Crystallographic orientation and morphology control of Sb2Se3 to sensitize TiO2 nanotube arrays for enhanced photoelectrochemical performances

Abstract Coupling the appropriate light-absorbing materials with titanium dioxide (TiO2) nanotube arrays (TNA) can significantly enhance the Performance of photoelectrochemical (PEC) devices. Anisotropic antimony selenide (Sb2Se3) is a promising photo-absorber, but optimizing its crystallographic orientation and morphology concurrently is challenging. Herein, we control the growth of Sb2Se3 utilizing the space-confined effect of TNA with varying electrodeposition strategies to regulate the nucleation position. The [2 1 1]-oriented rod-like Sb2Se3/TNA photoanode prepared by pulse electrodeposition generates a photocurrent of 3.02 mA cm−2 at 1.23 V (versus RHE) in an electrolyte of pH 7, which is ∼4.1- and ∼30.0-time as those of [2 3 0]-oriented octahedron-like Sb2Se3/TNA and bare TNA photoanodes, respectively. Photoelectron can travel easily along the vertical direction via the covalent bond of (Sb4Se6)n ribbons without the recombination loss along the van der Waals direction due to the optimized Sb2Se3 [2 1 1] orientation and 1D-1D array structure. In situ irradiation X-ray photoelectron spectroscopy is used to directly monitor photoelectron transfer from Sb2Se3 to TNA at the heterojunctions, which ensures the promoted photoelectron separation and extraction in the rod-like Sb2Se3/TNA photoanode at the positive bias. This work provides a new strategy for optimally orienting anisotropic semiconductors and a fundamental insight into their photoelectron separation for design of efficient photoanodes.