A novel proton exchange membrane based on sulfo functionalized porous silicon for monolithic integrated micro direct methanol fuel cells

A novel sulfo functionalized porous silicon membrane is presented, which can be used as proton exchange membrane (PEM) for monolithic integrated micro direct methanol fuel cells (μDMFCs). The porous silicon membrane is functionalized with sulfonic acid groups (SO3H) to induce proton conductivity via chemical grafting method. Electrical impedance analyses demonstrate that the sulfo functionalized porous silicon membranes exhibit excellent proton exchange capability, achieving a proton conductivity of 0.082 S/cm, which is 1.37 times larger than the value acquired on the most widely used Nafion® 117 membrane (0.060 S/cm). With the in-situ synthesis of 3D platinum nanoflowers on porous silicon presented in our previous work, a monolithic integrated micro fuel cell based on porous silicon is obtained for the first time, which achieves a power density of 5.5 mW cm−2. As such, we believe this work is more attractive for optimizing the integration and sizes of silicon-based μDMFCs.