Ce-Ce-Ti-Mn-O Perovskite-based materials for solar-driven thermochemical splitting of water and carbon dioxide

Background

Solar thermochemical cycles (TCCs) represent a promising approach for producing hydrogen and carbon monoxide—key building blocks for clean fuels—by splitting water and carbon dioxide using concentrated solar energy. The field has gained attention as the world seeks sustainable alternatives to fossil-fuel-derived hydrogen, which is currently produced mainly via steam methane reforming, a process that emits significant greenhouse gases. Solar-driven TCCs offer a carbon-neutral pathway by leveraging high-temperature redox reactions in metal oxides to convert solar energy directly into chemical energy, thus enabling the production of solar fuels without direct CO₂ emissions. The development of efficient and robust redox-active materials is central to advancing this technology and making large-scale solar fuel production viable.

Despite the promise of TCCs, current approaches are hampered by the limitations of existing redox materials, particularly ceria (CeO₂), which is widely regarded as the state-of-the-art. Ceria requires very high temperatures for reduction, which complicates reactor design and reduces overall efficiency. Its relatively low reduction entropy and limited oxygen exchange capacity restrict the amount of hydrogen or carbon monoxide that can be produced per cycle, making the process less economically attractive. Additionally, repeated cycling at high temperatures can lead to phase instability and material degradation, further limiting long-term performance. These challenges underscore the need for new materials that can operate efficiently at lower temperatures, offer higher redox capacity, and maintain structural stability over many cycles.

Technology

The technology is a novel perovskite material, specifically Ca₁₋ₓCeₓTi_yMn₁₋yO₃ where x ranges from 0.3 to 0.35 and y from 0.25 to 0.35, designed for solar thermochemical splitting of water and carbon dioxide. This material operates in a two-step redox cycle: first, it undergoes a high-temperature reduction (1700–2000 K) to create oxygen vacancies, then a lower-temperature re-oxidation (900–1500 K) with steam or CO₂ to produce hydrogen or carbon monoxide, respectively. The perovskite’s structure incorporates multiple redox-active cations—cerium and manganese—distributed across different lattice sites, which enhances the redox cycling process. High configurational entropy within the material ensures phase stability and reversible lattice changes during repeated cycles, making it robust for continuous operation in solar thermochemical reactors.

This solution is differentiated by its combination of multiple redox-active cations and high configurational entropy, which together optimize both the thermodynamics and structural stability required for efficient solar fuel production. Unlike conventional materials such as ceria, this perovskite exhibits a lower reduction enthalpy and higher reduction entropy, enabling more efficient oxygen vacancy formation and greater fuel yields at lower operating temperatures. Experimental and computational studies confirm that both cerium and manganese actively participate in the redox process, and the material maintains its phase integrity over many cycles. This unique combination of properties allows for improved efficiency, cyclability, and scalability in solar-driven hydrogen and carbon monoxide generation, positioning it as a significant advancement over existing thermochemical materials.

Benefits

• Enables efficient, carbon-free production of hydrogen and carbon monoxide using solar energy.
• Lower reduction enthalpy than conventional ceria, allowing easier and more energy-efficient reduction.
• High configurational entropy ensures phase stability and durability over multiple redox cycles.
• Multiple redox-active cations (Ce, Mn, Ti) enhance redox capacity and increase reduction entropy.
• Maintains structural integrity with reversible lattice changes during thermal cycling.
• Dual cation redox activity improves overall thermochemical cycle efficiency.
• Compatible with two-step solar thermochemical cycles using steam or CO₂ for fuel production.

Applications

• Solar hydrogen production plants
• Solar syngas (CO+H₂) generation
• Renewable fuel synthesis facilities
• Industrial decarbonization processes
• Grid-scale solar energy storage

Additional info

The Ca₁₋ₓCeₓTi_yMn₁₋yO₃ perovskite (x=0.3–0.35, y=0.25–0.35) facilitates solar thermochemical water and CO₂ splitting. Utilizing multiple redox-active cations (Ce, Mn), it optimizes reduction enthalpy and entropy compared to ceria. A two-step cycle involves high-temperature reduction (1700–2000 K) creating oxygen vacancies, followed by re-oxidation (900–1500 K) with steam or CO₂. High configurational entropy ensures structural stability and reversible lattice changes, enabling efficient, carbon-free hydrogen and carbon monoxide production.