Constructing lateral sulfur-gradient Sb2(SxSe1-x)3 heterostructures for Sb2Se3 nanorod photocathodes with enhanced photoelectrochemical properties

Abstract

Antimony selenide (Sb2Se3) has recently gathered intense attention as a light-harvesting material due to its unique optoelectronic properties. The identical crystal structure of Sb2Se3 and Sb2S3 allows the novel heterostructure to be designed for efficient photoelectrochemical water splitting. Here, we first report the Sb2(SxSe1-x)3 photocathode with lateral heterojunctions within nanorod and sulfur-gradient band structure via vapor transport deposition process followed by postsulfurization, which is beneficial for the charge carrier spatial migration. The lateral Sb2(SxSe1-x)3 nanorod photocathode with [101] preferred orientation achieves a higher photocurrent density (0.8 mA cm−2), which is 30 times higher than that of pure Sb2Se3 nanorod photocathode (0.025 mA cm−2). The high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images clearly demonstrates that the Sb2(SxSe1-x)3 photocathode is a novel sulfur-gradient nanorod structure with the gradient composition of the S/Se ratio, which is a cascaded band alignment. The Sb2(SxSe1-x)3 photoelectrode has superior H2 generation activity (13.04 μmol cm−2 h−1) without any noble metal as a cocatalyst and shows favorable stability after a continuous test for 1 h under neutral conditions. This novel lateral gradient nanorod structure provides a new insight into the design of efficient optoelectronic devices for antimony chalcogenides.