Oriented growth of ZnIn2S4/In(OH)3 heterojunction by a facile hydrothermal transformation for efficient photocatalytic H2 production

The construction of a composite photocatalyst with two suitable semiconductors is an effective strategy to improve the transport and separation of the photoexcited carrier pairs. Herein, it is the first time to report the new concept of anisotropic heterojunctions (H and J type) in layered ZnIn2S4 nanosheets as an example. Due to the anisotropic conductivity, the resistance of the electron transfer along ZnIn2S4 layers to a second semiconductor (J type heterojunction), is much less than that across the layers (H type heterojunction). As a result, the J type heterojunction can achieve higher photocatalytic activity than H type one. Furthermore, ZnIn2S4/In(OH)3 heterojunction with the J type structure was successfully fabricated by a simple approach, namely, In(OH)3 was selectively assembled at the rims of ZnIn2S4 nanosheets via hydrothermal transformation of the precursor precipitate with its mother solution obtained by adding Na2S into the solution of stoichiometric In3+ and excessive Zn2+. The intimate-contact J type heterojunction with in-situ photodeposited Pt shows efficient photocatalytic H2 evolution under visible irradiation, leading to a high apparent quantum yield of 38.3% at 420 nm with a low optimal Pt loading of 0.25 wt%. This work provides a new insight for the development of efficient heterojunction photocatalysts with layered semiconductors.