[10p-Z05-1~19] 6.4 Thin films and New materials

▼ [10p-Z05-16] Solid-State Electrochemical Protonation/Oxidation of Oxygen Sponge SrCoO_2.5 Films

〇(DC)Qian Yang¹, Bin Feng², Yuichi Ikuhara², Hyoungjeen Jeen³, Hai Jun Cho^1,4, Hiromichi Ohta^1,4 (1.IST-Hokkaido U., 2.U. Tokyo, 3.Pusan Nat'l U., 4.RIES-Hokkaido U.)

Keywords:Electrochemical Protonation and Oxidation, Solid-State Electrolyte

Due to the flexibility of the valence state of cobalt ion, brownmillerite SrCoO_2.5 can be protonated/oxidized by an electrochemical reaction with H⁺ / OH⁻ ions. Owing to the electrochemical protonation/oxidation, the physical properties of SrCoO_2.5 can be modulated from antiferromagnetic insulator (SrCoO_2.5, Co³⁺) to ferromagnetic insulator (HSrCoO_2.5, Co²⁺) / ferromagnetic metal (SrCoO₃, Co⁴⁺). Further, the color of SrCoO_2.5 can be modulated from colorless transparent (Co²⁺) to brown (Co³⁺) and black (Co⁴⁺). To utilize these changes in practical device applications, the solid-state device is favorable compared to liquid-state devices. In 2016, Katase et al. demonstrated electrochemical Redox reaction between SrCoO_2.5 and SrCoO₃ using amorphous NaTaO₃ film as the solid-electrolyte. However, there is no report on the solid-state protonation/deprotonation reaction between SrCoO_2.5 and HSrCoO_2.5. Here we demonstrate that solid-state electrochemical protonation/deprotonation of SrCoO_2.5 for the first time.