Chuanbo Cong

Improved performance of poly(vinyl pyrrolidone)/phosphonated poly(2,6-dimethyl-1,4-phenylene oxide)/graphitic carbon nitride nanocomposite membranes for high temperature proton exchange membrane fuel cells

To achieve desirable performance of a polymer electrolyte membrane with higher proton conduction and better mechanical strength is a challenging work in the development of the phosphoric acid (PA) doped solid-state membrane for high temperature proton exchange membrane fuel cells. Firstly, phosphonated poly(2,6-dimethyl-1,4-phenylene oxide) (pPPO) was prepared by the bromination and phosphonation of poly(2,6-dimethyl-1,4-phenylene oxide). Afterward, a series of poly(vinyl pyrrolidone)–phosphonated poly(2,6-dimethyl-1,4-phenylene oxide) (PVP/pPPO) blend membranes and poly(vinyl pyrrolidone)–phosphonated poly(2,6-dimethyl-1,4-phenylene oxide)–graphitic carbon nitride (PVP/pPPO/g-C3N4) nanocomposite membranes were prepared by a solution casting method. The PA uptake, volume swelling ratio, and proton conductivity of the PVP/pPPO blend membrane increased with increasing PVP content. But PA molecules drastically reduced the mechanical strength of the PVP/pPPO blend membrane. The incorporation of g-C3N4 improved the proton conduction and mechanical properties of the nanocomposite membrane due to the proton hopped sites provided by NH2 and the interaction of g-C3N4 and polymer chains. A higher proton conductivity of 74.4 mS cm−1 and a higher power density of 294 mW cm−2 at 180 °C without additional humidifying were observed for the PA doped PVP/pPPO nanocomposite membrane containing 5 wt% g-C3N4. The results show the PVP/pPPO nanocomposite membrane as a potential polymer electrolyte membrane for high temperature fuel cells.

Degradation of hydrogenated nitrile-butadiene rubber in aqueous solutions of H 2 S or HCl

The degradation of hydrogenated nitrile-butadiene rubber(HNBR) soaped in aqueous solutions of H2S and HCl was investigated. The samples unexposed and exposed to different solutions were characterized by 13C nuclear magnetic resonance, X-ray photoelectron and infrared spectroscopies. In contrast to those of unexposed samples and samples soaped in HCl solution, the mechanical properties of samples exposed to H2S solution significantly deteriorated, in which the new groups of C(=O)-NH2, C-S-C and C=S emerged. The mechanism of C=S and C-S-C formation was speculated, except for that of the formation of group C(=O)-NH2, which was widely discussed in acidic condition such as HCl solution. The formation of C-S-C was due to radical reaction initiated by mercapto radical and that of C=S was due to nucleophilic reaction initiated by mercapto cations. This finding is helpful to understanding the seal failure of HNBR in working environment containing H2S.