Unraveling Shuttle Effect and Suppression Strategy in Lithium/Sulfur Cells by In Situ/Operando X-ray Absorption Spectroscopic Characterization

The polysulfides shuttle effect represents a great challenge in achieving high capacity and long lifespan of lithium/sulfur(Li/S)cells.A comprehensive understanding of the shuttle-related sulfur speciation and diffusion process is vital for addressing this issue.Herein,we employed in situ/operando X-ray absorption spectroscopy(XAS)to trace the migration of polysulfides across the Li/S cells by precisely monitoring the sulfur chemical speciation at the cathodic electrolyte-separator and electrolyte-anode interfaces,respectively,in a real-time condition.After we adopted a shuttle-suppressing strategy by introducing an electrocatalytic layer of twinborn bismuth sulfide/bismuth oxide nanoclusters in a carbon matrix(BSOC),we found the Li/S cell showed greatly improved sulfur utilization and longer life span.The operando S Kedge XAS results revealed that the BSOC modification was bi-functional:trapping polysulfides and catalyzing conversion of sulfur species simultaneously.We elucidated that the polysulfide trapping-and-catalyzing effect of the BSOC electrocatalytic layer resulted in an effective lithium anode protection.Our results could offer potential stratagem for designing more advanced Li/S cells.

Photon-in/photon-out endstation for studies of energy materials at beamline 02B02 of Shanghai Synchrotron Radiation Facility

A new photon-in/photon-out endstation at beamline 02B02 of the Shanghai Synchrotron Radiation Facility for studying the electronic structure of energy materials has been constructed and fully opened to users.The endstation has the capability to perform soft x-ray absorption spectroscopy in total electron yield and total fluorescence yield modes simultaneously.The photon energy ranges from 40 eV to 2000 eV covering the K-edge of most low Z-elements and the L-edge of 3d transition-metals.The new self-designed channeltron detector allows us to achieve good fluorescence signals at the low photon flux.In addition,we synchronously collect the signals of a standard reference sample and a gold mesh on the upstream to calibrate the photon energy and monitor the beam fluctuation,respectively.In order to cross the pressure gap,in situ gas and liquid cells for soft x-ray absorption spectroscopy are developed to study the samples under realistic working conditions.

Titanium carbide nanosheets with defect structure for photothermal-enhanced sonodynamic therapy

Sonodynamic therapy(SDT)has attracted widespread interest in biomedicine,owing to its novel and noninvasive therapeutic method triggered by ultrasound(US).Herein,the Ti_(3)C_(2) MXene nanosheets(Ti_(3)C_(2) NSs)are developed as good sonosensitizers via a two-step method of chemical exfoliation and high-temperature treatment.With the high-temperature treatment,the oxygen defect of Ti_(3)C_(2) MXene nanosheets(H-Ti_(3)C_(2) NSs)is greatly increased.Therefore,the electron(e^(-))and hole(h^(+))generated by US can be separated faster due to the improved degree of oxidation,and then the recombination of e^(-)-h^(+)can be prevented with the abundant oxygen defect under US irradiation,which induced the sonodynamic efficiency greatly to improve around 3.7-fold compared with Ti_(3)C_(2) NSs without high-temperature treatment.After PEGylation,the H-Ti_(3)C_(2)-PEG NSs show good stability and biocompatibility.In vitro studies exhibit that the inherent property of mild photothermal effect can promote the endocytosis of H-Ti_(3)C_(2)-PEG NSs,which can improve the SDT efficacy.In vivo studies further display that the increased blood supply by the mild photothermal effect can significantly relieve hypoxia in the tumor microenvironment,showing photothermal therapy(PTT)enhanced SDT.Most importantly,the H-Ti_(3)C_(2)-PEG NSs can be biodegraded and excreted out of the body,showing no significant long-term toxicity.Our work develops the defective H-Ti_(3)C_(2) NSs as high-efficiency and safe sonosensitizers for photothermal-enhanced SDT of cancer,extending the biomedical application of MXene-based nanoplatforms.