以理論計算探討二氧化碳分子在矽與磷參雜石墨烯材料的電催化還原反應

在本篇論文中，為了解非金屬在單層石墨烯上參雜不同元素對於二氧化碳吸附和還原的影響，以理論計算的方法預測分子模型的電子位能，和每一步反應狀態變化的能量差，探討二氧化碳在非金屬催化劑上被還原成C1有機產物的反應機制。本研究中的石墨烯分成表面(Surface)和邊界(Edge)兩種基底模型，並參雜第三週期的矽和磷原子在表面上或鑲嵌在邊界上，研究並比較參雜矽和磷在二氧化碳的吸附和氫化還原的反應，並探討催化劑對二氧化碳還原反應的選擇性。從計算結果得知，以熱力學的觀點來看，由於矽對於電子貢獻的能力比磷好，在邊界甚至使二氧化碳發生自發性吸附。矽邊界較有可能進行CO2還原反應並產出甲醇和甲烷，且一氧化碳在矽邊界上的還原反應避免了CO對催化劑的毒化，而磷參雜的材料上CO2還原反應產出一氧化碳和甲酸，且一產出即容易脫附，比矽的表面更不容易中毒，另外矽與磷整體外在施加最小量電壓(Limiting Potential)大致分佈在1V以內，為未來電化學的電極材料選擇中，值得被考慮的材料之一。

關鍵字

電化學催化；二氧化碳還原反應；溫室效應；計算化學

並列摘要

To understand how graphene of single layer doped by different non-metallic elements affects CO2 adsorption and reduction, the theoretical electrostatic energy of molecular structure and the reaction energy for each hydrogenation step are calculated in this thesis to speculate the mechanism of carbon dioxide reduction reaction(CO2RR) giving C1 products. Two aspects of graphene structure are dis-cussed in this study, surface and edge, and they are doped and embedded by single silicon and phosphorus atom respectively which contribute to the result of CO¬2adsorption and hydrogenation reaction comparison. For the selectivity of thecatalysts in CO2RR to be known, the first step of it is compared with hydrogen evo- lution reaction. As known from the result, CO2 is more spontaneously adsorbed on the silicon doped or embedded graphene compared to the phosphorus one which gives one of the conclusions that a silicon atom is easier to share electrons withother atoms than a phosphorus atom from the point of thermodynamic view. Theproducts, methanol and methane produced by silicon-embedded edge of graphene are more possibly obtained in CO2RR. Despite of good adsorption of CO on silicon-embedded edge, CO is prone to further reduction which prevents the catalyst from toxication. And because of weak adsorption of CO and HCOOH in the phosphorus case, the catalyst is also free of toxication. Above all, for the material of electrodes to be chosen in CO2RR, the silicon and phosphorus doped or embedded graphene are worth a chance to be considered with limiting potentials within a range of 1 V.

並列關鍵字

Electrochemical catalysis ； Carbon dioxide Reduction Reaction ； Greenhouse effect ； Computational Chemistry

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以理論計算探討二氧化碳分子在矽與磷參雜石墨烯材料的電催化還原反應

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