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Coprecipitation mechanisms of Zn by birnessite formation and its mineralogy under neutral pH conditions

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Journal of Environmental Sciences 2022年第11期34卷 136-147页

作者： Shota Tajima Shigeshi Fuchida Chiharu Tokoro Graduate School of Creative Science and Engineering Waseda University3-4-1 OkuboShinjuku-kuTokyo 169-8555Japan Faculty of Science and Engineering Waseda University3-4-1 OkuboShinjuku-kuTokyo 169-8555Japan Faculty of Engineering The University of Tokyo7-3-1 HongoBunkyo-kuTokyo 113-8656Japan

Birnessite(δ-Mn(IV)O_(2))is a great manganese(Mn)adsorbent for dissolved divalent metals.In this study,we investigated the coprecipitation mechanism of δ-MnO_(2) in the presence of Zn(II)and an oxidizing agent(sodium hypochlorite)under two neutral pH values(6.0 and 7.5).Themineralogical characteristics and Zn–Mn mixed products were compared with simple surface complexation by adsorption modeling and structural analysis.Batch coprecipitation experiments at different Zn/Mn molar ratios showed a Langmuir-type isotherm at pH 6.0,which was similar to the result of adsorption experiments at pH 6.0 and 7.5.x-ray diffraction and x-ray absorption fine structure analysis revealed triple-corner-sharing innersphere complexation on the vacant sites was the dominant Zn sorption mechanism on δ-MnO_(2) under these experimental conditions.A coprecipitation experiment at pH 6.0 produced some hetaerolite(ZnMn(Ⅲ)_(2)O_(4))and manganite(γ-Mn(Ⅲ)OOH),but only at low Zn/Mn molar ratios(xperiment at pH 7.5 with a high Zn/Mn molar ratio of 5.This resulted in a Brunauer–Emmett–Teller(BET)-type sorption isotherm,in which formation was explained by transformation of the crystalline structure ofδ-MnO_(2) to a tunnel structure.Our experiments demonstrate that abiotic coprecipitation reactions can induce Zn–Mn compound formation on theδ-MnO_(2) surface,and that the pH is an important controlling factor for the crystalline structures and thermodynamic stabilities.

关键词： δ-MnO2 Zinc removal Surface complexation x-ray absorption fine structure

Unveiling anomalous lattice shrinkage induced by Pi-backbonding in Prussian blue analogues

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Journal of Energy Chemistry 2022年第7期31卷 121-128,I0004页

作者： Ju-Hyeon Lee Jin-Gyu Bae Hyeon Jeong Lee Ji Hoon Lee School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Department of Materials University of OxfordOxford OX13PHUnited Kingdom

Transition-metal(TM)-based Prussian blue and its analogues(TM-PBAs) have attracted considerable attention as cathode materials owing to their versatile ion storage capability with tunable working voltages. TM-PBAs with different crystal structures, morphologies, and TM combinations can exhibit excellent electrochemical properties because of their unique and robust host frameworks with well-defined ionic diffusion channels. Nonetheless, there is still a lack of understanding regarding the performance dependence of TM-PBAs on structural changes during charging/discharging processes. In this study, in situ x-ray diffraction and x-ray absorption fine structure analyses elucidate the TMdependent structural changes in a series of TM-PBAs during the charging and discharging processes.During the discharging process, the lattice volume of Fe-PBA increased while those of Ni-and Cu-PBAs decreased. This discrepancy is attributed to the extent of size reduction of the cyanometallate complex([Fe(CN)_(6)]) via pi-backbonding from Fe to C due to redox flips of the low-spin Fe^(3+/2+) ion. This study presents a comprehensive understanding of how TM selection affects capacity acquisition and phase transition in TM-PBAs, a promising class of cathode materials.

