Although it is in the summer, the researchers of the School of Chemistry and Chemical Engineering have not stopped their efforts because of this. In August of midsummer, the sun is scorching. On the banks of Furong Lake, beside Qunxian Building, good news spread frequently and fruitful results are abundant. The editor has specially compiled some of the scientific research achievements made by the college in August. Come and have a look!
A list of scientific research progress in August
(arranged in the order of reporting time)
team
content overview
journal
Professor Ye Longwu's research group
Gold catalytic nitrogen gauge transfer and carbene transfer reaction
Chemical
Chemical
Reviews
Professor Zheng Nanfeng and Professor Fu Gang's team
Overflow hydrogenation significantly reduces the amount of precious metals
Nature
Nanotechnology
Professor Yang Yong's research group
In-situ solid nuclear magnetic imaging technology visualization study of sodium dendrites in sodium batteries
Nature
Nanotechnology
Professor Wang Ye's research team
New direction of efficient use of biomass: a review of chemicals for photocatalytic conversion of lignocellulose
Chemical
Society Reviews
Academician Sun Shigang's research group
"Large-scale experimental device for energy chemistry based on adjustable infrared laser" has made important progress
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Professor Dong Quanfeng's research group
/
Research on solution phase catalyst of lithium oxygen battery
Advanced
Energy Materials
Deng Dehui researcher team
Research on electrocatalytic reduction of carbon dioxide in nitrogen-doped carbon materials
Cell Reports
Physical Science
Professor Yuan Youzhu's research on synthesis of p-xylene (PX)
Science
Advances
Professor Ren Bin's research group
In-situ electrochemical needle tip enhancement Raman spectroscopy technology reveals spatial distribution of plasmon heat carriers
Nature
Communications
Professor Hong Wenjing and Professor Xia Haiping's research group
Based on intelligent numbers According to analysis technology, the conformation recognition research on single-molecular scale
Chem
Chem
Angebra-level spatial resolution detection field strength distribution in plasmon hotspots
Nature
Naotechnology
Gold catalytic nitrogen transfer and carbene transfer reaction review
High-level spatial resolution detection of field strength distribution in plasmon hotspots
Nature
High-up study group of Professor Ye Longwu of our hospital, Chemical, a subsidiary of the American Chemical Society An invitation to the Reviews publication, writing a review titled "Nitrene Transfer and Carbene Transfer in Gold Catalysis", published online recently (Chem. Rev. 2020, DOI: 10.1021/acs.chemrev.0c00348).
catalytic reaction involving metal carbene is considered to be one of the most important research content in the field of homogeneous transition metal catalysis. Homogeneous gold catalysis has been a major research hotspot in the field of homogeneous catalysis in the past decade due to its advantages of high catalytic activity, mild reaction conditions and strong tolerance of functional groups. Among them, starting from cheap and easy-to-get alkynes, the production of gold-carbene intermediates through gold catalyzed nitrogen-bene transfer and carbene transfer is one of the important advances in the field of metal carbene chemistry.
Ye Longwu's research team has been committed to developing metal carbin chemistry. In recent years, using alkynes as substrates, gold carbene (Chem. Sci. 2014, 5, 4057; Chem. Sci. 2015, 6, 1265; J. Am. Chem. Soc. 2015, 137, 9567; Nat. Commun. 2017, 8, 1748; Sci. Bull. 2017, 62, 1201; ACS Catal. 2019, 9, 1019), platinum carbene (Angew. Chem. Int. Ed. 2017, 56, 605), and zinc carbene (Angew. Chem. Int. Ed. 2020, 59, 1666) and new generation methods of copper carbene (J. Am. Chem. Soc. 2019, 141, 16961; J. Am. Chem. Soc. 2020, 142, 7618; Angew. Chem. Int. Ed. 2020, DOI: 10.1002/anie.202007206). In particular, a new type of alkyne amination reagent, isoxazole, was developed to produce α-imidine carbene, and has been widely used by more than 20 research groups at home and abroad. This review summarizes the current application status of gold-catalyzed alkyne nitrogen transfer and carbene transfer reactions in the past decade. First, the nitrogen transfer reaction of gold-catalyzed alkynes and various new alkynes nitrogen transfer reagents such as azide, azalid, isoxazole, etc. are systematically introduced.Secondly, the carbene transfer reaction of gold catalyzed alkynes is systematically introduced, and thus a variety of oxygen transfer reagents of alkynes such as nitro compounds, nitro nitro sulfoxides, pyridine nitrogen oxides, etc. have been developed. The reaction mechanism of various alkynes participating in gold catalytic nitrogen-bene transfer and carbene transfer and their application in the full synthesis of natural products and biologically active molecules is also introduced in detail. In addition, the review also summarizes the problems and challenges in the research field of gold-catalyzed nitrogen-bene transfer and carbene transfer, and looks forward to future development trends and prospects.
