Light source selection in the study of photocatalytic CO2 reduction mechanism

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At present, one of the main scientific problems in the research of photocatalytic CO₂ reduction is the lack of a lot of research on reaction mechanism, and the selectivity of reduction products is difficult to control^{[1, 2]}。

Photocatalytic CO₂ reduction involves multiple reaction paths and complex intermediates ^[3]. Therefore, the study of reaction mechanism is helpful for the in-depth understanding of the complex reaction kinetics of CO₂ reduction by photocatalysis, and also for the rational design of photocatalysts with high activity and selectivity^[4]。

At present, researches on the mechanism of photocatalytic CO₂ reduction reaction mainly determine the reaction intermediates and catalytic active centers by in-situ characterization technique [4]. In situ characterization techniques mainly involved include in situ electron paramagnetic resonance (EPR), in situ diffuse UV-visible spectroscopy (UV-vis) and in situ infrared spectroscopy (DRIFTS) ^[5-7], of which in situ infrared spectroscopy (DRIFTS) is the most common^[8-13]。

In situ infrared diffuse reflection reaction cell is mainly composed of three Windows, two of which are made of ZnSe or KBr for incidence and reflection of infrared light. The third window material is SiO₂ for optical input, and the structure is shown in Figure 1.

Figure 1. Schematic diagram of in situ infrared diffuse reflection reaction cell

For the real reduction process, the spectrum and light intensity of the light source used in the in-situ infrared spectroscopy test are as consistent as possible with that used in the activity evaluation, which is generally adoptedXenon lamp source。

However, xenon lamp sources are large and difficult to move in small Spaces, resulting in serious space limitations for in situ infrared testing.Perfectlight atXenon lamp source On the basis of new PLS-300 optical fiber module，Light can be directed through optical fibers into the reaction cell. The size of the output spot is suitable, the diameter of the outlet spot is 5 mm; It occupies small space and is convenient to use.

Quartz fiber and liquid-core fiber are selected. The specific parameters are shown in Table 1.

Table 1. Specifications of optical fibers

The specific application scenario is shown in Figure 2.

In addition, in order to meet the experimental requirements of high intensity uniform light, Perfectlight Technology has also developed and designedPLS-FX300HU high uniformity integrated xenon lamp light source , add a focusing mirror barrel at the optical fiber outlet, used to converge light to improve the output optical power density, the maximum output optical power density ≥700 mW/cm². The square spot size is 10×10~50×50 mm² continuously adjustable, so that the spot completely covers the working area of the catalyst, the output spot uniformity is high, can meet the requirements of class A solar simulator, is a special xenon lamp light source for photoelectric catalysis research.

See Fig.3 and Fig.4 for the specific application scenario diagram and customer site diagram.

FIG. 3. Schematic diagram of application scenario of PLS-FX300HU integrated Xenon lamp source with high uniformity and in situ infrared diffuse reflection reaction pool

Figure 4. Customer field view of PLS-FX300HU high uniformity integrated Xenon lamp light source and in situ infrared diffuse reaction cell^[14]

Reference literature

[1]Shen Huidong, Peppel Tim*, Sun Zhenyu*, et. al., Photocatalytic reduction of CO₂ by metal-free-Based materials: recent advances and future perspective[J]. Solar RRL 2020, 4, 1900546.

 [2]Fu Junwei, Yu Jiaguo*, Liu Min*, et. al., Product selectivity of photocatalytic CO₂ reduction reactions[J]. Materials Today, 2020, 32, 222-243.

 [3]Behera Arjun, Kumar Kar Ashish, Srivastava Rajendra* et. al., Challenges and prospects in the selective photoreduction of CO₂ to C1 and C2 products with nanostructured materials: a review[J]. Materials Horizons, 2022, 9, 607-639. 

[4]Shen Huidong, Peppel Tim*, Sun Zhenyu*, et. al., Photocatalytic reduction of CO₂ by metal-free-Based materials: recent advances and future perspective[J]. Solar RRL 2020, 4, 1900546. 

[5]Lin Lin, Zhang Xuehua*, He Tao*, Highly efficient visible-light driven photocatalytic reduction of CO₂ over g-C3N4 nanosheets/tetra(4-carboxyphenyl)-porphyrin iron(III) chloride heterogeneous catalysts[J]. Applied Catalysis B: Environmental, 2018, 211, 312-319.

[6]Yang Sizhuo, Zhang Jian*, Huang Jier*, et. al., 2D covalent organic frameworks as intrinsic photocatalysts for visible light-driven CO₂ reduction[J]. Journal of the American Chemical Society, 2018, 140, 14614-14618.

[7]Zhao Junze, Ji Mengxia, Xia Jiexiang*, et. al., Interfacial chemical bond modulated Bi19S27Br3/g-C₃N₄ Z-scheme heterojunction for enhanced photocatalytic CO₂ conversion[J]. Applied Catalysis B: Environmental, 2022, 307, 121162.

[8]Kou Mingpu, Liu Wei, Ye Liqun*, et. al., Photocatalytic CO₂ conversion over single-atom MoN₂ sites of covalent organic framework[J]. Applied Catalysis B: Environmental, 2021, 291, 120146.

[9]Kou Mingpu, Liu Wei, Ye Liqun*, et. al., Photocatalytic CO2 conversion over single-atom MoN₂ sites of covalent organic framework[J]. Applied Catalysis B: Environmental, 2021, 291, 120146.

[10]You Feifei, Wan Jiawei, Wang Dan*, et. al., Lattice distortion in hollow multi-shelled structures for efficient visible-light CO₂ reduction with a SnS₂/SnO₂ junction. Angewandte Chemie International Edition, 2020, 59: 721.

[11]Feng Yibo, Wang Cong*, Han Xiaodong*, et. al, Ultrahigh photocatalytic CO₂ reduction efficiency and selectivity manipulation by single-tungsten-atom oxide at atomic step of TiO₂[J]. Advanced Materials, 2022, 34, 2109074.

[12]Meng Jiazhi, Duan Yongyu, Zhou Xiaoyuan*, et. al, Facet junction of BiOBr nanosheets boosting spatial charge separation for CO₂ photoreduction[J]. Nano Energy，2022.92, 106677.

[13]Liu Qiong, Cheng Hui*, Wang Fuxian*, et. al, Regulating the *OCCHO intermediate pathway towards highly selective photocatalytic CO₂ reduction to CH3CHO over locally crystallized carbon nitride[J]. Energy Environmental Science, 2022,15, 225-233.

[14]Ma Xiaohong, Li Danyang, Yuan Fangli*, et. al, Confined space and heterojunction dual modulation of ZnO/ZnS for boosting photocatalytic CO₂ reduction[J]. Solar RRL 2023. DOI: 10.1002/solr.202201093.