本研究利用基於密度泛函理論之第一原理計算，以原子級觀點建立模型，探討二氧化碳分子在以石墨烯為基底之過渡金屬單原子(鈧、鈦、釩、鉻、錳、鐵、鈷、鎳、銅、鋅)結構上的吸附反應。
單原子催化劑（Single-atom catalysts, SACs）與純金屬不同，具有極高的原子利用率，因為活性中心的結構均一，可以讓催化反應更穩定，更加精準的控制反應過程及合成產物。單原子催化劑實現了金屬表面無法實現的催化活性及選擇性，而且使用後易分離、回收性良好，因此近年來在各催化領域受到越來越多的關注。儘管單原子催化劑提供了迄今為止無法實現的化學物質的機會，但仍存在限制及挑戰，限制了其在工業上的長期應用，再加上目前為止仍沒有能夠精確模擬單原子催化劑的結構和反應機制，因此透過反覆數次理論計算的基礎，以期望能發展出更精確的理論計算模型。本研究以石墨烯為載體之過渡金屬單原子系統，利用第一原理計算預測二氧化碳在單原子金屬上的吸附行為。
第一部分利用第一原理預測過渡金屬原子在石墨烯上的吸附反應，並在石墨烯載體上選擇了三種不同的原子吸附位置(Top-site、Hollow-site和Bridge-site.)，首先計算過渡金屬原子的d帶中心，以預測不同過渡金屬原子(鈧、鈦、釩、鉻、錳、鐵、鈷、鎳、銅、鋅)與石墨烯基底間是否能產生吸附行為，接著計算過渡金屬原子(鈧、鈦、釩、鉻、錳、鐵、鈷、鎳、銅、鋅)與石墨烯系統優化後的幾何結構、態密度及能帶分布，第一部分的計算結果顯示，只有鈧(Sc)、鈦(Ti)、鉻(Cr)、錳(Mn)、鈷(Co)、銅(Cu)原子能夠成功在石墨烯上產生吸附反應，值得注意的是，由於鋅(Zn)的3d和4s軌道電子殼層已滿，因此不易與碳原子形成鍵結。第二部分承接第一部分，將能夠發生吸附反應之過渡金屬單原子系統，做下個階段的二氧化碳分子吸附反應，第二部分的計算結果顯示，鉻(Cr)金屬原子系統中，二氧化碳的吸附能相對於其他三個系統為最低者，此也與COHP (crystal orbital Hamilton population)的分析結果相符，因此在本次研究中，鈷金屬原子在此複合結構的吸附行為最為顯著，因此鉻(Cr)為此十種過渡金屬元素裡最適合做為吸附反應的材料候選人。

Density functional theory (DFT) has emerged as the leading computational approach for modeling and characterizing adsorption phenomena, offering valuable capabilities for understanding and optimizing adsorption processes. DFT calculations can guide experimental efforts and accelerate the discovery of novel materials for various applications. In recent years, driven by pressing environmental concerns, such as the increasing concentration of atmospheric CO2 and its impact on global climate, and fueled by the diverse range of potential applications in fields ranging from energy to chemical manufacturing, research on CO2 adsorbents has experienced a significant surge. This has fostered interdisciplinary collaborations between chemists, materials scientists, and engineers, accelerating the pace of discovery and innovation in this crucial area. This work employs DFT calculations to investigate the adsorption of carbon dioxide molecules. Our analysis encompasses optimized geometries, electronic density of states (DOS), d-band centers and COHP (crystal orbital Hamilton population) analysis. This comprehensive approach aims to predict the CO2 molecules adsorption behaviors on single atoms supported on graphene substrates. Specifically, we present a systematic investigation of single atom models with transition metal, featuring Scandium (Sc), titanium (Ti), Vanadium (V), chromium (Cr), manganese (Mn), Iron (Fe), Cobalt (Co), Nickel (Ni), copper (Cu) and Zinc (Zn). Throughout all works, DFT calculations utilizing the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional, were consistently employed in this study to investigate CO2 adsorption on these graphene-based systems. We anticipate that these findings will contribute to the advancement of single-atom graphene materials.

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