(93e) Thermochemical Hydrogen Production Via Ce(SO4)2/Ce2O3 Based H2O Splitting Cycle

The sulfur iodine cycle and the hybrid sulfur cycle are considered as the promising options due to their capacity to operate at lower temperatures as compared to the MO based thermochemical cycles. Furthermore, these cycles are comparable in terms of operating temperatures to hybrid photo-thermal sulfur–ammonia water splitting cycle. In sulfur iodine and hybrid sulfur cycle, SO₃ decomposition is considered as the most energy intensive step. To achieve a significant amount of conversion, the SO₃ decomposition needs to be carried out under catalytic conditions. Although various catalytic materials are examined for this purpose, only noble metal catalysts are found to be more suitable and stable to the sulfur poisoning. Due to the utilization of the noble metal catalyst, the cost of the H₂ production increases by a significant amount. In our recent studies, we have proposed a merging of the MO based and the sulfur iodine/hybrid sulfur water cycles. This hybrid cycle is termed as a ‘Metal Oxide – Metal Sulfate’ (MO-MS) thermochemical water splitting cycle. Utilization of inexpensive MOs (as compared to expensive noble metals) can reduce the cost of the H2 production considerably. In this study, as ceria is used as the state of the art redox materials in MO based thermochemical H2O splitting, a Ce(SO₄)₂/Ce₂O₃ redox pair is thermodynamically tested towards solar H₂ production. By identifying the equilibrium compositions and by applying the principles of second law of thermodynamics, the solar absorption efficiency of the solar reactor, net energy required to operate the cycle, solar energy input to the solar reactor, radiation heat losses from the solar reactor, rate of heat rejected to the surrounding from the water splitting reactor, and maximum theoretical solar energy conversion efficiency of the cycle is determined by performing the exergy analysis (over different solar reactor temperatures and with/without considering the heat recuperation). The results obtained will be presented in detail.