Abstract
For economical water splitting and degradation of toxic organic dyes, the development of inexpensive, efficient, and stable photocatalysts capable of harvesting visible light is essential. In this study, we designed a model system by grafting graphitic carbon nitride (g-C3N4) (g-CN) nanosheets on the surface of 2D monoclinic bismuth vanadate (m-BiVO4) nanoplates by a simple hydrothermal method. This as-synthesized photocatalyst has well-dispersed g-CN nanosheets on the surface of the nanoplates of m-BiVO4, thus forming a heterojunction with a high specific surface area. The degradation rate for bromophenol blue (BPB) shown by BiVO4/g-CN is 96% and that for methylene blue (MB) is 98% within 1 h and 25 min, respectively. The 2D BiVO4/g-CN heterostructure system also shows outstanding durability and retains up to ∼95% degradation efficiency for the MB dye even after eight consecutive cycles; the degradation efficiency for BPB does not change too much after eight consecutive cycles as well. The enhanced photocatalytic activities of BiVO4/g-CN are attributed to the larger surface area, larger number of surface active sites, fast charge transfer and improved separation of photogenerated charge carriers. We proposed a mechanism for the improved photocatalytic performance of the Z-scheme photocatalytic system. The present work gives a good example for the development of a novel Z-scheme heterojunction with good stability and high photocatalytic activity for toxic organic dye degradation and water splitting applications.
Highlights
Due to the environmental and growing energy crisis, more attention has been paid to the exploration of highly efficient photocatalyst materials that can endorse the direct use of abundant solar energy resources to drive several reactions.[1]
0.1 g of photocatalyst sample was put into a glass tube containing 100 mL aqueous solution of methylene blue (MB) (5 mg LÀ1) or bromophenol blue (BPB) (5 mg LÀ1)
The detection experiment was similar to the measurement of photocatalytic degradation activity (2.3) except that the MB medium was replaced by 5 Â 10À4 mol LÀ1 terephthalic acid in dilute NaOH (2 Â 10À3 mol LÀ1) solution
Summary
Among the photo-driven semiconductors, m-BiVO4 has attracted more attention due to nontoxicity, relatively high photocatalytic activity and chemical stability for the degradation of organic compounds and water splitting,[13,14,15] but BiVO4 alone cannot degrade dyes and split water efficiently because its conduction band is located at a more positive potential than the potential of water reduction [0 eV vs. NHE; H+/H2]. We demonstrate the construction of an efficient 2D heterojunction BiVO4/g-CN photocatalyst model system with 2D-m-BiVO4 nanoplates covered by discrete g-CN nanosheets with controllable surface coverage. The heterojunction structures of BiVO4/ g-CN can be modi ed to attain a controllable coverage of g-CN on the surface of BiVO4 by the hydrothermal process. These features provide us with a good platform to get insights into the signi cance of heterostructure engineering for fabricating heterojunction photocatalysts. The obtained samples were named according to the amount of g-CN as m-BiVO4/g-CN (weight of g-CN)
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