Herein we report a Cu ₂ O–TiO ₂ /rGO photocatalyst with phenomenal water splitting ability.

Combinations of different Advanced Oxidation Processes (AOPs) are being exploited for waste water treatment. The usage of ultrasound in photocatalysis finds much attention as the combined process offers some advantages over individual processes. Herein, we report the ultrasound assisted photocatalytic degradation of an organic pollutant (methyl orange as a model dye) in the presence of CuO-TiO2/rGO photocatalyst which was prepared by a simple wet impregnation method. A synergistic effect (3.7-fold) was observed by combining the sonolysis and photocatalysis processes. Influence of Cu loading and graphene oxide (GO) dosage over the photocatalytic performance of TiO2 was examined in detail. The catalyst dosage and initial concentration of MO were optimized based on a series of experimental studies. Besides, neutral pH was found to show an optimum efficiency for this sono-photocatalytic process.

Nitrogen-doped graphene quantum dots (N-GQDs) were decorated on a three-dimensional (3D) MoS₂–reduced graphene oxide (rGO) framework via a facile hydrothermal method. The distribution of N-GQDs on the 3D MoS₂–rGO framework was confirmed using X-ray photoelectron spectroscopy, energy dispersive X-ray elemental mapping, and high-resolution transmission electron microscopy techniques. The resultant 3D nanohybrid was successfully demonstrated as an efficient electrocatalyst toward the oxygen reduction reaction (ORR) under alkaline conditions. The chemical interaction between the electroactive N-GQDs and MoS₂–rGO and the increased surface area and pore size of the N-GQDs/MoS₂–rGO nanohybrid synergistically improved the ORR onset potential to +0.81 V vs reversible hydrogen electrode (RHE). Moreover, the N-GQDs/MoS₂–rGO nanohybrid showed better ORR stability for up to 3000 cycles with negligible deviation in the half-wave potential (E_1/2). Most importantly, the N-GQDs/MoS₂–rGO nanohybrid exhibited a superior methanol tolerance ability even under a high concentration of methanol (3.0 M) in alkaline medium. Hence, the development of a low-cost metal-free graphene quantum dot-based 3D nanohybrid with high methanol tolerance may open up a novel strategy to design selective cathode electrocatalysts for direct methanol fuel cell applications.