Intrinsic and extrinsic natures make changes on the ionic transportation - Response to: “Comments on Int J Hydrogen Energy 42 (2017) 17495–17503”

Solid State Ionics (SSI) and ionic conducting systems have been well investigated in intrinsic ionic conducting systems from the structure, aliovalent ions doping and coherently controlling their dynamics. However, for extrinsic ionic conducting systems a coupling to an external environment to introduce extrinsic ions remains largely unexplored, which is actually challenging SSI fundamentals for developing emerging material functionalities. Such open-systems with extrinsic ionic nature and changeable with the coupled external environment have demonstrated interesting ionic conductive advantages over the conventional intrinsic SSI system where the defects and mobile ion type and concentration remain constant. Herein we give several examples/literatures from this kind of system based on semiconductor ionic composite in response to comments made by Näfe. It is very necessary to establish a basic understanding of extrinsic ionic conduction in the new materials and systems where the semiconductor-ionic CuFeO₂-YSZ composite is belonging to. As said this field has not yet well studied in SSI, at the current status we may offer mostly experimental evidences and new aspects of understanding on such semiconductor-based systems with extrinsic ionic transportation properties.