Heterogeneous photocatalysis that employs photo-excited semiconductor materials to reduce water and oxidize toxic pollutants upon solar light irradiation holds great prospects for renewable energy substitutes and environmental protection. To utilize solar light effectively, the quest for highly active photocatalysts working under visible light has always been the research focus. Layered BiOX (X = Cl, Br, I) are a kind of newly exploited efficient photocatalysts, and their light response can be tuned from UV to visible light range. The properties of semiconductors are dependent on their morphologies and compositions as well as structures, and this also offers the guidelines for design of highly-efficient photocatalysts. In this review, recent advances and emerging strategies in tailoring BiOX (X = Cl, Br, I) nanostructures to boost their photocatalytic properties are surveyed.

The nanostructured AgI/BiOI composites were prepared by a facile, one-step, and low temperature chemical bath method with Bi(NO(3))(3), AgNO(3), and KI. Several characterization tools, such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), the Brunauer-Emmett-Teller (BET) surface area, photoluminescence (PL) spectra, and UV-vis diffuse reflectance spectroscopy, were employed to study the phase structures, morphologies, and optical properties of the samples. The PL intensity of AgI was greatly decreased when combined with BiOI, indicating the corresponding decreased recombination of the carriers. The photocatalytic properties of the as-prepared products were measured with the degradation of methyl orange and phenol at room temperature under visible light irradiation. The AgI/BiOI composites showed much higher photocatalytic performances over BiOI as well as AgI. It was also found that the AgI amount in the AgI/BiOI composites played an important role in the corresponding photocatalytic properties and the optimized ratio was obtained at 20%. The dramatic enhancement in the visible light photocatalytic performance of the AgI/BiOI composites could be attributed to the effective electron-hole separations at the interfaces of the two semiconductors, which facilitate the transfer of the photoinduced carriers. By the detection of hydroxyl radicals through a fluorescence technique, the photoinduced holes (h(VB)(+)) were considered to be the dominant active species in the photodegradation process, which was also deduced from the theoretical speculations. The photocatalytic performances of the AgI/BiOI composites were maintained for the cycling experiments. In addition, based on the XRD and XPS patterns of the AgI/BiOI composites before and after reaction, AgI was stable in the composites under visible irradiation, indicating that AgI/BiOI composites could be used as stable and efficient visible-light-induced photocatalysts.

Plasmonic materials have drawn emerging interest, especially in nontraditional semiconductor nanostructures with earth-abundant elements and low resistive loss. However, the actualization of highly efficient catalysis in plasmonic semiconductor nanostructures is still a challenge, owing to the presence of surface-capping agents in their synthetic procedures. To fulfill this, a facile non-aqueous procedure was employed to prepare well-defined molybdenum oxide nanosheets in the absence of surfactants. The obtained MoO(3-x) nanosheets display intense absorption in a wide range attributed to the localized surface plasmon resonances, which can be tuned from the visible to the near-infrared region. Herein, we demonstrate that such plasmonic semiconductor nanostructures could be used as highly efficient catalysts that dramatically enhance the hydrogen-generation activity of ammonia borane under visible light irradiation.

Heavily doped semiconductors have recently emerged as a remarkable class of plasmonic alternative to conventional noble metals; however, controlled manipulation of their surface plasmon bands toward short wavelengths, especially in the visible light spectrum, still remains a challenge. Here we demonstrate that hydrogen doped given MoO3 and WO3 via a facile H-spillover approach, namely, hydrogen bronzes, exhibit strong localized surface plasmon resonances in the visible light region. Through variation of their stoichiometric compositions, tunable plasmon resonances could be observed in a wide range, which hinge upon the reduction temperatures, metal species, the nature and the size of metal oxide supports in the synthetic H2 reduction process as well as oxidation treatment in the postsynthetic process. Density functional theory calculations unravel that the intercalation of hydrogen atoms into the given host structures yields appreciable delocalized electrons, enabling their plasmonic properties. The plasmonic hybrids show potentials in heterogeneous catalysis, in which visible light irradiation enhanced catalytic performance toward p-nitrophenol reduction relative to dark condition. Our findings provide direct evidence for achieving plasmon resonances in hydrogen doped metal oxide semiconductors, and may allow large-scale applications with low-price and earth-abundant elements.

A novel Ag/AgBr/BiOBr hybrid was prepared by a rational in situ ion exchange reaction between BiOBr hierarchical microspheres and AgNO(3) in ethylene glycol followed by light reduction, which displayed superior visible light driven photocatalytic activities in sterilization of pathogenic organism and degradation of organic dye compared to N-doped P25.