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Thirteen BaTiO3/γ-Bi2O3 heterojunctions (labeled as HS1 to HS13) were synthesized via solid phase method under different raw material ratio, calcination temperatures, and times with XRD, SEM, EDS mapping, TEM, XPS, and Raman spectra characterizations. The degradation efficiency of all samples is above 93% after 90 min upon initial concentration 10 mg/L tetracycline with the optimal HS6 as 97.95%. The first order reaction rate is above 0.059 min-1, faster than 0.031 min-1 of BaTiO3 and 0.011 min-1 of γ-Bi2O3. The catalyst masses, different water bodies, and pH values have a little effect on the final removal efficiency of tetracycline. Under the same test environment, the removal efficiency of 10 mg/L rhodamine B is over 73.62%, higher than BaTiO3 45.35% and γ-Bi2O3 63.34% and the best HS3, HS4, and HS5 samples have 100% degradation efficiency. The heterojunction can be recycled with excellent structural stability. The superior catalytic activity is attributed to electrons transfer along Z-type from γ-Bi2O3 conductor band (CB) to BaTiO3 valence band (VB) via work function and charge density difference analysis. The superoxide radical and hole are active substance in the process of tetracycline degradation while the rhodamine B removal is ascribed to superoxide and hydroxyl radicals attacking. The decomposition paths of two pollutants are revealed using high performance liquid chromatography mass spectroscopy (HPLC-MS).

A photocatalyst which consists of zero-dimension (0D) ZnFe2O4 (ZFO) and two-dimension (2D) Fe-doped g-C3N4 (Fe-CN) has been prepared successfully through a facile solvothermal method. The Fe doping into g-C3N4 lattice has been identified by both the infrared (IR) and X-ray photoelectron spectra (XPS), respectively. Introducing Fe into CN extends the spectral response to 700 nm while ZFO serves as a near infrared (NIR) photosensitizer of the Fe-CN component. The formation of Fe-CN heterostructure not only contributes to visible light absorption but also promotes the separation of photo-generated electron-hole pairs. Furthermore, the density functional theory (DFT) calculation indicated that the N2 molecules prefer to be adsorbed onto the Fe sites with a reduced potential barrier for N2 fixation. More importantly, the Fe atoms doped into the CN lattice acted as the reaction sites for accelerating photocatalytic N2 fixation reaction, which was also demonstrated by DFT. These factors lead to a high photocatalytic NH4+ generation rate of 25.3 mg g−1 h−1 under a full-spectrum irradiation, which is much higher than the value (4.4 mg g−1 h−1) of pure CN catalysts. This research might provide a novel approach for rationally designing full-spectrum-response N2 fixation photocatalyst.

Heterojunction composite plays an important role in enhancing photocatalysis activity through inhibit electron-hole recombination. In this paper, biphasic heterojunction BiVO4 and HoVO4 is insitu-grown and characterized through XRD, TEM, Raman, SEM, EDS, and XPS. These two structures form n type staggered band configuration using Mott-Schottky and DRS. Rhodamine B (RhB) photodegradation efficiency of the optimal sample is 90.7% after 90 min, higher than single BiVO4 54% and HoVO4 34.5%. The main reason is ascribed to fast photogenerated charge separation via O O bond connection according to photoluminescence, photocurrent response, and theory calculation. The RhB degradation path is revealed from intermediate products identification. Therefore this study unveils photodegradation dyes application of BiVO4/HoVO4 samples.