Team:HZNFHS Hangzhou/Description

HZNFHS_Hangzhou

TEAM DESCRIPTION

Since 1938, British meteorologist Carlinda analyzed the sporadic CO₂ observation data around the world at the end of the 19th century and pointed out that the CO₂ concentration at that time was 6% higher than that at the beginning of the century. People began to think that the content of CO₂ in the atmosphere will cause great harm to the world's climate environment and people's survival. The content of carbon dioxide in the atmosphere has become a concern of many scientists and has been monitoring and studying the object. Studies have shown that carbon emissions continue to rise during the outbreak of a rare short-term decline. The latest research suggests that the rising trend of atmospheric carbon dioxide concentration has not been reversed (see Figure 1).

Figure 1 Trend of carbon dioxide concentration Based on data from Monaloa Observatory| scripps.ucsd.edu

The concentration of carbon dioxide in the atmosphere varies seasonally, usually reaching the peak value in May every year. In May this year, the number of this peak reached a new high: according to the observation data of Monaloa Observatory in Hawaii, the average value of carbon dioxide concentration in May 2020 reached 417.1 ppm (parts per million), which exceeded the peak of 414.7 ppm last year and became the highest ever recorded. At present, although there are many ways to restrain the aggravation of the greenhouse effect, such as planting trees and banning CFCs. Although these methods have certain effects, the practice has proved that these methods have insurmountable weaknesses (long time cycle and slow effect) to solve the greenhouse effect. Because the greenhouse effect is mainly caused by carbon dioxide, it is very important to find a long-term, low-cost, efficient method to convert carbon dioxide and realize the capture and resource of CO₂. There are mainly chemical synthesis, electrochemical immobilization, photochemical reduction, and catalytic transfer hydrogenation. The main products of chemical synthesis are resin materials, polyacid ester compounds, and other polymer materials, but the reaction conditions are harsh, energy consumption is high, and the by-products are easy to generate harmful gases. The electrochemical immobilization method is mainly in the experimental stage, and there are energy consumption limitations in its popularization and application. The photochemical reduction method uses artificial light sources as energy sources, usually uses titanium dioxide as catalyst support, and the reaction conditions are mild, but the conversion efficiency is low, so it is difficult to be industrialized. The conversion efficiency of catalytic transfer hydrogenation is relatively high, and the main products are chemical raw materials such as methane, methanol, and formic acid. In recent years, the concept of bioelectrochemical synthesis has been proposed by combining electrochemistry and biotransformation technology. However, the highly selective C-C coupling reaction with CO₂ as the substrate has not been realized, so the current electrochemical system can only realize the high selective conversion of CO₂ to CO and formic acid, and the conversion of other long-chain carbon and compounds is still very difficult. This will lead to (1) low product value; (2) poor product selectivity; if biocatalyst is used to reduce the reaction activation energy, the reaction can be carried out under more mild conditions (usually normal temperature and pressure). At the same time, compared with inorganic catalytic products, biocatalysis greatly enriches the types of products by means of genetic engineering and makes it possible to transform CO₂ into high value-added products. And the unstable and discontinuous renewable energy is stored in the form of chemical energy.

Autotrophic microorganisms in nature can use energy to convert CO₂ into different compounds to achieve CO₂ reduction. If the biological system can be combined with the electrochemical system, microorganisms can use the hydrogen produced by the electrochemical system to provide energy for their metabolism, growth, and synthesis, and can achieve the reduction of CO₂. The system is called a microbial electrosynthesis system (MES), and the energy driving the system can come from renewable resources such as wind energy and solar energy. In this way, the conversion of electrical energy to chemical energy and CO₂ to target products can be realized in one device. Due to the use of biocatalyst, this technology can effectively reduce the activation energy of CO₂ reduction reaction and has the advantages of high product selectivity. Compared with natural photosynthesis, enzyme / inorganic system coupled semi-artificial photosynthesis, and pure inorganic artificial photosynthesis, microbial/inorganic system coupling semi-artificial photosynthesis showed more compromise characteristics in the active site density, stability, scalability, product complexity, and process efficiency, and no one aspect showed a particularly insufficient situation. Therefore, this form of semi-artificial photosynthesis is the most feasible scheme at this stage.

Reference Page:

[1] https://scripps.ucsd.edu/news/rise-carbon-dioxide-unabated [2] O'Neill, В. С. et al. Glob. Environ. Change 42, 169-180 (2017). [3]CHOI Y H, JANG Y J, PARK H, et al. Carbon dioxide fischer-tropsch synthesis: A new path to carbon-neutral fuels[J]. Applied Catalysis B: Environmental, 2017, 202: 605–610. [4]LEINO E, KUMAR N, MÄKI-ARVELA P, et al. Synthesis and characterization of ceria-supported catalysts for carbon dioxide transformation to diethyl carbonate[J]. Catalysis Today, 2018(306):128–137. [5]GANESH I. Electrochemical conversion of carbon dioxide into renewable fuel chemicals – The role of nanomaterials and the commercialization[J]. Renewable and Sustainable Energy Reviews,2016, 59: 1269–1297. [6]KIM H-Y, CHOI I, AHN S H, et al. Analysis on the effect of operating conditions on electrochemical conversion of carbon dioxide to formic acid[J]. International Journal of Hydrogen Energy, 2014,39(29): 16506–16512. [7]SUN Y, LI G, XU J, et al. Visible-light photocatalytic reduction of carbon dioxide over Sn S2[J]. Materials Letters, 2016, 174: 238–241. [8]RELI M, KOBIELUSZ M, MATĚJOVÁ L, et al. TiO2 processed by pressurized hot solvents as a novel photocatalyst for photocatalytic reduction of carbon dioxide[J]. Applied Surface Science, 2017,391(Part B): 282–287.