Energy shortage and global warming have become two major problems facing mankind. Due to the excessive use of fossil energy, on the one hand, the traditional fossil fuels that humans depend on are being exhausted; on the other hand, the concentration of carbon dioxide (CO2) in the atmosphere has increased, leading to the global greenhouse effect and bringing an irreversible ecological environment to the earth problem. If renewable energy is used to convert CO2 into industrial fuel, it will not only solve the problem of excessive concentration in the atmosphere, but also alleviate the urgent need for new energy to replace fossil energy.
The electrocatalytic reduction of CO2 to carbon-based fuels and chemical raw materials is considered by scientists as an important potential technical approach. However, the insufficient performance of the current CO2 reduction electrocatalyst and the high system cost restrict the application of this technology. How to design an efficient catalyst to improve the energy conversion efficiency and product selectivity of the reaction is an important issue to be solved urgently.
The team of Professor Liang Yongye from the Department of Materials Science and Engineering of Southern University of Science and Technology, and the team of Associate Professor Wang Yanggang from the Department of Chemistry and collaborators have jointly developed a molecularly dispersed electrocatalyst system and molecular engineering control methods, and constructed a high-performance CO2 reduction electrocatalyst based on metal phthalocyanine. Make the carbon monoxide (CO) product selectivity close to 100% at high current density, which is close to the requirements of industrial CO2 reduction. Related research results were published online in "Nature-Energy" recently.
Find the best catalyst
Since the end of the 19th century, the concentration of CO2 in the atmosphere has increased from 280ppm to the current 400ppm. The exploration of technologies that effectively consume CO2 and efficiently convert it into things that can be used by humans has become the focus of global scientists.
CO2 electrocatalytic reduction can use electricity from renewable energy sources to convert CO2 into high value-added carbon-based fuels and chemicals such as CO and hydrocarbons under normal temperature and pressure reaction conditions. It is considered very useful A promising technical approach.
"Reduction of CO2 to CO, an important industrial raw material, is a relatively mature technology. The current reaction selectivity and energy conversion efficiency are higher than those of other products. However, in practical applications, it is still necessary to solve the choice of catalyst products under high current density working conditions. The issue of sex and stability." Liang Yongye, one of the corresponding authors of the paper, told the China Science Daily.
In the application of CO2 electrocatalytic reduction, the catalyst is the key link. It must have high selectivity, low overpotential and good stability in order to efficiently produce valuable carbon-based products. In recent years, CO2 reduction electrocatalyst is a research hotspot, and many research progresses have been made.
Liang Yongye introduced that the current good catalysts include materials based on precious metals such as gold and silver, as well as single-atom electrocatalysts, but there are still many shortcomings, such as the high cost of catalysts that are difficult to be widely used, complex material structures, and insufficient selectivity. .
Recently, metal macrocyclic complex molecules such as cobalt phthalocyanine (CoPc) have been discovered to act as catalysts to convert CO2 to CO under the gas diffusion electrode. "But under high current, their stability is poor. In addition, the lack of understanding of the relationship between the structure and catalytic performance of single-atom catalysts and metal macrocyclic complex catalysts restricts the optimization of catalyst performance." Liang Yongye said.
In response to these problems, Liang Yongye’s team found that the cobalt phthalocyanine-carbon nanotube (CoPc/CNT) composite catalyst exhibits a higher catalytic performance for CO2 reduction than pure CoPc molecules, and this composite method can also reveal a series of The intrinsic activity of MePc (Me = Mn, Fe, Co) molecules greatly improves the electrocatalytic performance of CO2 reduction to CO.
This time, Liang Yongye's team has made new discoveries based on the past.
Ideal catalyst close to industry requirements
The CO2 reduction electrocatalysts of pure metal macrocyclic complexes have problems such as poor molecular conductivity and easy aggregation, which restrict their catalytic performance; and the single-atom catalysts prepared by pyrolysis have complex structures and difficult control, which also limit the research of such catalysts.