This work was completed by Professor Ye Longwu’s research team and Professor Liu Ruixiong from Tsinghua University in Hsinchu. The research work has been funded by the National Natural Science Foundation of China (21772161 and 21622204), the Fujian Provincial Natural Science Foundation Key Project (2019J02001), the Xiamen Science and Technology Plan Project-Science and Technology Cooperation Project (3502Z20183015), the Xiamen University President's Fund (20720180036), and the Ministry of Education Changjiang Scholars and Innovation Team Development Plan.
Overflow hydrogenation significantly reduces the amount of precious metals
Our college Professor Zheng Nanfeng and Professor Fu Gang's team have made important progress in the research on overflow hydrogenation of alloy catalysts. The related results "Facet Engineering Accelerates Spillover Hydrogenation on Highly Diluted Metal Nanocatalysts" were published in Nature Nanotechnology (DOI: 10.1038/s41565-020-0746-x).
Hydrogen overflow is an important phenomenon in catalysis. It has long been controversial whether hydrogen species overflowing to "inert" support have catalytic hydrogenation activity. The research team organically combines single-atom dispersion catalyst with nanosurface structure regulation to create Pd single-atom catalysts with clear structure and Cu loads on different surfaces, revealing that the hydrogenation capacity of overflow hydrogen species is closely related to the crystal surface of the Cu support. The study found that both catalysts Pd1/Cu(111) and Pd1/Cu(100) have high catalytic selectivity in alkyne semihydrogenation reaction, but their activity has a completely different dependence on the Pd loading. When the Pd loading is as low as dozens of ppm, the catalyst supported by Cu nanosheets has almost no hydrogenation activity, but the catalyst supported by Cu nanocube still has high hydrogenation catalytic activity, indicating that the H species formed by overflowing to the Cu(100) crystal plane after hydrogen is activated in the center of Pd, and the H species formed by overflowing to the Cu(100) crystal plane has hydrogenation ability. More importantly, this overflow hydrogenation process has also been confirmed by two experiments in terms of quantitative CO toxicity activity characterization and increasing the amount of Cu nanocubes can enhance catalytic activity, forming an effective strategy to judge whether overflow hydrogenation occurs. Theoretical calculations show that in addition to the binding energy of H and the surface, the adsorption energy of alkynes is also a very critical factor in overflow hydrogenation. Compared with the Cu(111) surface, the s-p-d orbital hybridization of the Cu(100) surface can effectively stabilize the hydrogenation transition state, reduce the reaction energy barrier, and promote overflow hydrogenation. The study also found that catalytic activity can be greatly improved with the increase in the scale of adding Cu nanocubes, and it was confirmed that the hydrogen overflow distance on the Cu surface can be greater than 500nm, which is much higher than the hydrogen overflow distance on the oxide surface. To this end, the study proposed that Cu(100) can be activated using extremely low Pd content (0.005 wt%, 50 ppm) to make it have high catalytic activity and create a "point copper into palladium" effect. This catalyst has high selectivity for alkyne semi-hydrogenation reactions modified by various substituents, and has considerable reactivity and selectivity for both liquid or gas phase reactions.
This work is jointly guided by Professor Zheng Nanfeng and Professor Fu Gang. The theoretical calculation and prediction part is mainly completed by postdoctoral fellow Jiang Lizhi, and the experimental part is mainly completed by graduated doctoral student Liu Kunlong. Graduated doctoral students Zhou Lingyun, Qin Ruixuan, Liu Pengxin, Professor Chen Haoming and Dr. Hong Songfu from National Taiwan University, as well as Researcher Gu Lin from the Institute of Physics, Chinese Academy of Sciences and Dr. Zhang Qinghua participated in some research and topic discussions. This work has been funded and supported by the National Key R&D Plan, the National Natural Science Foundation, and the basic scientific research business fees of central universities.
In-situ solid magnetic imaging technology visually study the growth process of sodium dendrites in sodium batteries
Our college Professor Yang Yong's research group has made important progress in the research on solid nuclear magnetic resonance technology of rechargeable sodium metal electrodes. The relevant results are titled "Visualizing the growth process of sodium microstructures in sodium batteries by in-situ 23Na MRI and NMR spectroscopy". It was published online on July 27, 2020 in "Nature Nanotechnology DOI: 10.1038/s41565-020-0749-7).
