A group of CINE researchers has developed a simple, cost-effective and low-environmental-impact method for purifying materials. With it, scientists were able to improve the efficiency of a film that can be used in some green hydrogen generation processes.

Known as mullite-type bismuth ferrite, the Bi_₂Fe_₄O_₉ material has been used as a photoelectrocatalyst in the generation of hydrogen by photoelectrooxidation, a process in which water or biomass derivatives molecules are oxidized using sunlight as an energy source. The role of bismuth ferrite films in the process is to absorb light and drive the electrochemical reactions that “separate” hydrogen from the original molecules (water, glycerol, ethanol, etc.).

However, the performance of these photoelectrocatalysts had limitations during hydrogen production, due, among other factors, to the presence of unwanted compounds within the material itself – the so-called secondary phases. Now, this research by CINE members, carried out at the State University of Campinas (Unicamp), has provided a solution to the problem: a purification method that managed to eliminate these unwanted compounds.

“The process significantly improved the material’s performance in the photoelectrooxidation of organic molecules,” says Pablo Fernández, a professor at Unicamp, a researcher at CINE and co-author of the article reporting the discovery in Electroquimica Acta. “Although we are still far from achieving adequate performance for application in a real system, because several other aspects need to be improved, this is an important step in the production of a cheap and sustainable material with applications in the generation of green hydrogen and water purification (among other applications) using photoelectrochemical methods,” adds the scientist.

Fortune favors the prepared

The study was conducted as part of Bruno Leuzinger da Silva’s doctoral research at the Institute of Chemistry at Unicamp, under the guidance of Professor Ana Flavia Nogueira. The student was testing the performance of bismuth ferrite films in the oxidation of glycerol molecules, with the aim of producing green hydrogen, when he noticed that the material changed over time.

Later, detailed studies revealed the reason for the changes: when interacting with glycerol and light, the material spontaneously purified itself. Finally, tests performed with purified films showed that they performed better in generating hydrogen than the not purified films.

Based on this discovery, the team formulated the photoelectrochemical purification method that was published in the scientific article. In this method, the material to be purified is placed in contact with glycerol. When it receives light, certain electrochemical reactions involving the material and glycerol occur, and the secondary phases disappear.

The method basically uses electricity, light and glycerol, which is renewable, biodegradable, non-toxic and widely available because it is an abundant byproduct of biodiesel production.

This discovery opens up possibilities for the development of high-purity, efficient and low-cost materials that can be used to drive several important photoelectrochemical reactions for applications such as the sustainable production of fuels and industrial compounds and the treatment of effluents.

The research was carried out with funding from Brazilian agencies CNPq, Capes and Fapesp, Shell, and the strategic support from ANP.

Paper reference: Bruno Leuzinger da Silva, Rafael Alcides Vicente, Pablo Sebastián Fernández, Ana Flávia Nogueira. Photoelectrochemical Bi2Fe4O9 phase purification – Removing the Bi2O3 phase from Bi2Fe4O9/Bi2O3 thin films. Electrochimica Acta 519 (2025) https://doi.org/10.1016/j.electacta.2025.145852

CINE members who authored the paper: Bruno Leuzinger da Silva (PhD student at the time of the work), Rafael Alcides Vicente (PhD student), Pablo Sebastián Fernández (researcher) and Ana Flávia Nogueira (researcher and director of the center).