Photo-catalytic degradation of methyl orange under visible light by MoS2 nanosheets produced by H2SiO3 exfoliation

• The H2SiO3 exfoliation was used to synthesize MoS2 nanosheets.
• The MoS2 nanosheets present excellent visible light absorbance properties.
• Methyl orange can be degraded by MoS2 nanosheets under visible light.
• H+ adsorbed by MoS2 facilitates producing free radicals of OH.

MoS2 nanosheets were for the first time prepared by H2SiO3 exfoliation, i.e., the precursors ((NH4)6Mo7O24·4H2O and thiourea) were embedded inside the hydrogel of H2SiO3 which provides steric hindrance for MoS2 growth. After removal of H2SiO3, MoS2 nanosheets were obtained. The appropriate dosage of hydrogel of silicic acid is the determining factor in preparing homogeneous nanosheets of MoS2. The prepared MoS2 nanosheets possess a high specific surface area of 37.8 m2/g, and present excellent UV–visible-NIR absorbance properties, and the absorption peaks of visible region are much higher than that of ultraviolet region. Therefore, they can be used as excellent catalysts for visible-light-driven degradation of methyl orange (MO). The effect of photo-degradation parameters of MO including pH value, dosage of catalyst and initial concentration was studied. The strongly acidic solution of MO facilitates producing free radicals of OH in this catalytic system. The MoS2 nanosheets can be reused 10 times with little change of degradation rate, indicating that they are stable under visible-light irradiation.

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