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Emerging single‐atom catalysts (SACs) are promising in water remediation through Fenton‐like reactions. Despite the notable enhancement of catalytic activity through increasing the density of single‐atom active sites, the performance improvement is not solely attributed to the increase in the number of active sites. The variation of catalytic behaviors stemming from the increased atomic density is particularly elusive and deserves an in‐depth study. Herein, single‐atom Fe catalysts (FeSA‐CN) with different distances (dsite) between the adjacent single‐atom Fe sites are constructed by controlling Fe loading. With the decrease in dsite value, remarkably enhanced catalytic activity of FeSA‐CN is realized via the electron transfer regime with peroxymonosulfate (PMS) activation. The decrease in dsite value promotes electronic communication and further alters the electronic structure in favor of PMS activation. Moreover, the two adjacent single‐atom Fe sites collectively adsorb PMS and achieve single‐site desorption of the PMS decomposition products, maintaining continuous PMS activation and contaminant removal. Moreover, the FeSA‐CN/PMS system exhibits excellent anti‐interference performance for various aquatic systems and good durability in continuous‐flow experiments, indicating its great potential for water treatment applications. This study provides an in‐depth understanding of the distance effect of single‐atom active sites on water remediation by designing densely populated SACs. [ABSTRACT FROM AUTHOR]

A zinc (Zn)‐based single‐atom catalyst (SAC) is recently reported as an active Fenton‐like catalyst; however, the low Zn loading greatly restricts its catalytic activity. Herein, a molecule‐confined pyrolysis method is demonstrated to evidently increase the Zn loading to 11.54 wt.% for a Zn SAC (ZnSA‐N‐C) containing a mixture of Zn−N4 and Zn−N3 coordination structures. The latter unsaturated Zn−N3 sites promote electron delocalization to lower the average valence state of Zn in the mix‐coordinated Zn−Nx moiety conducive to interaction of ZnSA‐N‐C with peroxydisulfate (PDS). A speedy Fenton‐like catalysis is thus realized by the high‐loading and low‐valence ZnSA‐N‐C for PDS activation with a specific activity up to 0.11 min L−1 m−2, outstripping most Fenton‐like SACs. Experimental results reveal that the formation of ZnSA‐N‐C−PDS* complex owing to the strong affinity of ZnSA‐N‐C to PDS empowers intense direct electron transfer from the electron‐rich pollutant toward this complex, dominating the rapid bisphenol A (BPA) elimination. The electron transfer pathway benefits the desirable environmental robustness of the ZnSA‐N‐C/PDS system for actual water decontamination. This work represents a new class of efficient and durable Fenton‐like SACs for potential practical environmental applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A close-connected p -AgI/ n -Bi 2 O 2 CO 3 heterojunction was synthesized by a one-step co-crystallization method. The visible-light-driven photoactivity of AgI was exceptionally enhanced by nearly 5 times through in-situ close contact with Bi 2 O 2 CO 3 . After seven cycling measurements, the photodegradation rate of 2-chlorophenol could be maintained at 88% and no Ag + and Bi 3+ could be detected in the reaction solution, indicating high photostability of the heterojunction photocatalyst. On the basis of the characterization of morphology, X-ray diffraction, Fourier-transform infrared spectra and X-ray photoelectron spectroscopy, AgI nanoparticles were selectively anchored on active {001} facets of layered Bi 2 O 2 CO 3 sheets, and a strong interfacial interaction between p -AgI and n -Bi 2 O 2 CO 3 was observed, which enhanced effective separation and transfer of the photo-generated electron-hole pair from AgI, resulting in the high photoactivity and photostability of AgI for the degradation and mineralization of 2-chlorophenol under visible light. By the studies of electron spin resonance and other experiments, the charge transfer process at the interface of p -AgI/ n -Bi 2 O 2 CO 3 was verified that the photoexcited electrons of the conduction band of AgI transferred to the conduction band of Bi 2 O 2 CO 3 to react with surface adsorbed oxygen into O 2 – , while the photoexcited holes of the valence band of AgI could oxidize organic pollutants in water. [ABSTRACT FROM AUTHOR]

