yao Xu

Enhancing visible-light photocatalytic activity of g-C3N4 by doping phosphorus and coupling with CeO2 for the degradation of methyl orange under visible light irradiation

CeO2/P-C3N4 composite photocatalysts were designed by doping phosphorus and coupling with CeO2 species. The structure and optical properties of the as-prepared samples were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. The photocatalytic activity of the CeO2/P-C3N4 was evaluated by photocatalytic degradation of methyl orange (MO) under visible light irradiation (λ > 420 nm). The results indicated that the optimum photocatalytic activity of CeO2/P-C3N4 at a weight content of 13.8% CeO2 for the degradation of MO was 7.4 and 4.9 times as high as that of pure CeO2 and g-C3N4, respectively. The remarkable enhancement of photocatalytic activity could be attributed to the synergistic effect between CeO2 and P-C3N4, which was found to extend the visible light absorption range, enhance visible light absorption and improve photogenerated electron–hole pairs separation efficiency after doping phosphorus and coupling with CeO2. Additionally, the superoxide radical anions (˙O2−) and holes (h+) were considered as the main reactive species during the photodegradation MO process, and a possible photocatalytic mechanism over CeO2/P-C3N4 composite photocatalyst was proposed based on the experimental results.

Synthesis and characterization of Z-scheme In2S3/Ag2CrO4 composites with an enhanced visible-light photocatalytic performance

The low photocatalytic performance of a single photocatalyst mainly originates from a fast recombination of photogenerated charge carriers. Rational design and construction of direct solid-state Z-scheme photocatalysts is an effective approach to improve the charge separation efficiency of photogenerated electron–hole pairs. In this study, a series of Z-scheme In2S3/Ag2CrO4 composite photocatalysts with a different content of In2S3 were synthesized using a facile chemical precipitation method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL) spectroscopy and photoelectrochemical measurements. The photocatalytic activity of the In2S3/Ag2CrO4 composites was evaluated through photodegradation of methyl orange (MO) under visible light irradiation (λ > 420 nm). The results demonstrate that the optimal Z-scheme In2S3/Ag2CrO4 composite with a theoretical weight content of 4.0% In2S3 provided a photodegradation rate constant for MO of 0.0087 min−1, which is approximately 2.8 and 5.4 times higher than those of pure In2S3 and Ag2CrO4, respectively. The enhanced photocatalytic activity may be attributed to the formation of a Z-scheme system between In2S3 and Ag2CrO4, effectively prolonging the lifetime of the photoinduced electrons generated by In2S3 and the photoinduced holes generated by Ag2CrO4, which was subsequently confirmed using active species trapping experiments, photoluminescence techniques and photoelectrochemical assays. This work may be useful for rationally designing new types of Z-scheme photocatalysts and provides some illuminating insights into the Z-scheme charge transfer mechanism for application in the solar energy conversion and environmental remediation fields.

Facile fabrication and enhanced visible-light photocatalytic activity of In2O3/Ag2CrO4 composites

A series of visible-light-driven In2O3/Ag2CrO4 composites were fabricated by a facile chemical precipitation method and characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and photoluminescence (PL) spectroscopy. The In2O3/Ag2CrO4 composites showed much higher photocatalytic activity and stability than those of individual Ag2CrO4 and In2O3 for the photodegradation of methyl orange (MO) under visible light irradiation (λ > 420 nm). Excitingly, the optimum degradation rate constant of the In2O3/Ag2CrO4 composite at a weight content of 4.0% In2O3 for the degradation of MO was 8.8 and 3.3 times as high as that of individual In2O3 and Ag2CrO4, respectively. The enhancement in photocatalytic activity and stability was predominantly attributed to the effective separation and transfer of photogenerated charge carriers as a result of the formation of a Z-scheme system composed of In2O3, Ag and Ag2CrO4. Furthermore, radical trap experiments depicted that both the holes and superoxide radical anions are main oxidative species of the In2O3/Ag2CrO4 composite for MO degradation under visible light irradiation. Finally, based on the experimental results, a possible photocatalytic mechanism has been proposed.

