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Science China chemistry 2024年第11期67卷 3675-3680页

作者： Yan Zeng Guangchao Han Yuanping Yi Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Organic Solids Institute of Chemistry Chinese Academy of Sciences University of Chinese Academy of Sciences

Molecular doping is essential to improve the electrical conductivity of organic semiconductors for high-performance organic electronic devices. However, the doping efficiency is influenced by several factors, such as the energy levels, energetic fluctuations, dielectric properties, and molecular packing structures of the doped films, and the underlying mechanisms for highefficiency doping are still unclear. Here, through multi-level theoretical simulations on a series of fullerene derivatives, we identify that the energetic fluctuations can play a decisive role in activating charge separation for molecular doping. In particular,the doping efficiency appears to be exponentially increased with the fluctuation of charge polarization energies. Therefore,although the charge mobility is somewhat decreased, the experimental electrical conductivity is improved with the increased energetic fluctuation. Moreover, it has been found that polarization energy fluctuation can be effectively enhanced by simply introducing side chains with greater flexibility into organic semiconductors. This article paves the way towards high-efficiency molecular doping of organic semiconductors.

关键词： doping efficiency polarization energies energetic fluctuations organic semiconductors

Unraveling the potential-dependent degradation mechanism in Fe–N–C catalysts for oxygen reduction reaction

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Science China chemistry 2024年

作者： Yuyi Chu Yuqing Cheng Pengbo Wang Jingsen Bai Xin Guan Shuo Wang Chang Lan Hongxiang Wu Zhaoping Shi Siyuan Zhu Wei Liu Changpeng Liu Meiling Xiao Wei Xing State Key Laboratory of Electroanalytic chemistry Jilin Province Key Laboratory of Low Carbon Chemistry Power Changchun Institute of Applied Chemistry Chinese Academy of Sciences School of Applied chemistry and Engineering University of Science and Technology of China State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied Chemistry Chinese Academy of Sciences

Fe–N–C is hailed as the most promising candidate for replacing costly platinum-based catalysts for proton-exchange membrane fuel cells(PEMFCs) owing to their impressive catalytic activity and low cost. However, the durability of Fe–N–C catalysts remains a major challenge, primarily due to an insufficient understanding of their degradation mechanisms. In this study, we monitor the real-time changes in the electrode during the oxygen reduction reaction(ORR), shedding light on the potentialdependent degradation mechanisms inherent to Fe–N–C catalysts. Utilizing in-situ differential electrochemical mass spectroscopy, we identify three distinct potential regions with varying degrees of performance loss, notably observing carbon corrosion signals at low potentials. theoretical calculations and fluorescence probe experiments corroborate that degradation mechanisms at high potentials are primarily driven by strong oxidative potentials that overcome the carbon oxidation energy barrier, whereas the degradation at low potentials is predominantly caused by the high concentrations of reactive oxygen species(ROS) generated during the ORR. The potential-dependent carbon corrosion consequently leads to a similar dependence of demetallation of active sites on the working potential. This study offers a comprehensive understanding of the intrinsic interrelations among various degradation mechanisms, thus paving the way for enhancing the durability of Fe–N–C catalysts in PEMFC applications.

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In situ tracking of the lithiation and sodiation process of disodium terephthalate as anodes for rechargeable batteries by Raman spectroscopy

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Nano Research 2024年第1期17卷 245-252页

作者： Xiu-Mei Lin Chong Han Xin-Tao Yang Jia-Sheng Lin Wei-Qiang Yang Hong-Xu Guo Yao-Hui Wang Jin-Chao Dong Jian-Feng Li Department of chemistry and Environment Science Fujian Province University Key Laboratory of Analytical ScienceMinnan Normal UniversityZhangzhou 363000China College of Energy College of Chemistry and Chemical EngineeringCollege of MaterialsState Key Laboratory of Physical Chemistry of Solid SurfacesiChEMXiamen UniversityXiamen 361005China institute of Optical and Electronic Technology China Jiliang UniversityHangzhou 310018China

Organic compounds represent an appealing group of electrode materials for rechargeable batteries due to their merits of biomass,sustainability,environmental friendliness,and *** terephthalate(Na_(2)C_(8)H_(4)O_(4),Na_(2)TP),an organic salt with a theoretical capacity of 255 mAh·g^(-1),is electroactive towards both lithium and ***,its electrochemical energy storage(EES)process has not been directly observed via in situ characterization techniques and the underlying mechanisms are still under ***,in situ Raman spectroscopy was employed to track the de/lithiation and de/sodiation processes of *** appearance and then disappearance of the–COOLi Raman band at 1625 cm^(-1) during the de/lithiation,and the increase and then decrease of the–COONa Raman band at 1615 cm^(-1) during the de/sodiation processes of Na2TP elucidate the one-step with the 2Li+or 2Na+transfer *** also found that the inferior cycling stability of Na2TP as an anode for sodium-ion batteries(SIBs)than lithium-ion batteries(LIBs)could be due to the larger ion radium of Na+than Li+,which results in larger steric resistance and polarization during *** Na2TP,therefore,shows greater changes in spectra during de/sodiation than de/*** expect that our findings could provide a reference for the rational design of organic compounds for EES.

