One-step in-situ fabrication by pulsed laser deposition for enhancing stability of Sb2Se3 photocathode

• One step in situ PLD creates an oxide free MoS 2 /Sb 2 Se 3 heterostructure. • In-situ growth completely prevents defective Sb 2 O 3 interfacial layers. • Type II band alignment robustly suppresses surface charge recombination. • The 23 nm MoS 2 layer acts as an optimal dual functional electrocatalyst. • The photocathode exhibits highly stable hydrogen evolution in strong acid. Antimony selenide (Sb 2 Se 3 ) is an earth-abundant and low-cost photocathode material with favorable optoelectronic properties, including a narrow bandgap of 1.0–1.3 eV and strong visible-to-near-infrared absorption. However, Sb 2 Se 3 typically shows limited operational stability in aqueous electrolytes, which is commonly associated with surface oxidation and increased interfacial recombination. Atomic layer deposition (ALD) titanium dioxide passivation mitigates photocorrosion, yet its low HER activity often necessitates wet cocatalyst loading that promotes interfacial Sb 2 O 3 and degradation. Here, a durable Sb 2 Se 3 photocathode is demonstrated using a bifunctional molybdenum disulfide (MoS 2 ) overlayer integrated by one-step, in-situ pulsed laser deposition (PLD). Sequential growth of Sb 2 Se 3 and MoS 2 within a single vacuum chamber enables air-free and solvent-free fabrication, preserving a clean, oxide-free interface. The MoS 2 overlayer provides both surface passivation and intrinsic HER catalysis, eliminating post-deposition wet processing. By tuning the MoS 2 thickness, an optimal balance between interfacial protection and charge-transfer efficiency is achieved, enabling sufficient exposure of MoS 2 edge sites that serve as active sites for hydrogen evolution. The optimized MoS 2 /Sb 2 Se 3 photocathode shows an onset potential shift of approximately 80 mV and delivers −8.3 mA cm −2 at −0.3 V versus RHE, compared with −0.78 mA cm −2 for bare Sb 2 Se 3 . The photocathode retains over 65% of its initial photocurrent after 30 h of continuous operation in 0.5 M sulfuric acid.