Graphene quantum dots as efficient, metal-free, visible-light-active photocatalysts

This paper reports on new applications of water-dispersible graphene quantum dots(GQDs) that we recently developed. The prepared GQDs not only show broad absorption in the visible spectrum from 400 to 700 nm, but can also serve as smart photosensitizers with high singlet oxygen(1O2) production under visible-light irradiation(≥420 nm). We showed that the prepared GQDs can potentially be used as a metal-free, visible-light-active, sensitized photocatalyst via energy transfer mechanism, in which the light energy was converted by GQDs to produce 1O2, which can kill nearby microorganisms and degrade organic dyes.

PbCrO_4 yellow-pigment nanorods: An efficient and stable visible-light-active photocatalyst for O_2 evolution and photodegradation

Here, PbCrO4 nanorods, a commonly used and low-cost yellow pigment, was synthesized via a simple pre-cipitation reaction and can serve as a highly efficient oxygen production and photodegradation photocatalyst. The obtained PbCrO4 nanorods exhibit excellent stability and pho-tocatalytic performance for O2 evolution from water. The production rate is approximately 314.0μmol h^-1 g^-1 under visible light, and the quantum efficiency is approximately 2.16% at 420±10 nm and 0.05% at 600±10 nm. In addition, the PhCrO4 shows good degradation performance for methylene blue, methyl blue, methyl orange and phenol under visible-light irradiation. These results indicate that it is potential to fabricate an effective, robust PbCrO4 photocatalyst by trans-forming heavy-metal pollutants Pb（II） and Cr（VI） into a highly efficient O2 evolution and photodegradation material. This strategy which uses pollutant to produce clean energy and degrade contaminants is completely green and environmentally benign, and thus could be a promising way for practical environmental applications. Keywords： 02 evolution, pollutant, PbCrO4 nanorods, visible-light-active, photocatalyst

Fabrication of novel ZnO/MnWO_4 nanocomposites with p-n heterojunction: Visible-light-induced photocatalysts with substantially improved activity and durability

We report, for the first time, binary ZnO/MnW04 nanocomposites with p-n heterojunction fabricated by a simple ultrasonic-calcination route. The phase structure, morphology, and optical along with tex- tural properties were comprehensively characterized. The photocatalytic performance was studied via degradations of rhodamine B, methyl blue and methyl orange （RhB, MB, MO）, and fuchsine pollutants under visible-light illumination. The ZnO/MnW04 nanocomposites exhibited better photocatalytic per-formance than their single components and the nanocomposite with 30 wt% MnW04 showed the highest activity. Photocatalytic performance of this nanocomposite is 22.5, 17.7, 26.8, and 23.9 times higher than that of the ZnO sample in degradations of RhB, MB, MO, and fuchsine dyes, respectively. The improved photocatalytic performance was ascribed to the formation ofp-n heterojunction between ZnO and MnW04 with high charge separation efficiency as well as strong visible-light absorption ability. The possible mechanism for the improved photocatalytic performance was proposed. This study revealed that the novel ZnO/MnW04 p-n heterojunction can act as a promising visible-light-active photocatalyst for environmental applications.