Effect of sintering temperature on structural characteristics and catalytic activity of sol-gel derived CeO2/CuO nanocomposite

In this work, CeO 2 /CuO nanocomposite was synthesized using a sol–gel combustion method and thermally treated at 400, 500, 600, and 800 °C to systematically examine the influence of calcination temperature on its structural and catalytic properties. Rietveld refinement of powder X-ray diffraction data confirmed the formation of two coexisting crystalline phases, cubic CeO 2 ( Fm -3 m ) and monoclinic CuO ( C 2/ c ), with their relative phase fractions varying with calcination temperature. FE-SEM analysis revealed the formation of agglomerated nanostructured particles with noticeable grain growth at elevated temperatures, while EDX analysis confirmed the presence of Ce, Cu, and O elements without any detectable impurities. HR-TEM studies further demonstrated the formation of well-defined nanocomposite structures with distinct interplanar spacing corresponding to CeO 2 and CuO phases, and the SAED patterns verified their polycrystalline nature. Nitrogen adsorption–desorption measurements revealed mesoporous characteristics, accompanied by a progressive decrease in specific surface area with increasing thermal treatment. The catalytic activity of the synthesized nano-catalysts was investigated through the aqueous reduction of nitroarenes using NaBH 4 , with 4-nitrophenol employed as a model substrate. Among the studied catalysts, CCO400 exhibited the highest catalytic efficiency, achieving 95% conversion of 4-nitrophenol to 4-aminophenol within 12 min, which can be attributed to its higher surface area, smaller crystallite size and greater availability of active sites. A plausible surface-mediated hydride transfer mechanism was proposed to explain the reduction process. Recyclability studies demonstrated that the CCO400 catalyst retained more than 87% of its activity even after eight consecutive cycles, confirming its stability and reusability under the applied reaction conditions.