Facile synthesis and enhanced photocatalytic activity of single-crystalline nanohybrids for the removal of organic pollutants.

This study focused on the synthesis of α-MoO3/rGO (rGO, reduced graphene oxide). One-dimensional nanohybrids under mild conditions and a low temperature wet chemical route produced highly pure single-crystalline orthorhombic α-MoO3 on GO sheets. Four nanohybrids, labeled as GMO-0, GMO-1, GMO-2 and GMO-3, were synthesized with different mass chargings of GO (0 mg, 40 mg, 60 mg and 100 mg, respectively). The photocatalytic performance for reduction of organic pollutants was analyzed. The presence of different amounts of GO in the prepared metal oxide hybrids altered the performance of the material as elaborated by the Brunauer-Emmett-Teller surface area, UV-visible diffuse reflectance spectra and the resulting reduction of organic dyes depicted by photocatalytic experiments. GO as a support material and active co-catalyst decreased the band gap of α-MoO3 (2.82 eV) to lower values (2.51 eV), rendering the prepared hybrids usable for visible-light-induced photocatalysis. The large specific surface area (72 m2 g-1) of the mesoporous α-MoO3/rGO nanohybrid made it an efficient photocatalyst for the elimination of azo dyes. Very fast reduction (100%) of Rhodamine B was observed in a few minutes, while Congo Red was degraded by 76% in 10 min, leading to the formation of stable intermediates that were completely neutralized in 12-14 h under light irradiation. The amount of GO loaded in the samples was limited to a point to achieve better results. After that, increasing the amount of GO decreased the extent of degradation due to the presence of a higher electron acceptor. Photocatalytic experiments revealed the synergistic effect, high selectivity of the prepared nanohybrids and degradation of azo dyes. The kinetics of the degradation reaction were studied and found to follow a pseudo first-order reaction.