Quasi-1D Sb₂S₃@Cd_0.5Zn_0.5Se S-scheme heterojunction enables ultrafast interfacial charge transfer for photoelectrochemical water splitting

Sb₂S₃, as a semiconductor material with an optimal bandgap (∼1.7 eV) and high light absorption coefficient (>10⁵ cm⁻¹), exhibits broad application prospects in the field of photoelectrochemical (PEC) water splitting. However, its inherent deep-level defects lead to severe carrier recombination, significantly limiting the improvement of photoelectric conversion efficiency. To address this critical scientific challenge, this study innovatively employed a one-step vapor transport deposition (VTD) method to prepare orientation-controlled Sb₂S₃ nanorods on FTO substrates and achieved regulation of carrier behavior through the construction of an Sb₂S₃@Cd_xZn_1−xSe (x=0.5) heterojunction. Experimental results demonstrate that: The bimetallic Cd_0.5Zn_0.5Se component effectively promotes spatial separation of photogenerated carriers by forming an S-scheme heterojunction, increasing charge separation efficiency to 73 %. Under AM1.5 G simulated sunlight, the optimized Sb₂S₃@Cd_0.5Zn_0.5Se photoanode achieves a photocurrent density of 8.16 mA/cm² at 1.23 V vs. RHE, representing a nearly 15-fold enhancement compared to pure Sb₂S₃. Systematic electrochemical characterization confirms that the quasi-one-dimensional (quasi-1D) heterojunction has been demonstrated to significantly enhance carrier mobility. Simultaneously, synergistic effect between bimetallic active sites can reduce the OER reaction energy barrier and enhance reaction kinetics. Meanwhile, the constructed S-scheme heterojunction provides an ultrafast pathway (τ₃ = 0.83 ps) for interfacial charge transfer. This work offers new material design principles for developing highly efficient and stable chalcogenide-based photoanodes.