The Effect of Ni Doping on FeOF Cathode Material for High-Performance Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have emerged as a promising alternative to lithium-ion batteries for large-scale energy storage systems due to the abundance and low price of sodium. Until recently, the low theoretical capacities of intercalation-type cathodes less than 250 mAh g-1 have limited the energy density of SIBs. On the other hand, iron oxyfluoride (FeOF) has a high theoretical capacity of ≈885 mAh g-1 as a conversion-type cathode material for SIBs. However, FeOF suffers from poor cycling stability, rate capability, and low initial Coulombic efficiency caused by its low electrical conductivity and slow ionic diffusion kinetics. To solve these problems, doping aliovalent Ni2+ on FeOF electrodes is attempted to improve the electronic conductivity without using a carbon matrix. The ionic conductivity of FeOF is also enhanced due to the formation of oxygen defects in the FeOF crystal structure. The FeOF-Ni1 electrode shows an excellent cycling performance with a reversible discharge capacity of 450.4 mAh g-1 at 100 mAh g-1 after 100 cycles with a fading rate of 0.20% per cycle. In addition, the FeOF-Ni1//hard carbon full cell exhibited a high energy density of 876.9 Wh kg-1 cathode with a good cycling stability.

Treatment of soil washing wastewater via adsorption of lead and zinc using graphene oxide.

In the present work, graphene oxide (GO) was synthesized via the modified Hummers method and utilized in treating real soil washing wastewater via adsorptive removal of lead (Pb) and zinc (Zn). Characterization analysis of GO was performed using X-ray diffraction, Brunauer-Emmett-Teller method, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and zeta potential analysis. The Van't Hoff, Eyring, and Arrhenius equations were applied to determine the activation and thermodynamic parameters namely activation energy (Ea), standard Gibbs energy change (ΔG°), standard enthalpy change (ΔH°), standard entropy change (ΔS°), change in activation Gibbs energy (ΔG#), change in activation enthalpy (ΔH#), and change in activation entropy (ΔS#). Based on the high coefficient of determination values (0.8882 ≥ R2 ≥ 0.9094) and low values of SSE (0.0292 ≤ SSE ≤ 0.0511) and ARE (0.8014 ≤ ARE ≤ 0.8822), equilibrium data agreed well with the Freundlich isotherm. The maximum adsorption capacity for Pb(II) and Zn(II) was determined to be 11.57 and 4.65 mg/g, respectively. Kinetic studies revealed that pseudo-second-order equation fitted well with the experimental data, which indicates that chemisorption is the rate-determining step of the adsorption system. Results have shown the possibility of GO as a potential adsorbent material in the treatment of soil washing wastewater.