Although photocatalytic hydrogen evolution (PHE) is ideal for solar-to-fuel conversion, it remains challenging to construct a highly efficient PHE system by steering the charge flow in a precise manner. Here we tackle this challenge by assembling 1T MoS₂ monolayers selectively and chemically onto (Bi₁₂O₁₇) end-faces of Bi₁₂O₁₇Cl₂ monolayers to craft two-dimensional (2D) Janus (Cl₂)-(Bi₁₂O₁₇)-(MoS₂) bilayer junctions, a new 2D motif different from van der Waals heterostructure. Electrons and holes from visible light-irradiated Bi₁₂O₁₇Cl₂ are directionally separated by the internal electric field to (Bi₁₂O₁₇) and (Cl₂) end-faces, respectively. The separated electrons can further migrate to MoS₂ via Bi–S bonds formed between (Bi₁₂O₁₇) and MoS₂ monolayers. This atomic-level directional charge separation endows the Janus bilayers with ultralong carrier lifetime of 3,446 ns and hence a superior visible-light PHE rate of 33 mmol h^-1 g^-1. Our delineated Janus bilayer junctions on the basis of the oriented assembly of monolayers presents a new design concept to effectively steer the charge flow for PHE.

Nature Communications 7, Article number: 11480 doi:10.1038/ncomms11480
Received 11 December 2015 Accepted 31 March 2016 Published 09 May 2016

http://www.nature.com/ncomms/2016/160509/ncomms11480/full/ncomms11480.html