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In this study, the properties and mechanism of Fe-N-C single-atom catalyst for reducing nitrophenols were investigated. A variety of Fe-N-C catalysts were prepared using the space-limited way with heating rate of 2 ℃ min−1, 5 ℃ min−1, and 10 ℃ min−1 during calcinating, respectively. FeNC-2 showed the best catalytic efficiency for 4-nitrophenol (4-NP) reduction due to the highest mesoporous content, defect degree and atomically dispersed Fe-N x site. Under optimal conditions, 0.2 mM 4-NP could be rapidly reduced to 4-AP within 80 s at a low catalyst dose (5 mg FeNC-2). Experiments and density functional theory (DFT) calculations confirmed that Fe-N x site could effectively catalyze the cleavage of the B-H bond. The electron transfer process of the reaction was confirmed by EPR spectra and chronoamperometry test. In addition, FeNC-2 also showed satisfactory cycle stability and practicality. This research supplies a new perspective for treating nitrophenols-containing wastewater with non-noble metal-based catalysts. [Display omitted] • The Fe-N-C single-atom catalyst showed high efficiency for nitrophenols reduction. • The influence factors and structure-activity relationship were analyzed in depth. • The electron transfer was confirmed by characterization and DFT calculation. • A new perspective was provided to replace noble metal-based catalyst. [ABSTRACT FROM AUTHOR]

The increasingly serious pollution of antibiotics brings an enormous threat to the ecological environment and human health. Graphite phase carbon nitride (g-C 3 N 4), as a popular photocatalytic material, is widely used in photocatalytic degradation of antibiotics in water. In order to make up for the shortage of g-C 3 N 4 monomer, CeO 2 /N-doped g-C 3 N 4 (CeNCN) composite photocatalysts co-modified with nitrogen doping and CeO 2 loading were designed and synthesized with the idea of expanding visible light absorption and promoting photogenerated carrier separation. CeNCN exhibits excellent photodegradation performance, the removal rate of tetracycline reached 80.09% within 60 min, which is much higher than that of g-C 3 N 4 (CN) and N-doped g-C 3 N 4 (NCN); and the quasi-first-order degradation rate constant is 0.0291, which is 7.86 and 2.29 times higher than CN and NCN. Electron spin resonance and free radical trapping experiments confirmed that h+, O 2 − and OH are the active substances in the photocatalytic system. After 5 cycles, the degradation efficiency of tetracycline still exceeds 75%, which indicates that CeNCN has good stability. This work proves that N-doping and CeO 2 loading can effectively broaden the photoresponse range of g-C 3 N 4 , facilitate the separation of photogenerated electron-hole pairs, and provide a reference for the construction of g–C 3 N 4 –based photocatalyst with high-efficiency photodegradation activity. [Display omitted] • CeO 2 /N-doped g-C 3 N 4 (CeNCN) photocatalyst was successfully first synthesized. • CeNCN exhibits excellent light response and the separation of charge carriers. • CeNCN exhibits significantly enhanced photocatalytic activity for TC degradation. • The proposed photocatalytic mechanism toward CeNCN photocatalyst is illustrated. [ABSTRACT FROM AUTHOR]

Photocatalysis is currently a hot research field, which provides promising processes to produce green energy sources and other useful products, thus eventually benefiting carbon emission reduction and leading to a low-carbon future. The development and application of stable and efficient photocatalytic materials is one of the main technical bottlenecks in the field of photocatalysis. Perovskite has excellent performance in the fields of photocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), carbon dioxide reduction reaction (CO 2 RR), organic synthesis and pollutant degradation due to its unique structure, flexibility and resulting excellent photoelectric and catalytic properties. The stability problems caused by perovskite's susceptibility to environmental influences hinder its further application in the field of photocatalysis. Therefore, this paper innovatively summarizes and analyzes the existing methods and strategies to improve the stability of perovskite in the field of photocatalysis. Specifically, (i) component engineering, (ii) morphological control, (iii) hybridization and encapsulation are thought to improve the stability of perovskites while improving photocatalytic efficiency. Finally, the challenges and prospects of perovskite photocatalysts are discussed, which provides constructive thinking for the potential application of perovskite photocatalysts. [Display omitted] • Propose method of perovskites modification to combine high stability and efficiency. • Apply methods of improving the stability of perovskites in photocatalysis. • The challenges and prospects for more stable perovskite catalysts are presented. [ABSTRACT FROM AUTHOR]

• Metal-carbon hybrid materials are promising catalysts for PS-AOPs. • Metal-carbon interaction favors reduced metal leaching and improved catalysis. • The modulation strategies for changing PS activation mechanism are elaborated. • The existing challenges and future research directions are summarized. Proper wastewater treatment has always been the focus of human society, and many researchers have been working to find efficient and stable wastewater treatment technologies. Persulfate-based advanced oxidation processes (PS-AOPs) mainly rely on persulfate activation to form reactive species for pollutants degradation and are considered to be one of the most effective wastewater treatment technologies. Recently, metal-carbon hybrid materials have been diffusely used for PS activation because of their high stability, abundant active sites, and easy applicability. Metal-carbon hybrid materials can successfully overcome the shortcomings of onefold metal catalysts and carbon catalysts by combing the complementary advantages of the two components. This article reviews recent studies about metal-carbon hybrid materials-mediated PS-AOPs for wastewater decontamination. The interactions of metal and carbon materials, as well as the active sites of metal-carbon hybrid materials, are introduced first. Then, the application and mechanism of metal-carbon hybrid materials-mediated PS activation are presented in detail. Lastly, the modulation methods of metal-carbon hybrid materials and their tunable reaction pathways were discussed. The prospect of future development directions and challenges is proposed to facilitate metal-carbon hybrid materials-mediated PS-AOPs to take a step further for practical application. [Display omitted] [ABSTRACT FROM AUTHOR]