Based on the above situation, Liang Yongye's team first obtained a molecularly dispersed electrocatalyst (MDE) by molecularly dispersing the metal macrocyclic complex on conductive carbon nanotubes. The double spherical aberration electron microscopy characterization revealed that its structure is similar to the single-atom electrocatalyst. The nickel phthalocyanine (NiPc) molecular MDE with a clear Ni-N4 structure has high selectivity for the reduction of CO2 to CO, and its catalytic activity and selectivity are better than Ni single-atom catalysts and aggregate NiPc molecules.
"But in application, we found that the catalyst has poor stability." Liang Yongye said. For this reason, they further used molecular engineering methods to control its catalytic performance by introducing different substituents on phthalocyanine (Pc).
Studies have found that the introduction of electron-withdrawing cyano (CN-) substitution can improve its activity, but the stability is still not good. The introduction of methoxy (OMe-) substitution for electronic properties can effectively improve the stability and further improve its selectivity, achieving nearly 100% CO selectivity.
Next, the researchers continued to apply the catalyst to the gas diffusion electrode device for testing, and found that NiPc-OMe MDE has a CO product selectivity in the range of 10~300mA cm-2 with a reduction current density of over 99.5%, and at 150mA cm- It can work stably for 40 hours under the reduction current of 2.
"Such results are close to the requirements of industrial CO2 reduction and have the prospect of industrialization." Liang Yongye said.
The mechanism revealed will guide the optimization of related electrocatalysts
In order to find the scientific principle behind the phenomenon, Liang Yongye cooperated with Wang Yanggang's team and the University of Oregon professor Feng Zhenxing's team, and further combined theoretical calculations and in-situ synchrotron radiation characterization to reveal in depth the mechanism of substituents regulating catalytic performance.
The study found that the CO2 reduction peak potential of nickel phthalocyanine molecularly dispersed electrocatalysts (NiPc MDEs) with Ni-N4 structure is closely related to the partial reduction of Ni center, rather than simply depending on the reaction energy barrier in theoretical calculations. CN-substitution can make the molecule easier to be reduced, so it has a more positive peak potential. In addition, OMe-substitution can increase the strength of the Ni-N bond during the catalytic process and promote the desorption of CO intermediates, thereby improving the catalytic stability.
The discovery of the mechanism will also provide guidance for the design and optimization of related electrocatalysts.
"Currently tested current density and working time are limited by the device technology. It is still necessary to further optimize its test conditions to test the performance under higher current density and longer working time." Liang Yongye said that they will continue to optimize the catalyst in the next step Design to achieve higher catalytic activity and further explore the conditions for preparing other reduction products. At the same time, strengthen the research in practical application devices to promote the application of such catalysts. (â– The reporter's trainee reporter Han Yangmei)
DAYUE has a large inventory of Mold Components and Precision Grinding wheels, which allows us to provide special shaped cutting Punches and dies in a short time.
Delivery plan:
·Cutting punch ISO 8020, DIN 9861, trombone neck punch, punch with 30° head.
·According to DIN 9845, ISO 8977 cutting bushing, according to DIN 9845, ISO 8978 punching guide bushing,
· Ejector Pins of DIN 1530 / ISO 6751, flat ejector, ejector Sleeve,
·DIN 172 and DIN 179 drill bit bushings are used for die-cutting stamps, and for die-cutting bushings, contour stamps, special designs.
After 25 years of development, China's major mold manufacturers have gradually relied on Mold Parts produced by Dayue Precision Technology to ensure quality and added value.
As a high-quality resource that meets the requirements of die-casting molds, injection molds, customized mechanical parts, CNC machining and precision grinding. We have advanced processing equipment and processing technology, combining traditional high-precision processing with professional technology. Undertake the design of mechanical parts and precision machining services of tooling and fixtures to better ensure the accuracy, process performance, output and production cycle of molds and products. We rely on professional technology and multi-functional facilities to support the most diverse customer needs, and provide better and complete services for different user groups to achieve stronger core competitiveness. Continuously improve with advanced concepts, focus on excellent quality, pursue world-class product performance, and establish the most competitive mold parts company.
Punch and die,Pilot Punches,Custom punches and dies,Punch Guide Bushings,DIN 9861 Punch,ISO 8020 Punches
Dayue Precision Technology (Dongguan) Co., Ltd. , https://www.dayuechn.com