关键词： Prussian blue analogues x-ray diffraction x-ray absorption fine structure Pi-backdonation Cyanides

Sub-2 nm ultra-thin Bi_(2)O_(2)CO_(3)nanosheets with abundant Bi-O structures toward formic acid electrosynthesis over a wide potential window

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Nano Research 2022年第4期15卷 2919-2927页

作者： Yuhong Wang Bin Wang Wenjun Jiang Zailun Liu Jiangwei Zhang Lizhen Gao Wei Yao Qian xuesen Laboratory of Space Technology China Academy of Space Technology104 Youyi RoadBeijing 100094China College of Environmental Science and Engineering Taiyuan University of TechnologyTaiyuan 030024China Dalian National Laboratory for Clean Energy&State Key Laboratory of Catalysis Dalian Institute of Chemical PhysicsChinese Academy of Sciences(CAS)Dalian 116023China State Key Laboratory of Structural Chemistry Fujian Institute of Research on the Structure of MatterChinese Academy of Sciences(CAS)Fuzhou 350002China

The electrocatalytic reduction of CO_(2)to HCOOH(ERC-HCOOH)is one of the most feasible ways to alleviate energy crisis and solve environmental problems.Nevertheless,it remains a challenge for ERC-HCOOH to maintain excellent activity and selectivity in a wide potential window.Herein,ultra-thin flower-like Bi_(2)O_(2)CO_(3)nanosheets(NSs)with abundant Bi-O structures were in situ synthesized on carbon paper via topological transformation and post-processing.Faraday efficiency of HCOOH(FEHCOOH)reached 90%in a wide potential window(-1.5 to-1.8 V vs.Ag/AgCl).Significantly,excellent FEHCOOH(90%)and current density(47 mA·cm^(-2))were achieved at-1.8 V vs.Ag/AgCl.The x-ray absorption fine structure(xAFS)combined with density functional theory(DFT)calculation demonstrated that the excellent performance of Bi_(2)O_(2)CO_(3)NS was attributed to the abundant Bi-O structures,which was conducive to enhancing the adsorption of CO_(2)^(*)and OCHO^(*)intermediates and can effectively inhibit hydrogen evolution.The excellent performance of Bi_(2)O_(2)CO_(3)NS over a wide potential window could provide new insights for the efficient electrocatalytic conversion of CO_(2).

关键词： CO_(2)reduction Bi_(2)O_(2)CO_(3)nanosheets Bi-O structures x-ray absorption fine structure wide potential window

Relating atomic local structures and Curie temperature of NdFeB permanent magnets:an x-ray absorption spectroscopic study

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Rare Metals 2018年第11期37卷 983-988页

作者： Mu-Nan Yang Hang Wang Yong-Feng Hu Liu-Yi-Mei Yang Aimee Maclennan Bin Yang Institute of Engineering Research Jiangxi University of Scienceand Technology Canadian Light Source University of Saskatchewan

Relationship between atomic local structures and Curie temperature of NdFeB permanent magnets was investigated semi-quantitatively using synchrotron radiation technique. Fe K-edge x-ray absorption spectroscopy(xAS) was employed to study the local structure of Fe atoms for samples before and after doping Dy, Tb or Gd. It is found that the bond lengths and coordination numbers are changed. Thus, the exchange interaction between Fe atoms increases with Dy, Tb or Gd doping, resulting in the improvement of Curie temperature of NdFeB permanent magnets. The doping effect is proven by experimental measurement of the magnetic properties. Microstructural characterization using scanning electron microscopy(SEM) was also used to further analyze the effect of different rare earth elements doping on Curie temperature of NdFeB permanent magnets.

关键词： Permanent magnet Synchrotron radiation x-ray absorption fine structure Crystal structure Curie temperature

Insights into the Ti^(4+) doping in P2-type Na_(0.67)Ni_(0.33)Mn_(0.52)Ti_(0.15)O_(2) for enhanced performance of sodium-ion batteries

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Journal of Materials Science & Technology 2021年第15期74卷 230-236页

作者： Shi Tao Wei ZhouaDajun Wu Zhicheng Wang Bin Qian Wangsheng Chu Augusto Marcelli Li Song School of Electronic and Inform ation Engineering Jiangsu Laboratory of Advanced Functional MaterialsChangshu Institute of TechnologyChangshu 215500China National Synchrotron Radiation Laboratory University of Science and Technology of ChinaHefei 230029China INFN-Laboratori Nazionali di Frascati Via E.Fermi 40Frascati00044Italy

