Ultrastable One-Dimensional Ti₂S Electride Support for an Efficient and Durable Bifunctional Electrocatalyst

Electrides, in which anionic electrons are trapped in structural cavities, have garnered significant attention for exceptional functionalities based on their low work function. In low-dimensional electrides, a strong quantum confinement of anionic electrons leads to many interesting phenomena, but a severe chemical instability due to their open structures is one of the major disadvantages for practical applications. Here we report that one-dimensional (1D) dititanium sulfide electride exhibits an extraordinary stability originating from the surface self-passivation and consequent durability in bifunctional electrocatalytic activity. Theoretical calculations identify the uniqueness of the 1D [Ti₂S]²⁺·2e⁻ electride, where multiple cavities form two distinct channel structures of anionic electrons. Combined surface structure analysis and in-situ work function measurement indicate that the natural formation of amorphous titanium oxide surface layer in air is responsible for the remarkable inertness in water and pH-varied solutions. This makes the [Ti₂S]²⁺·2e⁻ electride an ideal support for a heterogenous metal-electride hybrid catalyst, demonstrating the enhanced efficiency and superior durability in both the hydrogen evolution and oxygen reduction reactions compared to commercial Pt/C catalysts. This study will stimulate further exploratory research for developing a chemically stable electride in reactive conditions, evoking a strategy for a practical electrocatalyst for industrial energy conversions.