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Studies on oxidation states of Cobalt Extracted from Soils with EDTA·HO Ac·NH_4OAc

Pedosphere 1991年第2期1卷 109-116页

作者： CAIZU－CONG LIUZHENG InstituteofSoilScience AcademiaSinicaP.O.Box821Nanjing（China） InstituteofSoilScience AcademiaSinica

A method determining di-and tri-valeht cobalt extracted from soils with EDTA·2HOAc·NH4OAc solution (pH 4.65) was developed based on the difference of the stability constants of Co(II)EDTA and Co(III)EDTA. Analytical results indicated that soil cobalt existed in both two oxidation states, i. e. , di-and tri-valent cobalt. Extractable di-valent cobalt in 60 soil samples collected from various soils in China ranged from 0.02 ppm to 3.54 ppm, with the mean of 0.62 ppm, and extractable tri-valent cobalt from 0.04 ppm to 27.65 ppm, with the mean of 2.93 ppm.

关键词： cobalt soil extract oxidation states

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Super-exchange effect induced by early 3d metal doping on NiFe_(2)O_(4)(001)surface for oxygen evolution reaction

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Journal of Energy Chemistry 2023年第3期78卷 21-29,I0002页

作者： Shuhao Wang Xinyan Liu Xiang Chen Kamran Dastafkan Zhong-Heng Fu Xin Tan Qiang Zhang Chuan Zhao School of Chemistry The University of New South WalesSydneyNSW 2052Australia Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology Department of Chemical EngineeringTsinghua UniversityBeijing 100084China Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of ChinaChengdu 611731SichuanChina Integrated Materials Design Laboratory Department of Applied MathematicsResearch School of PhysicsThe Australian National UniversityCanberraACT 2601Australia

Understanding the intrinsic activity of oxygen evolution reaction(OER) is crucial for catalyst *** date,different metal-doping strategies have been developed to achieve this,but the involving mechanisms remain ***,the electronic structure of the transition metal-doped NiFe_(2)O_(4)(001) surface is scrutinized for OER intrinsic activity using density functional theory *** 3d-orbital filling metals(Ti,V,Cr,Mn,and Co) are introduced as dopants onto A-and B-layers of the NiFe_(2)O_(4)(001) surface,and variation of oxidation states over Fe sites is observed on *** the magnetic moment and charge transfer of surface cation sites reveals that the variation of Fe oxidation states originates from the super-exchange effect and is influenced by the t2g-electron configuration of 3d metal *** trend governs the generation of highly-active Fe3+sites on the B-layer,the adsorption strength of OER intermediates,i.e.,*O and*OH,and therefore the intrinsic *** finding of super-exchange mechanism induced by 3d early metal doping offers insights into electronic structure tailoring strategies for improving the intrinsic activity of OER electrocatalysts.

关键词： Oxygen evolution reaction NiFe spinel oxidation states Super-exchange mechanism Density functional theory

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Advances of ferrous and ferric Mossbauer recoilless fractions in minerals and glasses

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Geoscience Frontiers 2022年第2期13卷 78-89页

作者： Hongluo L.Zhang State Key Laboratory of Geological Processes and Mineral Resources China University of GeosciencesBeijing 100083China

Mössbauer spectroscopy has been used widely to characterize the ferric(Fe^(3+))and ferrous(Fe^(2+))proportions and coordination of solid *** obtain these accurately,the recoilless fraction is *** recoilless fractions(f)of iron-bearing minerals,including oxides,oxyhydroxides,silicates,carbonates,phosphates and dichalcogenides,and silicate glasses were evaluated from the temperature dependence of their center shifts or absorption area with the Debye model ***,the resolved Debye temperature(θ_(D))of ferric iron in minerals,except dichalcogenides,through their center shifts ranging from 400 to 550 K,is significantly larger than ferrous iron ranging from 300 to 400 K,which is consistent with the conclusion from previous *** resolved f(Fe^(3+))RT with the center shift model(CSM)ranges from 0.825 to 0.925,which is larger than that obtained for f(Fe^(2+))RT,which ranges from 0.675 to ***,the θ_(D) and f resolved from temperature-dependence of absorption are generally lower than from center shifts,especially for ferric *** significant difference between f(Fe^(3+))and f(Fe^(2+))indicates the necessity of recoilless fraction correction on the Fe^(3+)/(Fe^(3+)+Fe^(2+))resolved from Mössbauer spectra.

关键词： Mossbauer spectroscopy Recoilless fraction Debye temperature oxidation states Iron ratio

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