Photo courtesy of Wu Lizhu's research group on observing the photoreaction system
The melting of ice and snow and the rise of sea level ... As human consumption of fossil energy is increasing, the amount of greenhouse gases in the atmosphere has increased sharply, resulting in endless environmental and climate problems.
Carbon dioxide (CO2) is the highest in all greenhouse gases. How to reduce its concentration, or can there be a way to "turn waste into treasure"? This has always been a difficult problem that the team of Wu Lizhu, a researcher at the Institute of Physical and Chemical Technology, Chinese Academy of Sciences, hopes to overcome.
Recently, the team of Wu Lizhu reported for the first time the combination of solar-powered CO2 reduction and organic oxidation. She couldn't restrain her inner joy that the paper could be published in Chem, a sub-journal of Cell. "To achieve the coveted reaction of coupling CO2 reduction and oxidative organic conversion, the teachers and students of our research group have worked together for 8 years."
Challenging chemical reactions
Plant photosynthesis is the most effective process of fixing solar energy on the earth. The oil and natural gas consumed by human beings are actually direct or indirect products of plant photosynthesis in ancient times. If we simulate photosynthesis and reduce CO2 into valuable solar fuel or useful chemicals driven by sunlight, is it not a way to solve the greenhouse effect and energy crisis?
What is the distance between ideal and reality? For Wu Lizhu's research group, it is the process of converting solar energy into chemical energy.
"CO2 molecules have high bond energy, difficulty in activation, and complex intermediates involved in the reduction process. As a result, the efficiency and selectivity of photocatalytic CO2 reduction systems are generally low. Most systems require the addition of sacrificial reagents or water to consume photosensitizers. Photogenerated holes. The introduction of sacrificial reagents makes the reaction cost expensive, while the introduction of water significantly reduces the reaction efficiency. These unfavorable factors have limited the scale development of the photocatalytic CO2 reduction system. "Wu Lizhu analyzed.
Can a valuable organic reaction be used to replace the oxidation of sacrificial reagents or water to achieve both CO2 conversion and organic conversion reactions to produce important chemicals? The researchers were lost in thought.
As early as 2013, Wu Lizhu team first proposed the "hydrogen-releasing cross-coupling" reaction system, which realized the coupling of hydrogen production and oxidative organic reaction under visible light irradiation. "However, no one has been able to use solar energy to combine CO2 reduction and organic synthesis. This is not only a challenging chemical reaction, but also of great significance for solving the energy crisis and environmental pollution."
CO2 reduction combined with organic reaction
In response to this challenge, a multi-year exploration began.
Guo Qing, the first author of the paper and a Ph.D. from the Institute of Physical and Chemical Technology, Chinese Academy of Sciences, told the Chinese Journal of Science that the team added reactants (such as organic matter 1-phenylethanol and photocatalyst quantum dots) to the reaction cell, and then introduced CO2 gas. After sealing, the light experiment was performed under visible light.
"Since CO2 conversion products may be distributed in the gas and liquid phases, after a few hours of light, we first extract the gas in the system through the sampling needle and use conventional gas chromatography to detect the formation of gas phase products." Guo Qing introduced.
Surprisingly, the experimental staff detected the formation of a large amount of carbon monoxide (CO)-under optimal conditions, a few milliliters to tens of milliliters of CO2 can be quantitatively converted into CO in a 5 ml volume reaction tube. In the currently reported system, the amount of CO produced is in the order of microliters or even lower.
Subsequently, the experimenters post-processed the liquid phase reaction system, and found that the liquid phase product without CO2 by ion chromatography and nuclear magnetic detection produced a large amount of pinacol. The pinacol is the oxidative coupling product of 1-phenylethanol. Furthermore, the experimenters determined the structure of the substance by means of liquid-mass spectrometry and nuclear magnetic resonance. It is worth mentioning that the amount of reduction and oxidation products are perfectly matched.
In addition, the experimenters found that when the phenyl ring in 1-phenylethanol carries different substituents, the system can still be carried out efficiently.
"The experimental results mean that for the first time we have achieved efficient coupling of CO2 reduction and organic conversion reactions under visible light. Through this system, valuable gas-phase products (CO) and high-value-added liquid-phase product molecules (Pinna Alcohol) to maximize the conversion of solar energy to chemical energy. "Li Xubing, associate researcher at the Institute of Physics and Chemistry Technology, Chinese Academy of Sciences, told the China Science Journal.
Is expected to achieve solar-fuel conversion
Under the pressure of energy crisis and severe environmental pollution, it is urgent to resolve the energy shortage and control the emission of pollutants from combustion. In Wu Lizhu's view, this strategy provides an effective solution for the cost-effective reduction of CO2, and opens up a new and effective way for efficient solar-fuel conversion.
She said that from a scientific breakthrough point of view, this research has two outstanding characteristics.
First, through the synergistic use of photogenerated electrons and holes, both CO2 reduction and organic conversion reactions are realized. While generating solar fuel, high value-added chemical molecules are generated, thereby avoiding the introduction of sacrificial reagents and improving the economy of the reaction.
The second is that under the optimal reaction conditions, the CO generation rate can be as high as tens of millimoles per gram / hour. Compared with the currently reported system, the reaction rate has been increased by at least three orders of magnitude, with high efficiency and practicality. Application potential.
Facing the future, Wu Lizhu said that the research team will continue to forge ahead on the scientific road of developing solar fuel. "Next, we will develop more green, environmentally friendly, and efficient photocatalysts, reproduce natural photosynthesis, and efficiently convert CO2 into treasure in organic chemical reactions that are carried out efficiently." (Cheng Weijia, a trainee reporter of this newspaper)
Medical Gloves are disposable gloves used during medical examinations and procedures to help prevent cross-contamination between caregivers and patients. Medical gloves are made of different polymers including latex, nitrile rubber, polyvinyl chloride and neoprene; they come unpowdered, or powdered with corn starch to lubricate the gloves, making them easier to put on the hands.
Medical Gloves,Latex Medical Gloves,Medical Hand Gloves,Medical Disposable Gloves
Dongguan Yibao Technology Co., Ltd. , https://www.yibaomedical.com