Polybenzimidazole membranes for direct methanol fuel cell: Acid-doped or alkali-doped?

Polybenzimidazole (PBI) films immersed in 2 M phosphoric acid (H3PO4) or 6 M potassium hydroxide (KOH) solution form electrolytes for conducting proton or hydroxide, respectively. A direct methanol fuel cell (DMFC) with the alkali-KOH doped PBI gives 117.9 mW cm(-2) of power output which is more than 2 times greater than the power density of 46.5 mW cm(-2) with the H3PO4-doped PBI (vs.) when both of the DMFCs use a micro porous layer (MPL) in a gas-fed cathode and a MPL-free anode and are operated at 90 degrees C. When the MPL-free anode and cathode are used and the fuel flow rate is tripled, the peak power density of alkaline DMFC reaches 158.9 mW cm(-2). (C) 2015 Elsevier B.V. All rights reserved.