| Abstract Scope |
Proton-conducting mixed ionic-electronic conductors (MIECs) are vital for next-generation electrochemical devices. However, conventional designs relying on oxygen vacancy hydration often suffer from limited proton mobility due to acceptor-site trapping. We present a transformative approach: hydrogenation of n-type oxide semiconductors. Here, incorporated hydrogen acts as a donor, simultaneously generating mobile protons and electrons. This mechanism facilitates exceptionally fast proton transport, as demonstrated in hydrogenated WO3 and recently in Nb-doped TiO2. Using electron-blocking techniques, we quantitatively evaluated the intrinsic proton conductivity, revealing values comparable to or exceeding those of state-of-the-art proton-conducting MIECs and electrolytes at intermediate temperatures. Notably, proton diffusion coefficients in these systems are one to two orders of magnitude higher than in conventional hydration-based oxides. These findings establish hydrogenation as a robust strategy for high-performance MIECs. Finally, extending this concept to sulfides and suppressing electronic conduction for electrolyte applications are discussed, opening new design paradigms beyond conventional frameworks. |