• A synthesis temperature gradient was set to regulate the defect level of S-OMC. • Removal of sulfur heteroatom could bring more carbon defects. • A structure-activity relationship between defects and 1O2 production was built. • CIP removal reached 85.84% under unadjusted pH and slight S-OMC-1000. • S-OMC-1000/PDS system performed well in the presence of common interferents. The carbon-catalyzed persulfate-based advanced oxidation process (PS-AOP) has recently received much focus owing to the green, economical, and sustainable nature of carbon catalysts. In this study, sulfur-doped ordered mesoporous carbons (S-OMCs) were utilized to activate peroxydisulfate (PDS) for ciprofloxacin (CIP) removal. A synthesis temperature gradient was set to regulate the defect level of S-OMCs, since the thermal decomposition of oxygen- and sulfur-containing groups at different temperatures could release S and O and then create defects. In all S-OMCs/PDS systems, 1O 2 dominated CIP degradation. Interestingly, a high linear correlation (R2 = 0.9091) between defect level and 1O 2 yield was found, confirming the structure-activity relationship between defects and 1O 2 generation. Moreover, the impacts of several important reaction conditions and water matrix on S-OMC-1000/PDS activation system were surveyed. In the S-OMC-1000/PDS activation system, CIP removal could attain 85.84% under the condition of unadjusted pH (pH = 5.3) and small amount of S-OMC-1000 (50 mg/L). The S-OMC-1000/PDS activation system also exhibited relatively stable or even better performance in the presence of common inorganic anions and natural organic matter (NOM), manifesting its good potential for practical applications. In addition, the reusability of S-OMC-1000 was investigated. This study provides a practical and high-efficiency way for decontaminating antibiotic-polluted water, and gives an alternative approach for identifying the active site of catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

Recently, photo-Fenton technology has been widely used to degrade tetracycline (TC) because of its great efficiency and wide application range. Herein, Fe–Ni layered double hydroxides (FeNi-LDH)/Ti 3 C 2 photo-Fenton system was constructed in this study. The results showed the introduction of Ti 3 C 2 solved some problems of FeNi-LDH such as poor conductivity, easy aggregation, and high recombination rate of photoelectron. Benefiting from these advantages, FeNi-LDH/Ti 3 C 2 exhibited excellent TC removal rate of 94.7% while pure FeNi-LDH was only 54%. Besides, FeNi-LDH/Ti 3 C 2 possessed strong pH tolerance (2–11) and the removal efficiency was still up to 82% after the four-cycle experiment. Furthermore, the quenching experiments revealed the reaction mechanism, where ∙OH and ·O 2 − were the primary active radicals for degrading TC. Last, the results of the simulated wastewater treatment and the inorganic ion interference tests showed that FeNi-LDH/Ti 3 C 2 possessed practical application potential. In brief, this study shows that FeNi-LDH/Ti 3 C 2 can offer a certain theoretical basis for the actual development of hydrotalcite in heterogeneous photo-Fenton systems. [Display omitted] • A novel material FeNi-LDH/Ti 3 C 2 was successfully prepared by a facile method. • The incorporation of Ti 3 C 2 enhanced the photogenerated carrier separation. • The degradation efficiency of TC increased by 40% after introduce Ti 3 C 2. • FeNi-LDH/Ti 3 C 2 photo-Fenton system possessed great application prospect. • The possible mechanism and degradation pathways of TC were illustrated. [ABSTRACT FROM AUTHOR]

Peroxymonosulfate (PMS)-based advanced oxidation processes for wastewater treatment have received extensive attention in the past years. Here, a novel Mn, Ce co-modified g-C 3 N 4 (MnCe-CN) composite was successfully synthesized by one-step pyrolysis for activating PMS. The physical and chemical characterization of MnCe-CN/PMS was conducted, indicating that Mn and Ce were evenly distributed on g-C 3 N 4 and existed in the form of Mn-N structure and CeO 2 , respectively. The MnCe-CN/PMS system could effectively degrade pollutants such as acetaminophen (ACT), methylparaben (MeP), p -nitrophenol (PNP), and 2,4-dichlorophenol (2,4-DCP). Among them, 2,4-DCP could be rapidly degraded, reaching 100% within 30 min. The masking experiments and electrochemical testing results revealed that 2,4-DCP was degraded via superoxide radicals (O 2 ˙ˉ), singlet oxygen (1O 2), and electron transfer path. The cyclic experiments and real water treatment experiments testified that the oxidative system had excellent stability and applicability. This study provides a facile synthetic method to fabricate bimetallic co-modified g-C 3 N 4 for the enhancement of PMS activation. [Display omitted] • A facile synthesis way for Mn and Ce co-modified g-C 3 N 4 was developed. • Mn(Ⅱ)/Mn(Ⅲ) in the N-pot was proved to be the main active site. • The MnCe-CN composites had excellent stability and applicability. • O 2 ˙ˉ, 1O 2 played a major role in the degradation of 2,4-DCP. [ABSTRACT FROM AUTHOR]