Boron Doping-Induced Ultrahigh Ce³⁺ Ratio in Amorphous CeO₂/GO Catalyst for Low-Concentration CO₂ Photoreduction

Direct utilization of diluted CO₂ enables sustainable CO₂ conversion into valuable products, with reduced CeO₂ emerging as an attractive candidate due to its exceptional redox flexibility. The catalytic efficacy of CeO₂ is intimately tied to the electronic structure of 4f, yet the persistent challenge lies in maintaining a high and stable concentration of Ce³⁺. In this study, we propose a symmetry-breaking-induced amorphization strategy to achieve an exceptionally high Ce³⁺ ratio by B doping, which facilitates the reduction of Ce⁴⁺ to Ce³⁺ in amorphous CeO₂. First-principles calculations and infrared spectroscopy reveal that B doping with three excess electrons induces the formation of planar triangular B-O₃ units by disrupting the original high-symmetry $Fm\overline{3}m$ structure of CeO₂, facilitating the spontaneous transition to the amorphous phase. Electronic structure analysis confirms that even a modest 7.5% B doping can significantly elevate the Ce³⁺ ratio to 85.7%. The resulting amorphous B-doped CeO₂/GO shows a remarkable CO₂-to-CO conversion rate of 249.33 µmol g^-1 h^-1(under 15% CO₂) and 103.4 µmol g^-1 h^-1(under 1% CO₂), with 100% selectivity in both cases. This performance highlights how amorphization stabilizes defect states, making amorphous CeO₂/GO with high Ce³⁺ an effective material for CO₂ photoreduction and addressing key challenges in CO₂ capture and utilization.