Biopolymer-Assisted Hydrothermal Synthesis of Manganese Cobalt Spinel Oxide (MnCo2O4) Using Cellulose and Chitosan for Enhanced Catalytic Performance

This study reports the synthesis and photocatalytic performance of MnCo2O4 nanospinels fabricated with biodegradable stabilizers—chitosan (CHT) and biomass-cellulose (BC)—for the degradation of methylene blue (MB) under UV-rich solar irradiation. Structural and optical analyses (FTIR, XRD, XPS, PL, TGA, UV–Vis, and BET) revealed that the stabilizers significantly improved crystallinity, porosity, and charge-carrier separation while suppressing electron–hole recombination. Among the catalysts, MnCo2O4–CHT exhibited the best performance, achieving 96% MB degradation within 120 min, with the highest apparent rate constant (kapp = 0.0203 min−1) and shortest half-life (t1/2 = 34.2 min). In comparison, MnCo2O4–BC and MnCo2O4–Neat achieved 65% and 45% degradation, respectively. The enhanced activity of MnCo2O4–CHT is attributed to the chelation and electron-donating ability of chitosan’s –NH2 and –OH groups, which facilitate efficient charge transfer and reactive oxygen species (ROS) generation. These findings demonstrate the effectiveness of stabilizer-assisted synthesis in tuning the physicochemical properties of spinel oxides, offering a sustainable and high-performance photocatalyst for environmental remediation and wastewater treatment applications.