Thermo-electrochemical hydrogen production based on ceria

Two-step thermochemical cycles are efficient for producing H 2 with solar energy, however, they face challenges with thermal losses at high temperatures needed for metal oxide reduction. This study introduces the first experimental demonstration of a thermo-electrochemical cycle for water splitting using ceria (CeO 2 ). By applying electrical potential CeO 2 is reduced at temperatures under 1000 °C, significantly lower than the 1400 °C required in a conventional thermal-only process. This is followed by hydrogen production through re-oxidation with water without additional electrical input. This approach eases the conditions of two-step non-stoichiometric thermochemical cycles, showing CeO 2 reduction at 750–950 °C with oxygen partial pressure at 2 · 10 −6 bar and achieving reduction extents from 0.002 to 0.01 with 0.75–2 V electrical potential. The study explores pure CeO 2 and CeO 2 -YSZ composites, examining the impact of temperature and electrical potential on the degree of non-stoichiometry and demonstrating cyclability and hydrogen output. Moreover, incorporating a dielectric like YSZ reduces power consumption by two orders of magnitude under similar conditions. This research provides a proof-of-concept for a new thermo-electrochemical cycle, suggesting future exploration for other materials to improve conventional thermochemical cycle operating temperatures. • Thermo-electrochemical production of hydrogen on CeO 2 demonstrated. • CeO 2 is reduced below 1000°C with the help of an electrical potential. • Reduction extent up to 0.01 using at 850°C with 2 V. • 3 cycles of hydrogen production show continuous performance.