Precursor-Concentration-Regulated CuO-CeO₂ Catalysts with Tailored Oxygen Species and Redox Behavior for Efficient C₃H₆ Catalytic Combustion

Flame synthesis is a promising route for producing mixed-oxide catalysts, but the role of precursor concentration in regulating catalyst formation during self-sustained flame pyrolysis remains insufficiently understood. In this work, CuO-CeO₂ mixed-oxide catalysts were prepared by varying the total metallic precursor concentration from 0.04 to 0.28 mol·L^-1 while keeping the Cu/(Cu + Ce) molar ratio fixed at 35 mol.%. This strategy enables the influence of precursor concentration to be distinguished from that of metal composition and provides insight into the formation of CuO-CeO₂ catalysts under a self-sustained flame environment. The results show that precursor concentration strongly affects particle aggregation, crystallite growth, Cu species distribution and possible lattice incorporation, oxygen species distribution, and low-temperature reducibility. Among the prepared catalysts, CuCe0.20 exhibits the most favorable balance among textural characteristics, Cu-Ce interaction, oxygen species distribution and redox behavior, and surface reactive oxygen availability. As a result, CuCe0.20 achieves 90% C₃H₆ conversion at 380 °C and nearly complete conversion at 450 °C. More importantly, it maintains stable activity during a 600 min test at 450 °C with an apparent CO₂ selectivity of 99.9%. Post-reaction characterization further reveals that the CeO₂ framework and Cu-Ce interaction are largely retained, while the relative contribution of lattice oxygen increases after long-term reaction, accompanied by retained low-temperature reducibility. This work extends the design of flame-made CuO-CeO₂ catalysts from composition optimization to precursor-concentration engineering and demonstrates a practical strategy for preparing stable non-noble metal catalysts for VOC catalytic combustion.