We present a new type of dual-band terahertz metamaterial absorber formed by a patterned metallic strip and a dielectric layer on top of a metallic ground plane. It is found that besides a strong absorption in the fundamental resonance, a prominent high-order resonance with near-unity absorption is also unveiled. The origin of the induced dual-band absorption was elucidated. Importantly, the quality factor (Q) and the figure of merit (FOM) of the high-order resonance are 8.4 and 22.7 times larger than that of the fundamental resonance, respectively, which makes the proposed absorber to have significant potential in biological monitoring and sensing. Moreover, we demonstrate a dual-band and insensitive for two orthogonal polarizations terahertz absorber based on a metallic cross and a metallic ground plane separated by a dielectric layer. The Q and FOM of the high-order resonance are still larger than that of the fundamental resonance. The proposed absorbers appear to be very promising for solar cells, detection, and imaging applications.

A novel Ag₃PO₄/CeO₂ composite was fabricated by in situ wrapping CeO₂ nanoparticles with Ag₃PO₄ through a facile precipitation method. The photocatalytic properties of Ag₃PO₄/CeO₂ were evaluated by the photocatalytic degradation of MB and phenol under visible light and UV light irradiation. The photocatalytic activity of the composite is much higher than that of pure Ag₃PO₄ or CeO₂. The rate constant of MB degradation over Ag₃PO₄/CeO₂ is more than 2 times and 20 times than those of pure Ag₃PO₄ and CeO₂ under visible light irradiation, respectively. The Ag₃PO₄/CeO₂ composite photocatalyst also shows higher photocatalytic activity for the colorless phenol degradation compared to pure Ag₃PO₄. Moreover, the Ag₃PO₄/CeO₂ sample has almost no loss of photocatalytic activity after five recycles under the irradiation of visible light and UV light, indicating that the composite has good photocatalytic stability. The excellent photocatalytic activity of the Ag₃PO₄/CeO₂ composite is closely related to the fast transfer and efficient separation of electron–hole pairs at the interfaces of the two semiconductors derived from the matching band positions between CeO₂ and Ag₃PO₄. This newly constructed Ag₃PO₄/CeO₂ composite, with promising and fascinating visible light-driven photocatalytic activity as well as good stability, could find potential applications in environmental purification and solar energy conversion.

The oxygen evolution reaction (OER) activity of transition metal (TM)‐based (oxy)hydroxide is dominated by the number and nature of surface active sites, which are generally considered to be TM atoms occupying less than half of surface sites, with most being inactive oxygen atoms. Herein, based on an in situ competing growth strategy of bimetallic ions and OH⁻ ions, a facile one‐step method is proposed to modulate oxygen defects in NiFe‐layered double hydroxide (NiFe‐LDH)/FeOOH heterostructure, which may trigger the single lattice oxygen mechanism (sLOM). Interestingly, by only varying the addition of H₂O₂, one can simultaneously regulate the concentration of oxygen defects, the valence of metal sites, and the ratio of components. The proper oxygen defects promote synergy between the adsorbate evolution mechanism (AEM, metal redox chemistry) and sLOM (oxygen redox chemistry) of OER in NiFe‐based (oxy)hydroxide, practically maximizing the use of surface TM and oxygen atoms as active sites. Consequently, the optimal NiFe‐LDH/FeOOH heterostructure outperforms the reported non‐noble OER catalysts in electrocatalytic activity, with an overpotential of 177 mV to deliver a current density of 20 mA cm⁻² and high stability. The novel strategy exemplifies a facile and versatile approach to designing highly active TM‐LDH‐based OER electrocatalysts for energy and environmental applications.

Broadband absorbers have attracted considerable attention due to their great prospect for practical applications. The mechanism is usually a superposition of several sets of structures with different geometrical dimensions. Herein, we numerically investigate an unconventional to existing metamaterial-based broadband terahertz absorber based on the multilayer same-sized square plate structure. Greater than 99% absorption across a frequency range of 300 GHz with the central frequency ~ 1.96 THz can be obtained. The FWHM of this device can be up to 42% (with respect to the central frequency), which is 2.6 times greater than that of the single layer structure. Such a property is retained well at a very wide range of incident angles. The mechanism of the broadband absorber is attributed to longitudinal coupling between layers. The results of the designed metamaterial absorber appear to be very promising for solar cell, detection, and imaging applications.