Due to its rich resources and low cost, it is expected to be used in the field of large-scale energy storage batteries. In recent years, sodium-based batteries with safe and long life have aroused great interest. The sodium metal anode has a high theoretical specific capacity of 1165 mA h g-1 and a low operating voltage of -2.71 V, making it an ideal anode material for sodium-based batteries. However, the practical application is limited because sodium metal microstructures (SMSs, i.e., dendrite and mossy Na metals) are easily generated during charge and discharge and the accumulation of solid electrolyte interface (SEI) layers on the electrode surface. In addition, the growth of sodium metal microstructure evolves over time and is difficult to characterize through conventional non-in-situ analytical methods. An in-situ characterization technique is urgently needed to quantitatively study its growth and evolution process and understand its impact on the electrochemical dissolution-deposition process of sodium metal. Professor Yang Yong's team developed in situ 23Na magnetic resonance imaging (MRI) and in situ nuclear magnetic resonance (Operando NMR) technologies to provide spatially resolved and quantitative cognition for the formation and evolution of sodium metal microstructures. Experimental results show that the growing SMSs first lead to a linear increase in deposition overpotential until a transition voltage of 0.15 V is reached. At this time, the vigorous electrochemical decomposition of the electrolyte is triggered, resulting in the generation of moss-type SMSs and the rapid failure of the battery. In addition, the existence of NaH in the sodium metal surface SEI with the help of 23Na high-resolution magic angle rotation nuclear magnetic results also proved.
In recent years, Professor Yang Yong's research team has been committed to developing advanced solid nuclear magnetic technology for the research of electrochemical energy materials. For example, they use reasonable material structure design and bulk phase/interface regulation to charge and discharge reaction mechanisms of lithium-ion positive electrode materials (Nature Energy 2, 17074 (2017); Journal of Power Sources 412 (2019) 336–343), sodium-ion battery positive electrode materials (Angew.Chem. Int. Ed. 2018, 57,11918 –11923; Angew. Chem. Int. Ed., 2019, 58, 18086-18095; Nano Energy 67 (2020) 104252; Chem. Mater. 2020, 32, 4998−5008) and others have conducted in-depth research. The electrochemical-in-situ solid nuclear magnetic technology device jointly developed with the National High Magnetic Field Laboratory in the United States is used to study the charging and discharging mechanism of negative electrode materials (Journal of Materials Chemistry A, 2019, 7,19793) and track the growth of interface metal dendrites (Nature Nanotechnology (2020)).
This work has been supported and helped by Professor Fu Riqiang of the National Strong Magnetic Field Laboratory of the United States, Zhong Guiming (co-communication), an associate researcher at the Chinese Academy of Sciences Haixi, and Dr. Jin Yanting of the University of Cambridge. The first author of the paper is Xiang Yuxuan, a doctoral student in Professor Yang Yong's research group. The research work has been greatly funded and supported by the Ministry of Science and Technology’s key R&D Program (2018YFB0905400, 2016YFB0901502) and the National Natural Science Foundation (21935009, 21761132030, 21603231).
Review on chemicals for photocatalytic conversion of lignocellulosic cells
Our research team and researcher Wang Feng's research team from Dalian Institute of Chemical Physics, Chinese Academy of Sciences were invited to jointly write the review paper "Photocatalytic transformations of lignocellulosic biomass into chemicals" written as an external cover article published in Chemical Society Reviews, DOI: DOI:10.1039/d0cs00314j. This article comprehensively summarizes the research progress in the field of emerging solar-driven chemicals for lignocellulose conversion, discusses in detail the photocatalytic reaction mechanism of selective bond breakage and directional activation of functional groups of lignocellulose-related molecules, and makes in-depth thinking and forward-looking prospects for the current challenges and future development directions.
Lignocellulose is composed of polysaccharides (cellulose, hemicellulose) and lignin, accounting for 90% of the plant biomass on the earth, and is the most important renewable carbon resource. Converting lignocellulose into chemicals, especially organic oxygen-containing compounds with high added value, is one of the ideal ways to convert and utilize biomass. Selective breakage of C−O and C−C bonds under mild conditions and directional activation of specific functional groups are the keys for lignocellulose to convert high-value chemicals. After absorbing light energy, the photocatalyst can generate photogenerated charges or active species with high redox capabilities, and efficient and highly selective chemical conversion can be achieved under mild conditions. In recent years, many domestic and foreign research teams have made breakthroughs in selectively cutting off the C−O and C−C bonds of polysaccharides and lignin macromolecules, efficiently activate lignocellulose and designated functional groups in the derivatized platform molecules through photocatalytic methods, becoming an emerging research field for efficient utilization of biomass.