Due to the sodium abundance and availability,sodium-ion batteries(SIBs)have the potential to meet the worldwide growing demand of electrical energy storage.P2-type sodium transition-metal layer oxides with a high energy density are considered as the most promising cathode materials for SIBs.We present here a detailed study of the enhanced rate capability and cyclic stability of the Ti-doped Na_(0.67)Ni_(0.33)Mn_(0.67)O_(2)cathode material.The combined analysis of ex-situ x-ray absorption fine structure(xAFS)spectroscopy,aberration-corrected high resolution transmission electron microscopy(AB-HRTEM)and x-ray diffraction(xRD)show that the strong Ti–O bond in the transition metal layers stabilizes the local structure,destroy the Na+-vacancy ordering and arrest the irreversible multiphase transformation that occurs during the intercalation/deintercalation process.Actually,Na_(0.67)Ni_(0.33)Mn_(0.52)Ti_(0.15)O_(2)exhibits a reversible capacity of 89.6 mA h g^(-1)even at 5 C,an excellent cyclability with 88.78%capacity retention after 200 cycles at 0.5 C.This study provides a better understanding in optimization of the design of high-energy cathode materials based on titanium doped layered oxides for SIBs.

关键词： P2-type layer oxides Ti doping x-ray absorption fine structure Phase transition Sodium-ion batteries

Ceria supported platinum catalyst for CO oxidation reaction:Importance of metallic active species——Commemorating the 100th anniversary of the birth of Academician Guangxian xu

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Journal of Rare Earths 2021年第5期39卷 495-503页

作者： Luozhen Jiang xin Tao Li'na Li Wen xia Rui Si Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201204China University of Chinese Academy of Sciences Beijing 100049China Division of China TILON Group Technology LimitedShanghai 200090China

Ceria supported platinum catalyst has now been widely studied due to its excellent activity for CO oxidatio n.However,the electron state of active metal center is still an open question.In this work,a ce ria nanorod support was prepared and platinum(Pt)with 0.9 at%was deposited using an impregnation method to obtain Pt/CeO_(2)catalyst.With the help of"light-off"experiment and temperatureprogrammed reduction under CO(CO-TPR)test,the conclusion is proposed that the process of hydrogen reduction can enhance the activity of CO oxidation reaction for the generation of optimal active Pt site.An innovative near-situ x-ray absorption fine structure(xAFS)technique was used to investigate the chemical state of central Pt atom during the reaction process,clearly demonstrating that the high oxidized state of Pt does harm to the activity for CO oxidation while the relatively reductive Pt exhibits high activity,and the different oxidized state and chemical environment of Pt during every process has been identified.Furthermore,the activity of our Pt/CeO_(2)catalyst is superior to that of most of the previous reports about CO catalytic oxidation by Pt based catalyst.Moreover,the optimal active species(Pt-O_(4))have been identified after hydrogen reduction,which could be a possible key strategy to control the oxidation of Pt.

关键词： Platinum catalyst Ceria support CO oxidation structure-activity relationship x-ray absorption fine structure Rare earths

The variation of Mn-dopant distribution state with x and its effect on the magnetic coupling mechanism in Zn_(1-x) Mn_x O nanocrystals

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Chinese Physics B 2013年第10期22卷 516-521页

作者：程岩郝维昌李文献许怀哲陈蕊窦士学 Department of Physics and Center of Materials Physics and Chemistry Beihang University Institute for Superconducting and Electronic Materials (ISEM) University of Wollongong Solar Energy Technologies School of ComputingEngineering and MathematicsUniversity of Western Sydney State Key Laboratory of Inorganic Synthesis and Preparative Chemistry College of ChemistryJilin University

Zn1-xMnxO （x = 0.0005, 0.001, 0.005, 0.01, 0.02） nanocrystals are synthesized by using a wet chemical process. The coordination environment of Mn is characterized by x-ray photoelectron spectroscopy, Raman spectroscopy, and its x-ray absorption fine structure. It is found that the solubility of substitutional Mn in a ZnO lattice is very low, which is less than 0.4%. Mn ions first dissolve into the substitutional sites in the ZnO lattice, thereby forming Mn2＋O4 tetrahedral coordination when x ≤ 0.001, then entering into the interstitial sites and forming Mn3＋O6 octahedral coordination when x ≥ 0.005. All the samples exhibit paramagnetic behaviors at room temperature, and antiferromagnetic coupling can be observed below 100 K.