关键词： disodium terephthalate(Na_(2)C_(8)H_(4)O_(4) Na2TP) in situ Raman spectroscopy de/lithiation de/sodiation mechanisms

High-rate lithium-ion battery performance of a ternary sea urchin-shaped CoNiO_(2)@NiP_(6)Mo_(18)/CNTs composites

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Journal of Energy chemistry 2024年第9期96卷 516-525页

作者： Li-ping Cui Shuang Sun Kai Yu Shu Zhang Mei-lin Wang Jia-jia Chen Bai-bin Zhou Key Laboratory for Photonic and Electronic Bandgap Materials Ministry of EducationSchool of Chemistry and Chemical EngineeringHarbin Normal UniversityHarbin 150025HeilongjiangChina State Key Laboratory of Physical chemistry of Solid Surfaces Department of ChemistryCollege of Chemistry and Chemical EngineeringCollaborative Innovation Centre of Chemistry for Energy MaterialsXiamen UniversityXiamen 361005FujianChina

Bimetallic oxides are attractive anode materials for lithium-ion batteries(LIBs)due to their large theoretical ***,the low conductivity,short cycle life,and poor rate capability are the bottlenecks for their further *** overcome above issues,the basket-like polymolybdate(NiP_(6)Mo_(18))and carbon nanotubes(CNTs)were uniformly embedded on the urchin-shaped CoNiO_(2)nanospheres to yield a ternary composites CoNiO_(2)@NiP_(6)Mo_(18)/CNTs via electrostatic *** multi-level morphology of urchin spinules accelerates the diffusion rate of Li^(+);CNT improves the conductivity and enhances cycle stability of the material;and heteropoly acid contributes more redox activity ***,CoNiO_(2)@NiP_(6)Mo_(18)/CNTs as an anode of LIBs exhibits a high initial capacity(1396.7 mA h g^(−1)at 0.1 A g^(−1)),long-term cycling stability(750.2 mA h g^(−1)after 300 cycles),and rate performance(450.3 mA h g^(−1)at 2 A g^(−1)),which are superior to reported metallic oxides anode of *** density functional theory(DFT)and kinetic mechanism suggest that CoNiO_(2)@NiP_(6)Mo_(18)/CNTs delivers an outstanding pseudocapacitance and rapid Li^(+)diffusion behaviors,which is due to the rich surface area of the urchin-like CoNiO_(2)with the uniform embeddedness of NiP_(6)Mo_(18)and *** study provides a new idea for optimizing the performance of bimetallic oxides and developing high-rate lithium-ion battery composites.

关键词： Bi-metal oxides Transition metal oxides Polyoxometalates Nanocomposite LIBs

Mapping out the reaction network of humin formation at the initial stage of fructose dehydration in water

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Green Energy & Environment 2024年第6期9卷 1016-1026页

作者： Xing Fu Yexin Hu Ping Hu Hui Li Shuguang Xu Liangfang Zhu Changwei Hu Key Laboratory of Green chemistry and Technology Ministry of EducationCollege of ChemistrySichuan UniversityChengduSichuan610064China State Key Laboratory of Southwestern Chinese Medicine Resources Innovative Institute of Chinese Medicine and PharmacyChengdu University of Traditional Chinese MedicineChengduSichuan611137China

The formation of humins hampers the large-scale production of 5-hydroxymethylfurfural(HMF)in ***,a detailed reaction network of humin formation at the initial stage of fructose-to-HMF dehydration in water is delineated by combined experimental,spectroscopic,and theoretical *** bimolecular reaction pathways to build up soluble humins are *** is,the intermolecular etherification of β-furanose at room temperature initiates the C12 path,whereas the C-C cleavage of a-furanose at 130-150℃ leads to C11 path,and that of open-chain fructose at 180℃ to C11' *** successive intramolecular dehydrations and condensations of the as-formed bimolecular intermediates lead to three types of soluble *** show that the C12 path could be restrained by using HCl or AlCl_(3) catalyst,and both the C12 and C110 paths could be effectively inhibited by adding THF as a co-solvent or accelerating heating rate via microwave heating.

