二硫化鉬超薄膜於光催化二氧化碳還原反應之應用 Ultra-Thin Film MoS2 Photocatalysts for Photocatalytic CO2 Reduction Application

Date
2021
Authors
廖冠瑋
Liao, Kuan-Wei
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Abstract
隨著全球暖化的影響,地球上的環境也發生了巨大的變化,因此若能將二氧化碳有效轉換成碳氫化合物,必定能為地球減少許多負擔,因此本研究利用人造光合成系統將其轉換,作為新興的替代能源,期望能改善環境和能源議題。本論文使用的二維材料為過渡金屬二硫族化合物,並選擇二硫化鉬薄膜作為光觸媒材料。使用熱蒸鍍和化學氣相沉積法來合成三奈米二硫化鉬薄膜於不同基板上,如二氧化矽/矽、氧化鋁、二氧化矽、鈦酸鍶基板,並將這些材料作為光觸媒,並藉由應變效應將其應用在探討二氧化碳光催化還原上。在合成不同厚度二硫化鉬的製程中,我們可以有效的控制二硫化鉬薄膜的厚度,並將其藉由拉曼分析顯示,不同厚度的二硫化鉬薄膜其表面是非常均勻的,且具備良好的可見光吸收波段,並根據實驗結果得知三奈米二硫化鉬薄膜具有最好的光催化效率。並使用不同硫化的製程來將三奈米二硫化鉬薄膜優化,根據拉曼和光激發螢光結果得知,使用硫粉製程的三奈米二硫化鉬薄膜品質是最好的,並根據實驗結果得知其光催化效率比使用硫化氫較高。綜合以上實驗結果,我們選用硫粉製程的三奈米二硫化鉬薄膜,並成長在四種不同的基板上,而這些基板分別為二氧化矽/矽、氧化鋁、二氧化矽、鈦酸鍶基板,並藉由儀器分析,來測定其厚度、應變效應以及能隙大小,根據實驗結果可以得知,當應變較小時,其光催化效率不好,當應變增加到一定值時,其光催化效率為最高,而當應變太大時,其會增加光催化產物選擇性,而這些反應機制值得未來進一步地加以探討。
Due to global warming, many scientists are studying how to reduce the greenhouse effect. This study used the transition metal dichalcogenides (TMDCs) as the photocatalysts for CO2 photoreduction. Molybdenum disulfide (MoS2) thin-film has been particularly found in unique applications in catalysis, optoelectronics, transistors, etc.Lattice strain can enhance the activity and selectivity of electrochemical reactions by breaking the linear scaling relationship. Notwithstanding, the explicit use of strain to affect the CO2 reduction reaction (CO2RR) is rarely reported. In this perspective, we highlight the opportunity to use strain to affect the activity and selectivity of CO2RR photocatalysts. We use the thermal evaporation and chemical vapor deposition two-step process to synthesize the uniform molybdenum disulfide (MoS2)thin-film on 4 different kinds of substrates, such as silicon dioxide, sapphire, silica, and STO. By using different kinds of substrate molybdenum disulfide thin-film as photocatalysts, and investigate molybdenum disulfide (MoS2) thin-film strain effect for CO2 photoreduction.In our process, we can well control the different thicknesses of molybdenum disulfide (MoS2), and it shows good light absorption in the visible light region. Furthermore, the result of GC had shows 3 nm molybdenum disulfide (MoS2) thin-film possess the best photoreduction efficiency than other thickness. Meanwhile, we also do the different kinds of sulfurization processes to better our 3 nm molybdenum disulfide (MoS2) thin-film. The Raman and PL result shows that the sulfur powder process of 3 nm molybdenum disulfide (MoS2) thin-film has better quality than the others. It also shows the highest photoreduction efficiency than the H2S process.Combining the above results, we use the sulfur process to synthesize 3 nm molybdenum disulfide (MoS2) thin-film, and growing on 4 different kinds of substrates. According to Raman analysis, we can get the E12g and A1g vibration mode, using these two vibration modes to compute the strain and plot the strain-charge doping map (ε-n map). The GC result shows the lowest strain has the lowest photoreduction efficiency when the strain increases to a specific value it shows the highest photoreduction efficiency. If the strain increases too much, it will increase the selectivity of products, and these reaction mechanisms are worthy of further exploration in the future.
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光觸媒, 二氧化碳光催化還原, 三奈米二硫化鉬薄膜, 不同基板, 拉曼, 應變效應, 3 nm MoS2 thin film, CO2 photoreduction, photocatalysts, different substrates, strain effect, Raman
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