Construction Of Z-scheme System Research Articles

Construction of dual defect mediated Z-scheme photocatalysts for enhanced photocatalytic hydrogen evolution

The construction of Z-scheme system is a promising approach for photocatalytic hydrogen evolution (PHE). In this study, we fabricated a direct Z-scheme system consisting of defect-rich g-C3N4 nanosheets (DR-CNNS) crumpled nanosheets with defect-rich TiO2 (DR-TiO2) nanoparticles via a dual defective strategy. The optimized dual-defective rich TiO2/CNNS composite showed a superior PHE rate of ˜651.79 μmol/h with a turnover frequency of ˜419.3 h−1 as well as high stability and recyclability, which presented the highest value in single defective TiO2 or g-C3N4-based photocatalysts families reported previously. Furthermore, this protocol could also be extended to synthesize other dual defective g-C3N4/oxides (ZnO, SnO2, etc.) heterostructures. The improved photocatalytic performances could be ascribed to the following aspects: (1) rich dual defect, narrowing the band gap and providing more reactive sites for PHE; (2) intimate interface, facilitating interfacial migration and utilization of photogenerated charges; (3) Z-scheme structure, accelerating photogenerated electron-hole pair separation and thus leading to more efficient PHE. Our work highlights the critical role of defects in construction of Z-scheme system and provides the possibility of utilizing dual defective g-C3N4-based systems for other photocatalytic applications including CO2 reduction and water purification.

A new visible-light-induced Z-scheme photocatalytic system: Er3+:Y3Al5O12/(MoS2/NiGa2O4)-(BiVO4/PdS) for refractory pollutant degradation with simultaneous hydrogen evolution

A new visible-light-induced Z-scheme photocatalytic system, Er3+:Y3Al5O12/(MoS2/NiGa2O4)-(BiVO4/PdS), is designed and prepared by using hydrothermal and mixed-calcination methods And the prepared samples are characterized by X-ray diffractometer (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) and UV–vis absorption spectra. The photocatalytic activity is evaluated towards Orange G degradation with simultaneous hydrogen evolution under visible-light irradiation. The photocatalytic experiments indicate that the Er3+:Y3Al5O12/(MoS2/NiGa2O4)-(BiVO4/PdS) as photocatalyst displays very high photocatalytic activity. It can be ascribed to two sides. One is the use of Er3+:Y3Al5O12 offering ultraviolet-light to activate the wide-band gap NiGa2O4. Another is the construction of Z-scheme system between NiGa2O4 and BiVO4 which can result in a more efficient separation of photoexicited charge carriers, thus endowing it with much powerful oxidation and reduction capabilities. Moreover, the reusability study shows that the prepared photocatalyst can be effectively recycled for three repetitive cycles without an apparent deactivation. In addition, the possible Z-scheme mechanism of Er3+:Y3Al5O12/(MoS2/NiGa2O4)-(BiVO4/PdS) is also proposed, and further evidenced by photoluminescence (PL) spectra. The present work not only designs a new photocatalytic system but also well applies in photocatalytic degradation of refractory pollutant with simultaneous hydrogen evolution.