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

• A novel lateral sulfur-gradient nanorod heterojunctions within Sb 2 (S x Se 1-x ) 3 photocathodes is constructed via vapor transport deposition process followed by postsulfurization. • The Sb 2 (S x Se 1-x ) 3 photocathode is first reported in photoelectrochemical water splitting. • The growth of Sb 2 (S x Se 1-x ) 3 nanorods with [101] preferred orientation improves efficiency of carriers spatial migration. • A cascaded band alignment for sulfur-gradient Sb 2 (S x Se 1-x ) 3 facilitates charge separation and transportation. Antimony selenide (Sb 2 Se 3 ) has recently gathered intense attention as a light-harvesting material due to its unique optoelectronic properties. The identical crystal structure of Sb 2 Se 3 and Sb 2 S 3 allows the novel heterostructure to be designed for efficient photoelectrochemical water splitting. Here, we first report the Sb 2 (S x Se 1-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 Sb 2 (S x Se 1-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 Sb 2 Se 3 nanorod photocathode (0.025 mA cm −2 ). The high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images clearly demonstrates that the Sb 2 (S x Se 1-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 Sb 2 (S x Se 1-x ) 3 photoelectrode has superior H 2 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.