S/N-co-doped graphite nanosheets exfoliated via three-roll milling for high-performance sodium/potassium ion batteries

Due to its larger ionic radius,further studies are needed before graphite can be used as an anode for sodium/potassium-ion batteries(SIBs/KIBs).It is believed that doping and increasing the layer spacing can improve the Na+/K+storage.Herein,S/N co-doped graphite nanosheets(GNS)with an enlarged interlayer spacing of 0.39 nm were prepared via exfoliation with three-roll milling(TRM)combined with thiourea heated at different temperatures.This method generates abundant defects and active sites for GNS,as well as facilitates rapid access and transport of electrolytes and electrons/ions.The electrochemical results show that the S/N-doped GNS exfoliated 15 times and heated at 600°C(SNGNS15-600)with thiourea as the electrode delivers a discharge capacity of 94 mAh g–1 over 6000 cycles at 10 A g–1 with an enhanced rate capability and stable performance for application in SIBs.Calculations using density functional theory show that the increased interlayer spacing by TRM and S,N co-doping enhances the adsorption energies of Na+on graphite,thus improving the Na+storage.As the anode for KIBs,the SNGNS15-600 electrode has a capacity of 142 mAh g–1 after 5000 cycles at 0.5 A g–1.This study provides an essential theoretical basis for the effective exfoliation of layered graphite-based materials and their applications in energy storage.

Utilizing synergistic effects of bifunctional polymer hydrogel PAM-PAMPS for selective capture of Pb(Ⅱ)from wastewater

The preparation of hydrogel adsorbents with admirable performance for efficient selective remove Pb(Ⅱ)in complex wastewater still remains a great challenge.Herein,a novel bifunctional modified polymer hydrogel PAM-PAMPS was prepared by crosslinking acrylamide(AM)and 2-acrylamido-2-methylpropanesulfonic acid(AMPS).Compared with PEG,PAA and PAMPS,PAM-PAMPS exhibited both the maximum adsorption capacity of Pb(Ⅱ)(541.90 mg/g)and satisfactory selectivity for Pb(Ⅱ)in multiple heavy metal ions coexistence solutions.Various characterizations indicated that–SO3H and–NH2as active sites on PAM-PAMPS occur the synergistic effects of ion-exchange and coordination with Pb(Ⅱ)during the adsorption process,respectively.The adsorption energy Ead(PAM-PAMPS)obtained from density functional theory(DFT)calculations was lower than the other three hydrogels,manifesting that PAMPAMPS formed the most stable complex with Pb(Ⅱ),which further demonstrated that Pb(Ⅱ)preferred to combine with PAM-PAMPS to selective capture of Pb(Ⅱ).The practice utilization of PAM-PAMPS was assessed by wastewater of electroplate containing Pb(Ⅱ).Meanwhile,the removal ratio of PAM-PAMPS was maintained at about 89%after 4 adsorption-desorption cycles.This study establishes a new and effective idea for the design and fabrication of bifunctionalized modified polymer hydrogels.