Fabrication of an anion exchange membrane with textured structure for enhanced performance of direct borohydride fuel cells.

Developing electrolyte membranes with a simple preparation process and high performance is a top priority for the commercialization of fuel cells. Inspired by solar cell texturing to improve its conversion efficiency, this study prepares a textured membrane by increasing the roughness of a glass plate. The structures of the textured membrane and the flat membrane are characterized and compared. The membranes are assembled in fuel cells for performance testing. The surface area of the textured membrane is 1.27 times that of the flat membrane, which increases the size of the three-phase boundary in fuel cells. The maximum power density of the fuel cell using the textured membrane is 1.17 times of the cell using the flat membrane at 60 °C. The excellent performance of the cell using the textured membrane profit from the enlargement of the three-phase boundary. This work offers a simple way to develop outstanding-performance membranes by changing their surface roughness.

Bilayer Anion-Exchange Membrane with Low Borohydride Crossover and Improved Fuel Efficiency for Direct Borohdyride Fuel Cell.

The development of membranes with low fuel crossover and high fuel efficiency is a key issue in direct borohydride fuel cells (DBFCs). In previous work, we produced a poly(vinyl alcohol) (PVA)-anion-exchange resin (AER) membrane with a low fuel crossover and a low fuel efficiency by introducing Co ions. In this work, a bilayer membrane was designed to improve the fuel efficiency and cell performance. The bilayer membrane was prepared by casting a PVA-AER wet gel onto the partially desiccated Co-PVA-AER gel. The bilayer membrane showed a borohydride permeability of 1.34 × 10-6 cm2·s-1, which was even lower than that of the Co-PVA-AER membrane (1.98 ×10-6 cm2·s-1) and the PVA-AER membrane (2.80 × 10-6 cm2·s-1). The DBFC using the bilayer membrane exhibited a higher fuel efficiency (37.4%) and output power (1.73 Wh) than the DBFCs using the Co-PVA-AER membrane (33.3%, 1.27 Wh) and the PVA-AER membrane (34.3%, 1.2 Wh). Furthermore, the DBFC using the bilayer membrane achieved a peak power density of 327 mW·cm-2, which was 2.14 times of that of the DBFC using the PVA-AER membrane (153 mW·cm-2). The drastic improvement benefited from the bilayer design, which introduced an interphase to suppress fuel crossover and avoided unnecessary borohydride hydrolysis.