Insight into the role of ultrasound, morphology and crystal structure for enhancing the recycling and catalytic performance of Au-MoS2 nanocomposite catalyst in reduction of nitro-compounds

The chemical intercalation exfoliation of commercial MoS2 and the hydrothermal synthesis within their multi-step procedures and high cost have been reported as the prevalent approaches to produce 2D-MoS2 nanosheet, so far. In this study, the high-intensity ultrasound, as a novel straightforward sonochemical approach was utilized for the synthesis of 1 T-MoS2 nanosheets which were then decorated with small sizes of Au nanoparticles (similar to 10 nm) giving rise to the uniform dispersion. When reference materials of the same composition were synthesized in a classic hydrothermal medium, flower-like morphology with a 2-H structure was obtained with a broad and big size distribution of Au nanoparticles (>= 50 nm). The prepared materials were thoroughly characterized using XRD, SEM/TEM/EDS mapping, N-2-BET adsorption-desorption, and XPS. The nanocomposite morphology and structure were found to have a great effect on the catalytic reduction of hazardous chemicals (nitrobenzene and 3-nitroacetophenone), revealing the benefits of the sonochemically produced catalysts. Notably, the obtained catalytic results revealed that among the produced catalysts, the sonochemically synthesized Au/MoS2 NSs exhibited the highest aniline selectivity of 99 % at conversion ratio of 95 %, and 3-amino-acetophenone selectivity of 99 % at conversion ratio of 98 %. Moreover, the as-prepared sonochemically catalyst displayed high stability for at least 8 cycles of reaction while maintaining high reducing efficiency. The superior activity is discussed in terms of higher surface area and pore diameter, the sulfur deficient surface and the synergistic effect between Au-0 and Au+ species. The developed new sonochemical route opens up new opportunities for the facile production of the versatile MoS2 NSs-based core/satellite nanostructures with high catalytic activity. The fulfillment of the green chemistry principle of the ultrasonic technique (eliminating any toxic reducing agents, stabilizers, or organic surfactants) is emphasized.