Waste to wealth:Defect-rich Ni-incorporated spent LiFePO_(4)for efficient oxygen evolution reaction

The development of efficient strategies to recycle lithium-ion battery(LIB)electrode materials is an important yet challenging goal for the sustainable management of battery waste.This work reports a facile and economically efficient method to convert spent cathode material,LiFePO_(4),into a high-performance NiFe oxy/hydroxide catalyst for the oxygen evolution reaction(OER).Herein,Ni-LiFePO_(4)is synthesized via the wetness impregnation method and further evolves into defect-rich NiFe oxy/hydroxide nanosheets during the OER.The introduction of the Ni promoter together with in situ evolution strengthens the electronic interactions among the metal sites and creates an abundance of defects.Experimentally,the evolved Ni-LiFePO_(4)delivers a low overpotential of 285 mV at 10 mA cm-^(2)and a small Tafel slope of 45 mV dec^(-1),outperforming pristine LiFePO_(4)and is even superior to the benchmark catalyst RuO_(2).Density functional theory(DFT)calculations reveal that the introduction of Ni effectively activates Fe sites by optimizing the free energy of the*OOH intermediate and that the abundance of oxygen defects facilitates the oxygen desorption step,synergistically enhancing the OER performance of LiFePO_(4).As a green and versatile method,this is a new opportunity for the scalable fabrication of excellent electrocatalysts based on spent cathode materials.

Removal of trace Cr(VI) from water using chitosan-iron nanowires in porous anodic alumina

Chitosan-iron nanowires in porous anodic alumina （PAA） have been successfully prepared under ambient conditions as an ad- sorbent. The adsorbent was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and N2-BET surface area. The results showed that PAA can disperse and protect Fe0 nanorods from oxidation. The adsorption characteris- tics of trace Cr（VI） onto adsorbent have been examined at different initial Cr（VI） concentrations with pH 5. Batch adsorption studies show that the removal percentage of adsorbent for the removal of trace Cr（VI） is strongly dependent on the initial Cr（VI） concentrations. Langmuir and Freundlich isotherm models were used to analyze the experiment data. The adsorption of trace Cr（VI） by adsorbent is well modeled by the Langmuir isotherm and the maximum adsorption capacity of Cr（VI） is calcu- lated as 123.95 mg/g which is very closed to the experiment results. Intraparticle diffusion study shows that the intraparticle diffusion of adsorbent is not the sole rate-controlling step. The negative value of Gibbs free energy change,△G0, indicated that the process of Cr（VI） onto adsorbent was spontaneous. This work has demonstrated that chitosan-iron nanowires in porous anodic alumina as an adsorbent has promising potential for heavy metal removal at trace level.