Direct solar thermochemical CO₂ splitting based on Ca- and Al- doped SmMnO₃ perovskites: Ultrahigh CO yield within small temperature swing

Solar thermochemical CO₂ splitting is a promising route to reduce environment pollution and mitigate energy crisis. However, traditional redox materials are limited by low CO production, slow reaction kinetics, and poor cycling stability, which results in low solar-to-fuel efficiency. Here, Ca- and Al- doped SmMnO₃ perovskites are proposed for high-performance solar thermochemical CO₂ splitting. The average CO yield of Sm_0.6Ca_0.4Mn_0.8Al_0.2O₃ reaches a record-high value of 595.56 μmol g⁻¹ when swinging between 1350 °C and 1100 °C. The CO yield is about 4.22 times as high as that of undoped SmMnO₃ (140.97 μmol g⁻¹) under the same conditions, and remains stable over multiple cycling. The ultrahigh CO yield can be attributed to the transformation of reaction mechanism from solid-state surface reaction (F2) to bulk diffusion model (D2). Besides, Ca- and Al- doped SmMnO₃ perovskites possess high solar absorptance over 86.5% (in stark contrast to 12.1% of CeO₂), so that only solar concentration ratio of 898 (Sm_0.6Ca_0.4Mn_0.8Al_0.2O₃) is required to drive thermochemical reactions while benchmark CeO₂ needs 1936. This work provides novel approaches for high-performance solar thermochemical CO₂ splitting with high CO yield, good cycle stability, small temperature swing, and low solar concentration required.