Scalable Low-Band-Gap Sb2Se3 Thin-Film Photocathodes for Efficient Visible–Near-Infrared Solar Hydrogen Evolution

Abstract

A highly efficient low-band-gap (1.2–0.8 eV) photoelectrode is critical for accomplishing efficient conversion of visible–near-infrared sunlight into storable hydrogen. Herein, we report an Sb 2 Se 3 polycrystalline thin-film photocathode having a low band gap (1.2–1.1 eV) for efficient hydrogen evolution for wide solar-spectrum utilization. The photocathode was fabricated by a facile thermal evaporation of a single Sb 2 Se 3 powder source onto the Mo-coated soda-lime glass substrate, followed by annealing under Se vapor and surface modification with an antiphotocorrosive CdS/TiO 2 bilayer and Pt catalyst. The fabricated Sb 2 Se 3 (Se-annealed)/CdS/TiO 2 /Pt photocathode achieves a photocurrent density of ca . −8.6 mA cm –2 at 0 V RHE, an onset potential of ca . 0.43 V RHE, a stable photocurrent for over 10 h, and a significant photoresponse up to the near-infrared region ( ca . 1040 nm) in near-neutral pH buffered solution (pH 6.5) under AM 1.5G simulated sunlight. The obtained photoelectrochemical performance is attributed to the reliable synthesis of a micrometer-sized Sb 2 Se 3 (Se-annealed) thin film as photoabsorber and the successful construction of an appropriate p–n heterojunction at the electrode–liquid interface for effective charge separation. The demonstration of a low-band-gap and high-performance Sb 2 Se 3 photocathode with facile fabrication might facilitate the development of cost-effective PEC devices for wide solar-spectrum utilization.