(664b) Doped Ceria for Solar Thermal Water Splitting: What Works, What Doesn’t, and How to Improve It

Solar thermal water splitting (STWS) has the potential to achieve high solar to hydrogen efficiencies because of its use of the entire solar spectrum to split water. Two-step STWS uses a metal oxide oxygen carrier to couple two reduction/oxidation half reactions, one of which generates O₂ and the other which splits water to generate H₂. However, an optimal material which facilitates these reactions has not been identified. Among the candidate materials that are known to be capable of driving STWS, CeO₂ is considered the most promising. However it requires very high reduction temperatures (â?¥1500°C) to achieve acceptable H₂ production capacities. Many researchers have tried to dope ceria to bring down the reduction temperature, to varying degrees of success. In this work we use ab initio calculations based on density functional theory to develop a fundamental understand and explanation for why only Hf, and Zr have â??improvedâ? the STWS abilities of ceria. Based on this understanding we propose a novel set of dopant combinations and modifications strategies that, based on DFT results, improve the hydrogen production capacity of ceria at lower temperatures and/or result in higher H₂O conversion extents during the oxidation reaction.