A team of researchers from IMDEA Energy, in collaboration with the Complutense University of Madrid and the company GFM Fotovoltaica, has developed a strategy to enhance stainless steel electrodes using nanometric metal oxide coatings for electrochemical hydrogen production through urea electrolysis. Urea is a nitrogen-containing compound commonly found in agricultural, livestock and urban wastewater.

The study, published in Electrochimica Acta, focuses on the controlled preparation and deposition of very thin zirconium oxide films on stainless steel, an inexpensive, conductive material suitable for the hydrogen evolution reaction. Among the coatings studied, zirconium oxide (ZrO₂) calcined at the optimal temperature of 400°C showed particularly favourable performance, improving the electrode response and helping to increase its stability in alkaline and corrosive environments.

Conventional water electrolysis for hydrogen production requires a significant amount of energy. In this context, the team from IMDEA Energy’s Electrochemical Processes Unit addressed this challenge by precisely modifying the composition, thickness and thermal treatment of these coatings. This approach makes it possible to tailor the properties of the interface between the electrode and the electrolyte and improve its performance under demanding electrochemical conditions.

The electrodes were evaluated using urea as the compound to be decomposed in the electrolyte. Compared with the conventional water-splitting reaction, urea oxidation has a lower energy demand and can therefore help reduce the energy required for hydrogen production. An additional advantage was also identified: this approach is of interest for the future exploration of processes that combine hydrogen production with the valorisation or treatment of streams containing nitrogen compounds.

Beyond laboratory testing, the team is working to take these advances from the characterisation of materials and electrodes towards their evaluation in electrochemical configurations that more closely resemble operating conditions. The aim is to determine the extent to which the improvements observed at electrode scale can contribute to the performance and stability of the overall system.

The work, funded by the Institute for Energy Diversification and Saving (IDAE) through NextGenerationEU funds within the NITRO-D-CELL project, and by the Community of Madrid through the SOLENER-CM project, opens the door to further exploration of this low-cost coating strategy in other electrochemical processes related to hydrogen production.

Article reference: Cuartero-González, M., Adán, C., Dato-Vargas, V., Lado, J.J., Luján, S., Fueyo-González, F., García-Quismondo, E., Palma, J. “Interface engineering of stainless steel cathodes via porous oxide layers for high-rate urea electrolysis”. Electrochimica Acta, 576, art. no. 149653, 2026. DOI: 10.1016/j.electacta.2026.149653