On hydride diffusion in transition metal perovskite oxyhydrides investigated via deuterium exchange

Perovskite oxyhydrides may find diverse applications, ranging from catalysis, topochemical synthesis to solid state ionics, but the understanding of their hydride transport behavior has remained limited. Here, gaseous hydrogen exchange and release experiments were analyzed using the Kissinger method to estimate the activation energy (E-a) for H/D exchange and H-2 release in BaTiO3-xHx (x = 0.35-0.60) and LaSrCoO3H0.70. It is revealed that, for each BaTiO3-xHx, at a given hydride concentration (x), both H/D exchange and H-2 release experiments provide similar E-a values. For BaTiO3-xHx with different x, the obtained E-a values significantly decrease with increasing x until around 0.4; beyond 0.4, it becomes nearly constant (200-220 kJ mol(-1). This observation suggests that the diffusion process in the low hydride concentration (x < 0.4) includes oxide as well as hydride diffusion, whereas, for 0.4 < x (<0.75), only hydride migrates, with second-nearest-neighbor (2NN) jumps as a rate-determining process, which is supported by DFT calculations. The Kissinger analysis of LaSrCoO3H0.70 yielded a similar E-a of 170-190 kJ mol(-1), consistent with the 2NN hopping scenario. The presented method provides a facile tool for designing and improving hydride conductivity in oxyhydrides regardless of the presence of electronic conductivity.