The modulation of the discharge plateau of benzoquinone for sodium-ion batteries

p-Benzoquinone(BQ)is a promising candidate for next-generation sodium-ion batteries(SIBs)because of its high theoretical specific capacity,good reaction reversibility,and high resource availability.However,practical application of BQ faces many challenges,such as a low discharge plateau(~2.7 V)as cathode material or a high discharge plateau as anode material compared with inorganic materials for SIBs and high solubility in organic electrolytes,resulting in low power and energy densities.Here,tetrahydroxybenzoquinone tetrasodium salt(Na_(4)C_(6)O_(6))is synthesized through a simple neutralization reaction at low temperatures.The four-ONa electron-donating groups introduced on the structure of BQ greatly lower the discharge plateau by over 1.4 V from ~2.70 V to ~1.26 V,which can change BQ from cathode to anode material for SIBs.At the same time,the addition of four-ONa hydrophilic groups inhibits the dissolution of BQ in the organic electrolyte to a certain extent.As a result,Na_(4)C_(6)O_(6) as the anode displays a moderate discharge capacity and cycling performance at an average work voltage of ~1.26 V versus Na/Na^(+).When evaluated as a Na-ion full cell(NIFC),a Na_(3)V_(2)(PO_(4))_(3)||Na_(4)C_(6)O_(6) NIFC reveals a moderate discharge capacity and an average discharge plateau of ~1.4 V.This research offers a new molecular structure design strategy for reducing the discharge plateau and simultaneously restraining the dissolution of organic electrode materials.

Kinetics of enhanced adsorption by polarization for organic pollutants on activated carbon fiber

The adsorption kinetics for model pollutants on activated carbon fiber(ACF)by polarization was investigated in this work.Kinetics data obtained for the adsorption of these model pollutants at open-circuit,400 mV,and−400 mV polarization were applied to the Lagergren equation,and adsorption rate constants(Ka)were determined.With the anodic polarization of 400 mV,the capacity of sodium phenoxide was increased from 0.0083 mmol/g at open-circuit to 0.18 mmol/g,and a 17-fold enhancement was achieved;however,the capacity of p-nitrophenol was decreased from 2.93 mmol/g at open-circuit to 2.65 mmol/g.With the cathodal polarization of−400 mV,the capacity of aniline was improved from 3.60 mmol/g at open-circuit to 3.88 mmol/g;however,the capacity of sodium dodecylben-zene sulfonate was reduced from 2.20 mmol/g at open-circuit to 1.59 mmol/g.The enhancement for electrosorption changed with dif ferent groups substituting.Anodic polarization enhances the adsorption of benzene with the electron-donating group.But whether anodic or not,cathodal polariza-tion had less effect on the adsorption of electron-accepting aromatic compounds,and decreased the adsorption capacity of benzene-bearing donor-conjugate bridge-acceptor,while increasing its adsorption rate.Electrostatic interaction played a very important role in the electrosorption of ion-pollutants.

Tuning the helical twisting power of nematic liquid crystals induced by chiral 1,2-propanediol derivatives using varied substituents

In this study,a novel series of chiral 1,2-propanediol derivatives with different electron-donating and electron-withdrawing groups were synthesized and characterized by FT-IR and ~1H NMR.The helical twisting properties of all the chiral dopants were investigated by doping the chiral dopants into a nematic liquid crystal host（SLC-1717）.The results indicate that the donor-acceptor electron effect have a prominent influence on helical twisting property of the chiral nematic phase induced by the chiral dopants. Introducing electron-withdrawing groups into the terminal ends of chiral 1,2-propanediol can decrease the absolute values of the helical twisting power.In addition,the helix inversion temperatures of the induced chiral nematic phase are variational with the change of terminal groups.