Hydrogen-iodide decomposition over Pd CeO 2 nanocatalyst for hydrogen production in sulfur-iodine thermochemical cycle

Abstract A highly active and stable catalyst for hydrogen-iodide decomposition reaction in sulfur-iodine (SI) cycle has been prepared in the form of Pd CeO 2 nanocatalyst by sol-gel method with different calcination temperatures (300 °C, 500 °C, and 700 °C). XRD and TEM confirmed a size around 6–8 nm for Pd CeO 2 particles calcined at 300 °C. Raman study revealed large number oxygen vacancies in Pd CeO 2 -300 when compared to Pd CeO 2 -500 and Pd CeO 2 -700. With increase in calcination temperature, the average particle size increased whereas the specific surface area and number of oxygen vacancies decreased. Hydrogen-iodide catalytic-decomposition was carried out in the temperature range of 400°C–550 °C in a quartz-tube, vertical, fixed-bed reactor with 55 wt % aqueous hydrogen-iodide feed over Pd CeO 2 catalyst using nitrogen as a carrier gas. Pd CeO 2 -300 showed hydrogen-iodide conversion of 23.3%, which is close to the theoretical equilibrium conversion of 24%, at 550 °C. It also showed a reasonable stability with a time-on-stream of 5 h.