A team of Korean researchers has developed a technology that produces hydrogen by using egg shell, which is generally considered as food waste. The principle of the technology is to use egg shell as a catalyst for the conversion of alcohol to hydrogen. Once the reaction is complete, graphene is synthesized on the egg shell. This technology kills three birds with one stone because it produces both hydrogen and graphene while recycling waste.
A research team led by Professor Baek Jong-bum of the Department of Energy and Chemical Engineering at UNIST made calcium oxide using calcium carbonate, which is the main component of egg shell, and found out that it can be used as a catalyst to make hydrogen and graphene. Calcium oxide used as a catalyst allowed the reaction to proceed at a lower temperature than before, leading to production of hydrogen without any additional separation process. In the course of the reaction, a thin layer of carbon deposits on calcium oxide to synthesize graphene, which can easily be detached for usage after simple processing.
Hydrogen is obtained from substances that contain hydrogen, such as water, hydrocarbons, and alcohols, and this process requires a chemical reaction and a reaction-specific catalyst. Calcium oxide showed excellent catalytic performance in the process of producing hydrogen from alcohol.
As alcohol is obtained through fermentation of plants and microorganisms, it is an eco-friendly energy source that can continue to be mass-produced in the future. Because alcohol contains hydrogen, carbon, and oxygen, it can be converted to other useful forms. In fact, a technology of converting alcohol into steam at a high temperature over 700 degrees Celsius and producing hydrogen and carbon-based materials from the steam has already been developed and used. However, at a high temperature over 700 degrees Celsius, by-products like methane, carbon monoxide, and ethylene are generated in addition to hydrogen. Therefore, this technology requires an additional process to separate hydrogen from the produced gas mixture, which increases the hydrogen production unit price in turn.
Baek’s team resolved this problem in the alcohol-using hydrogen production by utilizingcalcium oxide made from egg shell as a catalyst and lowering the reaction temperature to 500 degrees Celsius. As a result, 99 percent of the produced gas was hydrogen, and graphene was also produced in state, where it could be used after calcium oxide removal with an acid with no further processing.