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標題: | 運用第一原理計算探討二氧化碳在石墨烯奈米材料支撐的銅奈米粒子上的還原行為 First-principles study of CO2 reduction on Cu nanoparticles supported on graphene nanomaterials |
作者: | 李哲瑞 Che-Jui Lee |
指導教授: | 郭錦龍 Chin-Lung Kuo |
關鍵字: | 第一原理計算,石墨烯,銅奈米粒子,二氧化碳還原, First-principles calculation,graphene,Cu nanoparticle,CO2 reduction reaction, |
出版年 : | 2023 |
學位: | 碩士 |
摘要: | 本論文運用第一原理計算探討石墨烯奈米材料支撐的銅奈米粒子電催化還原二氧化碳(CO2)的行為,並探討了銅相關材料的型態,石墨烯基材的摻雜對催化表現的影響,以提供催化劑設計準則。
在第一部份,我們探討了不同種類的銅金屬相關材料電催化還原CO2的行為,我們的計算結果顯示所有的銅金屬相關材料皆偏好相同的甲烷(CH4)生成反應路徑,且發現當催化劑由銅的(111)面變為Cu55奈米粒子時,反應的速率決定步驟改變。比較不同催化劑的反應行為也發現當催化劑的表面較不安定時,透過分子吸附會獲得較強的安定效應,使得分子吸附上去的自由能低於分子吸附在較安定表面的分子的自由能。 在第二部分,我們探討了吸附在帶缺陷石墨烯上的Cu55奈米粒子和Cu13奈米粒子催化CO2還原為CH4的行為,我們的研究結果顯示氮摻雜除了會降低空缺的表面生成能以產生更多空缺來吸附奈米粒子外,也會抑制銅奈米粒子與石墨烯基材之間的電荷轉移,對Cu55奈米粒子和Cu13奈米粒子的催化表現有截然不同的影響。對Cu55奈米粒子而言,吸附在帶缺陷石墨烯上會轉移電子到基材,此行為會在介面與奈米粒子內部生成偶極,此偶極會安定吸附在表面的中間物分子,因此基材與奈米粒子之間的電荷轉移對Cu55奈米粒子的催化表現有正面效應,而在石墨烯基材上進行氮摻雜會抑制Cu55奈米粒子與石墨烯基材之間的電荷轉移,因此在石墨烯上氮摻雜對Cu55奈米粒子的催化表現有負面效應。對Cu13奈米粒子而言,雖然吸附在帶缺陷石墨烯上與石墨烯基材之間的電荷轉移一樣會在介面與銅奈米粒子內生成偶極,但由於Cu¬13奈米粒子的電子數遠少於Cu55奈米粒子,吸附在石墨烯基材上反而會導致吸附在Cu13奈米粒子上的中間物分子電子損失,所以基材與奈米粒子之間的電荷轉移對Cu13奈米粒子的催化表現有負面效應,而在石墨烯上進行氮摻雜會抑制Cu13奈米粒子與石墨烯基材之間的電荷轉移,因此在石墨烯上氮摻雜對Cu13奈米粒子的催化表現有正面效應。 在第三部分,我們探討氮硼共摻雜石墨烯支撐的Cu55奈米粒子催化還原CO2的行為,我們的計算結果顯示氮硼共摻雜能有效地降低石墨烯的空缺生成能以產生更多空缺來吸附銅奈米粒子。Cu55奈米粒子吸附在氮硼共摻雜石墨烯上的結果顯示了在氮摻雜石墨烯基材中加入硼原子能夠有效提升Cu55奈米粒子與石墨烯基材之間的電荷轉移量。在CO2催化還原表現方面,吸附在氮硼共摻雜石墨烯基材上的Cu55奈米粒子的表現接近吸附在未摻雜石墨烯基材上Cu55奈米粒子的表現,優於吸附在氮摻雜石墨烯基材的Cu55奈米粒子的表現。 最後,根據三個部分的結果,我們給出催化劑的設計建議,縮小銅奈米粒子尺寸(如:Cu13奈米粒子)能夠有效地提升催化表現。若要使用基材支撐小尺寸奈米粒子,可以使用氮摻雜石墨烯基材。若要使用較大顆的奈米粒子(如:Cu55奈米粒子)作為催化劑,我們建議使用氮硼共摻雜的石墨烯基材來改善催化表現。 First-principles calculations are applied in this thesis with aim of investigating the electrocatalytic reduction of carbon dioxide (CO2) on copper nanoparticles supported on graphene nanomaterials. We also discuss the effect of the morphology of copper-related materials and doping of graphene substrates on catalytic performance to provide the design guidelines for catalysts. In the first part of the thesis, we investigated the CO2 reduction on different kinds of copper-related materials. Our results showed that all copper-related materials prefer the same methane (CH4) formation pathway. We also find that the rate determining-step of methane formation changes when Cu(111) planes converting into Cu55 nanoparticles. Comparing the reaction behavior of different catalysts, we also found that a stronger stabilizing effect will be obtained through adsorption of intermediate state when the surface is less stable, so that the free energy of molecules adsorbed on it is lower than the free energy of molecules adsorbed on a more stable surface. In the second part of the thesis, we investigated the CO2 reduction to CH4 on Cu55 nanoparticles and Cu13 nanoparticles adsorbed on defective graphene. Our results showed that nitrogen doping can not only lower the vacancy formation energy to generate more vacancies to adsorb Cu nanoparticles but also hinder the charge transfer between copper nanoparticles and