Kyushu University researchers have developed a solid-oxide fuel cell (SOFC) with high proton conductivity at 300°C, aiding the transition away from fossil fuels.
As global energy demand increases, researchers, industries, governments, and stakeholders are working together to develop new ways of meeting that demand.
While solid-oxide fuel cells are promising due to their high efficiency and long lifespan, one major drawback is that they require operation at high temperatures of around 700-800°C. Therefore, the utility of these devices would require costly heat-resistant materials.
Now, Kyushu University researchers have reported that they have succeeded in developing a new SOFC with an efficient operating temperature of 300°C.
The team expects that their new findings will lead to the development of low-cost, low-temperature solid-oxide fuel cells and greatly accelerate the practical application of these devices.
How do solid-oxide fuel cells work?
Unlike batteries, which release stored chemical energy as electricity, fuel cells convert chemical fuel directly into electricity and continue to do so as long as fuel is provided.
The heart of an SOFC is the electrolyte, a ceramic layer that carries charged particles between two electrodes.
In hydrogen fuel cells, the electrolyte transports hydrogen ions (a.k.a. protons) to generate energy. However, the fuel cell needs to operate at extremely high temperatures to run efficiently.
“Bringing the working temperature down to 300°C, it would slash material costs and open the door to consumer-level systems,” explained Professor Yoshihiro Yamazaki from Kyushu University’s Platform of Inter-/Transdisciplinary Energy Research, who led the study.
“However, no known ceramic could carry enough protons that fast at such ‘warm’ conditions. So, we set out to break that bottleneck.”
Altering the material’s physical properties
Researchers have explored different combinations of materials and chemical dopants –substances that can alter the physical properties of the solid-oxide fuel cell. This will improve the speed at which protons travel through electrolytes.
Yamazaki said: “Adding chemical dopants can increase the number of mobile protons passing through an electrolyte, but it usually clogs the crystal lattice, slowing the protons down.
“We looked for oxide crystals that could host many protons and let them move freely – a balance that our new study finally struck.”
The team found that two compounds, barium stannate (BaSnO3) and barium titanate (BaTiO3), when doped with high concentrations of scandium (Sc), were able to achieve the SOFC benchmark proton conductivity of more than 0.01 S/cm at 300°C, a conductivity level comparable to today’s common SOFC electrolytes at 600-700°C.
“Lattice-dynamics data further revealed that BaSnO₃ and BaTiO₃ are intrinsically ‘softer’ than conventional SOFC materials, letting them absorb far more Sc than previously assumed,” Yamazaki stated.
Long-term applications for decarbonisation
The findings overturn the trade-off between dopant level and ion transport, offering a clear path for low-cost, intermediate-temperature solid-oxide fuel cells.
Yamazaki concluded: “Beyond fuel cells, the same principle can be applied to other technologies, such as low-temperature electrolysers, hydrogen pumps, and reactors that convert CO₂ into valuable chemicals, thereby multiplying the impact of decarbonisation.
“Our work transforms a long-standing scientific paradox into a practical solution, bringing affordable hydrogen power closer to everyday life.”
