High-performance polymer electrolyte membranes incorporated with 2D silica nanosheets in high-temperature proton exchange membrane fuel cells

Silica nanosheets(SN)derived from natural vermiculite(Verm)were successfully incorporated into polyethersulfone-polyvinylpyrrolidone(PES-PVP)polymer to fabricate high-temperature proton exchange membranes(HT-PEMs).The content of SN filler was varied(0.1-0.75 wt%)to study its influence on proton conductivity,power density and durability.Benefiting from the hydroxyl groups of SN that enable the formation of additional proton-transferring pathways,the inorganic-organic membrane displayed enhanced proton conductivity of 48.2 mS/cm and power density of 495 mW/cm^(2) at 150℃ without humidification when the content of SN is 0.25 wt%.Furthermore,exfoliated SN(E-SN)and sulfonated SN(S-SN),which were fabricated by a liquid-phase exfoliation method and silane condensation,respectively,were embedded in PES-PVP polymer matrix by a simple blending method.Due to the significant contribution from sulfonic groups in S-SN,the membrane with 0.25 wt%S-SN reached the highest proton conductivity of51.5 mS/cm and peak power density of 546 mW/cm^(2) at150℃,48%higher than the pristine PES-PVP membranes.Compared to unaltered PES-PVP membrane,SN added hybrid composite membrane demonstrated excellent durability for the fuel cell at 150℃.Using a facile method to prepare 2D SN from natural clay minerals,the strategy of exfoliation and functionalization of SN can be potentially used in the production of HT-PEMs.

Freeze-assisted Tape Casting of Vertically Aligned MXene Films for High Rate Performance Supercapacitors

Conventional electrode preparation techniques of supercapacitors such as tape casting or vacuum filtration often lead to the restacking or agglomeration of twodimensional(2 D)materials.As a result,tortuous paths are created for the electrolyte ions and their adsorption onto the surfaces of the active materials can be prevented.Consequently,maintaining high rate performance while increasing the thickness of electrodes has been a challenge.Herein,a facile freeze-assisted tape-casting(Fa TC)method is reported for the scalable fabrication of flexible MXene(Ti3C2Tx)supercapacitor electrode films of up to 700μm thickness,exhibiting homogeneous ice-template microstructure composed of vertically aligned MXene walls within lamellar pores.The efficient ion transport created by the internal morphology allows for fast electrochemical charge–discharge cycles and near thickness-independent performance at up to 3000 m V s-1 for films of up to 300μm in thickness.By increasing the scan rate from 20 to 10,000 m V s-1,Ti3C2Tx films of 150μm in thickness sustain 50%of its specific capacitance(222.9 F g-1).When the film thickness is doubled to 300μm,its capacitance is still retained by 60%(at 213.3 F g-1)when the scan rate is increased from 20 to3000 m V s-1,with a capacitance retention above 97.7%for over 14,000 cycles at10 A g-1.They also showed a remarkably high gravimetric and areal power density of 150 k W kg-1 at 1000 A g-1 and 667 m W cm-2 at 4444 m A cm-2,respectively.Fa TC has the potential to provide industry with a viable way to fabricate electrodes formed from 2 D materials on a large scale,while providing promising performance for use in a wide range of applications,such as flexible electronics and wearable energy storage devices.