Molecular Engineering of CoII Porphyrins with Asymmetric Architecture for Improved Electrochemical CO2 Reduction
Molecular Engineering of CoII Porphyrins with Asymmetric Architecture for Improved Electrochemical CO2 Reduction
复制标题
具有不对称结构的 Co II 卟啉分子工程可改善电化学 CO 2 还原
DOI：
10.1002/cssc.202200090
复制
发表时间：
2022-03-16
期刊：
影响因子：
8.4
通讯作者：
Zhuang, Xiaodong
中科院分区：
文献类型：
--
作者：
Bao, Wenwen;Huang, Senhe;Zhuang, Xiaodong
基于分子催化剂的CO2电化学还原反应由于其明确的活性中心和合理的结构设计而备受关注。金属卟啉（PorMs）具有不同过渡金属的π共轭骨架，具有独特的CO2还原性能。然而，很少有工作集中在研究的对称结构的PorMs以及它们的聚集行为，以CO2还原。本工作以一系列具有对称和不对称取代基的钴-Ⅱ卟啉（PorCos）作为CO2还原的分子催化剂模型。由于2，6-二甲基苯（DMB）的给电子效应，配合物的禁带宽度随DMB数目的增加而变窄。作为电催化剂，所有的PorCos表现出良好的电催化CO2还原性能。在这三种分子中，不对称Co-II卟啉（as-PorCo）在相对于可逆氢电极的-0.6V下显示出-288mV的最低起始电位和超过93%的法拉第效率，这在所报道的现有技术卟啉基电催化剂中具有高度竞争力。CO2还原性能取决于PorCo与碳纳米管（CNTs）和相邻PorCo之间的π-π堆叠，这可以通过PorCo中原子定位的DMB容易地控制。密度泛函理论计算还表明，由于as-PorCo中的弱空间位阻，PorCo和CNT之间的电荷密度最高，为高效电化学CO2还原催化剂的分子设计提供了新的见解。
The electrochemical reduction of carbon dioxide (CO2) based on molecular catalysts has attracted more attention, owing to their well-defined active sites and rational structural design. Metal porphyrins (PorMs) have the extended pi-conjugated backbone with different transition metals, endowing them with unique CO2 reduction properties. However, few works focus on the investigation of symmetric architecture of PorMs as well as their aggregation behavior to CO2 reduction. In this work, a series of Co-II porphyrins (PorCos) with symmetric and asymmetric substituents were used as model of molecular catalysts for CO2 reduction. Owing to the electron donating effect of 2,6-dimethylbenzene (DMB), bandgaps of the complexes became narrower with the increasing number of DMB. As electrocatalysts, all PorCos exhibited promising electrocatalytic CO2 reduction performance. Among the three molecules, asymmetric Co-II porphyrin (as-PorCo) showed the lowest onset potential of -288 mV and faradaic efficiencies exceeding 93 % at -0.6 V vs. reversible hydrogen electrode, which is highly competitive among the reported state-of-art porphyrin-based electrocatalysts. The CO2 reduction performance depended on pi-pi stacking between PorCo with carbon nanotubes (CNTs) and adjacent PorCos, which could be readily controlled by atomically positioned DMB in PorCo. Density functional theory calculations also suggested that the charge density between PorCo and CNT was highest due to the weak steric hindrance in as-PorCo, providing the new insight into molecular design of catalysts for efficient electrochemical CO2 reduction.