关键词： Carbohydrates 5-hydroxymethylfurfural Reaction network Soluble humins Tautomer

Thermal Performance of a 4 K High-Frequency Pulse Tube Cryocooler with Different Working Fluids

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Journal of Thermal Science 2024年第4期33卷 1468-1479页

作者： GAO Zhaozhao YANG Biao FAN Xiaoyu CHEN Liubiao WANG Junjie Key Laboratory of Cryogenic Science and Technology Technical Institute of Physics and ChemistryChinese Academy of SciencesBeijing100190China University of Chinese Academy of Sciences Beijing100049China

The high-frequency pulse tube cryocooler(HPTC)represents a promising miniature cryocooling technology due to its compact structure and the absence of low-temperature moving ***,limited to the non-ideal gas effect of4He,the HPTC is hard to obtain high cooling performance in the liquid helium temperature range.3He as the working fluid can effectively improve the cooling performance of the HPTC,but the high cost hinders its wide *** consideration of both cooling performance and cost-effectiveness,this paper explores the feasibility of utilizing^(3)He-^(4)He mixtures as the working fluid for ***,the experimental results of a developed HPTC based4He are *** a total power consumption of 575 W,the lowest temperature of 3.26 K was *** the measured cooling power at 4.2 K was 20.8 *** the theoretical utmost efficiency of the cryocooler was calculated in terms of the thermophysical properties of the working fluids,using ^(3)He-^(4)He mixtures with different compositions as the working *** whole machine modeling of the HPTC was further carried out,and the influence of the working fluids with different components on the structural parameters such as double-inlet and inertance tube,and operating parameters such as pressure and frequency were *** calculated results show that the cooling power is expected to be increased to36 mW and 53 mW if the equimolar ^(3)He-^(4)He mixture and pure ^(3)He are used,respectively.

关键词： high-frequency pulse tube cryocooler ^(3)He-^(4)He mixture liquid helium temperature thermally coupled

Asymmetric Cu Sites for Enhanced CO_(2)Electroreduction to C_(2+)Products

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CCS chemistry 2024年第5期6卷 1231-1239页

作者： Weiwei Guo Xingxing Tan Shunhan Jia Shoujie Liu Xinning Song Xiaodong Ma Limin Wu Lirong Zheng Xiaofu Sun Buxing Han Beijing National Laboratory for Molecular Sciences Key Laboratory of Colloid and Interface and ThermodynamicsCenter for Carbon Neutral ChemistryInstitute of ChemistryChinese Academy of SciencesBeijing 100190 institute of Molecular Metrology College of Chemistry and Chemical EngineeringQingdao UniversityQingdao 266071 School of Chemical Sciences University of Chinese Academy of SciencesBeijing 100049 School of Materials Science and Engineering Anhui UniversityHefei 230601 institute of High Energy Physics Chinese Academy of SciencesBeijing 100049 Shanghai Key Laboratory of Green chemistry and Chemical Processes School of Chemistry and Molecular EngineeringEast China Normal UniversityShanghai 200062

Cu-based electrocatalysts can have excellent activity for the generation of C_(2+)products from a CO_(2)reduction reaction(CO_(2)RR).Cuδ+species is crucial in tuning the performance of the ***,we discovered that Si-doped Cu catalysts had excellent performance for electrochemical CO_(2)to C_(2+)products.A high Faradaic efficiency(FE)of 84.7%was achieved with a current density of 289mA cm^(−2)in the flow-cell *** situ experimental results showed that the significant reconstruction occurred during the electrolysis,resulting in the formation of the asymmetric Cu sites(Cu^(0)-Cu^(+)).The ratio of Cu^(0)and Cu^(+)could be tuned by changing Si *** experiments and theoretical calculations demonstrated that the asymmetric Cu sites caused by the appropriate Si doping promoted CO_(2)activation and strengthened the adsorption of^(*)CO *** was beneficial to the subsequent^(*)CO–^(*)CO dimerization step,and thus,accounted for the enhancement of C_(2+)selectivity.

