Orchestration of dual built-in electric field interfaces in a ternary copper oxide/zinc oxide/titanium dioxide step-scheme heterojunction for photocatalytic hydrogen sulfide degradation

초록

A central challenge in photocatalytic oxidation of gas-phase hydrogen sulfide (H2S) lies in constructing heterojunctions that synergistically promote charge separation without compromising the redox capability of the constituent semiconductors. This challenge is addressed by developing a ternary copper oxide (CuO)/zinc oxide (ZnO)/titanium dioxide (TiO2) step-scheme heterostructure with a CuO:ZnO:TiO2 molar ratio of 1:1:5, denoted as CZT-115, where precisely engineered interfaces create two distinct internal electric fields between p-type CuO and the two n-type semiconductors (ZnO and TiO2). These dual fields work cooperatively to direct interfacial charge migration, promoting the selective recombination of less energetic carriers while retaining high-energy electrons in CuO and high-energy holes in ZnO/TiO2 at spatially separated sites. Consequently, the photocatalyst achieves complete removal of 10 ppm H2S within 300 s under low-power ultraviolet light-emitting diode irradiation, yielding a clean air delivery rate of 17.6 ± 0.1 L min−1 and an exceptional apparent quantum yield of 0.77 ± 0.01%. The proposed mechanism is substantiated by photoelectrochemical and photoluminescence decay analyses, which confirm prolonged carrier lifetimes and suppressed recombination. In situ diffuse reflectance infrared Fourier transform spectroscopy, together with electron paramagnetic resonance spectroscopy, verifies the reaction pathway by revealing the oxidation of H2S to surface sulfate and the sustained co-generation of superoxide radicals (•O2−) and hydroxyl radicals (•OH). This work demonstrates that the strategic creation of multiple interfacial fields serves as a decisive design principle for engineering high-performance, multi-component photocatalysts.

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