This review systematically sorted out the chemical systems for photocatalytic lignocellulose-related molecular conversion in recent years, analyzed the advantages of photocatalysis in principle, and introduced in detail the application of photocatalysis in the key transformation of lignocellulose, including the breaking of cellulose C-O bonds; selective oxidation of the midaldehyde/hydroxyl group of monosaccharides and its derived furan platform molecules; the breaking of monosaccharides C-C bonds; the breaking of furan platform molecules; the breaking of lignin C-O and C-O bonds; the C-C coupling of lignin derived aromatic aldehydes, aromatic ketones, phenols, and other important reactions. The review focused on discussing key scientific issues such as the reaction path, reaction mechanism, active substances and intermediates of the molecular transformation process of photocatalytic lignocellulose, providing reference for the design of efficient and highly selective photocatalytic system, and summarized and prospected the challenges and opportunities in the field of photocatalytic lignocellulose conversion to chemicals.
The first author of this paper is Wu Xuejiao, a doctoral student at the iChEM Center of the 2015 Energy Materials Chemistry Collaborative Innovation Center of our college, Professor Wang Ye, Xie Shunji, and Professor Wang Feng from the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences, are the co-corresponding authors. The relevant research work in the paper has been funded by the National Natural Science Foundation of China (21690082, 21972115, 21721004, 21991094), the Strategic Pioneer Science and Technology Special Project of the Chinese Academy of Sciences (XDB17000000), and the Ministry of Science and Technology Key R&D Program (2018YFE0118100).
"Large-scale Energy Chemistry Experimental Device Based on Tunable Infrared Laser" has made important progress
Recently, the development of the national major scientific research instrument and equipment special project "Large-scale Energy Chemistry Experimental Device Based on Tunable Infrared Laser" has made important progress. The project was launched in 2014 with a total fund of 85 million yuan, jointly undertaken by Xiamen University, University of Science and Technology of China, Fudan University and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. This large-scale experimental device includes a tunable infrared free electron laser light source, as well as five experimental line stations: solid-liquid and solid-gas meter interface spectrum, high-space resolution spectrum, ultrafast time resolution spectrum, photodissociation spectrum and photoexcitation spectrum. This device is the first infrared free electron laser user device in China and the first infrared free electron laser device in the world to be researched in the field of energy chemistry. After construction, the ability to study the solid/gas and solid/liquid surface interface processes, cluster structures, their reaction kinetics and infrared vibration dynamics to stimulate molecular reaction kinetics from the atomic and molecular levels will be significantly improved, and a number of cutting-edge scientific problems in the field of energy materials chemistry will be effectively promoted. As an important energy chemistry research platform, this large experimental device will eventually be located in the National Laboratory of Synchronous Radiation (University of Science and Technology of China), open to operation around the world.
In May 2020, the project team's National Synchronous Radiation Laboratory Engineering Team carefully optimized the electron beam current, wavy parameters and beamline mirror attitude through repeated debugging of the infrared free electron laser device (IRFEL), achieving high-power stable output and efficient transmission of the mid-infrared band free electron laser, with a tuning range of 2.5 ~ 50 μm, a macro pulse width of 3 ~ 5 μs, and a maximum micro pulse energy exceeding 80 μJ, exceeding the acceptance indicators in the project plan (Figure 1).In June, the beam diagnosis system completed all technical verifications to achieve accurate diagnosis of low-frequency, ultra-short-pulse infrared laser light intensity and wavelength data. In July, the three experimental line stations, including solid-liquid and solid-gas meter interface spectra and ultrafast time-resolved spectra built by Xiamen University, and the high-space resolution spectra built by Fudan University, have completed the optical path construction and debugging work, successfully realizing docking with the infrared free electron laser beam line. Among them, the solid-liquid and solid-gas meter interface spectral experimental line station constructed by our school obtained the first infrared absorption spectrum diagram of infrared free electron laser (Figure 2).
Figure 1 left picture: overall infrared free electron laser light source; right picture: infrared free electron laser spot (wavelength: 9.9 mm)
Figure 2 left picture: infrared free electron laser wavelength diagnosis results (bandwidth ~1%); right picture: Comparison of polystyrene infrared absorption spectrum acquired based on IRFEL light source and infrared absorption spectrum acquired by conventional Fourier infrared spectrometer: spectral resolution 4 cm-1; number of scans: IRFEL spectrum 1, standard spectrum 32 times.
