In a new research, a team of scientists from Stanford University have designed an electrocatalytic mechanism based on mammalian lungs that enable conversion of water into fuel. It could help improve the efficiency of existing clean energy technologies, according to the scientists whose research work has been published in the journal Joule on December 20.
Respiration process of an organism including inhalation and exhalation may have been mistaken to be very simple, but the breathing process of a mammal is one of the most sophisticated systems for a two-way exchange of gas found in the nature. With each breath, air passes through small, passage-like bronchioles to reach tiny sacs called alveoli in the lungs. The gas then moves to the bloodstream without causing any diffusion which may lead to the formation of harmful bubbles.
Alveoli has unique structure; within the alveoli, a micron-thick membrane repels water molecules, while attracting them on the outside of the membrane, preventing bubbles formation and making the gas exchange more efficient. Inspired by this process, scientists at Stanford University’s Department of Materials Science and Engineering made new electrocatalysts that increase the rate of chemical reaction in an electrode.
According to the first author Jun Li, although clean energy technologies have shown the capability to quickly deliver gas reactant to the reaction interface, the reverse pathway remained challenging, limiting the efficient evolution of gas product from the electrolyte or catalyst interface.
Mimicking the alveolus, the researchers’ mechanism carried out two different processes, in order to enhance the reactions that influence sustainable approaches including metal-air batteries and fuel cells. The first process is analogous to the act of exhaling for mammalian lungs, while the second one is more like the inhaling process.
In the first mechanism to turn water into fuel, water splits to generate a clean fuel in the form of hydrogen gas, by reducing the water molecule in the cathode of a battery and oxidizing in the anode. Oxygen gas along with hydrogen gas is produced at a faster rate in polythene-based, alveolus-like membrane, with bubbles formation.
The second reaction consumes oxygen to produce energy; the catalyst receives oxygen gas at the electrode surface to use it as a reactant in electrochemical reactions. The design appears to be promising, though it is in the initial stages of development. According to the scientists, the thin nano-polythene membrane appears to stay hydrophobic longer than gas diffusion layer based on carbon. Further, the new model can achieve higher rate of current density and lower over-potential compared to conventional designs.
The lung-inspired design still needs improvement to be used in commercial applications. As the artificial membrane is polymer-based film, it cannot tolerate temperatures higher than 100 degree Celsius, which may limit its applications. As reported in the journal, the material can be replaced with equivalent thin, porous, nano-hydrophobic membranes that are able to withstand higher temperature. To completely explore the catalytic capabilities, the researchers are also planning to incorporate other electrocatalysts into the device.