Imagine a car that combines the advantages of an electric vehicle with the convenience of being fueled with a widely available fuel. This is the idea behind fuel cell cars. These electrochemical devices directly convert the chemical energy of a fuel into electrical energy, enabling vehicles to use, for example, ethanol to generate the electricity needed by the electric motor.

In an article that has just been published in the prestigious scientific journal Journal of Energy Chemistry, researchers from CINE and collaborators provide a detailed review of the advantages and challenges of a promising fuel cell technology, MS-SOFCs (acronym for Metal-supported Solid Oxide Fuel Cells). According to the authors, this technology, which has sparked interest in academia and industry over the past two decades, could help accelerate the energy transition in the automotive sector, especially in countries that have extensive production and distribution of biofuels, such as Brazil, the United States, Thailand, India and African countries.

“Our study highlights that MS-SOFCs represent a promising solution for the decarbonization of mobility, and could be an impactful alternative for the electrification of this sector,” says Gustavo Doubek, Professor at Unicamp and Researcher at CINE. “They combine high efficiency, durability and fuel flexibility, in addition to eliminating the current limitations of electrification, creating a solid path for the energy transition of the automotive sector, without the high costs of hydrogen or the limitations of conventional batteries in terms of recharge time,” he adds.

The review article was carried out through a collaboration between researchers from Unicamp, MackGraphe, UFES and KAUST (University of Saudi Arabia). The research is part of a larger effort within CINE, aligned with the search for viable technologies for the decarbonization of the transportation sector, which includes work on new materials and architectures for MS-SOFCs, as well as research on reformers and biofuels.

“CINE’s differential is not only in research, but also in the search for the connection between science and the market,” explains Hudson Zanin, who, like Doubek, is a Professor at Unicamp, a Researcher at CINE and one of the authors of the article. “The center works to take these innovations from the laboratory to real applications, ensuring that MS-SOFCs are completely demystified so that they become a practical and accessible solution in the energy transition,” he adds.

According to the authors of the article, MS-SOFCs offer a series of advantages compared to other mobility systems. Compared to conventional ethanol-powered cars, cars with MS-SOFCs are more energy efficient. In other words, the same amount of biofuel can provide more kilometers in a fuel cell vehicle than in a car with a combustion engine. In addition, electric cars are quieter, reducing noise pollution, and are more comfortable for drivers and passengers. Compared to battery-powered electric cars, fuel cell vehicles stand out for their faster refueling compared to recharging the battery. Another advantage is that it does not overload the power grid.

In addition, MS-SOFCs are capable of generating electricity from bioethanol, biogas, biomethane, green ammonia, and even fossil fuels. Thus, when compared to hydrogen cars, MS-SOFC vehicles are more practical, since they can be fueled with widely available and easily transportable fuels, while hydrogen stations are still very scarce.

Finally, the robustness and low cost of the fuel cell are the highlights when the technology is compared to other SOFCs that use only ceramics, instead of metals, to support the device.

Ethanol generates hydrogen that generates electricity

A car with a MS-SOFC can operate as follows. The tank is filled with some renewable fuel, such as ethanol (C₂H₅OH) produced from sugarcane. The bioethanol then passes through the reformer, a component responsible for “extracting” the hydrogen present in the fuel composition through chemical reactions. The hydrogen, in turn, passes through the fuel cell, where it is oxidized and, together with the oxygen in the air that is reduced, generates the electrons needed to charge the batteries and supercapacitors and power the electric motor.

As a residue, the process generates water, heat and a little carbon dioxide, which is offset by the CO₂ that the sugarcane consumes in photosynthesis, bringing net carbon emissions to a level close to zero.

The technology is not yet available in vehicles on the market, but it has already been used in a prototype of an ethanol-powered electric car from Nissan, the “e-Bio Fuel Cell”, which was launched in Brazil in 2016 and has been on the road throughout the country.

However, MS-SOFCs still present challenges in the research and development area to become commercially viable in terms of their performance, durability and costs. These challenges, in addition to the current status of the technology’s development, can be seen in the review paper, which was carried out with funding from FAPESP, Unicamp, CNPq and Shell, in addition to strategic support from ANP.

Paper reference: F. C. Antunes, J. P. J. de Oliveira, R. S. de Abreu, T. Dias, B. B. N. S. Brandão, J. M. Gonçalves, J. Ribeiro, J. Hunt, H. Zanin, G. Doubek. Reviewing metal supported solid oxide fuel cells for efficient electricity generation with biofuels for mobility, Journal of Energy Chemistry (2024) https://doi.org/10.1016/j.jechem.2024.10.056

CINE members who authored the paper: Fábio C. Antunes (postdoc), João P. J. de Oliveira (doctoral student), Thiago Dias (postdoc), Bruno B. N. S. Brandão (postdoc), Hudson Zanin (principal investigator of the Advanced Energy Storage division), Gustavo Doubek (co-principal investigator of the Advanced Energy Storage division).