Enhancement of visible-light photocatalytic activities of BiVO4 coupled with g-C3N4 prepared using different precursors

Graphitic carbon nitride: a sustainable photocatalyst for organic pollutant degradation and antibacterial applications

Recently, graphitic carbon nitride (GCN) has been found to be of great interest in various sustainable applications. In this study, a simple preparation method using urea was utilized to synthesize GCN. In order to understand various morphological, structural, and optical aspects of the as-prepared sample, GCN was characterized using X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, Brunauere-Emmette-Teller (BET), scanning electron microscopy (SEM), and diffused reflectance spectra (DRS) analysis. The visible-light-driven photocatalytic activity of prepared GCN was analyzed for various cationic dyes (Crystal violet, rose bengal, rhodamine B, auramine O, methylene blue) and anionic dyes (phenol red, xylenol orange, cresol red, methyl orange). The calculated efficiencies of degradation and values of apparent rate constant for all dye samples suggested that cationic dyes are more actively degraded using GCN than anionic dyes. In addition, GCN was further analyzed for its splendid antibacterial activity against pathogenic bacteria (Klebsiella pneumonia and Escherichia coli). The synthesized photocatalyst holds a bright scope for the efficient remediation of organic pollutants and bacterial disinfection in wastewater. Graphical abstract.

g-C3N4/CeO2 Binary Composite Prepared and Its Application in Automobile Exhaust Degradation

Vehicle exhaust seriously pollutes urban air and harms human health. Photocatalytic technology can effectively degrade automobile exhaust. This work prepared g-C₃N₄/CeO₂ photocatalytic material by constructing heterojunctions. Four kinds of g-C₃N₄/CeO₂ composite photocatalytic materials with different mass ratios were prepared. An indoor exhaust gas purification test was carried out under natural light and ultraviolet light irradiations. The optimum mass ratio of g-C₃N₄ material and CeO₂ material was determined by evaluating the exhaust gas degradation effective. Moreover, the structure and morphology of the g-C₃N₄/CeO₂ composite were investigated with microscopic characterization experiments (including XRD, TG-DSC, FT-IR, UV-Vis, SEM and XPS). The results obtained were that the optimum mass ratio of g-C₃N₄ material to CeO₂ material was 0.75. The degradation efficiencies under ultraviolet irradiation in 60 min for HC, CO, CO₂, NO_X were 7.59%, 12.10%, 8.25% and 36.82%, respectively. Under visible light conditions, the degradation efficiency in 60 min for HC, CO, CO₂ and NO_X were 15.88%, 16.22%, 10.45% and 40.58%, respectively. This work is useful for purifying automobile exhaust in the future.

Enhanced photocatalytic removal of amoxicillin with Ag/TiO2/mesoporous g-C3N4 under visible light: property and mechanistic studies

In present study, an efficient ternary Ag/TiO₂/mesoporous g-C₃N₄ (M-g-C₃N₄) photocatalyst was successfully synthesized through depositing Ag nanoparticles (NPs) on the surface of TiO₂/M-g-C₃N₄ heterojunction. Ag/TiO₂/M-g-C₃N₄ nanocomposite displayed the highest degradation efficiency for amoxicillin (AMX) compared to TiO₂/M-g-C₃N₄ heterojunction, M-g-C₃N₄, and bulk-g-C₃N₄ (B-g-C₃N₄). The removal efficiency of AMX in real situation, surface water (SW), hospital wastewater (HW), and waste water treatment plant (WWTP) also were studied to illustrate the effectiveness of Ag/TiO₂/M-g-C₃N₄ photocatalysts. The vulnerable atoms in AMX structure were revealed through DFT calculation. Additionally, the dominating active groups produced in time of the photocatalytic procedure were determined on account of free radical trapping experiments and ESR spectra. The mechanism of photocatalytic degradation was proposed and verified. The transfer of the electrons and the inhibition of the recombination of photogenerated electron-holes were enhanced effectively under the synergistic effect of the Ag NPs and TiO₂. As a consequence, the catalytic activity of the composite was improved under visible light.

