Design of Z-scheme heterojunction integrated two-compartment plasmonic fabry–perot cavities array with high solar absorptivity for atmospheric pure water splitting

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High charge combination and insufficient solar energy utilization are two main problems hindering the efficiency of photocatalytic hydrogen production. In this study, a two-compartment plasmonic moth-eye nanostructured Fabry-Perot (F-P) cavity integrating Z-scheme heterojunctions (TiO2/Au-WO3-Ag/nanohemisphere (NH)/Ag) is proposed to simultaneously reduce the charge recombination and achieve full-spectrum solar light utilization. The overall system comprises a large cavity structured from interconnected upper and under-layer F-P cavities, sharing a consistent nanostructure that facilitates plasmonic F-P enhanced Mie resonance. This design ensures the confinement of ultraviolet, visible, and infrared light within the upper cavity, broadening and intensifying light localization while exhibiting angle-insensitive characteristics. Since the Z-scheme heterojunction is positioned on the top half of the upper F-P cavity, the localized light interacts directly with the Z-scheme heterojunction (TiO2/Au-WO3), significantly boosting hydrogen production efficiency. As evidence, the TiO2/Au-100 nm WO3-Ag/NH/Ag configuration exhibits a solar absorptivity of 71.6 % and achieves H2 production rate of 5.2 mmol·m−2·h−1 for pure water splitting, which is 16.4 times higher than that of TiO2/Au alone under atmospheric condition and without the use of a sacrificial agent. More noteworthy is the fact that no hydrogen peak is detected on the pristine P25 under such conditions.