In nature, photosynthetic organisms can use photosynthetic pigments to convert carbon dioxide (or hydrogen sulfide) and water into organic matter under the sunlight, and release oxygen (or hydrogen). This process is the basis for the survival of the biological world An important medium for the carbon and oxygen cycle of the earth. Inspired by this, the use of visible light reduction to convert carbon dioxide into high value-added chemicals and / or solar fuels (such as CO, HCOOH, CH3OH, CH4, etc.) has attracted more and more attention from scientific researchers, and has also been It is regarded as one of the important ways to solve the energy crisis and environmental problems. How to develop a carbon dioxide artificial photoreduction catalyst with lower cost, better stability and higher efficiency has been a research hotspot in this field in recent years. Semiconductor quantum dots (QDs) have the advantages of low cost, easy preparation, strong visible light trapping ability, multi-exciton generation, easy carrier regulation, and abundant surface sites. They are currently the most potential materials for building efficient artificial photosynthesis systems. One, and has been widely used in photocatalytic hydrogen production, photocatalytic organic conversion and other fields. However, most reported carbon dioxide photoreduction systems currently require the addition of sacrificial reagents (such as ascorbic acid, sodium sulfite, triethanolamine, etc.) to remove photo-generated holes that cannot be consumed, which not only increases the cost of carbon dioxide reduction economically And waste the oxidizing ability of photo-generated holes.
Recently, the supramolecular photochemistry research team of the Institute of Physical and Chemical Technology of the Chinese Academy of Sciences proposed for the first time an example of combining solar-driven organic oxidation reactions with carbon dioxide reduction, making full use of excited electrons and holes to produce solar fuel (carbon monoxide). At the same time, high value-added organic chemicals (Pinacol) were obtained (Figure 1). Under visible light, the photo-generated electrons of CdSe / CdS semiconductor quantum dots (QDs) can convert CO2 to CO, and the holes oxidize triethylamine. As shown in Figure 2, the CO generation rate can be as high as ~ 412.8 mmol g-1 h-1, and the selectivity can be as high as ~ 96.5%. The number of catalytic cycles (TON value) and apparent quantum efficiency (AQY) of the system under 1.0 h of illumination were ~ 47360 and 32.7%, respectively. At the same time, the catalyst showed excellent stability, and the activity was not significantly reduced after repeated use. More importantly, the system can efficiently couple CO2 reduction and oxidative organic synthesis under visible light conditions. When 1-phenylethanol and its derivatives are used to replace triethylamine at the oxidation end, the reduction of CO2 to CO can still be carried out with high efficiency and high selectivity. At the same time, 1-phenylethanol and its derivatives in the system can be oxidatively coupled by photogenerated holes on the surface of quantum dots to form pinacol with a yield of up to 98%. This strategy can obtain valuable gas-phase products (CO) and high-value-added liquid product molecules (pinacol) at the same time, maximizing the conversion of solar energy to chemical energy.
Further, the research team summarized the latest progress of semiconductor quantum dots in the field of carbon dioxide photoreduction in recent years, deeply analyzed the unique photophysical and structural characteristics of semiconductor quantum dots, and revealed its important advantages as a photocatalytic carbon dioxide reduction catalyst. Further development in this area provides reasonable guidance. The article first systematically analyzes the reasons why quantum dots are widely used in the field of solar energy conversion from the aspects of visible light absorption, exciton generation, charge separation and transport, and surface reactions. After that, detailed discussion discusses II-VI semiconductor quantum dots (such as CdSe, CdS, ZnSe), I-III-VI semiconductor quantum dots (such as CuInS2, CuAlS2) and perovskite-type quantum dots (such as CsPbBr3, CH3NH3PbBr3, Cs2AgBiBr6) The latest research progress in the field of photocatalytic CO2 reduction. Finally, the authors pointed out the prospects and challenges faced by semiconductor quantum dots in the future of carbon dioxide photoreduction. They believe that the cooperative use of photogenerated electrons and holes to realize the coupling of CO2 and oxidative organic conversion is an important direction for future photocatalytic CO2 reduction (Figure 3). This strategy not only provides an effective solution for the realization of cost-effective photocatalytic CO2 reduction, but also opens up new horizons for solar-chemical energy conversion.
Relevant work was published in Chem and Adv. Mater. Under the title of Efficient and Selective CO2 Reduction Integrated with Organic Synthesis by Solar Energy and Semiconductor Quantum Dots: an Emerging Candidate for CO2 Photoreduction. The first authors of the article were Guo Qing and Wu Haolin, respectively. The teacher is researcher Wu Lizhu and associate researcher Li Xubing.
Figure 1. Semiconductor quantum dot photocatalytic CO2 reduction coupled oxidation organic synthesis reaction under visible light
Figure 2. Quantum dot photocatalytic reduction of CO2. (A) The photocatalytic CO2 reduction reaction rate of different semiconductor quantum dots as photocatalyst. (B) The photocatalytic CO2 reduction rate of CdSe quantum dots modified with different CdS shell thickness under the same conditions. (C) Recycling of catalyst. (D) AM1.5 light. (EF) 13C labeling experiment.
Figure 3. Semiconductor quantum dots catalyzed CO2 reduction by visible light
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Brand |
Wintape |
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Model |
STM-16 |
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Material |
ABS case, 65Mn steel |
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Case Size |
42mm*42mm*9mm |
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Pink or customized |
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White tape with black scale |
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Cm on one side |
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Customized |
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1pcs/poly bag; 50pcs/inner box; 500pcs/carton; Carton:36*23*28cm; GW/NW:13/14kg |
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