关键词： magnetic semiconductors x-ray absorption fine structure impurity distribution exchange andsuperexchange interactions

Influence of reducing anneal on the ferromagnetism in single crystalline Co-doped ZnO thin films

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Chinese Physics B 2010年第5期19卷 406-411页

作者：路忠林邹文琴徐明祥张凤鸣 Department of Physics Southeast University Physics Department and Institute of Innovations and Advanced Studies(IIAS) National Cheng Kung University Jiangsu Provincial Laboratory for Nanotechnology National Laboratory of Solid State Microstructureand Department of PhysicsNanjing University

This paper reports that the high-quality Co-doped ZnO single crystalline films have been grown on a-plane sapphire substrates by using molecular-beam epitaxy. The as-grown films show high resistivity and non-ferromagnetism at room temperature, while they become more conductive and ferromagnetic after annealing in the reducing atmosphere either in the presence or absence of Zn vapour. The x-ray absorption studies indicate that all Co ions in these samples actually substituted into the ZnO lattice without formatting any detectable secondary phase. Compared with weak ferromagnetism （0.16 μB/Co2＋） in the Zno.95 Co0.05 O single crystalline film with reducing annealing in the absence of Zn vapour, the films annealed in the reducing atmosphere with Zn vapour are found to have much stronger ferromagnetism （0.65 μB/Co2＋） at room temperature. This experimental studies clearly indicate that Zn interstitials are more effective than oxygen vacancies to activate the high-temperature ferromagnetism in Co-doped ZnO films, and the corresponding ferromagnetic mechanism is discussed.

关键词： Co-doped ZnO diluted magnetic semiconductors x-ray absorption fine structure single crystalline thin films

Manipulating coupling state and magnetism of Mn-doped ZnO nanocrystals by changing the coordination environment of Mn via hydrogen annealing

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Chinese Physics B 2016年第1期25卷 762-769页

作者：程岩李文献郝维昌许怀哲徐忠菲郑离荣张静窦士学王天民 Department of Physics and Center of Materials Physics and Chemistry Beihang UniversityBeijing 100191China Solar Energy Technologies School of ComputingEngineering and MathematicsUniversity of Western SydneyPenrithNSW 2751Australia Institute for Superconducting and Electronic Materials(ISEM) University of WollongongWollongongNSW 2522Australia Beijing Synchrotron Radiation Facility Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China

Mn-doped ZnO nanocrystals are synthesized by a wet chemical route and treated in H2/Ar atmosphere with different H2/Ar ratios. It is found that hydrogen annealing could change the coordination environment of Mn in ZnO lattice and manipulate the magnetic properties of Mn-doped ZnO. Mn ions initially enter into interstitial sites and a Mn3＋ 06 octahedral coordination is produced in the prepared Mn-doped ZnO sample, in which the nearest neighbor Mn3＋ and 02 ions could form a Mn3＋-O2--Mn3＋ complex. After H2 annealing, interstitial Mn ions can substitute for Zn to generate the Mn2＋O4 tetrahedral coordination in the nanocrystals, in which neighboring Mn2＋ ions and H atoms could form a Mn2＋-O2--Mn2＋ complex and Mn-H-Mn bridge structure. The magnetic measurement of the as-prepared sample shows room temperature paramagnetic behavior due to the Mn3＋-O2--Mn3＋ complex, while the annealed samples exhibit their ferromagnetism, which originates from the Mn-H-Mn bridge structure and the Mn-Mn exchange interaction in the Mn2＋-O2--Mn2＋ complex.

关键词： coordination environment magnetic coupling x-ray absorption fine structure