Molybdenum-doped few-layered SnS2 architectures with enhanced electrochemical supercapacitive performance

Molybdenum doped few-layered SnS2 (m-SnS2) architectures have been fabricated via a facile hydrothermal route. The results indicate that the resultant m-SnS2 is composed of numerous few-layered nanosheets and possesses a hierarchical architecture with mesoporous features. When evaluated as an electrode material for supercapacitors, the m-SnS2 architecture exhibits obviously enhanced electrochemical performance with high specific capacitance, good cycling stability and rate capability in comparison with the bare SnS2 sample. It is believed that the superior electrochemical properties can be attributed to the robust mesoporous architectures with large surface area, the few-layered nature as well as other positive factors such as expanded interlayer space and rich dislocations which originate from the molybdenum doping.

Fabrication and characterization of high efficiency and stable Ag3PO4/TiO2 nanowire array heterostructure photoelectrodes for the degradation of methyl orange under visible light irradiation

Ag3PO4/TiO2 nanowire array (ATNWs) heterostructure photoelectrodes were prepared by a sequential chemical bath deposition. The structure and optical properties of the ATNWs were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy and electrochemical techniques. The photocatalytic activity of the ATNWs was evaluated by photocatalytic degradation of methyl orange (MO) under visible light irradiation (λ > 400 nm). The results showed that Ag3PO4 nanoparticles were successfully formed on the surface of the TiO2 nanowires (NWs) causing no damage to the ordered structure of the nanowires. The p-type Ag3PO4 nanoparticles deposited on the n-type TiO2 NWs could promote the transfer of photo-generated holes, which inhibited the recombination of electrons and holes effectively, leading to a significant increase in the lifetime of the charge carriers. Moreover, the ATNWs show much higher photocatalytic activity and stability than that of the pure TiO2 NWs for the photocatalytic degradation of MO. The enhanced photocatalytic activity could be attributed to the visible-light photocatalytic activity of Ag3PO4 and the heterostructure between Ag3PO4 and TiO2.

Synthesis and enhanced photocatalytic activity of a BiOI/TiO2 nanobelt array for methyl orange degradation under visible light irradiation

A novel heterojunction by facet coupling of BiOI onto TiO2 nanobelt arrays (NBAs) as a visible light photocatalyst was achieved through a hydrothermal method. The BiOI/TiO2 heterojunction had been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), UV-Vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy and electrochemical techniques. The BiOI/TiO2 heterojunction presented a significantly enhanced photocatalytic performance in degrading methyl orange (MO) under visible light irradiation. The obviously reduced electron–hole recombination rates of BiOI/TiO2 were demonstrated from PL spectroscopy measurements and the photoelectrochemical evaluation. The 2-BiOI/TiO2 NBAs sample displays the highest photocatalytic activity toward the degradation of the MO solution under visible-light irradiation, corresponding to an apparent pseudo-first-order rate constant kapp of 0.0973 min−1. It is 5 times more than that of a pure TiO2 nanobelt array photocatalyst.

Synthesis of a hierarchical MoSe2/C hybrid with enhanced electrochemical performance for supercapacitors

A facile one-step hydrothermal strategy was successfully developed to fabricate a 3D hierarchical MoSe2/C hybrid with triethylene glycol as a structure-directing agent and carbon source. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy and nitrogen adsorption–desorption. The experiment results indicate that the hierarchical porous MoSe2/C hybrid is composed of numerous few-layered MoSe2 nanosheets and amorphous carbon derived from the decomposition of the triethylene glycol. As a consequence, the obtained hierarchical MoSe2/C electrode exhibited superior electrochemical supercapacitive performances such as high specific capacitance, excellent cyclic stability and significantly enhanced rate capability in comparison with the bare MoSe2. The prominent electrochemical performance could be attributed to the robust hierarchical porous architectures with large surface areas and effective integration with conductive amorphous carbon.

Dramatic visible light photocatalytic degradation due to the synergetic effects of TiO2 and PDA nanospheres

Dramatic visible light photocatalytic activity was obtained for the degradation of methyl orange using TiO2 photocatalysts modified with polydopamine (PDA) nanospheres. The high photocatalytic activity is due to the synergetic effect between PDA and TiO2, which promote the migration efficiency of photogenerated carriers at the interface of PDA and TiO2.