Graphitic carbon nitride (g-C3N4) has emerged as promising metal-free semiconductorbased photocatalysts for solar energy conversion. However, the photocatalytic performance of gC3N4 is still moderate, due to the lack of the architecture design, which enables solar light harvesting, excited electron-hole separation as well as extending their availability for redox reactions, and far from practical application. Herein, we engineer the structure of g-C3N4 through a polyethyleneimine (PEI)/alkaline co-assisted technique. The resulting materials show the high concentration of both N3C nitrogen vacancies and hydroxyl groups on the g-C3N4 surface. These features significantly contribute to enhancing electron-hole generation and separation and harvest solar light absorption, which boosts the photocatalytic hydrogen production compared to bare gC3N4 under solar irradiation. Keywords: Photocatalysis; g-C3N4; hydrogen production; N3C nitrogen vacancies; hydroxyl groups; solar light absorption
We have demonstrated the crucial role of nitrogen vacancies toward the enhancement of the plasmonic properties of Au/g-C3N4 nanocomposites, which were prepared via the alkali-assisted synthesis and postcalcination pathway, for the effective production of hydrogen through a photocatalytic process under simulated solar light. The resulting material consisted of the nitrogen defective crumpled nanolayers of gC3N4 with strongly integrated Au plasmonic nanoparticles. It is realized from the studies that the nitrogen vacancies facilitate a stronger interaction with Au NPs and create the coexistence of the states of Au and Au(δ−) , which is eventually found to be the origin of the observed enhanced plasmonic properties of the nanocomposite. Such features have not been observed in any other conventional methods for the preparation of Au/g-C3N4, where it significantly improved (i) the light utilization abilities of the materials and (ii) electron−hole generation and separation, which collectively led to the boosting of the photocatalytic performance toward hydrogen production under simulated solar light.
The over-exploitation of fossil fuels means that research into alternative sustainable energy sources is crucial for the scientific community. The harvesting of solar energy via photocatalysis is a key approach to developing these alternatives. Furthermore, photocatalytic materials show great promise for degradation of pollutants. However, limitations in incident light utilization and charge separation are major drawbacks that restrict the activity of current artificial photosystems. Construction of hollow nano-sized photocatalysts is emerging as a promising approach to fabricating novel and effective materials, as hollow photocatalysts possess unique properties that may be exploited to overcome these challenges. This review gives a concise overview of the advantages of hollow structures for this purpose, the methodology used to prepare hollow photocatalysts, and the current state-of-the-art in the development of hollow structure photocatalysts for energy production and environmental applications
This study aimed at providing a route towards the production of a novel exopolysaccharide (EPS) from fermented bamboo shoot-isolated Lactobacillus fermentum. A lactic acid bacteria strain, with high EPS production ability, was isolated from fermented bamboo shoots. This strain, R-49757, was identified in the BCCM/LMG Bacteria Collection, Ghent University, Belgium by the phenylalanyl-tRNA synthetase gene sequencing method, and it was named Lb. fermentum MC3. The molecular mass of the EPS measured via gel permeation chromatography was found to be 9.85 × 104 Da. Moreover, the monosaccharide composition in the EPS was analyzed by gas chromatography–mass spectrometry. Consequently, the EPS was discovered to be a heteropolysaccharide with the appearance of two main sugars—D-glucose and D-mannose—in the backbone. The results of one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance spectroscopy analyses prove the repeating unit of this polysaccharide to be [→6)-β-D-Glcp-(1→3)-β-D-Manp-(1→6)-β-D-Glcp-(1→]n, which appears to be a new EPS. The obtained results open up an avenue for the production of novel EPSs for biomedical applications.
This study developed a unique system by combining the novel vertical flow (NVF) using expanded clay (ExC) and free flow surface constructed wetland (FWS) for dormitory sewage purification and reuse. The NVF tank consisted of filter layers of ExC, sandy soil, sand, and gravel. The FWS consisted of sandy soil substrate and was installed after the NVF. Colocasia esculenta and Dracaena sanderiana was planted in NVF and FWS, respectively. The treatment system was operated and tested for more than 21 weeks by increasing the hydraulic loading rate (HLR) from 0.02 m/d to 0.12 m/d. The results demonstrated that effluents in the system changed proportionally to the HLRs, except for nitrate nitrogen. Furthermore, the maximum removal efficiencies for TSS, BOD5, NH4-N, and Tcol were 76 ± 13%, 74 ± 11%, 90 ± 3%, and 59 ± 18% (0.37 ± 0.19 log10MPN/100 mL), respectively. At HLRs of 0.04–0.06 m/d, the treatment system satisfied the limits of agriculture irrigation.
