One-step In-situ Fabrication by Pulsed Laser Deposition for Enhancing Stability of Sb2Se3 Photocathode

Abstract

Photoelectrochemical (PEC) water splitting is a promising technology for sustainable hydrogen production with zero carbon emissions. Antimony selenide (Sb2Se3) is an attractive photocathode material due to its narrow bandgap (~1.2 eV) and strong visible to near-infrared absorption, but it suffers from intrinsic instability during operation, mainly because of surface oxidation and the resulting rapid performance degradation. However, TiO2 protection has several intrinsic drawbacks. ALD processes that use H2O as an oxidant can partially oxidize Sb2Se3 at the interface, initiating undesirable surface reactions. In addition, the intrinsically low hydrogen evolution reaction (HER) activity of TiO2 necessitates the use of additional catalysts, which are typically deposited through wet-chemical processes such as hydrothermal growth or electrodeposition. These steps unavoidably expose Sb2Se3 to aqueous environments, promote interfacial Sb2O3 formation, and consequently lead to Fermi-level pinning, instability, and accelerated performance degradation. In this study, we demonstrate a durable MoS2/Sb2Se3 photocathode fabricated by a one-step in-situ pulsed laser deposition (PLD) process, which enables solvent-free, air-free growth and effectively suppresses Sb2Se3 degradation. MoS2 is chosen as the overlayer material because it exhibits robust chemical stability in strongly acidic electrolytes under HER operation, forms a favorable band alignment with Sb2Se3, and provides abundant edge sites that are highly active for the hydrogen evolution reaction. By precisely tuning the MoS2 overlayer thickness through the number of PLD pulses, we identify an optimal balance between interfacial protection and charge-transfer efficiency, thereby achieving both enhanced stability and high HER activity. As a result, the MoS2/Sb2Se3 photocathode delivers a photocurrent density of −8.3 mA cm−2 at −0.3 V versus the reversible hydrogen electrode (VRHE) and maintains its performance for over 10 hours in strongly acidic conditions. This work underscores the importance of in-situ dry fabrication routes for constructing oxide-free, catalytically active interfaces and offers a promising strategy for realizing efficient and durable Sb2Se3-based PEC photoelectrodes.