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Black TiO2 nanobelts/g-C3N4 nanosheets laminated heterojunctions (b-TiO2/g-C3N4) as visible-light-driven photocatalysts are fabricated through a simple hydrothermal-calcination process and an in-situ solid-state chemical reduction approach, followed by the mild thermal treatment (350 °C) in argon atmosphere. The prepared samples are evidently investigated by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption, and UV-visible diffuse reflectance spectroscopy, respectively. The results show that special laminated heterojunctions are formed between black TiO2 nanobelts and g-C3N4 nanosheets, which favor the separation of photogenerated electron-hole pairs. Furthermore, the presence of Ti3+ and g-C3N4 greatly enhance the absorption of visible light. The resultant b-TiO2/g-C3N4 materials exhibit higher photocatalytic activity than that of g-C3N4, TiO2, b-TiO2 and TiO2/g-C3N4 for degradation of methyl orange (95%) and hydrogen evolution (555.8 μmol h−1 g−1) under visible light irradiation. The apparent reaction rate constant (k) of b-TiO2/g-C3N4 is ~9 times higher than that of pristine TiO2. Therefore, the high-efficient laminated heterojunction composites will have potential applications in fields of environment and energy.

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Oxygen-doped MoS2 nanospheres/CdS quantum dots/g-C3N4 nanosheets are synthetized through hydrothermal and chemical bath deposition–calcination processes. The prepared materials are characterized by X-ray diffraction transient-state photoluminescence spectra, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical experiment. These results show that the ternary composite material has longer lifetime of photogenerated carriers and more active sites, thereby enhancing photocatalytic performance. CdS quantum dots act as a bridge between the intermediate transport charges in the ternary composite. The oxygen defect engineering prolongs the lifetime of carriers obviously, which is confirmed by transient-state photoluminescence. Moreover, the photocatalytic H2 evolution and photodegradation of bisphenol A for MoS2/CdS/g-C3N4 is up to 956 μmol h–1 g–1 and 95.2% under visible-light irradiation, respectively. Furthermore, excellent photocatalytic activity can be ascribed to the synergistic effect of defect engineering and formation of ternary heterostructures, which is with broad-spectrum response, longer lifetime of photo-induced electron–holes, and more surface active sites.

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