利用理論計算探討單原子金屬摻雜在雙空缺石墨烯催化氧氣還原反應

Single-atom catalysts doped double-vacancy graphene for oxygen reduction reaction: A computational study

邱楡婷(Yu-Ting Chiou)

指導教授 ： 陳欣聰

中原大學/理學院/化學系/碩士(2023年)

https://doi.org/10.6840/cycu202301079

摘要

本篇研究利用密度泛函理論(density functional theory)去計算18種不同金屬原子參雜在雙缺陷的石墨烯上形成四配位單原子金屬催化劑，再將其應用在氧氣還原反應(oxygen Reduction Reaction; ORR)的催化，因為金屬擁有較高活性，但由於其高活性容易導致形成金屬團簇，因此我們將金屬摻雜在石墨烯上較為穩定，接著去催化氧氣還原反應，比較不同金屬參雜在四配位石墨烯上的催化活性及穩定性，找出最穩定且最高的活性之反應路徑。ORR的反應包含4個步驟: (1) O2+H++e-+*→OOH* (2) OOH*+H++e-→O*+H2O (3) O*+H++e-→OH* (4) OH*+H++e-→H2O+*，金屬與每個中間物的吸附強度會影響整個ORR反應，藉由計算不同金屬對於每個中間物的吸附強度，找出最穩定的吸附方式，再計算其自由能，分析出最合適的ORR反應路徑。接著再去與單原子金屬摻雜在三配位石墨烯之催化活性比較，我們研究發現ORR的反應主要受到OH*的影響，這個步驟在整個反應中所需的過電位最大，因此為速率決定步驟，金屬與OH*吸附越強之後要脫去則需要更多的能量，例如鈷(Co)摻雜在四配位石墨烯所需的外加能量為1.04V，在三配位石墨烯所需的外加能量為1.20V，才能將OH*脫去完成整個反應，可看出四配位石墨烯比三配位來的容易完成反應。

關鍵字

密度泛函理論

並列摘要

We studied eighteen different kinds of metal doped on double-vacancy graphene to form four-coordinate single-atom catalyst for oxygen reduction reaction (ORR) by the density functional theory calculations. The metal is easy to lead to the formation of metal clusters due to its high activity. Therefore, we doped the metal on the graphene to be more stable, then catalyzed the oxygen reduction reaction, and compared the doping of different metals catalytic activity and stability on four-coordinate graphene to find out the most active reaction path. The ORR includes 4 processes, (1) O2 + H+ + e- + * → OOH* (2) OOH* + H+ + e- →O* + H2O (3) O* + H+ + e- → OH* (4) OH*+H++e-→H2O+* , the adsorption strength of the metal to each intermediate affects the overall ORR reaction. We calculated the different metals for each intermediate’s adsorption energy and gibbs free energy to analyst suitable pathway. Then, we compare the activity between metal doped on double vacancy and metal doped on single vacancy. According to our research, the ORR was effected by OH*. When the adsorption of OH* is higher, we need to have the greater energy to remove water. For instance, Co doped double vacancy graphene required 1.04V but single vacancy graphene required 1.20V. We can determine double vacancy graphene is more easy than single vacancy graphene to complete the ORR reaction.

並列關鍵字

DFT

參考文獻

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