Next, the project team will further cooperate closely on the basis of existing work, strive to complete the optimization of various parameters and the overall debugging of the device, strive to fully meet the acceptance indicators as soon as possible, and provide a high-quality infrared free electron laser light source and an advanced research platform for scientific research in the field of energy chemistry.
New progress in the research of lithium oxygen battery solution phase catalyst
Recently, our college Professor Dong Quanfeng's research group has made important progress in the research of lithium oxygen battery solution phase catalysts. The relevant research results were published in Advanced Energy Materials under the title "Highly Reversible O2 Conversions by Coupling LiO2 Intermediate through a Dual-Site Catalyst in Li−O2 Batteries" (DOI: 10.1002/aenm.202001592).
Lithium oxygen battery uses metal lithium as the negative electrode, and oxygen in the air is the active substance of the positive electrode, and has an extremely high theoretical energy density. However, there are still many problems in this system and cannot be commercially applied yet. The main reason is that its multiphase reaction kinetic hysteresis and its highly active intermediate LiO2 cause serious side reactions, which makes the battery less reversible and has a short cycle life. The research group has been committed to conducting research on oxygen electrodes for a long time. In the early stage, through the catalytic design and structural design of oxygen electrodes, a series of solid and liquid phase catalysts were constructed, targetedly improving the above problems, thereby significantly improving the electrochemical performance of lithium oxygen batteries (Chem, 2018, 4, 2685−2698; Adv. Energy Mater., 2018, 8, 1800089; Energy Environ. Sci., 2012, 5, 9765−9768; ACS Catal., 2018, 8, 7983−7990).
This work further carried out liquid phase catalysis research on oxygen electrodes based on previous studies, and for the first time, the use of iodine-ylphenyl (PhIO) organic small molecules with two sites (Lewis acid-base pairs) as a solution phase catalyst for lithium oxygen batteries. Combined with experimental and theoretical calculation results, it was found that based on the solution phase catalyst with two-site activity, a new solid/liquid contact interface was constructed, which greatly improved the reaction kinetics, and effectively captured the LiO2 species through its I3+=O2− (double-site), forming the LiO2-3PhIO intermediate product, inhibiting side reactions; compared with the traditional two-electron direct decomposition pathway, a more reversible and kinetic-friendly reaction pathway is provided, thereby improving the reversibility of lithium-oxygen batteries and greatly extending the cycle life of the battery.
This work was completed under the joint guidance of Professor Dong Quanfeng and Associate Professor Zheng Mingsen. Lin Xiaodong (graduated) of the 2015 iChEM doctoral student in our school and Sun Zongqiang, a doctoral student in the 2018 class, are the co-first authors of the paper. The theoretical calculation part was completed by Associate Professor Yuan Ruming, and Tang Chun (a doctoral student in iChEM class 2015, graduated), Xu Pan (a doctoral student in 2017), Cui Xueyang (a doctoral student in 2018) and others participated in some of the work. Professor Zhou Zhiyou and Dr. Hong Yuhao provided active help and support in differential electrochemical mass spectrometry. In addition, thanks to Teacher Yu Lajia for his help in the electron paramagnetic resonance experiment, Su Haisheng, Zhu Lilin and Feng Huishu for his help in the Raman spectroscopy test, and Tao Dandan for his help in the ultraviolet visible spectroscopy test.This work was supported by the National Natural Science Foundation of China (Project approval number: U1805254, 21673196, 21703186, U1705255, 21773192).
Study on the active essence of electrocatalytic reduction of carbon dioxide in nitrogen-doped carbon materials
Recently, the Deng Dehui researcher team of the Collaborative Innovation Center for Energy Materials Chemistry (iChEM) has made new progress in the research on electrocatalytic reduction of CO2 by metal-free nitrogen-doped carbon. By controlling the synthesis of nitrogen-doped carbon materials containing different nitrogen species and doping amounts, it is revealed that the nearest carbon regulated by graphite nitrogen is the active site for electrocatalytic reduction of CO2 to CO. This work provides a reference for a deep understanding of the mechanism of electrocatalytic reduction of CO2 and the rational design of catalysts. Related research results "Unveiling the Active Site of Metal-Free Nitrogen-doped Carbon for Electrocatalytic Carbon Dioxide Reduction" were published in Cell Reports Physical Science, DOI: https://doi.org/10.1016/j.xcrp.2020.100145.
Use renewable energy to convert CO2 into high value-added chemicals is an effective strategy to reduce carbon emissions and alleviate fossil resource shortages. Nitrogen-doped carbon materials have good conductivity and easy to modulate electronic properties, and have shown excellent catalytic performance in electrocatalytic reduction of CO2 to make CO2. However, due to the lack of a controllable preparation method for nitrogen-doped carbon active sites, the understanding of nitrogen-doped carbon is still controversial.
