化石燃料的過度使用導致二氧化碳含量不斷上升，危害了我們的環境及改變我們的氣候，因此有效地降低及利用二氧化碳是刻不容緩的議題。本篇研究我們將藉由密度泛函理論計算方法系統性地探討二氧化碳還原反應在以銅為基底之電催化劑其催化反應機制。
在本篇研究的第一部分，我們探討了二氧化碳還原反應在銅金合金、銅銀合金以及銅鋅合金等雙金屬催化劑生成一氧化碳的反應機制。結果顯示透過應變效應及配位基效應的作用下，可以改變重要中間產物COOH、CO及H的吸附能，進而改變反應催化效果。在這些雙金屬催化劑之中，銅金合金能有效地提升COOH吸附能及降低CO及H的吸附能，提升二氧化碳還原反應及降低產氫反應的進行，且透過相同機制，我們發現銅銀鋅三元合金比二元合金又能有更好的催化效果。
在本篇研究的第二部分，我們則是探討二氧化碳還原反應在以氧修飾之銅催化劑利用碳碳耦合形成二碳產物之反應機制。我們在此詳細地探討二氧化碳還原形成OCCHO中間產物在純銅(111)表面，以及當含有表面氧或含有次表面氧的銅表面之可能反應的路徑。結果顯示次表面氧的加入可以有效地提升反應的活性，然而表面氧反而會降低反應活性，其提升或降低催化活性的主要原因為表面銅價態的改變所造成。

To effectively reduce and utilize CO2 is an urgent and important topic as enormous CO2 emission from the overuse of fossil fuels detrimentally damage our environment and change our climate. In the present study, we systematically examined the reaction mechanism of catalytic CO2 reduction reaction (CO2RR) on Cu-based electrocatalysts by density functional theory calculation.
In the first part of this thesis, we investigated the mechanism of CO2RR for the production of CO on CuAu, CuAg and CuZn bimetals. Through the strain and ligand effects, the adsorption energies of key intermediates, COOH, CO and H, have been altered to enhance the catalytic activity. Among them, CuAu can effectively strengthen the adsorptions of COOH and weaken the adsorptions of CO and H to promote CO2RR and demote hydrogen evolution reaction (HER). Following the same mechanism, we optimized CuAgZn trimetals to further achieve better activity than the bimetallic catalysts.
In the second part of this thesis, we studied the mechanisms of CO2RR with C-C coupling forming C2 products on oxygen modified Cu catalysts. The reaction pathways from CO2 to OCCHO have been thoroughly examined on clean Cu(111) surface and with surface and subsurface oxygen. The results showed that the subsurface oxygen can effectively promote the activity, whereas surface oxygen likely to demote it. The enhancement or reduction of the catalytic activity are mainly attributable to the valance states of surface Cu.

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