Nanoscale two-dimensionaln anostructures have shown great potential as functional components in photocatalysis. Here, investigationso nt he synthesis of heterostructured hybrids, comprised of 0D CdS nanoparticles as semiconductor and 2D/2D graphene/MoS x as co-catalyst, are reported. The approach involves ar apid microwave-assisted reaction in autoclave conditions, by adopting either ao nestep or at wo-stepp rotocol. The chemical speciation of the nanocomposites was found to depend strongly on the compounding conditions of the precursors ubstances. The pho-tocatalytic activity was assessed by monitoring the photodegradation rate of 4-nitrophenol in solution using simulated solar light irradiation. The photocatalytic activity of the hybrids may be attributed to ac ombination of beneficial characteristics, strongly relatedt ot he chemical speciationo ft he composite components. Moreover,i ntimate contacts of the latter result in efficient heterojunctions. Overall, the present study provides valuable insighti nto the development of functional heterostructured photocatalystsc omprised of two-dimensional nanomaterials. Figure 5. Raman spectrafrom (a) MoGr@CdS and (b) CdS@MoGrt ernary hybrids at low laser dose (0.02 mW).

The photocatalytic reduction of Cr(VI) using pyrolytic char/TiO (PC/TiO) composite catalyst under simulated solar irradiation was studied. Response surface methodology (RSM) and experimental design were used for modeling the removal kinetics and for the optimization of operational parameters. RSM was developed by considering a central composite design with four input variable, i.e. catalyst concentration, initial concentration of Cr(VI), pH, and % (v/v) methanol concentration for assessing individual and interactive effects. A quadratic model was established as a functional relationship between four independent variables and the removal efficiency of Cr(VI). It was found that all selected variables have significant effect on Cr(VI) removal efficiency; however, the pH, the % concentration of methanol, and their interaction exhibited the major effects. Within the studied experimental ranges, the optimum conditions for maximum Cr(VI) removal efficiency (72.1 %) after 60 min of photocatalytic treatment were: catalyst concentration 55 mg L, Cr(VI) concentration 20 mg L, pH 4, and 5 % (v/v) methanol concentration. Under optimum conditions, Cr(VI) reductive removal followed pseudo-first-order kinetics, and nearly complete removal took place within 90 min. The results revealed the feasibility and the effectiveness of PC/TiO as photocatalyst in reduction reactions due to their ability of e-h pair separation increasing the transfer of the photogenerated e to the catalyst's surface and thus the reduction of Cr(VI).

Among the various organic pollutants and industrial chemicals, 4-nitrophenol has been one of the most monitored substances in aqueous environments, due to its enhanced solubility in such systems. This research reports for the first time the microwave-assisted synthesis of CdS/carbon/MoS x hybrids and the subsequent utilization of such systems as photocatalysts for 4-nitrophenol degradation. The hybrids demonstrated a variable photocatalytic activity, by using a variety of organic substances as precursors for the solvothermal carbonization step. By using ascorbic acid as precursor, the corresponding ternary composite exhibited excellent photocatalytic activity, with the 4-nitrophenol concentration been almost quantitatively decayed within 45 min of irradiation. This could be ascribed due to the generation of a high population of heterojunctions as well as the chemical speciation of Mo-based nanostructures. Such ternary hybrids may be utilized as potential photocatalytic systems in processes, where removal of toxic water-soluble substances is the key issue.

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