A plasmonic photocatalyst Ag-AgI supported on mesoporous alumina (Ag-AgI/Al(2)O(3)) was prepared by deposition-precipitation and photoreduction methods. The catalyst showed high and stable photocatalytic activity for the degradation and mineralization of toxic persistent organic pollutants, as demonstrated with 2-chlorophenol (2-CP), 2,4-dichlorophenol (2,4-DCP), and trichlorophenol (TCP) under visible light or simulated solar light irradiation. On the basis of electron spin resonance, cyclic voltammetry analyses under a variety of experimental conditions, two electron transfer processes were verified from the excited Ag NPs to AgI and from 2-CP to the Ag NPs, and the main active species of O(2)(*-) and excited h(+) on Ag NPs were involved in the photoreaction system of Ag-AgI/Al(2)O(3). A plasmon-induced photocatalytic mechanism was proposed. Accordingly, the plasmon-induced electron transfer processes elucidated the photostability of Ag-AgI/Al(2)O(3). This finding indicates that the high photosensitivity of noble metal NPs due to surface plasmon resonance could be applied toward the development of new plasmonic visible-light-sensitive photocatalysts and photovoltaic fuel cells.

Oxygen-doped graphitic carbon nitride (O−CN) was fabricated via a facile thermal polymerization method using urea and oxalic acid dihydrate as the graphitic carbon nitride precursor and oxygen source, respectively. Experimental and theoretical results revealed that oxygen doping preferentially occurred on the two-coordinated nitrogen positions, which create the formation of low and high electron density areas resulting in the electronic structure modulation of O−CN. As a result, the resultant O−CN exhibits enhanced catalytic activity and excellent long-term stability for peroxymonosulfate (PMS) activation toward the degradation of organic pollutants. The O−CN with modulated electronic structure enables PMS oxidation over the electron-deficient C atoms for the generation of singlet oxygen ( 1 O 2 ) and PMS reduction around the electron-rich O dopants for the formation of hydroxyl radical ( • OH) and sulfate radical (SO 4•− ), in which 1 O 2 is the major reactive oxygen species, contributing to the selective reactivity of the O−CN/PMS system. Our findings not only propose a novel PMS activation mechanism in terms of simultaneous PMS oxidation and reduction for the production of nonradical and radical species but also provide a valuable insight for the development of efficient metal-free catalysts through nonmetal doping toward the persulfatebased environmental cleanup.

A nonradical oxidation process via metal-free peroxymonosulfate (PMS) activation has recently attracted considerable attention for organic pollutant degradation; however, the origin of singlet oxygen ( 1 O 2 ) generation still remains controversial. In this study, nitrogen-doped carbon nanosheets (NCN-900) derived from graphitic carbon nitride were developed for activation of PMS and elucidation of 1 O 2 production. With a large specific surface area (1218.7 m 2 g −1 ) and high nitrogen content (14.5 at %), NCN-900 exhibits superior catalytic activity in PMS activation, as evidenced by complete degradation of bisphenol A within 2 min using 0.1 g L −1 NCN-900 and 2 mM PMS. Moreover, the reaction rate constant fitted by pseudofirst-order kinetics for NCN-900 reaches an impressive value of 3.1 min −1 . Electron paramagnetic resonance measurements and quenching tests verified 1 O 2 as the primary reactive oxygen species in the NCN-900/PMS system. Based on X-ray photoelectron spectroscopy analysis and theoretical calculations, an unexpected generation pathway of 1 O 2 involving PMS oxidation over the electron-deficient carbon atoms neighboring graphitic N in NCN-900 was unraveled. Besides, the NCN-900/PMS system is also applicable for remediation of actual industrial wastewater. This work highlights the important role of electron-deficient carbon atoms in 1 O 2 generation from PMS oxidation and furnishes theoretical support for further relevant studies.

The photodegradation of the widely used amine drugs including primary amine (mexiletine), secondary amine (propranolol, phenytoin), and tertiary amine (diphenhydramine, antipyrine) were investigated in the presence of nitrate and humic substances under simulated sunlight. All of the amine drugs were photodegraded by nitrate due to the attack of hydroxyl radicals ( • OH). The bimolecular rate constants for the reaction between each amine drug and • OH ranged from (2.1 ( 0.2) × 10 9 to (8.7 ( 0.3) × 10 9 M -1 s -1 . In contrast, only mexiletine, propranolol, and diphenhydramine were selectively photodegraded in the presence of humic substances (HS). Fulvic acid was a more efficient sensitizer than humic acid throughout. The HS triplet states were verified to be main reactive species in the photochemical reaction. Furthermore, an electron transfer mechanism for the reaction with the HS triplet states was proposed on the basis of all information obtained under a series of experiments. The electron transfer from the nonbonding electrons on nitrogen (N-electrons) of the amine drugs to the excited ketone of the HS occurred. The availability of N-electrons and presence of hydrogen on carbon R of amine (R-hydrogen) were two key factors for the electrontransfer interaction. Moreover, the photoproducts were identified by GC-MS and the degradation pathways were proposed. The results strongly suggest the impact of humic substances on the photochemical fate of amine drugs in the natural waters.

