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Australian researchers have developed electrolysis systems that use urea obtained from urine and wastewater to generate hydrogen at “significantly lower” energy costs than traditional water splitting methods. Researchers from the University of Adelaide and the Australian Research Councils Centre of Excellence for Carbon Science and Innovation (COE-CSI) have developed two electrolysis systems that harness the urea found in urine and wastewater to produce hydrogen, reducing electricity consumption by up to 27% compared to producing hydrogen from water. COE-CSI Principal Investigator Professor Yao Zheng said this approach not only makes green hydrogen economically competitive with fossil-fuel-derived alternatives, but also creates an elegant solution for wastewater treatment. “Although we havent solved all the problems, if these systems are scaled up, our systems produce harmless nitrogen gas instead of toxic nitrates and nitrites, and either system will use 20 to 27 percent less electricity than water electrolysis systems,” he noted. Hydrogen is typically generated through electrolysis to split water into oxygen and hydrogen. The research team stated that this process is expensive and energy-intensive, requiring 1.23 V to activate the reaction, whereas they were able to split urea, which as a hydrogen carrier has a lower thermodynamic decomposition barrier than water, at just 0.37 V. In their first study, the team used a membrane-less electrolysis system powered by a copper-based catalyst with pure urea as the feedstock. This urea was produced using the Haber-Bosch ammonia synthesis process. To avoid this energy-intensive and carbon-generating process, a second system was designed to utilize the urea found in urine. “We need to reduce the cost of hydrogen production, but in a carbon-neutral way,” Zheng said. “The system in our first paper, although it uses a unique membrane-less system and a novel copper-based catalyst, used pure urea, which is produced through the energy-intensive and CO2-releasing Haber-Bosch process.” “We solved this by using a green source of urea, human urine, which is the basis of the system examined in our second paper.” Although a promising source of urea, urine presents its own challenge. It contains chloride ions that can trigger unwanted chemical reactions during electrolysis. These reactions produce chlorine gas, which corrodes the systems anode and impairs long-term functionality. To address this, the researchers second system features a chlorine-mediated oxidation mechanism that redirects the reaction pathway using carbon-supported platinum-based catalysts. The researchers noted that this approach not only protects the anode but also maintains efficient hydrogen production from urine, adding that the platinum-based system achieves electrical consumption as low as 4.05 kWh per cubic meter of hydrogen, outperforming traditional water electrolysis (4.70–5.00 kWh). “The financial implications of this breakthrough could transform the green hydrogen landscape,” they said, adding that calculations suggest the hydrogen produced through their system costs less than “gray hydrogen” traditionally extracted from fossil fuels. “The membrane-free industrial electrolyzer based on this system successfully reduces the cost of hydrogen production to $1.81 per kilogram, lower than that of gray hydrogen and below the U.S. Department of Energy’s 2030 technical target of $2.00–2.50 per kilogram,” the researchers said. The team is now working on building complete membrane-free systems that recover green hydrogen and remediate nitrogen-rich wastewater. They also recognize that using platinum as a catalytic material is not sustainable and are developing non-precious metal alternatives. |
