本研究利用氧化鎳和二氧化鈦在紫外線程序中光還原二氧化碳，並分別探討初始二氧化碳濃度、相對溼度與不同重量濃度比的氧化鎳和二氧化鈦。除此之外，觸媒特性用BET, UV-visible, XRD 和SEM 來分析。
在這程序中，初始二氧化碳濃度為影響二氧化碳光還原反應之重要因素。由實驗結果來看，可得知反應迅速。約於120分鐘後，二氧化碳濃度會維持在一樣的濃度。實驗結果顯示不同濃度比的氧化鎳和二氧化鈦在紫外線程序中光還原二氧化碳，在反應條件為初始二氧化碳濃度為600 ppm和相對溼度是10%皆可產生最高的甲烷產量。
另一方面，相對濕度和不同劑量的氧化鎳也會影響甲烷的產量。結果顯示甲烷產量會隨著相對濕度和氧化鎳劑量增加。然而，更進一步增加相對濕度和氧化鎳劑量會減少甲烷的產量，因為過量水含量會影像觸媒的活性位置而20wt% 氧化鎳和二氧化碳透過BET, UV-visible結果顯示會影響孔洞體積，能帶隙和光觸媒活性。
本研究初步認為，以利用氧化鎳和二氧化鈦在紫外線程序中光還原二氧化碳，其最適操作條件為：初始二氧化碳濃度600ppm、10wt% 氧化鎳和二氧化鈦和相對溼度10%。在此操作條件下，甲烷最高產量為400 ppm/(gcatalyst)。

Photocatalytic reduction of carbon dioxide in gas phase by UV illumination and NiO/TiO2 process was studied under various initial carbon dioxide concentration, relative humidity, and coupled NiO dosage to evaluate the production of methane. In addition of that, the catalyst was detected by X-ray diffraction (XRD), field emission scanning electron (FE-SEM) microscope, UV-vis diffuse reflectance spectrometer (UV-DRS) and BET surface area analyzer.
In this system, the initial carbon dioxide concentration is a significant factor to effect the photocatalytic reduction of carbon dioxide. As can be seen, this experiment is continuous reaction. And, this result presents that photoreduction of CO2 reacts quickly. After around 120 minutes, the carbon dioxide concentration keeps in the same concentration. The experimental results reveal that photoreduction of carbon dioxide using different loading of NiO on TiO2 surface can produce the highest amount of methane at initial 600 ppm carbon dioxide when the relative humidity is 10%. However, it also shows that initial carbon dioxide concentration limits the product formation once the CO2 concentration is too high.
On the other hand, the relative humidity and coupled NiO dosage influence the production of methane. Results show that the production of methane increased with increasing relative humidity and couple NiO dosage. However, further addition of relative humidity and couple NiO dosage decrease the amount of methane because of the excessive of water content can influence the activated site and 20wt% NiO/TiO2 influence the pore size volume, energy gap and photocatalytic activity through BET surface area analyzer and UV-vis diffuse reflectance spectrometer (UV-DRS) result.
In this study, the optimum operating conditions for photocatalytic reduction of carbon dioxide in gas phase by UV illumination and NiO/TiO2 process is as following: initial carbon dioxide concentration 600 ppm, 10wt% NiO/TiO2, and relative humidity 45%. According to the conditions, the maximum amount of methane is 400 ppm/(gcatalyst).

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