Defect-surface engineering of La-doped ceria for microwave-assisted hydrogen production

Abstract

Hydrogen plays a pivotal role in decarbonizing the energy and chemical sectors, yet current production methods are limited by high temperatures and energy demands. Microwave-assisted thermochemical redox cycles offer a promising low-temperature, contactless alternative by coupling electromagnetic energy with reducible oxides. In this study, we explore La-doped ceria (Ce_1−xLa_xO_2−δ) as a tunable platform to enhance microwave-driven hydrogen production. We demonstrate that introducing La³⁺ into the ceria lattice reduces the bandgap and increases dielectric permittivity, enabling Ce⁴⁺ to Ce³⁺ reduction at temperatures as low as 110 °C. Among the series, Ce_0.9La_0.1O_1.95 exhibits optimal performance, balancing high ionic mobility and microwave absorption. Combined with tailored surface area, this composition achieves an unprecedented hydrogen production rate of 2.60 mL g⁻¹ per cycle at temperatures below 400 °C. Correlations between dopant concentration, polarization behavior, and redox kinetics reveal the key role of band structure breakdown and defect formation in driving non-equilibrium reduction. Our findings uncover mechanistic insights into microwave–material interactions and establish design principles for next-generation redox materials. This approach provides a framework for scalable, electrified hydrogen production via electronic structure and defect engineering in oxide systems.