Dend Association research team based on long-term in-depth research on graphene limited-domain single-atom catalysts (Sci. Adv. 2015, 1, e1500462; Nat. Nanotechnol. 2016, 11, 218; Angew. Chem. Int. Ed. 2016, 55, 6708; Nano Energy 2017, 32, 353; Chem 2018, 4, 1902; Angew. Chem. Int. Ed. 2018, 57, 16339; Chem. Rev. 2019, 119, 1806; Adv. Mater. 2019, 31, 1901996), innovatively used the method of assisting pyrolysis of phthalocyanine molecules by silicon oxide sphere templates to control the preparation of a series of nitrogen-doped foam carbon catalysts containing different nitrogen species and doping amounts. Electrochemical activity test results show that samples with high graphitic nitrogen content show the highest CO selectivity compared to samples with relatively high pyridine nitrogen and pyrrole nitrogen content, with CO Faraday efficiency as high as 95% at -0.5 V vs. RHE. Theoretical calculation studies show that the electrocatalytic reduction of CO2 to CO at the adjacent carbon atom sites of graphite nitrogen is significantly lower than the overpotential of its electrolytic hydrolysis hydrogen (HER), which can effectively promote CO2 reduction; pyridine nitrogen itself is blocked due to strong adsorption of H*, and the overpotential of HER reaction on nearby carbon atoms is lower than that of CO2 reduction; pyrrole nitrogen has no obvious promotion effect on both reactions. Therefore, compared with pyridine nitrogen and pyrrole nitrogen, the introduction of graphite nitrogen effectively promotes the catalytic activity of CO2 reduction in its nearest carbon atoms.
Zhang Zheng, a doctoral student in our school in 2016, and associate researcher Yu Liang, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, are the co-first authors of the paper. The above work has been funded by the Ministry of Science and Technology’s key R&D program projects, the National Natural Science Foundation of China, the Strategic Pioneer Science and Technology Special Project of the Chinese Academy of Sciences, the Cooperation Fund Project of the Institute of Clean Energy Innovation of the Chinese Academy of Sciences, and the Ministry of Education’s Energy Materials Chemistry Collaborative Innovation Center (2011-iChEM).
p-xylene (PX) synthesis research
Our school’s research group has made progress in the p-xylene (PX) synthesis route and designed a new synthesis route that couples CO2 hydrogenation and toluene alkylation. The relevant research results are published in Science Advances (Sci. Adv. 6, eaba5433 (2020), DOI: 10.1126/sciadv.aba5433).
PX is one of the basic organic chemical raw materials in the petrochemical industry, and is mainly used to produce three major synthetic materials - synthetic resin, synthetic fiber and synthetic rubber. With the rapid development of my country's downstream industries, the demand for PX has grown rapidly, and the degree of import dependence is greater than 50%. Using selective alkylation reaction of methanol and toluene to make PX is a popular and economical technical route. Although many R&D institutions and companies at home and abroad have invested a lot of manpower and material resources to develop, their reaction temperature is as high as 420~480 °C, which is close to the reaction temperature of methanol to olefin (MTO), which is prone to side reactions. The main reason for the high reaction temperature is that methanol is more difficult to convert to reactive alkylated groups.Professor Yuan Youzhu's research team, in the early stage of CO2 hydrogenation and methanol production (Appl. Catal. B: Environ. 2019, 251, 119; Catal. Sci. Technol. 2018, 8, 1062), noticed the methoxy intermediate of the formate path reaction mechanism of CO2 catalytic hydrogenation and methanol production. Therefore, they proposed to use CO2 and H2 instead of methanol as toluene alkylation reagents, and use the methoxy intermediates generated by CO2 and H2 at relatively low temperatures (without methanol) to directly alkylate with toluene.
