Engineering of g-C3N4 nanoparticles/WO3 hollow microspheres photocatalyst with Z-scheme heterostructure for boosting tetracycline hydrochloride degradation

The emergence of antibiotics in surrounding environment has aroused serious concerns. In this work, a direct Z-scheme heterojunction was constructed by integrating g-C3N4 nanoparticles (g-C3N4 NP) with WO3 hollow microsphere composed of nanosheets (WO3 NHMs) and developed as highly efficient photocatalyst for tetracycline hydrochloride (TC) removal. The hierarchical structure of WO3 NHMs not only enhanced the optical absorption of catalyst by multiple reflecting and scattering of photons, but also promoted the adsorption of reactant molecules owing to the high surface area generated from the self-assembly interconnected nanosheets. The close contact between the interfaces of g-C3N4 NP and WO3 NHMs led to effective charge separation and transfer, and the optimized Z-scheme architecture preserved the oxidation and reduction capacity of each component to the greatest extent. After optimizing the component ratio, the corresponding g-C3N4 NP/WO3 NHMs hybrid delivered a significantly prominent photocatalysis towards TC degradation, whose kinetic constant was 2.42 times as high as that of bulk g-C3N4, and 6.88 folds as great as that of pristine WO3 NHMs. As far as we know, this is the first report of integrating C3N4 NP with WO3 NHMs to enhance TC photodegradation through the synergistic effect of light absorption, quantum efficiency and adjusted surface characteristics. The active species capture experiments testified that h+ and OH originated from the reaction of electrons with oxygen played important roles in the photocatalytic process. Under the attack of reactive oxygen species, TC underwent demethylation, deacylation, and ring-opening processes, and ultimately mineralized into CO2 and H2O. This research can open up a new way to develop photocatalysts with high TC removal efficiency through reasonable structural configuration.