• The Fenton-like Cu-PAN 3 catalysts is first synthesized by co-precipitation and carbon thermal reduction method. • Dual reaction centers are constructed around graphene-like carbon and Cu species. • The pollutants as electron donors inhibit the ineffective decomposition of H 2 O 2 at the electron-poor centers. • The pollutant removal mainly relies on the surface cleavage at the electron-poor centers. High energy consumption has seriously hindered the development of Fenton-like reactions for the removal of refractory organic pollutants in water. To solve this problem, we designed a novel Fenton-like catalyst (Cu-PAN 3) by coprecipitation and carbon thermal reduction. The catalyst exhibits excellent Fenton-like catalytic activity and stability for the degradation of various pollutants with low H 2 O 2 consumption. The experimental results indicate that the dual reaction centers (DRCs) are composed of Cu-N-C and Cu-O-C bridges between copper and graphene-like carbon, which form electron-poor/rich centers on the catalyst surface. H 2 O 2 is mainly reduced at electron-rich Cu centers to free radicals for pollutant degradation. Meanwhile, pollutants can be oxidized by donating electrons to the electron-poor C centers of the catalyst, which inhibits the ineffective decomposition of H 2 O 2 at the electron-poor centers. This therefore significantly reduces the consumption of H 2 O 2 and reduces energy consumption. [Display omitted] [ABSTRACT FROM AUTHOR]

Fe–Al layered double hydroxides (Fe–Al LDH, the molar ratio of Fe(II) to Fe(III) was about 1:10) was successfully supported and highly dispersed on mesoporous Al 2 O 3 based on the X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. Fe–Al LDH/Al 2 O 3 was more efficient in inhibiting BrO 3 − formation and removing organic pollutant taking ozonation alone as control. Further investigation indicated that BrO 3 − reduction by surface Fe(II) was responsible to the complete inhibition of BrO 3 − formation. Fe(II) was reduced from the Fe(III)-intermediates complex via an electron transfer process and the reaction of Fe(III) and HO 2 − /O 2 − in catalytic ozonation. The amount of surface Fe(II) in catalytic ozonation of amitrole (AMT), phenazone (PZ) and 2,4-dichlorophenoxyacetic acid (2,4-D) was 0.34, 2.47 and 3.30 μmol/g, which proved that most of Fe(II) was generated from the reaction of ozone and Fe–Al LDH/Al 2 O 3 since 0.33 μmol/g of Fe(II) existed within the catalyst. The increase of ozone amount and the formation of Fe(III)-intermediates complex could enhance the Fe(II) generation, leading to more efficient inhibition of BrO 3 − formation. Finally, Fe–Al LDH/Al 2 O 3 still showed effectiveness in the inhibition of BrO 3 − and TOC removal for a raw drinking water under the realistic conditions, which could be applied to the BrO 3 − mineralization in catalytic ozonation of Br − -containing drinking water. [ABSTRACT FROM AUTHOR]

BiOI is widely used as photocatalysts for pollutant removal, water splitting, CO 2 reduction and organic transformation due to its excellent photoelectric properties. Here, we report for the first time that a light-free catalyst consisting of the flower-like BiOI microspheres ( f -BiOI MSs) exposing (1 0 1) and (1 1 0) crystal planes prepared by a hydrothermal method in ethylene glycol environment can rapidly eliminate the refractory BPA within only ∼3 min through a Fenton-like process. The reaction activity is ∼190 times higher than that of the conventional Fenton catalyst Fe 2 O 3 . A series of characterizations and experiments reveal the formation of the dual reaction centers on f -BiOI MSs. The electron-rich O centers efficiently reduce H 2 O 2 to OH, while the electron-poor oxygen vacancies capture electrons from the adsorbed pollutants and divert them to the electron-rich area during the Fenton-like reactions. By these processes, pollutants are degraded and mineralized quickly in a wide pH range. Our findings address the problems of the classical Fenton reaction and are useful for the development of efficient Fenton-like catalysts through constructing dual reaction centers. [ABSTRACT FROM AUTHOR]

Solid solution of BiOBr and BHO (BiO(OH) 0.06 Br 0.94 ) with abundant oxygen vacancies was supported on Ag/AgBr using precipitation and deposition–precipitation methods. The photocatalyst showed high and stable photocatalytic activity for the degradation of chlorophenols and azodyes in water under visible to NIR light irradiation without any release of Ag + , which came from visible-excited AgBr and the SPR of Ag NPs in the visible and NIR region. The different interfacial charge-transfer processes were verified on the basis of cyclic voltammetry analyses and all experimental information. The conduction band (CB) electrons of photoexcited AgBr reacted with the adsorbed oxygen forming O 2 •− , while the valence band (VB) holes of AgBr were transported the VB of BiO(OH) 0.06 Br 0.94 to oxidize organic pollutants or H 2 O to • OH. The plasmon-induced electrons from Ag NPs transferred to the CB of AgBr reacting with the adsorbed oxygen to O 2 •− , while the electrons trapped on the oxygen vacancies of BiO(OH) 0.06 Br 0.94 transferred to Ag NPs recombining with the plasmon-induced holes, inhibiting the release of Ag + , and the resulted VB holes of BiO(OH) 0.06 Br 0.94 oxidized organic compound. These interfacial charge transfers evidenced the high photoactivity and photostability of BiO(OH) 0.06 Br 0.94 /Ag/AgBr. [ABSTRACT FROM AUTHOR]

