rGO/Fe-doped g-C3N4 visible-light driven photocatalyst with improved NO removal performance

Optimizing study on the NH3-SCR activity of Ce-W-Ti@g-C3N4 catalyst: influence of graphite carbon nitride types

Herein, three g-C3N4(MCN/TCN/UCN), obtained by the direct pyrolysis of melamine/urea/thiourea respectively, were introduced as supports to optimize the NH3-SCR activity of Ce-W-Ti catalyst. Compared to CWT-400-Air, CWT@g-C3N4(2)-300-N2 exhibits lower crystalline anatase TiO2 and larger specific surface area, which improves the dispersion of Ce/W/Ti species on catalysts surface. Furthermore, the introduction of g-C3N4 as supports also contributes to doping C/N elements into Ce-W-Ti catalyst and increases the Ce3+/(Ce3++Ce4+) and Oα/(Oα+Oβ) molar ratios on catalyst surface. These all are advantageous to the NH3-SCR activity. However, UCN shows better promotional effect than MCN and TCN. This might be mainly attributed to the loose and porous stacked layered fold structure of UCN, the larger BET surface area, higher dispersion of Ce/W/Ti species and moderate weak/medium-strong acid sites of CWT@UCN(2)-300-N2. At the same time, the influence of carbon nitride amount, calcination atmosphere and calcination temperature on the NH3-SCR activity of CWT@g-C3N4 catalyst were also investigated.

Fe-g-C3N4/reduced graphene oxide lightless application for efficient peroxymonosulfate activation and pollutant mineralization: Comprehensive exploration of reactive sites

To overcome the shortcomings of homogeneous Fe ion activating peroxymonosulfate (PMS), such as high pH-dependence, limited cycling of Fe(III)/Fe(II) and sludge production, graphite carbon nitride (g-C₃N₄) is chosen as a support for Fe ions, and reduced graphene oxide (rGO) is employed to facilitate the electron transfer process, thereby enhancing catalysis. Herein, a ternary catalyst, Fe-g-C₃N₄/rGO, is first applied under lightless condition for PMS activation, which exhibits ideal performance for contaminant mineralization. 82.5 % of the total organic carbon (TOC) in 100 mL of 5 mg/L bis-phenol A (BPA) was removed within 20 min by the optimal catalyst named 30%rFe_0.2CN, which shows a strong pH adaptability over the range of 3-11 compared with a common Fenton-like system. Moreover, the highly stable Fe-g-C₃N₄/rGO/PMS catalytic system resists complex water matrices, especially those with high turbidity. To unveil the mechanism of PMS activation and pollutant degradation, the physicochemical properties of the as-prepared catalysts are comprehensively characterized by multiple techniques. The Fe(III) contained in both the Fe-N group and α-Fe₂O₃ component of 30%rFe_0.2CN not only directly reacts with PMS to produce sulfate radicals (SO₄^-) and hydroxyl radicals (OH), but also combines with PMS to form the essential [Fe(III)OOSO₃]⁺ active complex, thereby generating superoxide radicals (O₂^-) and singlet oxygen (¹O₂). Among the various reactive oxidizing species, ¹O₂ plays an important role in pollutant removal, which is additionally generated by the CO moiety of the catalyst activating PMS as well as PMS self-oxidation, indicating the dominance of the non-radical pathway in the pollutant degradation process. Due to the advantages of high efficiency, wide pH adaptability and stability, the proposed lightless Fe-g-C₃N₄/rGO/PMS catalytic system represents a promising avenue for practical wastewater purification.

Rapid fabrication of MgO@g-C3N4 heterojunctions for photocatalytic nitric oxide removal

Nitric oxide (NO) is an air pollutant impacting the environment, human health, and other biotas. Among the technologies to treat NO pollution, photocatalytic oxidation under visible light is considered an effective means. This study describes photocatalytic oxidation to degrade NO under visible light with the support of a photocatalyst. MgO@g-C₃N₄ heterojunction photocatalysts were synthesized by one-step pyrolysis of MgO and urea at 550 °C for two hours. The photocatalytic NO removal efficiency of the MgO@g-C₃N₄ heterojunctions was significantly improved and reached a maximum value of 75.4% under visible light irradiation. Differential reflectance spectroscopy (DRS) was used to determine the optical properties and bandgap energies of the material. The bandgap of the material decreases with increasing amounts of MgO. The photoluminescence spectra indicate that the recombination of electron-hole pairs is hindered by doping MgO onto g-C₃N₄. Also, NO conversion, DeNOx index, apparent quantum efficiency, trapping tests, and electron spin resonance measurements were carried out to understand the photocatalytic mechanism of the materials. The high reusability of the MgO@g-C₃N₄ heterojunction was shown by a five-cycle recycling test. This study provides a simple way to synthesize photocatalytic heterojunction materials with high reusability and the potential of heterojunction photocatalysts in the field of environmental remediation.

Element-doped graphitic carbon nitride: confirmation of doped elements and applications

Doping is widely reported as an efficient strategy to enhance the performance of graphitic carbon nitride (g-CN). In the study of element-doped g-CN, the characterization of doped elements is an indispensable requirement, as well as a huge challenge. In this review, we summarize some useful characterization methods which can confirm the existence and chemical states of doped elements. The advantages and shortcomings of these characterization methods are discussed in detail. Various applications of element-doped g-CN and the function of doped elements are also introduced. Overall, this review article aims to provide helpful information for the research of element-doped g-CN.

The exploration of metal-free catalyst g-C3N4 for NO degradation

We propose a new metal-free scheme of the reaction between the molecules CO and NO on a g-C₃N₄ monolayer. We first investigate the electronic properties of the related molecules CO, NO, N₂, and CO₂ adsorbed g-C₃N₄ systems, and then figure out the possible reaction pathways. It is shown that all the molecules will be physisorbed above the triangular cavity. Also, we find the NO binding on g-C₃N₄ is stronger than CO. The NO dissociation will be the rate-determining step of the reaction, and the formation of NCO· intermediate will play a critical role for the reaction process. This research presents a new route of applying g-C₃N₄ as a catalyst in the NO catalytic degradation reaction.