Lowering the operating temperature with enhanced performance and better efficiency is considered a universal  R&D bottleneck for the progress of low-temperature (<520 ◦C) solid oxide fuel cells (SOFCs) or ceramic fuel cells  (CFCs) to avail the opportunities of commercialization. Bulk doping is the primary ionic conduction mechanism  in traditional electrolyte materials for CFC, mainly influenced by the operating temperature and bulk density,  thus resulting in high operational temperature. Herein, we proposed a new mechanism for tunning Ce0.9Gd0.1O2-δ  (GDC) electrolyte based on a nanocrystalline structure from surface or grain boundary conduction to interfacial  conduction by introducing the carbonates to form the heterostructure, exhibiting an extremely high ionic conductivity of (0.2 S⋅cm− 1 ) at 520 ◦C. At first, we noticed that the grain boundary conduction of GDC is causing to  enhance the charge carrier leading to establishing surface conduction. We further modify the GDC with carbonates to form the core–shell heterostructure to boost ionic conduction. The constructed cell with core–shell  heterostructure has exhibited a remarkable performance of 968 mW/cm2 .  In contrast, 578 mW/cm2 was achieved from the surface conduction of GDC, and at the same time, we  observed immensely low grain-boundary resistance from the impedance analysis. The mechanism of core–shell  structure formation has been discussed in detail, and the ionic conduction at the surface and interfaces can be  considered the dominant conduction mechanism for GDC electrolytes. This work has explored a new approach by  tuning the ionic property from surface to interface to develop advanced CFCs, significantly improving the stateof-art GDC electrolyte via enhancing surface/interface conductions. This may be developed as a more functional  approach for advanced energy materials, e.g., battery and electrolysis devices.