalyst.

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