Defect-Mediated Catalysis for Low-Temperature Formation of Graphene-Based Materials.

Achieving low-temperature graphene formation remains a major challenge in carbon materials chemistry. Here we reveal a defect-mediated catalytic mechanism in which dynamically generated oxygen vacancies on ceria (CeO) activate acetylene (CH) and direct the structural evolution of carbon networks at remarkably low temperatures. The oxygen-vacancy-driven redox dynamics of CeO enables CH decomposition to proceed at temperatures as low as 113 °C, initiating carbon nucleation and leading to graphene domain formation below 300 °C. The temperature-dependent evolution─from graphene quantum dots (GQDs, 300 °C) to aggregated graphene (450 °C) and porous graphene frameworks (600 °C)─illustrates a designable transition in carbon connectivity directed by defect chemistry. Mechanistic studies combining spectroscopy, thermogravimetry, and density functional theory reveal that the reaction follows a temperature-dependent transition from a radical to a carbene pathway, governed by the oxygen-vacancy chemistry of CeO. Together, these results define a defect-mediated catalytic paradigm that couples oxide redox dynamics with carbon dimensionality control, offering a general principle for low-temperature formation of graphene-based sp carbon materials.