As an efficient active oxidant for the selective degradation of pollutants in wastewater, the high-valent copper species Cu­(III) with persulfate activation has attracted substantial attention in some Cu-based catalysts. However, the systematic study of a catalyst structure and mechanism about Cu­(III) with peroxydisulfate (PDS) activation is challenging owing to the coexistence of multiple Cu species and the structural symmetry of PDS. Herein, we anchored a Cu atom with two pyridinic N atoms to synthesize a single-atom Cu catalyst (CuSA-NC). Experimental characterizations and theoretical calculations complemented each other well because of the uniform atomic active sites. The single-atom Cu was identified as the active site, and the unsaturated Cu-N2 configuration was more conductive to PDS activation than the saturated Cu-N4 configuration. Benefiting from the generation of Cu­(III), CuSA-NC exhibited an obvious selective and anti-interference performance for pollutant degradation in a complex matrix. The superior catalytic activity of CuSA-NC compared with that of other reported Cu-based catalysts and good durability in a continuous-flow experiment further revealed the potential of CuSA-NC for practical applications. This work strongly deepens the understanding of the generation of Cu­(III) in a single-atom Cu catalyst with unsaturated Cu-N2 sites under PDS activation and develops an efficient approach for actual water purification.

Single‐atom catalysts (SACs) are widely investigated in Fenton‐like reactions for environmental remediation, wherein their catalytic performance can be further improved by coordination structure modulation, but the relevant report is rare. Herein, a series of atomically dispersed cobalt catalysts with diverse coordination numbers (denoted as CoNx, x represents nitrogen coordination number) are synthesized and their peroxymonosulfate (PMS) conversion performance is explored. The catalytic specific activity of CoNx is found to be dependent on coordination number of single atomic Co sites, where the lowest‐coordinated CoN2 catalyst exhibits the highest specific activity in PMS activation, followed by under‐coordinated CoN3 and normal CoN4. Experimental and theoretical results reveal that reducing coordination number can increase the electron density of single Co atom in CoNx, which governs the Fenton‐like performance of CoNx catalysts. Specifically, the entire Co–pyridinic NC motif serves as active centers for PMS conversion, where the single Co atom, and pyridinic N‐bonded C atoms along with nitrogen vacancy neighboring the unsaturated Co–pyridinic N2 moiety account for PMS reduction and oxidation toward radical and singlet oxygen (1O2) generation, respectively. These findings provide a useful avenue to coordination number regulation of SACs for environmental applications.

The plasmon-induced photocatalytic inactivation of enteric pathogenic microorganisms in water using Ag-AgI/Al(2)O(3) under visible-light irradiation was investigated. The catalyst was found to be highly effective at killing Shigella dysenteriae (S. dysenteriae), Escherichia coli (E. coli), and human rotavirus type 2 Wa (HRV-Wa). Its bactericidal efficiency was significantly enhanced by HCO(3)(-) and SO(4)(2-) ions, which are common in water, while phosphate had a slightly positive effect on the disinfection. Meanwhile, more inactivation of E. coli was observed at neutral and alkaline pH than at acid pH in Ag-AgI/Al(2)O(3) suspension. Furthermore, the effects of inorganic anions and pH on the transfer of plasmon-induced charges were investigated using cyclic voltammetry analyses. Two electron-transfer processes occurred, from bacteria to Ag nanoparticles (NPs) and from inorganic anions to Ag NPs to form anionic radicals. These inorganic anions including OH(-) in water not only enhanced electron transfer from plasmon-excited Ag NPs to AgI and from E. coli to Ag NPs, but their anionic radicals also increased bactericidal efficiency due to their absorbability by cells. The plasmon-induced electron holes (h(+)) on Ag NPs, O(2)(•-), and anionic radicals were involved in the reaction. The enhanced electron transfer is more crucial than the electrostatic force interaction of bacteria and catalyst for the plasmon-induced inactivation of bacteria using Ag-AgI/Al(2)O(3).

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