Thermodynamic evaluation of water splitting by a cation- excessive (Ni, Mn) Ferrite

摘要

Water-splitting potential by cation-excessive (Ni, Mn) ferrite, Ni_0.5(1+ε) Mn 0.50 (1+ε) Fe 1.99 (1+ε) O_4 was evaluated using he standard Gibbs free energy change (ΔG°) for the cation-excessive ferrite formation in different O_2 partial pressures. The cation-excessive degree betweenε ranged from 0.026 to 0.16 in pO_2 values of 7.9 × 10~-7 to 1.0 × 10~-1. From the relation between ε value of (Ni, Mn) ferrite and oxygen partial pressure, equilibrium constant K (th) was determined. Furthermore ΔH°s for O_2 releasing and water-splitting reactions with cation-excessive (Ni, Mn) ferrite were evaluated From the van't Hoff plot and compared with that for magnetite-wustite system; where ΔH°s were assumed to be the Same values for both (Ni, Mn) ferrite and magnetite-Wustite system: + 300 kJ for O_2 releasing and -35 - -63 kJ For water-splitting.