Novel SiQDs–MoS2 heterostructures with increasing solar absorption for the photocatalytic degradation of malachite green

Abstract

Novel heterostructures based on silicon quantum dots and molybdenum disulfide nanosheets (SiQDs–MoS2) were synthesized by a hydrothermal method, in which the introduced SiQDs play a determining role in manipulating the morphology, phase and band structure of MoS2. The resultant SiQDs–MoS2 is uniform flowerlike 3D microspheres assembled from petallike 2D MoS2 nanosheets anchored with 0D SiQDs, possessing abundant active sites. Besides, the primary MoS2 nanosheets consist of both semiconductive 2H and metallic 1T phases accompanied with intralayer mesopores and expanded interlayer spacing, endowing the resulting architectures with effective electron transfer. Significantly, the as-synthesized SiQDs–MoS2 exhibits intense full solar-spectrum absorption, indicating efficient solar energy harvesting. First-principles calculations simulate similar increased spectral absorption of monolayer MoS2 adhered with a Si cluster, suggesting the existence of new energy states associated with the integration of SiQDs and MoS2 nanosheets as evidenced by photoluminescence (PL) spectral analysis. As expected, the current SiQDs–MoS2 heterostructures demonstrate substantial photocatalytic activity even under visible and near-infrared (NIR) light on degradation of malachite green (MG). The type II electronic structure of SiQDs–MoS2 was proposed, enabling sufficient photogenerated electrons and holes for the photocatalytic reactions. This study may establish a new frontier on the rational design and feasible development of the hybrid structures with the desirable morphologies, phase compositions and band structures for the catalysis and beyond.