Full-Spectrum-Responsive Au@Cu₇S₄-Decorated Monoclinic TiO₂ Nanowires for Solar Hydrogen Production

Developing photocatalysts that can efficiently capture light across a broad spectrum, from ultraviolet to near-infrared, is crucial for maximizing solar energy utilization. Such broad-spectrum responsiveness enhances solar energy utilization in photocatalysis, enabling a more sustainable and efficient pathway for hydrogen production. The limited availability of photocatalysts capable of responding to near-infrared irradiation underscores the urgent need for the development of versatile near-infrared-responsive photocatalysts. In this work, TiO₂ nanowires in the monoclinic phase, a less common crystallographic form of TiO₂, were synthesized, followed by a decoration with Au particles surrounded by a hollow Cu₇S₄ shell. The resulting TiO₂-Au@Cu₇S₄ heterostructure nanowires exhibited remarkable properties conducive to efficient solar hydrogen production. The band structure alignment among TiO₂, Au, and Cu₇S₄ induced a Z-scheme charge separation mechanism, which boosted both the carrier utilization efficiency and redox powers. Furthermore, incorporating Au@Cu₇S₄ significantly broadened the absorption capability of TiO₂ into the visible and near-infrared spectral ranges. This enhancement arose primarily from the inherent bandgap absorption of Cu₇S₄, as well as the plasmonic properties of Au and Cu₇S₄ components. Additionally, the hydrophilic surface of TiO₂-Au@Cu₇S₄ enhanced the water accessibility, which promoted interactions between water molecules and the photocatalyst surface. By integrating these characteristics, TiO₂-Au@Cu₇S₄ heterostructure nanowires demonstrated noteworthy efficiency in solar hydrogen production across a wide spectral region, achieving notable apparent quantum yields of 10.51% at 300 nm, 4.38% at 450 nm, 4.17% at 800 nm, and 3.66% at 1800 nm. Notably, TiO₂-Au@Cu₇S₄ surpassed all of the near-infrared-responsive TiO₂-based photocatalysts ever reported in hydrogen production. The findings can provide a practical strategy to design a full-spectrum-responsive TiO₂-based photocatalyst for widespread use in photocatalytic processes.