Poly(benzimidazole)/silica-ethyl-phosphoric acid hybrid membranes for proton exchange membrane fuel cells

► PBI membrane hybridzing with silica phosphoric acid. ► The hybrid membrane has a better mechanical property than PBI membrane. ► The hybrid membrane has a higher conductivity than PBI membrane. ► The hybrid membrane has a better PEMFC performance than PBI membrane. Poly(benzimidazole) (PBI) is one of the excellent candidates of proton exchange membranes for high temperature (150–200 °C) proton exchange membrane fuel cells (PEMFCs). When applying to PEMFCs, the PBI membrane is usually doped with phosphoric acid to improve its proton conductivity and therefore PEMFC performance. In this work, we modify the PBI membranes by hybridizing PBI with diethyl phosphate ethyl-triethoxysilane (DEPE-TEOS). The self crosslink reactions of the DEPE-TEOS molecules and the inter-crosslink reactions between DEPE-TEOS and PBI imidazole –NH groups are then proceeded in the hybrid membrane, leading to the formation of crosslinked silica-ethyl phosphoric acid (SiP) nano-particles either bonding or without bonding to PBI. We show the mechanical properties, proton conductivity, and PEMFC performance of the PBI membrane are improved by hybridizing it with SiP nano-particles.