Urine, not water for efficient production of green hydrogen

Researchers have developed two unique energy-efficient and cost-effective systems that use urea found in urine and wastewater to generate hydrogen.

The unique systems reveal pathways to economically generate ‘green’ hydrogen, a sustainable and renewable energy source, and the potential to remediate nitrogenous waste in aquatic environments.

Typically, we generate hydrogen through the electrolysis of water where water is split into oxygen and hydrogen. It is a promising technology to help solve the global energy crisis, but the process is energy intensive, which renders it cost-prohibitive when compared to extracting hydrogen from fossil fuels (grey hydrogen), itself an undesirable process because of the carbon emissions it generates.

In contrast to water, an electrolysis system that generates hydrogen from urea uses significantly less energy.

Despite this advantage, existing urea-based systems face several limitations, such as the low conversion efficiency of urea to hydrogen and the generation of undesirable nitrogenous by-products (nitrates and nitrites) that are toxic and compete with hydrogen production, further reducing overall system efficiency.

Finding solutions

Researchers from the Australian Research Council Centre of Excellence for Carbon Science and Innovation (COE-CSI) and the University of Adelaide developed two urea-based electrolysis systems that overcome these problems and can generate green hydrogen at a cost that they have calculated is comparable or cheaper than the cost of producing grey hydrogen.

“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,” says COE-CSI Chief Investigator, Professor Yao Zheng.

The research for each system was published in separate papers, one in Angewandte Chemie International, the other in Nature Communications.

“We need to reduce the cost of making hydrogen, but in a carbon neutral way. The system in our first paper, while using a unique membrane-free system and novel copper-based catalyst, used pure urea, which is produced through the Haber-Bosch ammonia synthesis process that is energy intensive and releases lots of CO₂,” says Prof Zheng.

“We solved this by using a green source of urea – human urine – which is the basis of the system examined in our second paper,” he says.

And yes, the researchers stepped up for the cause of science and donated their urine, alongside lab-made simulated urine. Urine or urea can also be sourced from sewage and other wastewater high in nitrogenous waste.

Urine in an electro-catalytic system, however, presents another issue. Chloride ions in urine will trigger a reaction generating Chlorine that causes irreversible corrosion of the system’s anode where oxidation and loss of electrons occurs.

Thus, a new reaction mechanism that could suppress the chlorine corrosion was found.

“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,” says Professor Shizhang Qiao, Deputy Director and Chief Investigator of COE-CSI.

Alternatives to precious and finite metal catalysts

Platinum is an expensive, precious and finite metal and its increasing demand as a catalytic material is unsustainable. It is a core mission of the ARC Centre of Excellence for Carbon Science and Innovation to enable transformative carbon catalyst technologies for the traditional energy and chemical industries.

The University of Adelaide team plan further experiments to develop 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.

More information

Prof Yao Zheng: yao.zheng01@adelaide.edu.au

Prof Shizhang Qiao: s.qiao@adelaide.edu.au

Jason Major: Communication & Outreach Officer, COE-CSI: jason.major@unsw.edu.au

Papers

Gao, X., Wang, P., Sun, X., Jaroniec, M., Zheng, Y., & Qiao, S. (2025). Membrane‐Free Water Electrolysis for Hydrogen Generation with Low Cost. Angewandte Chemie International Edition, 137(6), e202417987. https://doi.org/10.1002/anie.202417987

Wang, P., Gao, X., Zheng, M., Jaroniec, M., Zheng, Y., & Qiao, S. (2025). Urine electrooxidation for energy–saving hydrogen generation. Nature Communications, 16(1), 2424. https://doi.org/10.1038/s41467-025-57798-3