Vertical MoSon SiO/Si and Graphene: Effect of Surface Morphology on Photoelectrochemical Properties.

Two-dimensional materials have attracted intensive attention recently due to their unique optical and electronic properties and their promising applications in water splitting and solar cells. As a representative layer-structured of transition metal dichalcogenides, MoShas attracted considerable devotion owing to its exceptional photo and electro properties. Here, we show that the chemical vapour deposition (CVD) growth of MoSon Si photocathode and graphene/Si photocathode can be used to prepare photoelectrocatalysts for water splitting. We explore a bottom-up method to grow vertical heterostructures of MoSand graphene by using the two-step CVD. Graphene is first grown through ambient-pressure CVD on a Cu substrate and then transferred onto SiO2/Si substrate by using the chemical wet transfer followed by the second CVD method to grow MoSover the graphene/SiO/Si. The effect of the growth temperatures of MoSis studied, and the optimum temperature is 800 °C. The MoSproduced at 800 °C has the highest photocurrent density at -0.23 mA cmin 0.5 M NaSOand -0.51 mA cmin 0.5 M HSOat -0.8 V vs. Ag/AgCl. The linear sweep voltammetry shows that MoSin 0.5 M HSOhas about 55% higher photocurrent density than MoSin NaSOdue to the higher protons (H) in the HSOelectrolyte solution, which are sufficiently charged to reduce to Hand, therefore hydrogen evolves more rapidly where the photocurrent density and hydrogen generation can be enhanced. MoS/graphene/SiO/Si (MGS) has -0.07 mA cmat -0.8 V vs. Ag/AgCl of photocurrent density, which is 70% lower than that of bare MoSbecause MGS is thicker compared with MoS. Thus, MoShas potential as a photocatalyst in photoelectrochemical water splitting. The structure and the morphology of MoSplay an important role in determining the photocurrent performance.