Engineering a GO-Gd₂TiO₅/g-C₃N₄ ternary nanocomposite for enhanced electrochemical performance and biodiesel...

A ternary GO-Gd₂TiO₅/g-C₃N₄ nanocomposite was developed as a recyclable heterogeneous nanocatalyst for sustainable biodiesel production from waste cooking oil (WCO). The catalyst was comprehensively characterized by structural, morphological, surface, thermal, and electrochemical techniques. Electrochemical analysis using CV, GCD, and EIS demonstrated favorable interfacial behavior, with 97% capacitance retention after 7000 cycles, a 0-100 µM linear response, 0.064 µA µM^-1 sensitivity, and 0.19 µM detection limit. Under optimized transesterification conditions (30 mg catalyst, 12 : 1 methanol/oil ratio, 65 °C, and 210 min), a maximum biodiesel yield of 98.74% was obtained. The temperature increases from 35 to 65 °C enhanced conversion, whereas the yield decreased to 90.50% at 75 °C. Kinetic analysis favored the pseudo-first-order model (R ² = 0.9612) over the pseudo-second-order model (R ² = 0.5832). Thermodynamic parameters of ΔH° = 81.05 kJ mol^-1, ΔS° = 261.04 J mol^-1 K^-1, and ΔG° = -7.24 kJ mol^-1 at 65 °C indicated an endothermic and favorable process. GC-MS confirmed FAME formation, with methyl stearate (40.59%), methyl oleate (27.81%), methyl linoleate (20.51%), and methyl palmitate (9.83%) as the major components. The catalyst maintained 92.4% biodiesel yield after five reuse cycles, corresponding to 93.58% activity retention. Overall, the combination of high catalytic efficiency, favorable kinetics and thermodynamics, electrochemical stability, and recyclability highlights GO-Gd₂TiO₅/g-C₃N₄ as a promising multifunctional nanocomposite for sustainable biodiesel production and related electrochemical applications.