Enhanced Hydrogen Production in Microwave-Driven Water-Splitting Redox Cycles by Engineering Ceria Properties

Abstract

Sustainable hydrogen, produced from renewable sources such as solar or wind, plays a decisive role in driving industrial decarbonization. Among hydrogen production technologies, steam electrolysis, and solar-driven thermochemical cycles using reducible solid oxides show promise but face challenges due to high operation temperatures. Microwave-driven redox chemical looping enables the direct, contactless electrification of the process, reducing the operation temperature and complexity. Previous works showed that microwaves can efficiently drive reduction/water-splitting cycles using Gd-doped ceria at low temperatures (<250 °C), but adjustment of material properties is needed. Here, the key properties of materials are explored that affect the redox mechanism by screening a series of doped ceria materials to enhance microwave-driven hydrogen production. Evaluation of trivalent dopants (La3+, Gd3+, Y3+, Yb3+, Er3+, and Nd3+) reveals that reduction correlates with lattice and electronic properties. The composition Ce0.9La0.1O2-δ achieves 1.41 mL g−1, the highest hydrogen production among the studied series. Its narrower bandgap allows for reaching higher conductivity upon microwave-driven reduction at lower temperatures, while a larger ionic lattice size boosts solid-state oxygen diffusion. Overall, this research remarks on the critical properties of ceria-based materials that enhance hydrogen production in microwave-driven water-splitting cycles, supporting the design of more efficient materials for sustainable chemical production technology.