Hydrogen-iodide decomposition over Pd-CeO2 nanocatalyst for hydrogen production in sulfur iodine thermochemical cycle

A highly active and stable catalyst for hydrogen-iodide decomposition reaction in sulfur iodine (SI) cycle has been prepared in the form of Pd-CeO2 nanocatalyst by sol-gel method with different calcination temperatures (300 degrees C, 500 degrees C, and 700 degrees C). XRD and TEM confirmed a size around 6-8 nm for Pd-CeO2 particles calcined at 300 degrees C. Raman study revealed large number oxygen vacancies in Pd-CeO2-300 when compared to Pd-CeO2-500 and Pd-CeO2-700. 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 degrees C-550 degrees C in a quartz-tube, vertical, fixed-bed reactor with 55 wt % aqueous hydrogen-iodide feed over Pd-CeO2 catalyst using nitrogen as a carrier gas. Pd-CeO2-300 showed hydrogen-iodide conversion of 23.3%, which is close to the theoretical equilibrium conversion of 24%, at 550 degrees C. It also showed a reasonable stability with a time-on-stream of 5 h. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.