Comparison of Computed and Experimental Redox Thermodynamics and High-Throughput DFT Studies of Metal Oxides for Solar Thermochemical Water-Splitting Applications*

Thermochemical water-splitting offers a renewable alternative to fossil fuels by utilizing solar energy for the production of hydrogen via a two-step redox reaction sequence involving a metal oxide. Current and past efforts have been aimed at identifying the best candidates for such reactions based on thermodynamic and kinetic properties, and in the present work, we focus on the enthalpy of reduction, a key quantity impacting the temperature and extent of reduction possible for a given oxide.
Through a quantitative comparison of DFT oxygen vacancy formation energy calculations with newly available experimental data generated by our collaborators, we confirm the predictive value of our computational approach, as well as investigate the effect of structural choice and dynamical stability.
We then leverage the insights gained through such comparison, and the efficiency of high-throughput DFT, to quickly explore a large structural and compositional space, screening for suitable thermodynamics for thermochemical water splitting applications. As well as identifying several new promising metal oxide compounds, we also demonstrate the extent of the influence of factors such as the choice of redox-active cation and the degree of structural distortion.