催化学报 ›› 2022, Vol. 43 ›› Issue (12): 3089-3094.DOI: 10.1016/S1872-2067(21)63957-8

• 快讯 • 上一篇    下一篇

胍基铁卟啉显著提高了水溶液中电催化二氧化碳还原的活性和选择性

郭鸿波, 梁作中, 郭凯, 雷海涛, 王亚博, 张伟, 曹睿()   

  1. 陕西师范大学化学与化工学院, 应用表面与胶体化学教育部重点实验室, 陕西西安710119
  • 收稿日期:2022-03-23 接受日期:2022-05-11 出版日期:2022-12-18 发布日期:2022-10-18
  • 通讯作者: 曹睿
  • 基金资助:
    国家自然科学基金(21773146);霍英东青年教师基金;结构化学国家重点实验室开放基金;中央高校基本科研业务费专项基金;陕西师范大学科研业务费专项基金

Iron porphyrin with appended guanidyl group for significantly improved electrocatalytic carbon dioxide reduction activity and selectivity in aqueous solutions

Hongbo Guo, Zuozhong Liang, Kai Guo, Haitao Lei, Yabo Wang, Wei Zhang, Rui Cao()   

  1. Key Laboratory of Applied Surface and Colloid Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an 710119, Shaanxi, China
  • Received:2022-03-23 Accepted:2022-05-11 Online:2022-12-18 Published:2022-10-18
  • Contact: Rui Cao
  • Supported by:
    National Natural Science Foundation of China(21773146);Fok Ying-Tong Education Foundation for Outstanding Young Teachers in University;Open Fund of State Key Laboratory of Structural Chemistry;Fundamental Research Funds for the Central Universities;Research Funds of Shaanxi Normal University

摘要:

电催化CO2还原反应(CO2RR)可以制造燃料和增值化学品, 为使用化石燃料带来的相关问题提供了理想的解决策略, 因此, 开发具有高效率、高选择性的CO2RR电催化剂引起了人们的广泛关注. 最近的研究表明, 第一过渡金属配合物包括Mn, Fe, Co, Ni和Cu, 均可作为CO2RR电催化剂. 在众多配合物中, 铁卟啉化合物是研究结构-功能关系的理想模型复合物之一, 因为卟啉大环化合物可以为中心金属离子提供强大而稳定的配位环境, 并且可以通过引入各种官能团进行系统修饰, 同时也因其在非水溶液中可以高效地催化CO2转化为CO的而备受关注. 然而, 与非水溶液体系不同, 铁卟啉在水溶液中CO2RR表现出较差或中等的选择性, 其原因在于当使用水作为反应介质时, 竞争性析氢反应会变得严重. 众所周知, 使用水作为电催化反应溶剂, 不仅绿色环保, 而且可以充分提供二氧化碳还原过程中所需的质子. 因此, 开发水溶剂中铁卟啉CO2RR电催化剂, 使其在水溶液中表现出高活性高选择性具有重要的现实意义.

本文设计并合成了带有胍基的铁卟啉化合物1以及简单的A4型铁卟啉化合物2, 利用核磁共振、质谱分析等手段对化合物进行了表征, 研究了两种化合物在非水溶液(均相电催化)和水溶液(多相电催化)中对CO2RR的电催化性质. 在乙腈溶液中, 铁卟啉1及铁卟啉2均能有效地将CO2转化为CO, 转化频率表现为1 (3.9 × 105 s-1)比2 (1.7 × 104 s-1)大一个数量级, 表明了胍基在提高电催化CO2RR活性方面的关键作用. 更重要的是, 胍基具有生物相容性, 可以在pH ≤ 7的水溶液中被质子化, 因此将化合物负载在碳纳米管(CNTs)上, 研究其在0.1 mol L‒1 KHCO3水溶液中催化CO2RR活性, 结果表明, 1/CNT显示出非常高的电催化CO2-CO转化选择性, 法拉第效率为96%, 而2/CNT仅为65%, 同时1/CNT在水溶液中长时间电解的CO2RR电催化效率仍然优于2/CNT. 综上, 本文研究结果表明胍基对提高铁卟啉CO2RR电催化的活性和选择性具有重要意义.

关键词: CO2还原, 分子电催化, 铁卟啉, 静电相互作用, 质子转移

Abstract:

Iron porphyrins have high activity and selectivity for electrocatalytic CO2 reduction reaction (CO2RR) in nonaqueous solutions, but they usually display poor or moderate selectivity for CO2RR in aqueous solutions because of the competitive hydrogen evolution reaction. Using water as the electrocatalytic reaction solvent is more favored because not only it is cheap, green and abundant but also it can sufficiently provide protons required for CO2RR. Therefore, developing Fe porphyrins as electrocatalysts for efficient and selective CO2RR in aqueous solutions is of both fundamental and practical significance. Herein, we report the design and synthesis of Fe porphyrin 1 with an appended guanidyl group and its electrocatalytic features for CO2RR in both nonaqueous and aqueous solutions. In acetonitrile, Fe porphyrin 1 and its guanidyl-free analogue, tetrakis(3,4,5-trimethoxyphenyl)porphyrin 2, are both efficient for electrocatalytic CO2-to-CO conversion, but the turnover frequency with 1 (3.9 × 105 s-1) is one order of magnitude larger than that with 2 (1.7 × 104 s-1), showing the critical role of the appended guanidyl group in improving electrocatalytic CO2RR activity. More importantly, in 0.1 mol L-1 KHCO3 aqueous solutions, 1 showed very high selectivity for electrocatalytic CO2-to-CO conversion with a Faradaic efficiency of 96%, while 2 displayed a Faradaic efficiency of 65% for the CO2-to-CO conversion. This work is of significance to show the effect of appended guanidyl group on improving both activity and selectivity of Fe porphyrins for CO2RR electrocatalysis.

Key words: CO2 reduction, Molecular electrocatalysis, Iron porphyrin, Electrostatic interaction, Proton relay