Proton Transistors for Controlling Structural and Physical Properties of Transition Metal Oxides

In this research report, we show that electrochemical redox reactions in transistor structures with gate layers of proton-conducting electrolytes (Nafion) can be utilized for inserting and extracting protons from transition metal oxides like SrFeO2.8 and SrCoO2.5 even at room temperature, allowing one to control and explore oxides’ structural and physical properties. Our characterizations before and after electrochemical proton insertions reveal that inserting and extracting proton modulate structural and physical properties of such oxides in reversible and non-volatile manners. We also find that the ordered arrangement of oxygen vacancies plays a role in suppressing the formation of oxygen vacancies upon electrochemical hydrogen injection and promoting hydrogen accumulation in oxide lattices. Our results demonstrate the usefulness of electrochemical proton insertion and extraction for controlling the structural and physical properties of metal oxides and provide guidelines for enhancing the protonation of oxides.