Ultrasound assisted synthesis of reduced graphene oxide (rGO) supported InVO₄-TiO₂ nanocomposite for efficient...

Herein, a ternary nanocomposite, comprising metal oxide (InVO₄ and TiO₂) photocatalysts supported on rGO sheets was prepared via the hydrothermal method in the presence and absence of ultrasound irradiation. The photocatalytic performance of the prepared rGO/InVO₄-TiO₂ nanocomposites was evaluated for H₂ evolution activity from water splitting with glycerol as a sacrificial agent. Interestingly, a synergistic effect (6-fold) was observed with rGO/InVO₄-TiO₂ nanocomposite prepared with the help of ultrasound compared to the samples prepared without ultrasound. The optimized nanocomposite (rGO/InVO₄-TiO₂) exhibited a maximum H₂ evolution of 1669 μmol h^-1, a ∼13-fold enhancement compared to the bare TiO₂. This remarkable enhancement is mainly due to the synergistic effect induced by ultrasonic irradiation along with the shifting of the optical band gap of TiO₂ from 3.20 eV to 2.80 eV by loading of InVO₄ and rGO and also strong chemical bonding between metal (Ti) and C through Ti-C bond formation, as identified by UV-vis DRS spectra and XPS spectra, respectively. Moreover, a significant quenching of PL emission intensity and smaller radius arc of the Nyquist plot in the EIS were observed when the rGO and InVO₄ were loaded in TiO₂, indicating the efficient charge carriers separation and transfer in the presence of rGO sheet, resulting in enhanced photocatalytic activity. Thus, application of ultrasound has played significant and important roles in substantially enhancing hydrogen evolution along with rGO and InVO₄ acting as support and co-catalyst, respectively.