Reduction enthalpy and charge distribution of substituted ferrites and doped ceria for thermochemical water and carbon dioxide splitting with DFT+U

D A Dimitrakis; N I Tsongidis; A G Konstandopoulos

doi:10.1039/c6cp05073e

Reduction enthalpy and charge distribution of substituted ferrites and doped ceria for thermochemical water and carbon dioxide splitting with DFT+U

Phys Chem Chem Phys. 2016 Aug 24;18(34):23587-95. doi: 10.1039/c6cp05073e.

Authors

D A Dimitrakis¹, N I Tsongidis¹, A G Konstandopoulos¹

Affiliation

¹ Aerosol & Particle Technology Laboratory, CPERI/CERTH, 57001 Thessaloniki, Greece. dimitrakis@cperi.certh.gr and Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124, Greece.

PMID: 27507281
DOI: 10.1039/c6cp05073e

Abstract

The thermal reduction step of substituted ferrites (MFe2O4 where M = Fe, Ni, Co, Gd) and doped ceria (MxCe1-xO2, where M = Ce, Zr, Hf and x = 0.25) in two-step thermochemical cycles for H2O and CO2 splitting is investigated within the DFT+U framework. This thermal reduction step is described as the oxygen vacancy formation energy (reduction enthalpy), i.e. the energy required to create an oxygen vacancy in the crystal lattice. Oxides with a lower oxygen vacancy creation energy are easier to reduce. A Bader charge analysis of the reduction mechanism is carried out providing the charge distribution of the bulk and reduced ions, enabling interrelations of the substitute ions and the resulting reduction energies. Based on the approach presented here, interesting solar fuels producing materials are CoFe2O4, NiFe2O4 and Hf0.25Ce0.75O2.