Electrici-wee? Getting energy from wastewater

Could we ever use urine to power batteries? An international team of chemists have come a step closer with a new catalyst for urea reactions.

“Urea is globally abundant in wastewater and can be used to power fuel cells as an alternative to conventional technology, which uses clean water in an electrolyser,” explains Yao Zheng, an associate professor at the University of Adelaide’s School of Chemical Engineering and Advanced Materials.

Urea – a nitrogen-rich substance that comes from mammal waste – has long been suggested as a store of chemical energy. It can be used in electrolysers to make hydrogen, which can then be used as a clean source of electricity.

But the reaction that could produce hydrogen (the urea oxidation reaction, or UOR) isn’t super-efficient, so wastewater isn’t yet worth harvesting for power.

“We sought to improve on existing UOR catalysts, which tend to perform poorly,” says Professor Shizhang Qiao, director of the Centre for Materials in Energy and Catalysis at Adelaide.

Read more: Tiny parasite could solve wastewater problem

The researchers found that a compound called nickel ferrocyanide could catalyse the urea oxidation reaction, making it much faster and more efficient.

“Our new catalyst made from nickel ferrocyanide requires less energy input and could also reduce the urea content of wastewater,” says Zheng.

“We have shown for the first time that we can make the process in the electrolyser work more efficiently so it can reduce the energy input and produce more hydrogen, than those that use existing catalysts.”

Qiao says that in addition to making clean energy, the UOR helps to remove urea from wastewater.

“Electrocatalytic techniques can convert urea-rich wastewater, which has become a big threat to human health, to hydrogen for clean energy generation as well as reducing its harmful effects on the environment.”

In a paper describing the research, published in Nature Energy, the researchers say that nickel ferrocyanide should be simple to make at larger amounts. They’re now working on the design of their electrolyser, with plans to scale the technology up.

Please login to favourite this article.