Semi-chemical interaction between graphitic carbon nitride and Pt for boosting photocatalytic hydrogen evolution

Multilevel immobilized CNT/SCN purification beads and the removal efficiency over TCHCl/clay composite pollutant in the underwater environment

Natural water bodies often contain a significant amount of suspended colloidal particles, which not only reduce water transparency but also have a high adsorption capacity for soluble pollutants. These composite pollutants can migrate rapidly with water flow, which are usually difficult to degrade and remove by traditional methods. Aiming at suspended contaminated waterbodies, this study introduced a multilevel loading method to prepare carbon nanotube/sulfur doped carbon nitride (CNT/SCN) composite photocatalytic purification beads. The surface of the obtained core-shell structured purification beads is loaded with CNT/SCN photocatalysts which exhibit three-dimensional conductive and porous characteristics. TCHCl was introduced as the target pollutant, and the removal efficiency of the composite purification beads under different water turbidity and hydrodynamic conditions were investigated. The results showed that during 15 h of degradation process, at the depth of 20 cm, with the flow rate of 0.015 m3/h and water turbidity of 10.3 NTU, the purification beads achieved a removal efficiency of 54.9 % for tetracycline hydrochloride (TCHCl), which was 2.03 times higher than that of SCN purification beads. The three-dimensional porous structure of the surface exhibited excellent adsorption and trapping capabilities for suspended colloidal particles. The introduction of carbon nanotubes enhanced charge transfer ability of the surface layer and reduces the local charge accumulation effect caused by surface adsorption, which effectively enhances the adsorption of suspended colloid, and also significantly improved the degradation efficiency of TCHCl. This study provides a valuable insight for the engineering application of photocatalytic technology.

S-scheme carbon doped-TiO2/ZnIn2S4 heterojunction for enhanced photocatalytic degradation of microcystin-LR and hydrogen evolution

Photocatalytic degradation of pollutants coupled with hydrogen (H2) evolution has emerged as a promising solution for environmental and energy crises. However, the fast recombination of photoexcited electrons and holes limits photocatalytic activities. Herein, an S-scheme heterojunction carbon doped-TiO2/ZnIn2S4 (C-TiO2/ZnIn2S4) was designed by substituting oxygen sites within C-TiO2 by ZnIn2S4. Under visible light irradiation, the optimal C-TiO2/ZnIn2S4 exhibits a higher degradation efficiency (88.6%) of microcystin-LR (MC-LR), compared to pristine C-TiO2 (72.9%) and ZnIn2S4 (66.8%). Furthermore, the H2 yield of the C-TiO2/ZnIn2S4 reaches 1526.9 μmol g-1 h-1, which is 3.83 times and 2.87 times that of the C-TiO2 and ZnIn2S4, respectively. Experimental and theoretical investigations reveal that an internal electric field (IEF) informed in the C-TiO2/ZnIn2S4 heterojunction, accelerates the separation of photogenerated charge pairs, thereby enhancing photocatalytic efficiency of MC-LR degradation and H2 production. This work highlights a new perspective on the development of high-performance photocatalysts for wastewater treatment and H2 generation.

Regulating the Assembly of Precursors of Carbon Nitrides to Improve Photocatalytic Hydrogen Production

Two-dimensional graphitic carbon nitrides (2D g-C3N4) are promising photocatalysts for water splitting to hydrogen due to their non-toxicity and high stability. However, the bulk g-C3N4 has some intrinsic drawbacks, such as rapid electron–hole recombination and low charge-carrier mobility, resulting in poor photocatalytic activity. Here, 2,4-diamine-6-phenyl-1,3,5-triazine was employed as a precursor to regulating the assembly of melamine and cyanuric acid in water. The resulting g-C3N4 not only improved the visible light absorption and electron–hole separation but also provided more catalytic sites for enhanced photocatalytic hydrogen evolution. The modified g-C3N4 (CNP10-H) showed a hydrogen-releasing rate of 2184 μmol·g−1·h−1, much higher than the bulk g-C3N4.

Highly efficient removal of organic contaminant with wide concentration range by a novel self-cleaning hydrogel: Mechanism, degradation pathway and DFT calculation

A novel carbon nitride based self-cleaning hydrogel photocatalyst (KI-PCN gel, potassium and iodine co-doped carbon nitride confined in alginate) has been successfully constructed by a facile method. Fabricated photocatalyst showed enhanced synergistic adsorption-photocatalytic degradation property on a high concentration of methylene blue (HMB) because of enhanced carrier separation efficiency and improved light adsorption capacity of KI-PCN. As expected, the KI-PCN gel showed the highest apparent rate constant value ₍K_app =0.0310 min^-1), which was about 38.8 and 5.8 times as that of blank hydrogel (K_app=0.0008 min^-1) and PCN gel (K_app=0.0053 min^-1), respectively. Meanwhile, KI-PCN gel can continuously adsorb low concentration of MB (LMB), and the MB-adsorbed KI-PCN gel can self-clean under light irradiation. The bench-scale experiments simulating real river showed that KI-PCN gel can effectively and continuously remove LMB (0.1-20 ppm), indicating the possibility for the removal of contaminants in natural rivers. Furthermore, the possible degradation pathways were proposed by combining the density functional calculations (DFT) and intermediates identified by liquid chromatography-mass spectrometry (LC-MS). This work proposed a new perspective to acquire a novel self-cleaning and easily recyclable photocatalyst for treatment of wide concentration range organic wastewater as well as remediation of natural waterbody.