Layer-by-layer Proton Donor and Acceptor Membrane for an Efficient Proton Transfer System in a Polymer Electrolyte Membrane Fuel Cell

The high performance proton transfer in polymer electrolyte membranes (PEMs) is known to be achieved through cooperating of proton donors and acceptors. In order to obtain the effective and efficient proton transfer, the present work proposes a membrane with proton donors and proton acceptors in layer-by-layer (LbL) structure. By applying sulfonated poly (ether ether ketone) (SPEEK) as the substrate membrane and soaking alternatively with the proton donor polymer, i.e. poly(acrylic acid) (PAA), and the proton acceptor heterocycles, i.e. benzimidazoles (BI), the LbL SPEEK/BI/PAA membranes can be achieved. The systematic variation based on the branching benzimidazole groups suggest that the LbL SPEEK/BI/PAA membrane obtained shows an increase in proton conductivity compared to the neat SPEEK, especially in the case of the membrane with trifunctional benzimidazole (B4) is as high as 1-2.5 orders of magnitude over the temperature range of 30-170 degrees C. The present work points out the simple surface modification of the proton conductive membrane by layer-by-layer approach as a practical and simple way to enhance the performance of polymer electrolyte membrane.