Bio-Derived Graphite from Pterocarpus marsupium Leaves for rGO-MoO$_3$ Nanocomposites with Enhanced Photocatalytic Efficiency

This study presents a sustainable approach to synthesize bio-graphite from Pterocarpus marsupium (Indian Kino) leaves without using chemical catalysts, activating agents, or organic solvents. The resulting bio-graphite was used to produce reduced graphene oxide (rGO) via a modified Hummers method. The bio-graphite derived rGO was further incorporated with orthorhombic structured MoO$_3$ at different percentages (1, 3, and 6 wt.%) using ultrasonication. Structural, morphological, and functional characterizations were conducted using XRD, FESEM, FTIR, and UV-Vis DRS spectroscopy, revealing a bandgap of 2.82 eV for the rGO(3 wt.%)-MoO$_3$ composite. Photocatalytic activity was evaluated via methylene blue degradation under natural sunlight. The rGO(3 wt.%)-MoO$_3$ nanocomposite showed superior performance, achieving 90% degradation in 150 minutes when compared to 65% by pure MoO$_3$. The Scavenger tests confirmed superoxide radicals $(\cdot O_2^-)$ as the main reactive species. This work highlights the potential of bio-graphite derived rGO-MoO$_3$ nanocomposites as efficient, eco-friendly photocatalysts for wastewater treatment.