Preparation and solar thermochemical properties analysis of NiFe₂O₄@SiC/ @Si₃N₄ for high-performance CO₂-splitting

The solar-driven thermochemical CO₂-to-CO conversion is an effective way to achieve the mission of carbon peaking and carbon neutrality. However, synthesizing porous reacting materials with excellent thermal stability, hardness and long-term cyclic stability, oxygen exchange capacity, and higher CO₂-to-CO conversion are the most important challenges associated with the thermochemical CO₂-splitting approach and technological upscaling to large-scale applications. This study presented the development of NiFe₂O₄ oxygen carriers, the synthesis method of SiC and Si₃N₄ supports, and solar-to-fuel processing of the newly prepared materials through CO₂-splitting under a highly concentrated solar radiative heat flux. The newly synthesized NiFe₂O₄@SiC porous redox material resulted in higher solar energy absorption and CO₂ conversion capability with an instantaneous CO production of 410 μmol/g and direct CO₂-to-CO conversion rate of 18.1 % at 1073–1273 K reaction temperature. The media composite of NiFe₂O₄@SiC exhibited high-temperature thermal changes, good thermochemical reaction stability, and a higher CO production rate through six redox cycles compared to NiFe₂O₄@Si₃N₄ porous reacting material. The high oxidation potential and remarkably solar radiative heat flux absorption and thermochemical CO₂-splitting capacities of the newly developed materials were demonstrated through experimental analysis. The synergistic effect of the oxygen carriers (NiFe₂O₄) and substrate materials including SiC and Si₃N₄ skeletons for CO₂-splitting is highlighted. This study provided comprehensive and novel experimental insights that can be used as guidance for theoretical research and application in CO₂ conversion into high-value-added energy products.