On proton conduction mechanism for electrolyte materials in solid oxide fuel cells

Proton-conducting solid oxide fuel cell is an emerging technology to deliver sustainable energy conversion with the benefit of fuel flexibility. A low proton conduction energy barrier in the perovskite-type electrolytes facilitates the fuel cells to operate at lower temperatures. The design of electrolytes heavily relies on a better understanding of the proton conduction mechanism in the lattice. However, the manifestation of multiple cations, vacancies, and structural distortion in the electrolyte materials raises complexities in the proton conduction mechanism. This article briefly reviews the proton conduction mechanism to explain the roles of electronegativity, dopants, and sintering aids on the hydration behavior. The impact of acceptor dopants on protonic defect formation and mobility is discussed with particular emphasis on the proton trapping effect.