Thermodynamic properties of hercynite (FeAl2O4) for thermochemical water splitting applications: A first-principles approach

FeAl2O4 is considered as a potential material to produce solar thermochemical hydrogen. However, its temperature and pressure dependant thermodynamic properties have not yet been well explored. In this work, first-principles calculations have been applied to investigate the structural, mechanical, electronic and thermodynamic properties of FeAl2O4. The temperature and pressure-dependent thermal expansion coefficient and Grüneisen parameter have been calculated, leading to the calculation of molar heat capacity, cp = 5.50907 + 0.39378 T-202345.44153 T-2-94039T2 at 0 GPa. Change in Gibb's energy can be calculated at a given temperature and pressure during the reduction and oxidation cycle to computationally assess the suitability of FeAl2O4, as a catalyst for thermochemical water splitting. This approach may be further extended using suitable substitution and subsequent compositional variation of Fe and Al atoms, to explore more efficient catalyst. The molar heat capacity of FeAl2O4 can be calculated using DFT cp = cv(1 + αγT) where α is thermal expansion coefficient and γ is the Gruneisen Parameter which can be further used for compositional optimization for water splitting application. [Display omitted] •The thermal properties of hercynite have been calculated for the first time in a temperature (0-1800 K) and a pressure (0-40 GPa) range.•The computed thermal expansion coefficient and Grüneisen parameters have been used for computation of molar heat capacity, cp.•The expressions of the cp may be used to computationally evaluate the suitability of Hercynite as potential redox-mediator.•Using compositional variation of Fe and Al atoms, more efficient catalysts may be explored.