A novel Ce-doped manganese oxide octahedral molecular sieve (Ce-OMS-2) was prepared by a reflux method and characterized by field emission scanning electron microscope, high resolution transmission electron microscopy, Fourier-transform infrared spectra, nitrogen adsorption/desorption isotherms, X-ray diffraction and X-ray photoelectron spectroscopy. The Ce(0.48)-OMS-2 with Ce/Mn molar ratio of 0.48 was highly effective and stable for the degradation of ciprofloxacin in water. The characterized results indicated that Ce mainly entered the tunnel structure of OMS-2, significantly increasing the BET surface area from 72 m 2 /g for OMS-2 to 304 m 2 /g for Ce(0.48)-OMS-2. Moreover, the surface oxygen defects and surface labile oxygen significantly increased after the introduction of Ce into OMS-2, being determined by the O1s spectra and O 2 -TPD analysis. The ESR and activity tests under different conditions suggested that the reduced manganese Mn(II) could interact with surface labile oxygen to form O 2 − and Mn(IV), resulting in the high activity of Ce(0.48)-OMS-2 to degrade the piperazine ring and the quinolone moiety of CIP into small molecular products. Simultaneously, the release of Mn(II) was inhibited by the electron transfer process on the micro-interface of Ce(0.48)-OMS-2. [ABSTRACT FROM AUTHOR]

The Ni 3 S 2 (100) surface exhibits promising bifunctional catalytic activity towards ORR and OER. Most important of all, the ORR catalytic activity of Ni 3 S 2 (100) can be enhanced by the doping of Cu, and the OER catalytic activity of Ni 3 S 2 (100) can be improved by the doping of Se. [Display omitted] • Ni 3 S 2 (100) exhibits bifunctional catalytic activity towards ORR and OER. • The ORR catalytic activity of Ni 3 S 2 (100) can be enhanced by the doping of Cu. • The OER catalytic activity of Ni 3 S 2 (100) can be improved by the doping of Se. • A descriptor derived from the electron affinity was developed. Developing highly efficient and nonprecious electrocatalysts for oxygen-involving energy conversion reactions is crucial for the development of clean and sustainable energy technologies. Herein, the intrinsic relationship between the atomic structure and the catalytic activity of Ni 3 S 2 was investigated based on density functional theory. It was found that the Ni 3 S 2 (100) surface exhibits promising bifunctional catalytic activity towards the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The ORR catalytic activity of Ni 3 S 2 (100) can be enhanced by the doping of Cu, and the OER catalytic activity of Ni 3 S 2 (100) can be improved by the doping of Se. Furthermore, a descriptor derived from the electron affinity was developed, which correlate Ni 3 S 2 microstructures with their catalytic activities. This study provides a systematic understanding to the intrinsic activity of transition metal sulfides, paving the way to the rational design and development of advanced electrocatalysts for renewable energy technology. [ABSTRACT FROM AUTHOR]

• N-doped porous carbon was prepared using g-C 3 N 4 as template and nitrogen source. • NC-900 exhibits unexpectedly higher reactivity in the activation of PDS than PMS. • NC-900 surpasses existing N-doped carbon materials in persulfate activation. • PMS activation on NC-900 involves PMS reduction and oxidation mainly producing 1O 2. • PDS activation on NC-900 consists in PDS reduction for the generation of OH. Metal-free activation of peroxymonosulfate (PMS) has been reported to be more efficient than peroxydisulfate (PDS) due to the asymmetrical structure of PMS. However, we report for the first time that the nitrogen-doped porous carbon (NC-900) templated from graphitic carbon nitride exhibits unexpectedly higher catalytic activity in the activation of PDS than PMS, as evidenced by 1.74-fold greater rate constant of NC-900/PDS (0.80 min−1) than that of NC-900/PMS (0.46 min−1). Moreover, NC-900 shows superior reactivity and stability to existing nitrogen-doped nanocarbons in persulfate activation. Experimental and theoretical results revealed that PMS activation involves PMS reduction over the electron-rich graphitic N and PMS oxidation around the electron-deficient carbon atom adjacent to graphitic N in NC-900, in which PMS oxidation is the main reaction rendering singlet oxygen (1O 2) the major reactive species. By contrast, PDS reduction over the electron-poor carbon atom dominates PDS activation on NC-900 for hydroxyl radical (OH) generation. The large amount of OH with stronger oxidation capability than 1O 2 contributes to the superiority of NC-900/PDS over NC-900/PMS in organic pollutant degradation. This work provides profound insights into the difference in metal-free PMS and PDS activation and presents fundamental frameworks in the design of advanced carbon-based catalysts toward sustainable environmental remediation. [ABSTRACT FROM AUTHOR]