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A series of novel BiPO4–BiOBrxI1−x p–n heterojunctions were successfully prepared by a facile solvothermal method. The morphology, structure and optical properties of photocatalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and ultraviolet visible diffuse reflectance spectroscopy. The visible light photocatalytic activities of BiPO4–BiOBrxI1−x heterojunctions were investigated by photocatalytically reducing CO2. After 4 hours of irradiation, the 5% BiPO4–BiOBr0.75I0.25 heterojunction showed the highest photocatalytic activity with the yields of CO and CH4 up to 24.9 and 9.4 μmol gcat−1 respectively. The improved photocatalytic activity may be due to the formation of BiPO4–BiOBrxI1−x p–n heterojunctions which can effectively restrict the recombination rate of the photoexcited charge carriers. Moreover, the energy band structure of BiPO4–BiOBrxI1−x heterojunctions could be easily adjusted by changing the mole ratio of I and Br. The possible mechanism of the enhancement of the photocatalytic performance was also proposed based on experimental and theoretical analysis. The present study may provide a rational strategy to design highly efficient heterojunctions with an adjustable energy band for environmental treatment and energy conversion.

In this article, the direct electrochemical behavior of nitrite at a Au nanoparticles (AuNPs)/carbon paper (CP) electrode made using a rapid electrochemical deposition method was investigated. The morphology of the AuNPs on the CP surface was characterized by scanning electron microscopy (SEM). The existence of the Au element was verified by energy dispersive spectroscopy (EDS). The crystal structure of the AuNPs was verified by X-ray diffraction (XRD). Cyclic voltammetry (CV) was applied to evaluate the electrochemical behavior of nitrite oxidation. Under the optimum conditions, the AuNPs/CP electrode exhibited a very strong response to nitrite; the oxidation peak current linearly increased with increasing nitrite in the ranges of 1 μM to 30 μM and 40 μM to 100 μM with correlation coefficients of 0.99883 and 0.99789, and a low detection limit of 0.093 μM. The suggested sensor demonstrated high sensitivity, good reproducibility and good recovery.

A visible-light-driven AgI/BiOIO3 nanohybrid photocatalyst was prepared via a successive hydrothermal-deposition process. The microstructures, morphologies, and composition of the obtained photocatalysts were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and energy-dispersive spectroscopy (EDS). The UV-vis diffuse reflectance spectrum (DRS) showed that the light absorption of the AgI/BiOIO3 nanohybrid is broadened from the UV to visible light region. The effect of AgI loading on BiOIO3 for photodegrading Rhodamine B (RhB) under visible light irradiation was investigated. The AgI/BiOIO3 nanohybrid exhibited superior photocatalytic activities to the bare AgI and BiOIO3, with the 30% AgI/BiOIO3 sample showing the highest photocatalytic degradation efficiency. Based on the energy band structure and the analysis of reactive species, the probable mechanism of enhanced photocatalytic reaction was discussed.

Novel, visible light-induced, Zn-doped BiOBr hierarchical nanostructures were successfully prepared by solvothermal methods. The photocatalytic activity of the samples was evaluated using RhB as the target pollutant. The Zn-doped BiOBr hierarchical nanostructures exhibited significantly enhanced visible light-induced photocatalytic efficiency for the degradation of RhB compared with pure BiOBr. The Zn-doped BiOBr with RZn = 0.1 (RZn is defined as the atomic ratio of Zn to Bi) showed the highest photocatalytic activity with decolorization efficiency of almost 100% after 15 min. The enhanced photocatalytic ability could be attributed to the efficient separation of photogenerated electron–hole pairs. Moreover, the role of the active species was also evaluated by adding different scavengers during the photodegradation of RhB. A possible mechanism for the enhancement of visible light performance of Zn-doped BiOBr photocatalysts was also proposed on basis of the experimental results.

In this study, C3N4/Zn1−xCdxS (0 ≤ x ≤ 1) heterostructures with adjustment of the band gap were successfully prepared by calcination and a hydrothermal synthesis method. The photocatalytic properties of C3N4/Zn1−xCdxS composite photocatalysts were evaluated by the photocatalytic degradation of RhB under visible light irradiation. The results showed that the combination of the two semiconductor photocatalysts (C3N4 and Zn1−xCdxS) greatly enhanced the photocatalytic degradation efficiency of RhB compared to the pure C3N4 and Zn1−xCdxS under visible light irradiation. Among them, the 0.1C3N4/Zn0.8Cd0.2S composite photocatalyst exhibited the highest photocatalytic activities with the degradation efficiency of RhB arriving to 97.9% within 90 min. The remarkable photocatalytic activity of the 0.1C3N4/Zn0.8Cd0.2S composite photocatalyst was mainly attributed to the appropriate band structure and the effective separation of photogenerated electron–hole pairs. Additionally, a possible basic mechanism of the composite semiconductor photocatalytic process was also discussed. Moreover, it was also investigated that O2˙− and h+ were the main reactive oxidative species in this photocatalytic process of the degradation of RhB on the 0.1C3N4/Zn0.8Cd0.2S heterostructure photocatalyst.