Protonated and layered transition metal oxides as solid acids for dehydration of biomass-based fructose into 5-hydroxymethylfurfural

A serial of protonated and layered transition metal oxides, including layered HTaWO6, HNbMoO6 as well as HNbWO6, were synthesized by solid-state reaction and ion-exchange. The layered HTaWO6 has been systematically studied as a solid acid to realize the dehydration of fructose to 5-hydroxymethylfurfural (HMF). The transition metal oxide samples were characterized with ICP-OES, EDS, XRD, XPS, SEM, TGA, FT-IR, N-2 adsorption-desorption and NH3-TPD. The influential factors such as reaction temperature, reaction time, solvent, catalyst amount and substrate concentration were deeply investigated. The optimized fructose conversion rate of 99% with HMF yield of 67% were achieved after 30 min at 140 degrees C in dimethylsulfoxide. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Understanding voltage hysteresis and decay during anionic redox reaction in layered transition metal oxide cathodes:A critical review

The emergence of anionic redox reactions in layered transition metal oxide cathodes provides practical opportunity to boost the energy density of rechargeable batteries.However,the activation of anionic redox reaction in layered oxides has significant voltage hysteresis and decay that reduce battery performance and limit commercialization.Here,we critically review the up-todate development of anionic redox reaction in layered oxide cathodes,summarize the proposed reaction mechanism,and unveil their connection to voltage hysteresis and decay based on the state-of-the-art progress.In addition,advances associated with various modification approaches to mitigate the voltage hysteresis/decay in layered transition metal oxide cathodes are also included.Finally,we conclude with an appraisal of further research directions including rational design of high-performance layered oxide cathodes with reversible anionic redox reactions and suppressed voltage hysteresis/decay.Findings will be of immediate benefit to the development of layered oxide cathodes for high performance rechargeable batteries.

Progress on multiphase layered transition metal oxide cathodes of sodium ion batteries

As one of the most promising secondary batteries in large-scale energy storage,sodium ion batteries(SIBs) have attracted wide attention due to the abundant raw materials and low cost.Layered transition metal oxides are one kind of popular cathode material candidates because of its easy synthesis and large theoretical specific capacity.Yet,the most common P2 and O3 phases show distinct structural characteristics respectively.O3 phase can serve as a sodium reservoir,but it usually suffers from serious phase transition and sluggish kinetics.For the P2 phase,it allows the fast sodium ion migration in the bulk and the structure can maintain stable,but it is lack of sodium,showing a great negative effect on Coulombic efficiency in full cell.Thus,single phase structure almost cannot achieve satisfied comprehensive sodium storage performances.Under these circumstances,exploiting novel multiphase cathodes showing synergetic effect may give solution to these problems.In this review,we summarize the recent development of multiphase layered transition metal oxide cathodes of SIBs,analyze the mechanism and prospect the future potential research directions.

Insights into Ti doping for stabilizing the Na_(2/3)Fe_(1/3)Mn_(2/3)O_(2)cathode in sodium ion battery

Iron-and manganese-based layered metal oxides,as cathodes for sodium ion batteries,have received widespread attention because of the low cost and high specific capacity.However,the Jahn-teller effect of Mn^(3+)ions and the resulted unstable structure usually lead to continuously capacity decay.Herein,Titanium(Ti)has been successfully doped into Na_(2/3)Fe_(2/3)Mn_(2/3)O_(2)to suppress the Jahn-Teller distortion and improve both cycling and rate performance of sodium ion batteries.In situ high-energy synchrotron X-ray diffraction study shows that Ti-doped compound(Na_(2/3)Fe_(1/3)Mn_(0.57)Ti_(0.1)O_(2))can maintain the single P2 phase without any phase transition during the whole charging/discharging process.Various electrochemical characterizations are also applied to explore the better kinetics of sodium ions transfer in the Na_(2/3)Fe_(1/3)Mn_(0.5)7 Ti_(0.1)O_(2).This work provides a comprehensive insight into the Ti-doping effects on the performance from both structural and electro kinetic perspectives.

Empowering higher energy sodium-ion battery cathode by oxygen chemistry

Sodium(Na)ion batteries(SIBs)promise low-cost energy storage systems but are still restricted by insufficient energy density.Introducing oxygen(O)redox into the design of the Na-storage cathode is presently considered an effective avenue to generate extra capacity in solving the energy density bottleneck.The succeeding issues are how to overcome the irreversible electrochemical behavior accompanied by O release.Meanwhile,the O redox chemistry and subsequent structural evolution remain ambiguous so far.Here,we deliberate on the O redox mechanism in Na-storage transition metal oxides.Challenges associated with the reaction irreversibility and structural collapse are summarized by virtue of the advanced characterization techniques.Beyond that,strategies that potentially enhance the electrochemical properties of O redox and future research perspectives on exploring useable O redox cathode materials are outlined.