Poly (vinyl alcohol) and poly (benzimidazole) blend membranes for high performance alkaline direct ethanol fuel cells

Abstract

A series of poly(vinyl alcohol)-blend-poly(benzimidazole) (PVA:PBI) membranes are synthesized with different ratios of PVA and PBI (2:1, 4:1, 6:1 and 8:1) using the casting method. These materials are doped in KOH 6M solution in order to study their suitability for fuel cell applications. The Infra-red (IR) and Raman spectra confirm the successful doping of the membranes and the dimensional changes due to water and KOH uptakes during the doping are similar to other PBI-based membranes. XPS measurements are performed to evaluate the characteristics of these materials after the doping process. The thermal stability of the membranes is excellent in the range of desired temperatures (below 100 °C) and the conductivity values found are between 10-2 and 10-1 S cm-1. These results are optimal to consider these membranes as candidates for anion exchange membranes (AEMs) and they are ACCEPTED MANUSCRIPT tested in a single cell with ethanol as fuel. The PVA:PBI 4:1 membrane have the best behaviour in fuel cell, reaching a power density of 76 mW cm-2 , approximately 50% better than the doped PBI in the same conditions. These important results can be considered highly promising for the future application of these membranes in alkaline polymer electrolyte membrane fuel cells (APEMFC).

Application of Crosslinked Polybenzimidazole-Poly(Vinyl Benzyl Chloride) Anion Exchange Membranes in Direct Ethanol Fuel Cells

“…Comparing these results with those of PBI and previously developed PVA:PBI 4:1 membranes [ 24 ] ( Figure 7 b), the ultimate strength values of PBI-c-PVBC and PBI-c-PVBC/Cl membranes are in the same range as doped PBI and PVA:PBI membranes—52 and 36 MPa, respectively—but lower than pristine PBI—161 MPa [ 24 ]. As these membranes exhibit high fuel cell performance, we consider that the obtained mechanical properties for PBI-c-PVBC/Cl membranes are adequate for final device applications.…”

“…Figure 2 shows the N 1s peaks of (a) pristine PBI, (b) pure DABCO, (c) PBI-c-PVBC 1:2 membrane and (d) PBI-c-PVBC/Cl 1:2 membrane after quaternization with DABCO. As can be observed, the pristine PBI membrane displays two peaks at 400.3 ± 0.3 and 398.7 ± 0.3 eV ( Figure 2 a) which are attributed to nitrogen of amine (–NH–) and imine (=N–) in the imidazole rings, respectively [ 24 ]. The ratio of imine to amine is close to one, as expected from the structure of the PBI molecule.…”

“…Previously obtained PBI-c-PVBC/OH membranes were sandwiched between anode and cathode, yielding MEAs with a 2.89 cm 2 active area. Commercial pristine PBI membranes (M40 Dapozol ® membrane, 40 µm, Danish Power Systems Ltd, Kvistgaard, Denmark) used for comparison followed the same procedure, but they were doped in KOH 6 M for 5 days (considered the optimum doping time required for this membrane to achieve its maximum conductivity [ 24 ]) before their use. Arbin Fuel Cell Test System (Arbin Instruments, College Station, TX, USA) was used to produce the polarization curves.…”

Alkaline membrane fuel cells: anion exchange membranes and fuels

“…A power density of 18 mW cm À2 has been achieved with an FeCo/C cathode and a commercial Pd/C anode, but an increased power density of 26 mW cm À2 has been achieved with an anode nanocatalyst Pd-NiO/C and Pd/C cathode. Herranz et al 186 tested a series of PVA : PBI membranes with different ratios of PVA and PBI. The highest power density was noted with a PVA and PBI 4 : 1 ratio, and it was 76 mW cm À2 at 90 C with a Pt cathode and a PtRu anode.…”

Nanocatalysts for Electrocatalytic Oxidation of Ethanol

“…[1] Specifically,g rowing interest in using direct alcohol fuel cells (DAFCs) in al arge range of powera pplicationsi s rooted in their desirable features, such as relativelyl ow operating temperatures (80-200 8C), compact system design, and higher volumetric energy densities compared with those of hydrogen fuel cells. [2][3][4][5][6][7][8] DAFCs rely on the oxidation of variousa lcohols at the anode on ac atalystl ayer to form CO 2 .H ydrogen ions produced by alcoholo xidation are transported across the proton-exchange membrane to the cathode, where they react with O 2 to form water.T he overall reaction occurring in a DAFC is 2C n H 2n + 1 OH + 3 nO 2 !2 nCO 2 + 2(n + 1)H 2 O. In the case of methanol, ethanol, and1 -o r2 -propanol as fuels, the number of electrons involved in the reactiona re 6, 12, 18, and 18, respectively.…”