Application of chromium oxide-based redox reactions for hydrogen production via solar thermochemical splitting of water

Thermodynamic equilibrium, as well as efficiency analysis of the Cr2O3/Cr water splitting (Cr-WS) cycle, was conducted in this study. The thermodynamic properties required for the computations were obtained from an HSC Chemistry 9.9 software. An increase in thermal reduction (TR) temperature (T-H) from 1800 K to 2230 K was responsible for the rise in the percentage TR of Cr2O3 (Tr-Cr) from 0% to 100%. The equilibrium analysis additionally indicates that the re-oxidation of Cr into Cr2O3 via WS reaction is feasible at any temperature from 300 to 3000 K (we have selected 1300 K for this study). The efficiency analysis indicates that the (Q) over dot(solar-reactor-Cr-WS) and (Q) over dot(solar-heater-Cr-WS) were enhanced by 3636.8 kW and 260.0 kW due to the increment in the T-H from 1800 K to 2230 K. The increase in the (Q) over dot(solar-reactor-Cr-WS) and (Q) over dot(solar-heater-Cr-WS) resulted into a rise in the (Q) over dot(solar-cycle-Cr-WS) by 3896.8 kW. The eta(solar-to-fuel-Cr-WS) increased from 9.5% to 26.4% when the T-H was augmented from 1800 K to 2000 K. A further rise in the T-H from 2000 K to 2230 K resulted in a reduction in the eta(solar-to-fuel-Cr-WS) from 26.4% to 21.3%. After employing the 100% heat recuperation, the eta(solar-to-fuel-HR-Cr-WS) of the Cr-WS cycle was improved up to 48.3% at T-H = 2000 K.