No abstract

No abstract

approach involving fi xing HPW into a polyvinylpyrrolidone (PVP) and polyethersulfones (PES) matrix. A high proton conductivity of 0.066 S cm -1 is achieved at 60 °C with fully hydrated conditions when the HPW content is 30 wt%, which is very competitive with that of Nafi on115 under the same test conditions. Most signifi cantly, the proton conductivity of PES/PVP-HPW is remarkably stable under a continuous fl ow of deionized (DI) water on both sides of the electrolyte membrane for a test period of more than 500 h. A PEMFC single cell based on the PES/PVP-HPW membrane exhibits impressive performance with a maximum power density of 618 mW cm −2 at 50 °C in H 2 /O 2 , and shows no obvious loss within 500 h. This hybrid PES/PVP-HPW holds great potential applications as a novel PEM due to the comparable performance and signifi cantly reduced cost compared to Nafi on.The synthesis and formation of the HPW self-anchored PES/PVP-HPW PEM through a one-step route was given in Scheme 1 . PVP, PES (mass ratio PVP:PES = 90:10) and HPW with desired content (e.g., 10 wt%, 20 wt%, or 30 wt%) were mixed in N , N -dimethylformamide (DMF) and stirred to form a transparent and homogeneous casting solution. This solution was cast onto a glass plate and dried at 343 K for 24 h to remove the solvent and obtain a PES/PVP-HPW. In the hybrid PEM, PVP that contains an N-heterocycle plays a key role in the formation of membrane and offers self-anchored site for HPW. The self-anchored HPW in the membrane acts as the sole proton conductor and cross-linking agent. PES was added to the membrane as a skeleton, to improve membrane formation and enhance the mechanical strength of the hybrid membrane, which could be replaced with other engineering plastics, for example, polysulfone, polyvinylidene fl uoride, or polyarylsulfone. Figure 1 a-c shows a photograph and cross-sectional scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images of the as-prepared PES/PVP-HPW. The photograph shown in Figure 1 a shows that the membrane was highly transparent and fl exible. The SEM image of the PES/PVP-HPW membrane cross-section exhibited no obvious phase separation, which indicates that these membranes were homogeneous (Figure 1 b). The energy-dispersive X-ray spectroscopy (EDS) tungsten (W) map (inset of Figure 1 b) indicates that the element W (green spots) was homogeneously dispersed in the membrane, which was further demonstrated by the TEM image of the hybrid membrane (Figure 1 c). The average HPW nanoparticle size was determined to be ca. 2.2 nm with a narrow distribution (Supporting Information Figure S1), which was about two HPW molecule size. [ 8 ] The X-ray diffraction (XRD) patterns of the hybrid membrane (see Supporting Information Figure S2) contained no characteristic diffraction peaks The development of proton exchange membranes (PEMs) with improved performance is critical for advancing electrochemical energy devices such as fuel cells and water electrolyzers. [ 1 ] However, the large-scale application of state-of...

Outstanding performance in VRFBs: a novel polysulfone–polyvinylpyrrolidone membrane with high ion selectivity, superior stability and low cost is constructed for VRFBs. The VRFB with the PSF–PVP–50 membrane exhibits impressive CE (98%), EE (89%), and excellent stability during the 2000 h continuous charge–discharge cycling test.

It is a great challenge to obtain high performance carbon fluoride (CF x ) cathodes with high specific capacity and good rate performance due to the electronic conductivity of CF x being known to decrease with an increase in the specific capacity. Herein, we propose a novel fluorinated graphene (FG)/sulfur hybrid cathode to enhance both the energy density and power density of lithium/carbon fluoride (Li/CF x ) batteries. Impressive enhancements of the specific capacity, discharge voltage, and rate capability are demonstrated with the novel FG/sulfur hybrid cathode. In comparison with the pristine FG cathode, the hybrid cathode exhibits higher electrochemical activity, lower overpotential, and faster ion transfer over the main discharge range. Furthermore, when the melt-diffusion method is used to prepare the hybrid cathode, the uncommon monoclinic sulfur is presented under ambient temperature. A significant synergistic effect which reduces the reaction resistance effectively is demonstrated with the presence of monoclinic sulfur, leading to the highest energy density of 2341 W h kg À1 and a power density up to 13 621 W kg À1 at 8.0 A g À1 . Our results are expected to introduce a new generation of high energy and high power density lithium primary cells, based on a simple and effective strategy employing FG/S hybrid cathodes.