Uncovering proton transportation enabled via the surface and interfacial engineering for ceramic fuel cells

Ultra-wide bandgap semiconductor Ceria oxide attracts tremendous interest because of its high stability and electrical properties. The ionic transport properties of CeO₂ have tremendously been elaborated in terms of electrolytes, especially using bulk doping like Sm doped Ceria and gadolinium doped Ceria, but challenges remain. In this work, we propose the surface doping of Sn into CeO₂ for the engineering of the electronic structure of CeO₂ with a focus on surface properties. The Sn doping into CeO₂ enables the Fermi-level to lower level, which further induces a local electric field, dramatically enhancing the surface proton transport at the surface and interface. Furthermore, higher concentrations of Oxygen vacancies and lattice disturbance on the surface layer are mainly ascribed to surface modification, which eventually promotes proton transport. The prepared fuel cell device based on Ce_0.9Sn_0.1O₂ as an electrolyte has delivered a total high performance of 905 mW cm⁻² and proton performance of 787 mW/cm² along with an ionic and protons conductivity of 0.21 and 0.19 S cm⁻¹ at 520 °C. The surface doping of Sn in CeO₂ builds continuous surfaces as proton channels for high-speed transport. This work presents a reasonable methodology to develop high-performance, low-temperature ceramic fuel cells.