On/Off Boundary of Photocatalytic Activity between Single- and Bilayer MoS 2

• Published in: ACS nano Vol. 14; no. 6; pp. 6663 - 6672
• Main Authors: Taniguchi, Takaaki, Nurdiwijayanto, Leanddas, Li, Shisheng, Lim, Hong En, Miyata, Yasumitsu, Lu, Xueyi, Ma, Renzhi, Tang, Dang-Ming, Ueda, Shigenori, Tsukagoshi, Kazuhito, Sasaki, Takayoshi, Osada, Minoru
• Format: Journal Article
• Language: English
• Published: United States 23-06-2020
• Subjects: two-dimensional materials; photocatalyst; MoS2; nanosheets; photodeposition
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/acsnano.9b09253

Molecularly thin two-dimensional (2D) semiconductors are emerging as photocatalysts owing to their layer-number-dependent quantum effects and high charge separation efficiency. However, the correlation among the dimensionality, crystallinity, and photocatalytic activity of such 2D nanomaterials remains unclear. Herein, a Ag photoreduction technique coupled with microscopic analyses is employed to spatially resolve the photocatalytic activity of MoS
as a model catalyst. Interestingly, we find that only monolayer (1L)-MoS
is active for a Ag photoreduction reaction. The photocatalytic activity of 1L-MoS
is enhanced by a built-in electrical field originated from the MoS
/SiO
interface, instead of by the specific surface structure and quantum electronic state of 1L-MoS
. Furthermore, we observe photocatalytic active sites to be geometrically distributed on triangular 1L-MoS
crystals, wherein the Ag particles are preferentially deposited on the outermost zigzag edges and defective inner parts of the triangular grains. The degradation of photocatalytic activity and electron mobility with the formation of Mo(VI) species indicates that the species inhibit the in-plane diffusion of the photogenerated electrons to the reductive sites. The monolayer-selectivity, activation, and inactivation mechanisms, unveiled in this work, will offer future directions in designing 2D nanophotocatalysts.