Barium Indate–Zirconate Perovskite Oxyhydride with Enhanced Hydride Ion/Electron Mixed Conductivity

Oxyhydrides have excellent potential as electrochemical and catalytic materials owing to the synergistic effects of the conductivity and redox activity of the hydride (H–) ion. However, harsh preparation conditions and their pyrolytic nature limit their applications. Herein, we discover highly durable oxyhydride perovskite BaZr0.5In(II)0.5O2.25H0.5 with enhanced H– ion–electron mixed conductivity. BaZr0.5In(III)0.5O2.75, as the parent phase, was reductively hydrogenated to BaZr0.5In(II)0.5O2.25H0.5 via simple H2 gas annealing at 800 °C under an ambient pressure with the incorporation of H– ions with simultaneous oxygen vacancy formation. Membrane devices comprising dense BaZr0.5In0.5O2.25H0.5 films on porous Ni-cermet supports were fabricated by conventional sintering and postreduction because low lattice contraction (−0.07%) following hydrogenation allowed for the bulk hydrogenation of BaZr0.5In0.5O2.75 sinters without structural collapse. The resulting devices exhibited higher hydrogen permeability than protonic ceramic ones at 500 °C because BaZr0.5In(II)0.5O2.25H0.5 allows H– ion hopping between the nearest-neighbor anion sites due to the significantly high oxygen deficiency (25% of O sites are vacant), giving rise to a H– ion conductivity of 10–3 S cm–1. Given their superior H– ion conductivity and ease of manufacturing, the synthesized materials have great potential for applications in mixed conducting electrodes and hydrogen-permeable membrane supports of ceramic electrochemical cells.