Surface and Interface Engineering in Ag2S@MoS2 Core-Shell Nanowire Heterojunctions for Enhanced Visible Photocatalytic Hydrogen Production

An Ag2S@MoS2 core-shell nanowire heterojunction, facilely synthesized by simultaneous sulfuration of Ag nanowires (NMs) and growth of MoS2, is used as a model system to disclose how the surface and interface structures influence the photocatalytic activity. The Ag2S@MoS2 NWs with different loading amounts of MoS2 are used as photocatalysts for H-2 production. It is found that the highest photocatalytic activity is realized by a moderate loading amount of MoS2. A lower loading amount of MoS2 not only reduces the interfacial contact for insufficient electron-hole separation but also decreases the number of catalytic active sites for H-2 production, while a higher loading amount of MoS2 increases the light-shielding effect of Ag2S and extends the distance of electron transfer to the catalytic active sites for H-2 production. Furthermore, with the same loading amount of MoS2, Ag2S@MoS2 NWs also exhibit superior H-2 production activity in comparison with pre-Ag2S@MoS2 NWs with MoS2 grown on pre-synthesized Ag2S nanowires. The proposed reason is that the simultaneous sulfuration of Ag nanowires and growth of MoS2 results in an intimate contact between Ag2S and MoS2 for smooth interfacial charge transfer, while the two-step synthetic method leads to a lower quality of the MoS2-Ag2S interface and thus poor interelectron transfer. This work highlights the importance of a rational surface and interface design of semiconductor heterojunctions for realizing high-performance photocatalytic applications.