Exploitation of Bulk and Surface Exsolution in Perovskites Oxide for Hydrogen Production and Power Generation

Abstract

Exsolution entails the in-situ growth of catalytically active nanoparticles directly from an oxide-metal solid solution (perovskite) lattice.1 The exsolution process has been advantageous in developing solid oxide cells for hydrogen production or power generation, but not necessarily for both simultaneously, which would be required for reversible solid oxide cells (RSOC).2 RSOC could address renewable intermittency by working as an electrolytic cell for hydrogen production and, in reverse mode, as a fuel cell for power generation.3 For example, exsolution enhances surface nanoparticles' stability and resilience to agglomeration and deactivation, while bulk exsolution can enhance conductivity.4 Additional functionalities such as high electronic and ionic conductivity and catalytic activity must be maintained for RSOC when switching between electrolysis and fuel cell mode.3 Here, we seek to develop new perovskite materials that fulfil these requirements, using both surface and bulk exsolution to achieve this. The target compositions would belong to a family of A-site deficient perovskite with a stoichiometric composition such as (Sr,Ca)1-α(Ti,Fe,Ni)O3. Such A-site deficiencies are known for their ability to drive B-site exsolution while attempting to revert the perovskite to a defect-free or stable ABO3 stoichiometry.1,5 To this end, we examine the parameters related to synthesising such new perovskite materials in this work. The thermogravimetry analysis (TGA) result revealed Fe2O3, NiO, and CaO as the decomposition products from three precursors. These decomposition products (oxides) could combine with SrCO3 and TiO2 to form the desired A-site deficient perovskite.1,5 The scanning electron microscopy (SEM) result has revealed the morphologies of the respective precursor materials. It could be used to study the effect of such parameters on the resulting perovskite microstructure and the synthesis reaction. Therefore, this study's result has given insight into the need to properly understand precursor materials before their selection for a given perovskite synthesis.