Computationally Accelerated Discovery of Gd-based Perovskite Oxides for Solar Thermochemical Applications

Solar thermochemical (STC) processes are important chemical pathways for carbon capture and renewable energy production. In particular, solar thermochemical hydrogen, or STCH, production is a promising method to generate carbon neutral fuels from steam using concentrated solar energy. Two-step STCH production processes incorporate metal oxide redox mediators to facilitate the dissociation of steam and generate hydrogen, several of which originate from the complex AxA’1-xByB’1-yO6 perovskite oxide chemical space. However, known redox mediators suffer from a variety of shortcomings, including slow water splitting (WS) kinetics, low hydrogen yields, poor cyclability, and thermal reduction (TR) temperatures that exceed the operating conditions of conventional reactor materials. Identifying novel metal oxides with improved H2 production capacity and rapid reduction and oxidation kinetics continues to be a primary goal of the STCH community. We therefore present a high-throughput computational framework to identify novel, STCH-active perovskite oxide mediators, with particular emphasis on Gd-containing multinary perovskite oxides (compositions Gd2BB’O6, GdA’B2O6, and GdA’BB’O6). Our computational scheme employs a combination of DFT and non-DFT approaches to evaluate the stabilities, electronic properties and oxygen vacancy thermodynamics of these materials. We report a rank ordered list of 76 promising STCH candidate perovskite oxides from 8,977 Gd-containing compositions, three of which have been referred for experimental characterization and exhibit STCH activity. Ultimately, we demonstrate that our high-throughput computational scheme--- which evaluates Gd-containing compositions for their synthesizability as perovskites and estimates their STCH-relevant enthalpies and entropies of reduction, ΔHTR and ΔSTR --- can accelerate the discovery of novel STCH active redox mediators with reasonable computational expense.