The effect of the characteristic size and morphology of ceria nanoobjects on the operational temperatures of water splitting

The use of hydrogen fuel is a promising eco-friendly technology that avoids carbon dioxide pollution. Today, the cheapest sources of energy are solar energy and industrial waste heat. These energy sources are used to produce hydrogen by splitting water using multi-step or 2-step thermochemical cycles. The main disadvantage of 2-step thermochemical cycles is the high operating temperature (usually more than 1700 K), which is significantly lower in multi-step cycles. This article shows that the use of ceria nanoparticles reduces operating temperatures at the recovery step by 500–700 K. The melting point of ceria nanoparticles also decreases with a decrease in their characteristic size. In turn, the temperature at which sintering begins is proportional to the melting point, so the sintering temperature also decreases. For example, if ceria nanoparticles of about 20 nm in size are used as the redox material, the operating temperature of the recovery stage is in the range of 1000–1300 K, which is significantly lower than the temperature of 1500 K, at which intensive sintering of ceria nanoparticles begins.