关键词： carbon dioxide electrocatalysis asymmetric Cu sites C-C coupling green chemistry

Electrochemical reconstruction: a new perspective on Sn metal-organic complex microbelts as robust anode for lithium storage

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Rare Metals 2024年第1期43卷 76-86页

作者： Jin-Ke Shen Nai-Teng Wu Li-Yuan Wang Gang Jiang Dong-Lei Guo Jin Li Gui-Long Liu Hong-Yu Mi Huan Pang Xian-Ming Liu Key Laboratory of Function-oriented Porous Materials of Henan Province College of Chemistry and Chemical EngineeringLuoyang Normal UniversityLuoyang 471934China State Key Laboratory of chemistry and Utilization of Carbon Based Energy Resources School of Chemical Engineering and TechnologyXinjiang UniversityUrumqi 830046China School of chemistry and Chemical Engineering Institute for Innovative Materials and EnergyYangzhou UniversityYangzhou 225009JiangsuChina

Tin-based materials with high theoretical capacity and suitable working voltage are ideal anode materials for lithium-ion batteries(LIBs). However, to overcome their shortcomings(volume expansion and inferior stability), the preparation processes are usually complicated and expensive. Herein, a tin-based metal-organic complex(tin 1,2-benzenedicarboxylic acid, Sn-BDC)with one-dimensional microbelt morphology is synthesized by a facile, rapid and low-cost co-precipitation method, and served as anode material for LIBs without any post-treatment. Sn-BDC exhibits a high reversible capacity with609/440 m Ah·g^(-1) at 50/2000 m A·g^(-1), and robust cycling stability of 856 m Ah·g^(-1) after 200 cycles at 200 m A·g^(-1),which are obviously superior to that of the Sn Ox/C counterparts. Moreover, an electrochemical reconstruction perspective on the lithium storage mechanism of Sn-BDC is proposed by systematic ex-situ characterizations. The reconstructed SnO_(2) replaces Sn-BDC and becomes the active material in the subsequent cycles. As the by-product of the lithiation reaction, the formed Li-based metal-organic complex(Li-BDC, wrapped around the reconstructed SnO_(2)) plays an important role in alleviating volume expansion and accelerating the charge transfer *** work is beneficial to design and construct the new electrode materials based on the electrochemical reconstruction for advanced LIBs.

关键词： Electrochemical reconstruction Metal-organic complex Anode Lithium storage mechanism Lithium-ion batteries

Selective synthesis of the B_(11)H_(14)^(-) and B_(12)H_(12)^(2-) borane derivatives and the general mechanisms of the B-H bond condensation

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Science China chemistry 2024年第3期67卷 876-881页

作者： Yi Jing Xinghua Wang Hui Han Xin-Ran Liu Xing-Chao Yu Xi-Meng Chen Donghui Wei Lai-Sheng Wang Xuenian Chen College of chemistry Green Catalysis CenterZhengzhou UniversityZhengzhou 450001China School of chemistry and Chemical Engineering Henan Key Laboratory of Boron Chemistry and Advanced Energy MaterialsHenan Normal UniversityXinxiang 453007China Department of chemistry Brown UniversityProvidenceRI 02912USA

Polyhedral boranes are a class of well-known boron molecular clusters with unique physical and chemical properties,and great efforts have been made in the past decades to find more effective synthetic ***,the established synthetic methods suffer from low efficiency and low selectivity because the mechanism of the B-H bond condensation reaction,critical for the synthesis of the polyhedral boranes,is not well *** we report highly selective and efficient synthetic methods of the salts of the tetradecahydridoundecaborate(1-)(B_(11)H^(-)_(14)) and dodecahydrido-dodecaborates(2-)(B_(12)H_(12)^(2-)) anions by employing commercially available and inexpensive starting *** theoretical and experimental investigations are carried out to elucidate the reaction *** have found that the nature of the B-H bond condensation is the dihydrogen bonding interaction in which the positively charged hydrogens(bridged hydrogens) play a crucial *** current study has not only led to more effective and selective synthetic methods for B_(11)H^(-)_(14) and B_(12)H_(12)^(2-) but also unveiled the nature of the B-H bond condensation and the general formation mechanisms of polyhedral *** finding will facilitate the development of more effective synthetic methods for polyhedral boranes and spur their wide application.

关键词： Boranes polyhedral boranes dihydrogen bond nucleophilicity

Increasing polymer scission rate by tying an overhand knot

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Science China chemistry 2024年第11期67卷 3498-3499页

作者： Yuheng Hu Jennifer T.Ou Jim Y.Huang Yuanning Feng Department of chemistry and Biochemistry The University of Oklahoma

Similar to the phenomenon of knotted ropes in life, knotted climbing ropes will reduce their strength due to knots. Although computer simulations [1], theoretical speculation[2,3], and intuition [3] suggest that similar processes may occur at the nanoscale, this hypothesis has not been experimentally proven before. With the increasing maturity of molecular recognition and self-assembly, a research communication by Leigh et al. [4] published in Nature chemistry introduced a molecular overhand knot into a polymer to study its effect on the scission rate of the polymer chain under tension.

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