Membraneless fuel cell could resist voltage loss

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Canadian researchers have demonstrated a prototype fuel cell with no membranes, which was able to power an LED for four hours using just 0.234ml of methanol.

Conventional fuel cells lose voltage through use and eventually stop working. This is caused by alcohol molecules (methanol or ethanol) in the fuel cell’s anode compartment crossing the membrane separating it from the cathode compartment. Oxygen molecules in the cathode compartment react with this leaked alcohol, causing a drop in voltage over time.

Scientists have unsuccessfully attempted to develop a membrane which prevents alcohol molecules passing through it. Professor Mohamed Mohamedi, an energy systems expert at Quebec’s Institut national de la recherche scientifique, took a different direction by developing a fuel cell without a membrane at all.

The solution costs less and requires fewer steps to manufacture, although a key challenge remained: when the membrane is removed, the alcohol reacts with the oxygen just as it does with conventional fuel cells.

“To prevent voltage drops, we had to develop selective electrodes in the cathode compartment. These electrodes […] remain inactive in the presence of alcohol molecules but are sensitive to the oxygen that generates electricity,” said Mohamedi.

The researchers began by running simulations, which allows them to test different configurations of selective electrodes in the fuel cell.

“Conventional fuel cells are like sandwiches, with the membrane in the middle. We chose instead to work on a single-layer design. We had to determine how to arrange and space the electrodes the maximise fuel use while keeping ambient air oxygen concentration in mind,” Mohamedi explained.

The researchers then tested a prototype which became a proof of concept. The prototype powered an LED for four hours using just 0.234ml of methanol. Next, the researchers want to optimise the fuel cell such that it can use ethanol, a greener fuel which can be produced from agricultural waste and other biomass and which provides more power per unit volume.

The fuel cell is also unique in that it draws oxygen from the air surrounding it.

Unlike conventional batteries which must be recharged, fuel cells continue to produce energy as long as fuel is available: “This energy supply method is particularly effective when recharging is not possible,” said Mohamedi. “Imagine being in the middle of the desert, without electricity. You could recharge your mobile phone using a small capsule of ethanol that you connect to the device.”

Mohamedi and his colleagues expect that the fuel cell could power portable electronics, such as phones, and microsystems, such as air pollution sensors. Despite the device only being at prototype, it has already attracted significant industry attention.

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