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Semiconductor-based photocatalysts have attracted considerable attention due to their great potential in environmental protection and solar energy conversion. Owing to their advantages of nontoxicity and low cost, ZnO and TiO2 are promising candidates for use as semiconductor photocatalysts; however, their development and large-scale applications have always been limited by poor absorption in the visible light region and high charge carrier recombination rates. In this work, hydrogenated ZnO inverse opals (IOs), hydrogenated TiO2 IOs, and their inverse-opal heterostructures with advanced visible light absorption properties were prepared. The hydrogenated ZnO IOs exhibit superior absorption capacity within the incident light range of 300–800 nm and a transient photocurrent density of around 1.4 mA cm−2, which is 2.8 times that of pristine ZnO IOs. Meanwhile, the photocurrent density of hydrogenated TiO2 increases by 6 times. Three different types of heterostructures were successfully fabricated to obtain the optimal photoelectrochemical performance using hydrogenated ZnO and hydrogenated TiO2 IOs. In particular, the heterostructure, comprising hydrogenated TiO2 inverse opals prepared by atomic layer deposition as the bottom-layer material and hydrogenated ZnO inverse opals prepared by electrochemical deposition as the top-layer material, exhibits a remarkable absorptivity reaching ∼94% across the entire visible light range except for the photonic band gap. It demonstrates an advanced photocurrent density of ∼1.77 mA cm−2 under an incident illumination of 100 mW cm−2. [ABSTRACT FROM AUTHOR]

The development of metamaterials for advanced optical functions, especially optical metamaterials that can be synthesized through a colloidal assembly route, holds significance in nanophotonic research. A broadband absorber based on hyperbolic metamaterials (HMMs) with cuboidal patterns, constructed using 3D assembled nanorod arrays, is fabricated with the assistance of SU‐8 photoresist filling, photolithography, and atomic layer deposition (ALD) of Pt. The formation of cuboidal patterns creates a rod‐based metamaterial waveguide, enabling slow‐light dispersion in the visible frequency range. Slow light frequencies can be adjusted by varying the metal thickness and metal type, while they are minimally influenced by the width of each cuboidal framework. In addition to the absorption attributed to the rod metamaterial waveguides, the gap between the neighboring cuboidal frameworks induces a coupling effect that enhances light capture. The presence of curving morphologies on the side of each cuboidal framework further enhances optical absorption. The optimized broadband rod metamaterial absorber in cuboidal patterns can achieve an average absorptivity of 96.9% in the 400–1100 nm wavelength range. [ABSTRACT FROM AUTHOR]