Synthesis of the MoS2@CuO heterogeneous structure with improved photocatalysis performance and H2O adsorption analysis.

MoS2@CuO heterogeneous structure nanoflowers were synthesized through a two-step hydrothermal method for the first time. The valence band offset (VBO) and conduction band offset (CBO) of the MoS2@CuO heterojunction, and the bases for the design of the heterogeneous structure were determined by X-ray photoemission spectroscopy (XPS). For the increased specific surface area and the formation of staggered type-II band alignment of the composite structure, a significantly enhanced photocatalytic ability of the MoS2@CuO heterojunction was obtained by studying the photodegradation of methylene blue (MB). After irradiation for 100 min, the residual MB in solution was about 27.5% for pristine MoS2 nanoflowers while it was 4.3% for MoS2@CuO hetero-nanoflowers, respectively. The humidity sensing properties of the two nanostructures were also studied for comparison. The results showed that better response/recover times were obtained. In order to give a theoretical explanation for this phenomenon, we performed first-principles calculation to analyse the corresponding humidity sensing mechanisms of MoS2 and MoS2@CuO in detail. The calculated results showed that water molecules could bind stronger to the CuO surface compared to MoS2, which is in line with the experimental observations.