In situ construction of hierarchical WO3/g-C3N4 composite hollow microspheres as a Z-scheme photocatalyst for the degradation of antibiotics

Elegant Z-scheme WO3/g-C3N4 composite hollow microspheres (CHMs) were constructed through precisely controlled in situ hydrolysis and a polymerization process consecutively. The formation of intact and welldefined hollow microspheres can be realized through optimizing the ratio of precursors for WO3 and g-C3N4. The shell of these hollow microspheres consist of well-distributed WO3 and g-C3N4 nanoparticles, and excellent heterojunctions with numerous interfaces and highly exposed oxidation-reduction active sites have thus been built. By virtue of this special architecture, more incident photons are expected to be trapped in the hollow cavities, which contribute to more electrons and holes available for photocatalytic reactions. Moreover, these photoinduced hole-electron pairs could be effectively separated, and the lifetime of charge carriers reaches 2.23 ns, which is obviously prolonged compared with the WO3. WO3/g-C3N4 CHMs as an optimized Z-scheme system retains the original oxidation and reduction abilities for the components without change of the oxidation and reduction potential. Combined with the long survival time of holes and electrons, this photocatalyst showed enhanced degradation rates towards tetracycline hydrochloride (TC-HCI) and ceftiofur sodium (CFS).