《Acc. Chem. Res.》: Fundamentals and Challenges of Engineering Charge Polarized Active Sites for CO₂ Photoreduction toward C₂ Products

Yang Wu,⁺ Qinyuan Hu,⁺ Qingxia Chen,^* Xingchen Jiao,^* and Yi Xie^*

Excessive emissions of carbon dioxide (CO₂) are contributing to global warming and climate deterioration, and the conversion of CO₂ into carbon-containing fuels using solar energy can simultaneously mitigate both climate deterioration and energy shortages. In the past decade, although CO₂ photoreduction research has made great achievements, it still faces great challenges in terms of product selectivity and activity. On current catalysts, CO₂ photoreduction usually yields C₁ products, and due to the kinetic challenges of C-C coupling of C₁ intermediates,it is difficult to obtain C₂ products with high economic value and energy density. Therefore, in order to realize CO₂ photoreduction to C₂ fuel, it is important to design highly active photocatalysts to accelerate C-C coupling.

Currently, the mechanism of CO₂ photoreduction for the preparation of C₂ fuels is usually uncertain, which may be due to the difficulty in determining the actual catalytic site of the C-C coupling step and the difficulty in monitoring the low concentration of active intermediates in the multi-electron transfer process. In view of this, this paper focuses on various strategies for the photocatalytic reduction of CO₂ to C₂ fuels including vacancy engineering, doping engineering, loading engineering, and heterojunction engineering for designing charge-polarized active sites to facilitate C-C coupling. Meanwhile, various in situ characterization techniques such as in situ X-ray photoelectron spectroscopy, in situ Raman spectroscopy and in situ Fourier transform infrared (FTIR) spectroscopy are outlined in this paper for identifying the charge-polarized active sites and monitoring the reaction intermediates, which can help to gain insights into the internal catalytic mechanism for the generation of C₂ products by CO₂ photoreduction.

The first authors of this article are Dr. Yang Wu from the University of Science and Technology of China, and Qinyuan Hu, master student, Jiangnan University. The corresponding authors are Prof. Yi Xie from the University of Science and Technology of China, Prof. Xingchen Jiao from Jiangnan University. Associate Prof. Qingxia, Chen from Jiangnan University.

link:https://doi.org/10.1039/D2CS00688J

Figure 1. Possible CO₂ photoreduction processes at (a) charge-balance active sites and (b) charge-polarization active sites

Figure 2. CO₂ photoreduction process of C2 products on charge polarized photocatalyst