Thermochemical reactivity of 5-15Â mol% Fe, Co, Ni, Mn-doped cerium oxides in two-step water-splitting cycle for solar hydrogen production

The thermochemical two-step water-splitting cycle using transition element-doped cerium oxide (M-CeO2−δ; M = Fe, Co, Ni, Mn) powders was studied for hydrogen production from water. The oxygen/hydrogen productivity and repeatability of M-CeO2−δ materials with M doping contents in the 5-15 mol% range were examined using a thermal reduction (TR) temperature of 1500 °C and water decomposition (WD) temperatures in the 800-1150 °C range. The temperature, steam partial pressure, and steam flow rate in the WD step had an impact on the hydrogen productivity and production rate. 5 mol% Fe- and Co-doped CeO2−δ enhances hydrogen productivity by up to 25% on average compared to undoped CeO2, and shows stable repeatability of stoichiometric oxygen and hydrogen production for the cyclic thermochemical two-step water-splitting reaction. In addition, 5 mol% Mn-doped CeO2−δ, 10 and 15 mol% Fe- and Mn-doped CeO2−δ show near stoichiometric reactivities.