[ Instrument R&D of Instrument Network ] In recent years, two-dimensional (2D) materials have been widely used in the field of electrocatalysis due to their unique physical and chemical properties. Especially the 2D metallenes with thick atomic layer, its good conductivity, abundant defects and coordinated unsaturated sites, extremely high atom utilization rate, special quantum size effect and stress effect, etc. The unique and excellent electrocatalytic performance of this type of material can be used as a promising new type of electrocatalytic material, and has emerged. Bismuth (Bi) nanomaterials can convert CO2 to formic acid with a higher activity through an electrocatalytic process, thus attracting people's attention. However, most of the Bi-based electrocatalysts reported so far have insufficient exposure of active sites due to their large particle size or thickness, which severely limits their electrocatalytic performance. Therefore, bismuthene (Bi-ene, bismuthene) with ultra-thin two-dimensional structure will be a very promising high-efficiency CO2 reduction reaction (CO2RR) electrocatalyst, but one of the difficulties in current research is how to design and synthesize The oligolayer and even single layer Bi-ene nanomaterials with ultra-thin structure.
Based on this, Zhu Qilong, a researcher at the State Key Laboratory of Structural Chemistry at the Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, and Xu Qiang, a professor at the Japan Institute of Industrial Technology, cooperated with the National Natural Science Foundation of China for the first time using 2D bismuth-based metal-organic thin-layer materials (Bi-MOLs, Bi-based metal–organic layers) are precursors, and ultra-thin oligo-layer Bi-ene nanosheets with graphene-like structure were successfully prepared by in-situ electrochemical conversion, with a thickness of only 1.28-1.45 nm , Corresponding to 3-4 atomic layers. The unique structure of this Bi-ene not only gives it an extremely high electrochemically active area, but also greatly enhances the intrinsic activity of metal atoms. It is directly used as an electrocatalyst in CO2RR, and it can show very excellent electrocatalytic performance: the current density can exceed 70 mA cm-2, and it can be used at ~100% Faraday in a wide potential range of -0.83 to -1.18 V. The efficiency converts CO2 to formic acid, while having high catalytic stability. Further using the self-designed flow cell, Bi-ene can provide a high current density of more than 300 mA cm-2, which initially meets the requirements of industrial applications (200 mA cm-2) and has high application prospects. In addition, through in-situ infrared testing and theoretical calculations, the team members discovered a new mechanism for formate formation: that is, some HCO3- groups in the electrolyte can directly participate in the reaction to obtain formate products, which is the same as the currently reported HCO3- The group only serves as a proton source or the mechanism for accelerating the reaction by balancing CO2 is different.
In summary, this work provides new ideas for the preparation of high-performance CO2RR electrocatalysts and ultra-thin two-dimensional metal olefin materials; at the same time, it also further understands the CO2RR process and provides experimental and theoretical support for improving the overall performance of CO2RR. The related work has been published online in "German Applied Chemistry" (Angew. Chem. Int. Ed. 2020, DOI: 10.1002/anie.202005577). The first author of this paper is Cao Changsheng, a doctoral student under the guidance of Zhu Qilong.
In addition, the research group recently systematically summarized the research progress of MOFs for photocatalytic CO2 reduction in recent years. Related results were published in EnergyChem 2020, 2, 100033.
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