Anomalous Electronic and Protonic Conductivity of 2D Titanium Oxide and Low‐Temperature Power Generation Using Its Protonic Conduction

Abstract

results are being reported. [6][7][8][9] On the other hand, studies on 2D materials for solid-state ionics such as fuel cells are lacking to date. In particular, it is hard to find an example of a solid electrolyte or electrode for a solid oxide fuel cell (SOFC).SOFC is a next-generation fuel cell that has been intensively researched for several decades. [10][11][12] However, due to high temperature operation, efforts to reduce operating temperatures for its commercialization are still continuing, which has raised inherent problems such as low durability and high cost. [13,14] This temperature reduction, however, results in a decrease in the ionic conductivity of the solid electrolyte, a key component of fuel cells, and so the search for materials is being extensively carried out. [15,16] As a result of these efforts, an interesting study was reported recently that said 3D ceramic nanostructures show protonic conduction at very low temperature. [17] In intensive fundamental studies, it was found that the protonic charge carrier transports through the parallel grain boundary (gb) of the nanostructure. [18][19][20] Accordingly, attempts to increase the gb density by reducing the grain size have been made. [20,21] However, it is difficult to make the grain size several nanometers due to the ceramic sintering process, so that protonic conduction faces a limitation. [18,19] Contrary to the top-down method, in this work, the density of interfaces was maximized by fabricating a nanosheet film by stacking 1-nm-thick nanosheets (a bottom-up strategy). This can be a concept that breaks through the current interfacial density and further overcome the limitation of the protonic