Study On Sulfonated Poly(Ether Ether Ketone)/functionalized Black Phosphorus Nanosheets Composite Membrane For Vanadium Redox Flow Battery Applications

The preparation and analysis of a novel sulfonated polyether ether ketone(SPEEK)membrane for vanadium redox flow battery(VRFB)is introduced.S/bPn blend membranes were prepared by using two-dimensional orthorhombic crystal structured black phosphorus nanosheets with different loading amounts.The physicochemical and electrochemical properties of S/bPn blend membranes were studied to explore whether they can be used as alternative materials for the proton exchange membrane(PEM)of vanadium fuel cells.Black phosphorus is a two-dimensional structure material with an orthorhombic crystal structure.Two-dimensional black phosphorus was synthesized by high-energy mechanical ball milling(HEMM)with basic allotropic red phosphorus as raw material at an appropriate ball to powder ratio.Furthermore,Raman spectra confirmed the successful recognition of two-dimensional black phosphorus with an orthorhombic crystal structure.The nanosheets were prepared by further processing black phosphorus under liquid-phase exfoliation.The nanosheets were examined by high-resolution transmission electron microscopy(HR-TEM)to check whether the exfoliated black phosphorus layer remained in its 2D atomic structure.Later,a simple solution casting method was used to prepare membranes.Scanning electron microscopy(SEM)was used to observe the morphology of the blend films.It was found that bPn nanosheets had absolute dispersion in the SPEEK polymer matrix due to the highly synergistic effect of bPn and SPEEK,which was also confirmed by Fourier transform infrared spectroscopy.The increase of bPn content in SPEEK polymer significantly improved the performance of the membrane.The increase of bPn content in the matrix polymer indicates that the permeability of vanadium ion(VO2+)in S/bPn membrane decreases.bPn nanocomposite films with different concentrations(10%,30%,50%)were prepared.The gradual incorporation of bPn nanosheets into the membrane acts as a solid vanadium ion blocker,resulting in a significant decrease in vanadium ion permeability.30wt.%composite film has the best performance.In VRFB single cell,the coulomb efficiency(CE)of S/bPn film is 7%higher than that of nafion212,the energy efficiency(EE)is 4%higher than that of nafion212,and the capacity loss is lower than that of nafion212.The composite membrane has good battery performance,low-capacity loss,and strong vanadium ion barrier performance,possessing a great potential for the VRFB application,which would provide continuous and stable electricity for bioelectrochemical processes,such as the conversion of biomass to value-added compounds and sewage treatment.