In this study, they optimized the composition of the bifunctional catalyst composed of ZnZrOx and ZSM-5 and the alkylation reaction conditions to regulate the matching between CO2 hydrogenation reaction and toluene alkylation reaction, and obtained 81.1% xylene selectivity (excluding the reverse water gas transformation reaction), of which PX accounted for 70.8%. When methanol is used as the alkylation reagent under year-on-year conditions, xylene selectivity is only 49.4%, of which PX accounts for 32.7%. Through the H2/D2 and CO2/13CO2 isotope experiments, it was revealed that two methyl groups in xylene come from toluene and the other comes from CO2 hydrogenation reaction, which proved that xylene does not come from the disproportionation reaction of toluene; at the same time, the reaction had a clear anti-isotope effect (kH/kD=0.80), indicating that the CO2 hydrogenation reaction may undergo a formate (HCOO*) path. Compared with the traditional methanol alkylation path, the toluene alkylation path using CO2 hydrogenation can reduce the reaction temperature to 360°C, and the catalyst is stable after continuous operation for 100 hours. Although there is still a lot of room for improvement in indicators such as substrate conversion and PX selectivity on the existing catalyst system, when high xylene and PX product selectivity are obtained, MTO side reactions are effectively avoided, and the gaseous hydrocarbon selectivity is less than 1%. This work provides new ideas for the research on CO2 resource utilization, and also opens up new ways for the synthesis of high-value chemical PX.
This work was completed under the guidance of Professor Yuan Youzhu. Zuo Jiachang, a doctoral student in the 2018 class of our school, is the first author of the paper. PhD student Chen Weikun, master student Liu Jia, and Dr. Duan Xinping and Dr. Ye Linmin, a National Engineering Laboratory for Clean Production of Alcohol Ether Ester Chemicals (Xiamen University) participated in part of the paper's research. This work has been funded by the National Key R&D Program (2017YFA0206801), the National Natural Science Foundation of China (21972113, 91545115) and the Ministry of Education Innovation Team (IRT_14R31). The research results have applied for Chinese invention patents (application number 201911149539.2, 2019) and international patents (application number PCT/CN2020/077412, 2020).
In-situ electrochemical needle tip enhancement Raman spectroscopy technology reveals the spatial distribution of plasmon heat carriers
Our college Professor Ren Bin's research group has made important progress in characterizing the spatial distribution of plasmon heat carriers. The related result "Probing nanoscale spatial distribution of plasmonically excited hot carriers" is published online in Nature Communications (DOI: 10.1038/s41467-020-18016-4).
Surface plasmon (SP) effect can produce thermal electron-hole pairs (hot carriers) far higher than Fermi energy energy under thermal equilibrium, which can trigger and promote related photoelectric or chemical processes, providing an extremely effective means for efficient use of light energy on the nanoscale to achieve material and energy conversion, and thus has aroused widespread interest in the fields of photocatalysis, photovoltaics, photovoltaic devices, etc. The precise characterization of the spatial distribution of SP hot carriers and their transport distance can guide the design of the application system, thereby achieving efficient capture of hot carriers in space, avoiding the emergence of invalid areas, and improving the efficiency of matter and energy conversion. However, accurate measurement of in-situ measurement of SP hot carriers in real space distribution remains challenging to date.
This work uses the electrochemical needle tip enhanced Raman spectroscopy technology (EC-TERS, J. Am. Chem. Soc., 2015, 137, 11928; Anal. Chem., 2019, 91, 11092), which leverages the advantages of TERS needle tips with SP effect that both catalytic reactions and enhances Raman signals in surface species, and characterizes the regulation process and mechanism of catalytic reaction efficiency of SP hot carriers in situ. Furthermore, this work uses the advantages of TERS high spatial resolution to characterize the spatial distribution of reactions generated at high potential by regulating the reaction catalyzed by the hot carrier of the potential switch SP, that is, triggering the reaction at high potential and then not reacting at low potential.This method realizes nano-resolved imaging of effective hot carrier catalytic reaction regions, visualizing the distribution of the reaction regions in real space. The transport distance of effective hot carriers was obtained experimentally, thus demonstrating that the higher the energy, the more it is necessary to collect and capture within the shorter transport distance range.
This work was completed under the joint guidance of Professor Ren Bin and Associate Professor Wang Xiang. The experiment was mainly completed by Huang Shengchao, a graduated doctoral student in our school. Theoretical calculations are mainly completed by Associate Professor Zhu Jinfeng from the School of Electronic Science and Technology and Richard Wei, a graduated master student. In addition, our college graduates, including Zhao Qingqing, He Yuhan, Hu Shu, and others, also participated in some research and topic discussions. This research work has been funded and supported by the National Natural Science Foundation of China and the Ministry of Science and Technology.
