2D/2D type-II Cu2ZnSnS4/Bi2WO6 heterojunctions to promote visible-light-driven photo-Fenton catalytic activity

In this work, a set of novel Cu2ZnSnS4/Bi2WO6 (CZTS/BWO) two-dimensional (2D)/two-dimensional (2D) type-II heterojunctions with different CZTS weight ratios (1%, 2%, and 5%) were successfully synthesized via a brief secondary solvothermal process. The successful formation of the heterojunctions was affirmed by characterization methods such as X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. The photocatalytic activity results showed that the prepared CZTS/BWO heterojunctions had excellent photocatalytic behaviors for organic degradation, especially when the mass fraction of CZTS with respect to BWO in the composite was 2%. Moreover, the addition of hydrogen peroxide (H2O2) could further improve the dye and antibiotic degradation efficiencies. The reinforced photocatalytic and photo-Fenton degradation performance were primarily attributable to the introduction of BWO, which afforded increased active sites, expanded the solar spectral response range, and accelerated the cycle of Cu(II)/Cu(I); after four cycling times, its catalytic activity did not decrease significantly. In addition, reasonable hypotheses of the photocatalytic and photo-Fenton catalytic mechanisms were formulated. This study is expected to provide a visual approach for designing a novel photo-Fenton catalyst to jointly utilize the photocatalytic and Fenton activities, which can be better applied to the purification of residual organics in wastewater.