In situ implantation of cross-linked functional POSS blocks in Nafion® for high performance direct methanol fuel cells

Polyhedral oligomeric silsesquioxane (POSS) has attracted increasing attention because of its organic/inorganic, nanosize, easily functional nature, especially in the applications of direct methanol fuel cells (DMFCs). In this work, we have successfully synthesized a novel bifunctional POSS ( Vi -POSS-SO 3 Na) with vinyl and sulfonic acid groups by thiol-ene click reaction. Vi -POSS-SO 3 Na was introduced into Nafion® matrix and cross-linked by in-situ simply thermal treatment. The implantation of the bifunctional POSS filler gives significant improvements in the performance of such proton exchange membranes (PEMs). The cross-linked hybrid membrane with 12 wt% of Vi -POSS-SO 3 Na ( X -Nafion@POSS-12) has a high proton conductivity (121 mS cm −1 ) at 80 °C, excellent dimensional stability and the lowest methanol permeability (5.4 × 10 −8  cm 2  s −1 ). The highest power density of the DMFCs was obtained by using the X -Nafion@POSS-12 as PEM in DMFC at 80 °C, and its value (34.93 mW cm −2 ) is twice higher than that of Nafion 212 membrane (14.90 mW cm −2 ). The novel in-situ fabrication method gives a simple and potential approach for the preparation of PEMs used in DMFCs.