Amid the climate crisis and the urgent need to reduce greenhouse gas emissions, hydrogen has emerged as one of the most promising energy sources for the transition to a low-carbon economy. When produced from renewable sources, it can serve as a clean fuel, strategic industrial input, and means of energy storage.
In the Brazilian context, hydrogen production from ethanol, especially when derived from biomass, is a particularly promising pathway. Brazil has a well-established infrastructure for producing, distributing, and using this biofuel, opening the door to technological solutions that add value to ethanol and expand its role in the energy transition.
A study led by Fabio Coral Fonseca , a senior researcher at the Institute of Energy and Nuclear Research ( IPEN ), made significant progress in this direction. The study demonstrated that fine-tuning the processing of a perovskite-type ceramic catalyst is crucial for maximizing the conversion of ethanol into hydrogen. This increases the stability of the system and reduces costs. It also eliminates the need for noble metals that are traditionally used in this type of reaction. The study was published in the International Journal of Hydrogen Energy.
The conversion is carried out through a process known as ethanol steam reforming (ESR). In simple terms, this involves reacting ethanol with steam at high temperatures to produce hydrogen and carbon dioxide. The ideal overall reaction, which maximizes hydrogen production, can be represented as follows: C₂H₅OH + 3 H₂O → 2 CO₂ + 6 H₂. However, in practice, the process involves several intermediate steps. This makes the role of the catalyst central to directing the reaction, maximizing hydrogen yield, and avoiding undesirable pathways. One such pathway is the formation of coke, or carbon deposits, which rapidly degrade the material.
"Catalysis is a surface property. What we want are very small particles that are very well distributed and stable over time," says Fonseca. "The problem is that, at high temperatures, these particles tend to shift, agglomerate, and lose activity."
To address this challenge, the study used a perovskite-type ceramic oxide. Unlike conventional catalysts, however, the active element in the reaction, nickel (Ni), is not impregnated onto the surface of the ceramic; rather, it is incorporated into the crystalline structure of the material during synthesis. "Rather than placing the metal on top of the support, as in classical catalytic methods, we introduce the nickel into the crystal structure. Then, under controlled conditions, that nickel emerges on the surface," the researcher explains.
This phenomenon, known as "exsolution," causes metallic nickel nanoparticles (Ni⁰) to emerge on the surface of the solid. They are strongly anchored to the substrate, which gives them much greater stability against sintering and carbon deposition. "The metal comes from the inside out. It doesn't move around the surface as it does in impregnated catalysts. That gives the system much greater stability," says Fonseca.
The central breakthrough of the study was demonstrating that a seemingly simple parameter – the calcination temperature of the precursor oxide prior to the reduction step – controls the entire performance of the catalyst. The researchers synthesized the material chemically and calcined it at three different temperatures: 650 °C, 800 °C, and 1,200 °C. This step, which precedes the actual catalytic reaction, determines the microstructure of the solid, particularly the size of the ceramic particles and the available surface area.
"If we heat the perovskite to very high temperatures, it grows too much. And that hinders the exsolution of nickel later on," Fonseca notes. The results showed that calcination at 650 °C preserves a larger surface area, whereas higher temperatures promote grain coalescence, drastically reducing this area. Smaller ceramic particles favor nickel exsolution and the formation of smaller, more active nanoparticles. "The key point of the study was to show that substrate size controls exsolution. If the particles are large, the nickel doesn't exsolve well. If they're smaller, it exsolves more efficiently," the researcher summarizes.
In ethanol steam reforming tests, the catalyst that was calcined at 650 °C produced significant results: 100% ethanol conversion, a yield of 4.04 moles of H₂ per mole of ethanol, and stable operation for up to 85 hours with low coke formation. In contrast, materials calcined at 800 °C and 1200 °C exhibited lower nickel exsolution, lower conversion, and a shift in reaction selectivity, favoring the simple dehydrogenation of ethanol over complete reforming for hydrogen production. "It isn't enough to choose the right elements. How the material is manufactured is decisive. A relatively simple adjustment in processing completely changes the performance," emphasizes Fonseca.
The researcher places the study within a broader technological agenda. According to Fonseca, converting ethanol into hydrogen is not always the best solution from an energy standpoint, especially when considering mobility. "Ethanol is a very valuable molecule. To obtain it, you have to go through agriculture, fermentation, and distillation. Simply breaking it down to produce hydrogen and then electricity may not be the best choice," he notes. For this reason, the group is investigating direct ethanol fuel cells, which can convert the liquid fuel directly into electricity. "Ultimately, we study these perovskites because they fit very well with that technology," Fonseca adds.
Perovskites are materials defined less by their specific chemical composition and more by their characteristic ABO₃ crystalline structure. This structure, first observed in the natural mineral calcium titanate (CaTiO₃) – the original perovskite – is now reproduced synthetically and in various ways in the laboratory. In this architecture, various elements can occupy the A and B sites of the crystal lattice, giving these materials extraordinary structural flexibility to tailor their electrical, ionic, magnetic, and catalytic properties.
The work on nickel is part of a broader strategy to explore metal exsolution in perovskites. In a previous study conducted with groups in the United States as part of a project supported by FAPESP and the National Science Foundation (NSF), the IPEN team obtained significant results with ruthenium exsolved from lanthanum chromite (LaCrO₃)-based perovskites. In this case, ruthenium – an even more active metal in reforming reactions – is initially incorporated into the crystal lattice. During the ethanol reforming reaction, it emerges as metal nanoparticles that are strongly anchored to the support. This study was also coordinated by Fonseca and published in the journal Catalysis Science & Technology .
Studies with polycrystalline powders, as described in the two articles, are just one part of the IPEN scientists' research program. The team is transitioning to more controlled systems based on epitaxial thin films produced by pulsed laser deposition. "Epitaxial" refers to material that grows in an ordered manner on top of another material, copying its crystalline structure. "In this case, what we do is compact the powder, transform it into a ceramic wafer, and then sublimate that material with a high-energy laser. The vapor deposits onto a well-ordered substrate and forms a nearly perfect crystal," Fonseca describes. This approach enables the study of exsolution at the atomic level using advanced characterization techniques at Sirius, the Brazilian synchrotron light source.
By demonstrating that high catalytic performance can be achieved with abundant, low-cost metals offering strong stability, the studies point to a concrete path toward reducing dependence on noble metals and making sustainable hydrogen production more viable. In the Brazilian context, where ethanol is abundant and demand for low-carbon energy solutions is growing, these results reinforce the potential of the ethanol-hydrogen route. More broadly, they reinforce the potential of exsolved perovskites as a strategic resource for the energy transition.
Support for the nickel study came from FAPESP through the Thematic Project "Advanced Electrochemical Devices for Molecular Conversion and Energy Production" , Research Grants 17/11937-4 , 18/19251-7 , and 24/00989-7 , as well as a Doctoral Scholarship .
About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.
