Hot electron injection and electron relay integrated into PbS/Au/ZnO sandwich nanotube arrays boost visible-light responsive photoelectric property

Abstract In this study, by integrating Schottky heterojunction and electron relay into a ternary heterostructure, we demonstrate a visible light responsive photoanode of PbS/Au/ZnO sandwich nanotube arrays (NTAs) for photoelectrochemical water splitting. The localized surface plasmon resonance (LSPR) of Au nanoparticles (NPs) and the superior visible light harvesting ability of PbS NPs enable the fabricated PbS/Au/ZnO sandwich NTAs exhibit substantially improved visible light absorption from 400 to 800 nm. Experimental measurements reveal that the PbS/Au/ZnO sandwich nanotube array photoanode presents significantly enhanced photoelectrochemical (PEC) capability for water splitting. The photocurrent density of the PbS/Au/ZnO sandwich NTAs increases by 6 and 2 times, respectively, in contrast with the Au/ZnO and PbS/ZnO nanotube array photoanodes. Furthermore, the photoconversion efficiency is 18 and 5 times that of the Au/ZnO and PbS/ZnO heterojunction nanotube array photoanodes, respectively. Comparative studies for the PEC water splitting apparently demonstrate that the Au NPs plays two crucial roles as a provider to inject hot electrons into the conduction band of ZnO and an electron relay to transfer the photoinduced electrons from PbS to ZnO within the PbS/Au/ZnO sandwich NTAs. The synergetic effects of the LSPR and electron relay of the Au nanoparticle enable the photoexcited electrons within the PbS/Au/ZnO sandwich NTAs to be effectively used to conduct water splitting reaction, leading to drastically enhanced PEC property.