Mn-ferrite based solar thermochemical water splitting cycle: A thermodynamic evaluation

Abstract

By utilizing the data obtained from the HSC Chemistry software, the thermodynamic equilibrium and efficiency analysis of the Mn-ferrite based water splitting (MFWS) cycle was conducted. All the thermodynamic calculations were performed by varying the partial pressure of O2 (PO2), thermal reduction (TH), and water splitting temperature (TL). The degree of non-stoichiometry (δ) allied with the Mn-ferrite was observed to be increased as the PO2 was decreased from 10−1 to 10−5 atm and the TH was upsurged from 1500 to 2100 K. This rise in the δ resulted into a higher amount of H2 production via water splitting (WS) reaction. To achieve upper δ, elevated TH was required and hence the solar energy required to run the MFWS cycle (Q̇solar-cycle) was observed to be higher. In contrast, as the TL was increased, due to the drop in the temperature gap between the TH and TL, the Q̇solar-cycle was reduced. The solar-to-fuel energy conversion efficiency (ηsolar-to-fuel) of the MFWS cycle was observed to be maximum when the PO2 and TH were lowest and the TL was the highest. For instance, at PO2 = 10−5 atm, TH = 1500 K, and TL = 1400 K, the uppermost ηsolar-to-fuel = 39.8% was attained in case of MFWS cycle which was higher than Ni-ferrite based water splitting (NFWS) cycle by 8.5%.