(84c) Hydrogen Production Via Solar Driven Metal Oxide/Metal Sulfate Water Splitting Cycle

Authors: 
Bhosale, R., Qatar University
Sutar, P. N., Institute of Chemical Technology
Kumar, A., Qatar University
Ghosh, U. K., Qatar University
Solar thermochemical water splitting cycles are considered as one of the most promising options for hydrogen production. In a long list of solar thermochemical water splitting cycles, the sulfur-iodine cycle and its variation the hybrid sulfur cycle are more appealing as the required operating temperatures are lower as compared to other thermochemical cycles. For both cycles, the most energy intensive step is the dissociation of SO3 into SO2 and O2, which is possible only under catalytic conditions. As sulfation poisoning is a major concern related to such reactions, simply the noble metal catalysts were observed to be active towards the endothermic dissociation of SO3. Although, the noble metal catalysts are attractive for such reactions, they are less preferable due to the limited availability and high cost. To overcome this issue, we propose a solar driven metal oxide – metal sulfate based water splitting cycle for the production of hydrogen. As per previous studies, the zinc oxide is a very attractive redox material towards water splitting reactions. Therefore, in this study, zinc oxide – zinc sulfate (ZnO-ZnS) water splitting cycle was investigated. At first, the computational thermodynamic analysis of this cycle was performed to identify the required temperatures, pressures, and inert gas flowrates required to run the ZnO-ZnS water splitting cycle. Also, this analysis helps to find the efficiency of this cycle in terms of the conversion of solar energy into hydrogen. The obtained results indicate that the solar-to-fuel conversion effienciey for ZnO-ZnS water splitting cycle is higher as compared to other thermochemical water splitting cycles. After performing the computational thermodynamic analysis, the ZnO-ZnS water splitting cycle was experimentally investigated using a high temperature TGA and a packed-bed reactor set-up. Multiple cycles were performed and it was observed that the temperatures needed for the ZnO-ZnS water splitting cycle to produce significant amount of hydrogen are considerably lower as compared to other thermochemical water splitting cycles. Details results associated with the thermodynamic analysis and experimental investigation will be presented.