doi:10.1038/nindia.2018.37 Published online 21 March 2018
Researchers at the Indian Institute of Science Education and Research (IISER) in Pune report having developed a novel fuel cell1 that not only generates electricity but also "exhales" hydrogen, the very fuel it uses to produce that electricity.
Conventional fuel cell, such as the Proton Exchange Membrane Fuel Cell (PEMFC), converts chemical energy into electricity through the electrochemical reaction of hydrogen with oxygen or another oxidising agent. It consists of an anode, a cathode and an electrolyte. At the anode, a catalyst causes the fuel (hydrogen) to undergo oxidation reaction and generate protons and electrons. The protons flow from anode to cathode through the electrolyte while electrons are drawn from the anode to the cathode through an external circuit, producing an electric current. At the cathode, another catalyst causes hydrogen ions and oxygen (from air) to react, forming water.
The PEMFCs employing hydrogen are of much interest globally, since the byproduct in these hydrogen-oxygen fuel cells is water. A major limitation of hydrogen as the fuel is the difficulty associated with its storage. A novel concept in this context is the production of hydrogen within the fuel cell itself, by a judicious choice of electrolytes.
IISER researchers led by Muhammed Musthafa have now demonstrated this concept in a practical fuel cell device. They have developed a new type of fuel cell that produces electricity and at the same time gives out hydrogen. The Fuel Exhaling Fuel Cell (FEFC) — as they call it — consists of an anode in an alkaline environment and a cathode immersed in an acidic environment separated by a nafion membrane. Hydrogen functions as electron donor in alkaline solutions, and as electron acceptor under acidic conditions. This results in the conversion of hydrogen into water at the anode (which is in alkaline solution), while the acidic environment at the cathode leads to the reduction of hydronium ion (H3O+) to form hydrogen.
"The FEFC utilizes the "neutralization energy," released in the reaction between an acid and alkali, for driving this unique reaction," Musthafa told Nature India. According to their report, the FEFC yielded an open circuit voltage of ∼900mV and delivered a peak power density of 70 mW/cm2 at a current density of 160 mA/cm2 with Hydrogen output of ∼80 mL in one hour at the cathode.
M. V. Sangaranarayanan, professor of electrochemistry at the Indian Institute of Technology in Chennai called this a milestone in the field of hydrogen-oxygen fuel cell. "Since hydrogen is generated in the fuel cell, a complete closed-loop fuel cell is possible without storing hydrogen externally but by generating it in situ," he told Nature India. While the above study employed expensive platinum electrodes, "it is not difficult to look for non-platinum based systems," he pointed out.
The novel fuel cell will have practical applications, says Musthafa. Firstly, it is possible to double the voltage generation, power, and energy output using the same fuel stream by linking the FEFC in a tandem configuration with the conventional fuel cell. "Secondly, the device has the potential to convert acidic and alkaline wastes into electricity with the liberation of clean energy carrier molecule hydrogen, thereby offering possibilities for water purification," says Musthafa whose team includes Zahid Manzoor Bhat and Ravikumar Thimmappa.