graphene substrates, which has completely different effect on the catalytic performance of Cu55 and Cu13 nanoparticles. For Cu55 nanoparticles, adsorption on the defective graphene transfers electrons to the substrate, generating dipoles on the interface and the interior of nanoparticles. The dipoles stabilize the intermediate molecules adsorbed on the surface, so the charge transfer between the substrate and the nanoparticles has a positive effect on the catalytic performance of Cu55 nanoparticles. Nitrogen doping of the graphene hinders the charge transfer between Cu55 nanoparticles and graphene substrates, thus nitrogen doping of graphene has a negative effect on the catalytic performance of Cu55 nanoparticles. For Cu13 nanoparticles, adsorption on the graphene substrate causes the loss of electrons of intermediate molecules adsorbed on the Cu13 nanoparticles because the number of electrons of Cu13 nanoparticles is far less than that of Cu55 nanopartilces, although the charge transfer between defective graphene and nanoparticles generates dipoles on the interface and interior of the nanoparticles when adsorbed on the defective graphene. Therefore, the charge transfer between the substrates and the nanoparticles has negative effect on the catalytic performance of Cu13 nanoparticles. Nitrogen doping of graphene hinders the charge transfer between Cu13 nanoparticles and graphene substrate, therefore nitrogen doping of graphene has a positive effect on the catalytic performance of Cu13 nanoparticles. In the third part of the thesis, we investigate CO2 reduction on Cu55 nanoparticles supported on nitrogen-boron co-doped graphene. Our results show that nitrogen-boron co-doping can effectively lower the vacancy formation energy of graphene to generate more vacancies adsorbing copper nanoparticles. The results of Cu55 nanoparticles adsorbed on nitrogen-boron co-doped graphene show that adding boron to nitrogen-doped graphene can effectively boost the charge transfer between Cu55 nanoparticles and graphene substrate. In terms of CO2 catalytic reduction performance, the performance of Cu55 nanoparticles adsorbed on nitrogen-boron co-doped graphene is close to that of Cu55 nanoparticles adsorbed on undoped graphene and is better than that of Cu55 nanoparticles adsorbed on nitrogen doped graphene. Finally, based on the results of previous three parts, we give suggestions for the design of catalysts. Reduce the size of copper nanoparticles to smaller size (e.g. Cu13 nanoparticles) to improve the catalytic performance effectively. Nitrogen-doped graphene is a good choice to support the small-sized nanoparticles. If we choose larger nanoparticles (e.g. Cu55 nanoparticles) to serve as catalysts, nitrogen-boron co-doped graphene is recommended to serve as the substrate to improve the catalytic performance. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/87576 |
DOI: | 10.6342/NTU202300593 |
全文授權: | 未授權 |
顯示於系所單位: | 材料科學與工程學系 |
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