Thin flexible fuel cell has record specific volume power density

June 20, 2017 // By Julien Happich
Thin flexible fuel cell has record specific volume power density
In an effort to make fuel cells more portable and compliant for wearable applications, a multidisciplinary team of Chinese scientists has designed a stripped down version of an air-breathing Proton Exchange Membrane Fuel Cell (PEMFC) removing the heavy, rigid and bulky graphite or metal plates typically used in such fuel cells.

The trick was to design an efficient replacement for these rigid parts. Before they could build their flexible PEMFC, the researchers designed a novel composite electrode by stacking a highly flexible and micro-perforated CNT membrane with carbon paper.

Published their findings in the ACS Nano journal under the title "Flexible and Lightweight Fuel Cell with High Specific Power Density", the researchers explain how with their novel design, they were able to remove completely the metal or graphite plates on the cathode side, while replacing the plate on the anode side with a light, flexible and cheap plastic membrane through which they could flow hydrogen. This is because the composite electrode efficiently functioned as the current collector while the light plastic membrane on the anode side operated as the flow field for the hydrogen (fed through a plastic tube).

Comparing different PEMFC structures: (a) a traditional PEMFC. Air or O2 is pumped into the PEMFC. (b) A traditional air-breathing PEMFC. Air naturally diffuses into the PEMFC. (c) A flexible air-breathing PEMFC where air naturally diffuses into the PEMFC. Here the plate on the cathode side has been totally removed, and the plate on anode side has been replaced by a light, flexible, and cheap plastic plate.

The paper reports a 1x1cm2 flexible air-breathing PEMFC as light as 0.065 g and as thin as 0.22mm. This new PEMFC exhibits an astounding specific volume and weight power densities as high as 5190W L−1 and 2230W kg−1, several orders of magnitude higher than that of conventional air-breathing PEMFCs and even higher than conventional PEMFCs while being flexible.

To test the mechanical and power output stability of their novel fuel cell, the researchers built a 4cm long and 1cm wide flexible PEMFC whose output they monitored while subjecting it to hundreds of bending cycles (to 50 degrees).

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