The simultaneous removal of heavy metals and organic contaminants over a Bi2WO6/mesoporous TiO2 nanotube composite photocatalyst

In this study, Bi₂WO₆/mesoporous TiO₂ nanotube composites (BWO/TNTs) were successfully synthesized to remove the heavy metal Cr(vi) and refractory organic compound dibutyl phthalate (DBP) from contaminated water under visible light. Coupling TNTs with BWO can greatly improve the photocatalytic activity of the catalyst for treating Cr(vi)–DBP mixed pollutants because of synergetic effects from Cr(vi) and DBP. Specifically, the visible-light photocatalytic activities of 3% BWO/TNTs for removing DBP and Cr(vi) from mixed pollutant solutions were 10.8 and 3.8 times higher than those of BWO. Firstly, this system can take full advantage of charge carriers and can spatially separate reduction sites and oxidation sites in the photocatalyst. Secondly, TNTs has a unique multiscale channel structure that can enhance mass transfer and light utilization. These characteristics lead to very obvious photocatalytic activity improvements. In addition, the BWO/TNTs composite photocatalysts exhibited excellent stability and durability under visible and UV light irradiation. This work demonstrated a feasible method for fabricating composite photocatalysts and applied them to the simultaneous removal of heavy metal and refractory organic pollutants from contaminated water.

In this study, Bi₂WO₆/mesoporous TiO₂ nanotube composites (BWO/TNTs) were successfully synthesized to remove the heavy metal Cr(vi) and refractory organic compound dibutyl phthalate (DBP) from contaminated water under visible light.

One-pot sonochemical synthesis of 3D flower-like hierarchical AgCl microsphere with enhanced photocatalytic activity

A highly uniform 3D flower-like hierarchical AgCl microsphere was prepared by sonochemical method with the existence of β-dextrin. The 3D flower-like hierarchical structure can be ascribed to the existence of β-dextrin, which provides nucleation sites for the growth of nanosheets because of the strong interaction between β-dextrin and Ag⁺. The 3D flower-like hierarchical AgCl microspheres were assembled by numerous interleaving nanosheet petals with small thickness. Benefiting from the unique structural features, the as-prepared 3D flower-like hierarchical AgCl microsphere exhibited higher degradation efficiency with degrading 98.17% of methylene blue (MB) and 88.50% of tetracycline (TC) within 40 min, which were both remarkably higher than those of irregular AgCl under visible light irradiation. Besides, the photocatalytic degradation rate constant of 3D flower-like hierarchical AgCl microsphere (0.063 min^-1) for MB was 3.94 times higher than that of irregular AgCl (0.016 min^-1). Moreover, a possible mechanism for the formation and excellent photocatalytic performance of 3D flower-like hierarchical AgCl microsphere was also proposed.

Enhanced performance of alkali-modified Bi2WO6/Bi0.15Ti0.85O2 toward photocatalytic oxidation of HCHO under visible light

Photocatalytic oxidation of formaldehyde (HCHO) is considered as one of the promising ways to resolve indoor air HCHO pollution. TiO₂ has been well known as the most extended application in photocatalysis due to its strong oxidizing ability and stability. Owing to high activity under visible light irradiation, TiO₂ and Bi₂O₃ doping mixed with Bi₂WO₆ was analyzed in this study. The formation of two kinds of heterojunction caused efficient charge separation, leading to the effective reduction in the recombination of photo-generated electron and hole. The special structure and enhanced performance of these catalysts were analyzed. For the first time, the loading of alkali salts was researched for photocatalytic oxidation. In order to understand the reaction mechanism of alkali salts enhanced effects, the catalysts were investigated by using BET, XRD, UV-Vis, FT-IR, SEM, and XPS. The results found more than 2 wt% of Na₂SO₄ loading and the mixed methods with different solutions were key factors affecting the performance of catalysts. Nearly 92% HCHO conversion could be completed over Bi₂WO₆/Bi_0.15Ti_0.85O₂ (Na₂SO₄), and the concentration of HCHO was only 0.07 mg/m³ for 24 h, which was below the limit of specification in China. The results also indicated that the solution mixing method was more favorable to increase the HCHO conversion due to decrease the size of Bi_0.15T_i0.85O₂ particles. The catalysts with Na₂SO₄ loading provided more surface-adsorbed oxygen that facilitated the desorption of CO₂ and markedly increased the photocatalytic oxidation of HCHO. Graphical abstract Plausible mechanism over W-Bi2WO6/ Bi0.15Ti0.85O2-Na2SO4 (1:4) catalysts.