Chiang Mai Journal of Science

This study investigates the degradation of Methyl Orange (MO) using CuSnO₃ (CSO) modified with monoethanolamine (MEA) as a chelating and structure-directing additive and synthesized by the sol–gel method. The effects of MEA concentration on the structural, morphological, optical, and photocatalytic properties of CSO were systematically examined. X-ray diffraction (XRD) confirmed that all samples exhibited the cubic spinel CuSnO₃ phase, and MEA enhanced crystallinity and improved structural order. Scanning electron microscopy (SEM) showed that MEA altered particle morphology from irregular, strongly agglomerated grains to more uniform spherical and octahedral structures. Ultraviolet diffuse reflectance spectroscopy (UV–DRS) and Tauc plot analysis indicated optical band gap values of 2.4, 3.13, 2.79, and 2.65 eV for the unmodified, 1:1, 1:2, and 2:1 MEA samples, respectively. Fourier transform infrared spectroscopy (FTIR) confirmed the formation of the metal–oxygen oxide framework. Photocatalytic degradation of MO showed that the unmodified CSO achieved only 39.28% degradation (k_app = 0.0059 min⁻¹), whereas the 1:1 MEA-modified CSO achieved 78.56% degradation (k_app = 0.0124 min⁻¹). Pseudo-first-order kinetics was confirmed for all samples. These results demonstrate that MEA acts as an effective structure-directing and chelating agent that enables precise control over the physicochemical properties of CuSnO₃ and substantially enhances its photocatalytic performance.