A study of constructing heterojunction between two-dimensional transition metal sulfides (MoS2 and WS2) and (101), (001) faces of TiO2

The present study focuses on anatase TiO2 with various crystal facets, such as {101} and {001} combined with two-dimensional (2D) WS2 nanolayers to form a heterojunction and the related photocatalytic activity. The {101} facets of anatase TiO2 is superior in the compositing of WS2; the composite shows a 90% enhancement compared with pristine TiO2 than the composited WS2 on the {001} facets which only boosted 7%. However, in our previous study, anatase TiO2 with coexposed {101} and {001} facets demonstrated great improvement in photocatalytic activity in the composited MoS2. Results reveal that when anatase TiO2 with coexposed {101} and {001} facets are composited with 2D transition metal sulfide (MoS2 and WS2), dual heterojunction will form. Some {101} facets are co-exposed with {001} facets, and this co-exposure will construct a crystal facet heterojunction. Moreover, a semiconductor heterojunction exists between TiO2 and MoS2 or WS2. This dual heterojunction is found to have a synergistic effect. It is revealed that the position of energy band plays a decision role in the dual heterojunction. This finding offers a deeper understanding in the construction of heterojunction on different crystal facets. (C) 2017 Elsevier B.V. All rights reserved.