Studies On DMFC Using Flexible Proton-conducting Glass-based Composite Membranes

The fuel of direct methanol fuel cell(DMFC) is abundant, cheap, easy to carry and store. DMFC has more huge advantage on portable mobile power than PEMFC using hydrogen and oxygen because its structure is simpler. But there are still some problems to be solved like membrane methanol permeability and catalyst having low efficiency at room temperature.As we studied before, Nafion/phosphosilicate(NPS) glass membrane prepared by tetraethoxysilane(TEOS), orthophosphoric acid(H3PO4) and Nafion resin has high performance in a PEMFC using hydrogen and oxygen.In this study, we propose some new flexible composite membrane based on the NPS glass to use in DMFC. Based on NPS and sulfonated poly(ether ether ketone) SPEEK polymer, we prepare NPS/SPEEK flexible composite membrane. Based on NPS and Nafion solution, we prepare NPS/Nafion flexible composite membrane. We test the proton conductivity and methanol permeability of NPS/SPEEK membrane and methanol permeability of NPS/Nafion. The performances of the single DMFCs are tested under different conditions. For a single DMFC equipped with the NPS/SPEEK membrane, a peak power density is 73.1mW/cm2 under temperature of 85?C, cathode flow rate of 200ml/min, cathode backpressure of 0.2MPa, anode flow rate of 1ml/min, anode methanol concentration of 2M, and anode backpressure of 0. For a single DMFC equipped with the NPS/Nafion membrane, a peak power density is 55mW/cm2 under temperature of 90?C, cathode flow rate of 1ml/min, cathode backpressure of 0.16 MPa, anode flow rate of 1ml/min, anode methanol concentration of 3M, and anode backpressure of 0.12 MPa.We also assemble a DMEC stack of 4 single cells equipped with NPS/Nafion. The performances of the stack under different cathode backpressure and anode backpressure are tested.