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.