Researchers have discovered an efficient, low-carbon way to generate green hydrogen by using urea that's found in urine and wastewater.
Their unique method offers a pathway toward cost-effective production of this sustainable energy source, while reducing some of the harmful offshoots of the process, according to a report from the Australian Research Council Centre of Excellence for Carbon Science and Innovation.
Hydrogen produced through dirty fuel sources like natural gas dominates the industry. While it's a cheap process, it releases significant amounts of carbon dioxide (CO2) into the atmosphere, making it unsustainable.
Alternatively, many are using electrolysis to split water into oxygen and hydrogen, but this is often an energy-intensive process, leading many to explore more efficient methods.
There are existing systems that use urea-based electrolysis, which consume much less energy, but they have a low conversion efficiency, the report explained. They also generate undesirable byproducts like nitrates and nitrites, which are toxic and compete with hydrogen production, reducing overall efficiency.
Teams from the Australian Research Council Centre of Excellence for Carbon Science and Innovation (COE-CSI) and the University of Adelaide have developed two new urea-based electrolysis methods that they say are comparable or cheaper than the dirtier alternative.
"While we haven't solved all the problems, should these systems be scaled up, our systems produce harmless nitrogen gas instead of the toxic nitrates and nitrites, and either system will use between 20%-27% less electricity than water splitting systems," said COE-CSI Chief Investigator professor Yao Zheng in a statement.
Urea can be sourced from sewage and other wastewater that's high in nitrogenous waste, which supports a circular economy and can be part of water treatment efforts.
"Hydrogen is today enjoying unprecedented momentum. The world should not miss this unique chance to make hydrogen an important part of our clean and secure energy future," said Dr. Fatih Birol, executive director of the International Energy Agency.
It's a sustainable, energy-dense, and storable medium that produces no planet-heating gases or other pollutants, and can be used in a variety of clean energy applications.
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Hydrogen can be used to heat buildings, power electric vehicles, and even store renewable energy to help balance power grids.
The power needed to drive the process of creating hydrogen can even be created by sustainable energy sources like solar and wind power to further improve its environmental footprint.
Using urine in an electrocatalytic system, however, leads to chlorine generation, which irreversibly corrodes the system's anode, leading the researchers to develop a second process to solve this problem.
"In the first system we developed an innovative and highly efficient membrane-free urea electrolysis system for low-cost hydrogen production. In this second system, we developed a novel chlorine-mediated oxidation mechanism that used platinum-based catalysts on carbon supports to generate hydrogen from urine," said professor Shizhang Qiao, deputy director and chief investigator at COE-CSI.
Platinum is a rare and precious metal that's increasingly in demand and therefore not a long-term sustainable solution, which means their work is far from done.
"The University of Adelaide team will build on this fundamental research by developing carbon-supported, non-precious metal catalysts for constructing membrane-free urine-wastewater systems, achieving lower-cost recovery of green hydrogen while remediating the wastewater environment," the report concluded.
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