A fuel cell uses the chemical energy of fuels or hydrogen to efficiently produce the electricity. If we use hydrogen as fuel, then the products will be electricity, water, and heat. Fuel cells have wide range of uses, like they can be used to provide electricity to a small laptop computer, a vehicle or may be providing power to a large system like utility power station.
If we can replace the batteries with fuel cells, it can give us a host of benefits. The batteries will die after certain use, but fuel cells can continue to function as long as the reagents are supplied. In a fuel cell, a single device will be able to generate fuel and oxidant from water and with a flipping of switch can convert the fuel and oxygen into electricity and water. It will have multiple benefits for terrestrial, space and military applications. It is going to have low impact on environment to high energy density. So, developing of efficient unitized regenerative fuel cells or URFCs is one of the target topics for the researchers over the years.
The focus in making a really efficient URFC is to develop a bifunctional catalyst. This catalyst should function in two ways, when it is in electrolyzer mode, it should facilitate the breakdown of water into hydrogen and oxygen and when it is in fuel cell mode, it should facilitate their recombination into water.
Distinguished university professors Roma B. and Raymond H. Wittcoff, working Vijay Ramani lab, has been able to find an excellent bifunctional catalyst for the oxygen electrode. This has been published in the journal proceedings of the National Academy of Sciences. Identification of a suitable catalyst for oxygen electrode is much more difficult than for hydrogen electrode, because of the sluggish kinetics of oxygen reduction and evolution.
The bifunctionality index for a catalyst is basically measuring its ability to facilitate both forward and reverse direction of a reaction. It should be as low as possible, zero ideally. The new catalyst is having the bifunctionality index to be as low as 0.56 volts, which is remarkably low if we compare the other catalysts reported till now. This catalyst, when used in the laboratory for a URFC device developed in the laboratory, enabled a round-trip efficiency (RTE) of 75%, which is basically the highest in this type of URFC.
As the efficiency rate is quite high, this type of URFC is very well suited for applications such as drones, submersibles, space stations, space crafts, off grid energy storage etc.
This can bring a revolution in the fuel industry. The URFC has the potential to provide economical means for long-term, efficient, seasonal, energy storage and the obviously the on-demand conversion back to electrical energy. There were certain issues like physical corrosion, higher cost of polymer membrane, severe carbon corrosion and durability of the membrane in the unit cell regions, but experimental and intellectual awareness in the context of the URFC system development, new strategies has been suggested to develop novel structured and much advanced URFCs applications in near future.
Citation
https://www.sciencedaily.com/releases/2021/10/211006160111.htm