Single-molecular scale conformation recognition research based on intelligent data analysis technology
Our college professor Hong Wenjing and Professor Xia Haiping's research team have made important progress in the research on single-molecular conformation recognition. The relevant research results were published in "Chem" under Cell Press (DOI: 10.1016/j.chempr.2020.07.024).
conformational isomerization is a basic problem in chemistry. However, for flexible molecules such as cyclohexane, due to their extremely fast tautomeric process at room temperature, ensemble-based characterization methods (such as nuclear magnetism, etc.) can only obtain results with average contributions to all conformations. Therefore, the quantitative analysis and characterization of flexible molecular conformations is extremely challenging under room temperature conditions. In order to meet this challenge, they developed a conformation recognition technology based on single-molecular electrical characterization, that is, based on single-molecular electrical characterization, intelligent data analysis technologies such as data dimensionality upgrade and discrete data mining were applied to statistical analysis of single-molecular events, and successfully achieved electrical characterization and proportional recognition of two chair conformations of cyclohexane under room temperature conditions. At the same time, through the confined domain effect of nanoelectrode gap on molecules, we found that extremely unstable torsional intermediates at the macroscopic scale can exist stably at the single molecule scale, which provides an important characterization method for the study of unstable intermediates.
This research work was completed under the joint guidance of Professor Hong Wenjing and Professor Xia Haiping. iChEM direct doctoral student Tang Chun and graduate student Tang Yongxiang of the Department of Chemical Engineering are the co-first authors of the paper. Associate Professor Shi Jia and Associate Researcher Liu Junyang provided guidance for the work. Postdoctoral fellow Chen Zhixin, doctoral student Chen Lijue, and graduate students Ye Yiling, Yan Zhewei and Zhang Longyi participated in the work. This work has been funded by the Ministry of Science and Technology's National Key R&D Program, the National Natural Science Foundation and other projects, and has also been supported by the National Key Laboratory of Solid Surface Physics and Chemistry Collaborative Innovation Center.
Angstrom level spatial resolution detection field strength distribution in plasmon hotspots
Our college Professor Li Jianfeng's research team made progress in the detection of field strength distribution in the plasmon nanocavity. The relevant results were published in "Nature Nanotechnology" (Nature Nanotechnology, DOI: 10.1038/s41565-020-0753-y).
The intensity distribution of electric field in plasmon materials and devices is an important basis for plasmon technology and its application. Although the development of needle-tip enhanced spectral imaging technology has achieved lateral spatial resolution of subnanometers and discovered inhomogeneity of subnanometer-scale electric fields, few are still known about the longitudinal field strength distribution of electric fields to date. Although theoretical studies have shown that molecules in the nanocavity have a strong self-focusing effect, people are still accustomed to consider molecules as uniform media and believe that the field strength in the plasmon nanocavity is uniformly distributed in the longitudinal axis direction. To this end, it is urgent to develop high-space resolution methods to detect the field strength distribution in the plasmon nanocavity cavity to achieve a comprehensive understanding of the plasmon field.
In view of this, Professor Li Jianfeng's research team designed a molecular ruler with a spatial resolution of ~2Å, using gold single crystal substrate and shell to isolate gold nanoparticles to build a plasmon nanocavity, and accurately directly characterizes the highly uneven field intensity distribution in the longitudinal axis direction in the nanocavity through the Raman signal intensity of the molecular ruler. Professor Luo Yi's research team from the University of Science and Technology of China used local field spectroscopy theory based on quantum field theory to accurately simulate the field distribution in the plasmon nanocavity that is consistent with the experiment, and discovered the "plasmon comb" caused by the self-focusing action of molecules. This work provides a general and effective method to quantitatively characterize the field strength distribution of nanocavity, improves the understanding of the basics of plasmons, and provides guidance for ultra-high spatial resolution Raman spectroscopy imaging, optical force regulation molecular assembly, and single-molecular reaction manipulation.
This work was completed under the joint guidance of Professor Li Jianfeng and Professor Luo Yi of the University of Science and Technology of China. The experimental part was mainly completed by Li Chaoyu (first author of the thesis, graduated doctoral degree), Wen Baoying (doc in the current doctoral degree), and Li Songbo (doc in the post). Researchers from Duan Sai of Fudan University (co-first author of the thesis) and Chen Shu (doc in the post) conducted local field spectroscopy theoretical calculations. Xie Liqiang (graduated doctoral degree) and Professor Mao Bingwei helped complete the scanning probe microscopy experiment. Professor Zhou Xiaoshun and Professor Wang Yahao from Zhejiang Normal University provided important assistance in characterization of self-assembly membranes. Professor Kathiresan and Professor Ye Longwu's research team from India and Professor Lu Zhan's research team from Zhejiang University have provided important assistance in molecular synthesis. Professor Wandlowski, Professor Wandlowski, University of Bern, Switzerland, provided guidance on the work. This research work has been funded and supported by the National Natural Science Foundation, the National Key R&D Plan, and the Anhui Province Quantum Information Technology Guidance Special Project.
Review and editing: Dake
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