Indomethacin–V ₂ O ₃ –Reduced Graphene Oxide Nanocomposites as Catalysts in the Electro-Fenton Process

A single-step sonochemical method (20 kHz) is demonstrated for the functionalization of reduced graphene oxide (rGO) with V 2 O 3 and indomethacin complexes to form catalytically efficient an indomethacin–V 2 O 3 –rGO nanocomposite with rodlike shape and average diameter (44.6 ± 8.3) nm without any surface active additives in an aqueous medium. UV–vis absorption, infrared, and Raman spectroscopies confirm that the formation of an indomethacin–V 2 O 3 –rGO nanocomposite relies on sonochemical complexation of indomethacin with vanadium trioxide and rGO through covalent binding with V–O–V, C–C ring, and −C(═O)–OH groups involving H-bond formation. Sonochemically designed indomethacin–V 2 O 3 –rGO nanocomposites can accelerate the single-electron transfer reaction in the redox couple Fe(CN) 6 3– /S 2 O 3 2– by ∼25.6 times higher than that in pristine indomethacin. The enhanced catalytic activity of nanocomposites is due to covalently bonded V 2 O 3, rGO, and indomethacin, including complexes of indomethacin with vanadium and VO(IV), conjugated indomethacin–rGO structure, and H-bond formation. Indomethacin–V 2 O 3 –rGO nanocomposites are efficient hydroxyl radical scavengers in the electro-Fenton process due to indomethacin–vanadium complexes, with the activity being by ∼13.6 times higher than that of pristine indomethacin and not accessible by V 2 O 3 –rGO.