High proton conductivity achieved in new perovskite materials
Scientists at the Tokyo Institute of Technology (Tokyo Tech) have developed a new perovskite, BaSc0.8W0.2O2.8, which exhibits high proton conductivity at low and intermediate temperatures. This progress is achieved by donor doping with large W6+ cations, which increases water uptake and reduces proton capture. These findings could lead to the development of new perovskites for protonic ceramic fuel cells (PCFCs) and proton conductive electrolysis cells (PCECs).
Fuel cells are becoming critical in converting chemical energy into electrical energy as part of global clean energy initiatives. Of these, PCFCs, which use solid electrolytes, offer advantages in safety and stability. However, conventional perovskite electrolytes in PCFCs suffer from low proton conductivity at low and intermediate temperatures.
A research team led by Professor Masamoto Yashima of Tokyo Tech, in collaboration with High Energy Accelerator Research Organization (KEK), has investigated this problem. Their study, published in the Journal of Materials Chemistry A on May 3, 2024, focuses on the low conductivity of conventional proton conductors, caused by proton capture and low proton concentration.
“A major problem with the conventional proton conductors is a phenomenon known as proton capture, in which protons are captured by acceptor dopant via electrostatic attraction between the dopant and the proton,” Yashima explains. “Another major problem with such proton conductors would also be their low proton concentration due to the small amount of oxygen vacancies.”
To overcome these challenges, the researchers developed BaSc0.8W0.2O2.8 with high oxygen vacancies, resulting in a higher proton concentration. Full hydration of the material converts it to BaSc0.8W0.2O3H0.4, allowing high proton conductivity due to increased water uptake and reduced proton capture. The positive charge of the large W6+ dopant repels protons, facilitating their migration through the material, as confirmed by molecular dynamics simulations.
This study provides fundamental design principles for future proton-conducting perovskites. “The stabilization of perovskites with disrupted intrinsic oxygen vacancies and complete hydration, enabled by doping of large donor dopants, could be an effective strategy for the next generation of proton conductors,” Yashima noted.
These proton conductors are essential for both PCFCs and PCECs and contribute to sustainable energy technologies.
Research report:High proton conduction due to complete hydration in perovskite with a high oxygen deficiency
