Dopant Incorporation in Ceria for Enhanced Water-Splitting Activity during Solar Thermochemical Hydrogen Generation

Abstract

Ceria has emerged as an attractive candidate for solar thermochemical hydrogen production; however, the necessary temperatures for CeO2 reduction to Ce2O3 are too high for conventional solar concentrating systems, while the reduction to nonstoichiometric CeO2−δ below 1500 °C shows restricted chemical yield. Doping ceria with another metal can improve the reactivity at lower temperatures. This study focuses on the doping of ceria with different metals such as tantalum or trivalent lanthanides (La, Sm, and Gd) to form binary oxides and on the doping of ceria–zirconia solid solutions to form ternary oxides. Ceria materials doped with tantalum show a high reducibility, but the structural evolution during thermal treatment leads to the formation of a secondary phase that hinders the water dissociation reaction. Besides, the doping with trivalent lanthanides results in an improved thermal stability during consecutive cycles, while the hydrogen production is unchanged compared to ceria. Concerning ternary oxides...