All solid-solution S-scheme heterojunction with adjustable internal electric field for highly efficient photocatalytic activity

Developing an efficient photocatalyst is the key to realize the practical application of photocatalysis. The S-scheme heterojunction has great potential in photocatalysis due to its unique charge-carrier migration pathway, effective light absorption and high redox capacity. However, further enhancing the built-in electric field of the S-scheme, accelerating carrier separation, and achieving higher photocatalytic performance remain unresolved challenges. Herein, based on the continuously adjustable band structure of continuous solid-solution, a novel 0D/2D all solid-solution S-scheme heterojunction with adjustable internal electric field was designed and fabricated by employing a solid-solution of Zn_xCd_1–xS and Bi₂Mo_yW_1–yO₆ respectively as reduction and oxidation semiconductors. The synergistic optimization of effective light absorption, fast photogenerated carrier separation, and high redox potential leads can be tuned to promote photocatalytic activity. Under visible light, the S-scheme system constructed by Zn_0.4Cd_0.6S quantum dot (QDs) and Bi₂Mo_0.2W_0.8O₆ monolayer exhibits a high rate for photocatalytic degradation C₂H₄ (150.6 × 10^–3 min^–1), which is 16.5 times higher than that of pure Zn_0.4Cd_0.6S (9.1 × 10^–3 min^–1) and 53.8 times higher than pure Bi₂Mo_0.2W_0.8O₆ (2.8 × 10^–3 min^–1). Due to the unique charge-carrier migration pathway, photo-corrosion of Zn_xCd_1–xS is further inhibited simultaneously. In-situ irradiation X-ray photoelectron spectroscopy, photoluminescence spectroscopy, time-resolved photoluminescence, transient absorption spectroscopy and electron paramagnetic resonance provide compelling evidence for interfacial charge transfer via S-scheme pathways, while in-situ diffuse reflectance infrared Fourier transform spectroscopy identifies the reaction pathway for C₂H₄ degradation. This novel S-scheme photocatalysts demonstrates excellent performance and potential for the practical application of the fruits and vegetables preservation at room temperatures.