Search

By rationally adjusting the coordination environment and constructing the more electron‐enriched active site in single‐atom catalysts, the effect of heterogenous peroxymonosulfate (PMS)‐based Fenton‐like reactions can be effectively improved, yet remains a severe challenge. In this study, the electron‐rich Ru dual‐atom site is successfully immobilized onto N‐doped carbon (Ru2N6‐C) for PMS activation in water purification. The presence of electron‐rich Ru dual‐atom sites not only provides more electrons for PMS but also facilitates the formation of a Yeager adsorption configuration on the catalyst surface, which enhances O─O bond cleavage and leads to an increase in •SO4− and •OH generation. Moreover, the Ru2N6‐C catalyst exhibits exceptional durability and reliability, achieving an ultra‐high efficiency with a turnover frequency of 153.95 min−1 M−1 for the naproxen degradation. A membrane reactor is further developed for the purification of wastewater, which is expected to provide a viable approach to controlling water pollution through the design of metal dual‐atom sites carbon‐based catalysts. [ABSTRACT FROM AUTHOR]

Metal-free porous biochars are popularly utilized as catalysts for peroxydisulfate (PDS) activation. The enhancement effect of PDS activation of porous biochars fabricated by employing both hard template and alkali metal activating agent has not been explored completely. In addition, the role of the inherent carbon defect in PDS activation has not been clearly elucidated. Hence, a series of carbonaceous catalysts were fabricated using a sole template (KCl), a sole activating agent (Na2S2O3) or a combination of template and activating agent (KCl/Na2S2O3, KCl/KHCO3, KCl/NaHCO3, and KCl/Na2C2O4), to systematically investigate the effect of specific surface area (SSA) and intrinsic defect of porous biochar on its PDS activation ability. The biochar synthesized by KCl and Na2S2O3 (SK-C) exhibited the optimum degradation performance. The SK-C was found to possess an interconnected hollow cage with three-dimensional mesh structure showing the largest surface area, pore volume and C-sp3 edge defect content among all the catalysts, which explained its paramount catalytic ability. The SSA and C-sp3 content together can determine the catalytic performance in a quantitative relationship. The single electron transfer pathway from SDZ to inner-sphere bound SK-C/PDS* was the protagonist of pollutant oxidation. The degradation intermediates were detected and recognized and their toxicities were evaluated. This study for the first time comprehensively identified the synergistic effect between the SSA and inherent defects on improving the catalytic performance of biochar for PDS activation to removal contaminants. Highlights: Several porous biochars with various surface area and defect degree were fabricated. These catalysts were used for peroxydisulfate activation to degrade sulfadiazine. The catalyst made by employing Na2S2O3 and KCl exhibited the optimum performance. The surface area and C-sp3 together determined quantitatively the catalytic effect. The single electron transfer from organic to inner-sphere catalyst/peroxodisulfate* was dominant. [ABSTRACT FROM AUTHOR]

The activity of heterogeneous photocatalytic H2O2 activation in Fenton‐like processes is closely related to the local electron density of reaction centre atoms. However, the recombination of electron‐hole pairs arising from random charge transfer greatly restricts the oriented electron delivery to active center. Here we show a defect engineered iron single atom photocatalyst (Fe1‐Nv/CN, single Fe atoms dispersed on carbon nitride with abundant nitrogen vacancies) for the activation of H2O2 under visible light irradiation. Based on DFT calculations and transient absorption spectroscopy results, the engineered nitrogen vacancies serve as the electron trap sites, which can directionally drive the electrons to concentrate on Fe atoms. The formation of highly concentrated electrons density at Fe sites significantly improves the H2O2 conversion efficiency. Therefore, the optimized single atom catalyst exhibiting a higher ciprofloxacin degradation activity, which was up to 18 times that of pristine CN. [ABSTRACT FROM AUTHOR]

[Display omitted] The Sabatier principle in heterogeneous catalysis provides guidance for designing optimal catalysts with the highest activity. We report a new Sabatier phenomenon induced by nanoclusters on different atomic scales in gas-sensitive reactions. We prepared a series of Ag nanocluster catalysts with coordination structures ranging from Ag 0 to Ag 13 through a surface coordination strategy. When used as catalysts for gas-sensitive reactions, a volcano-type relationship between the coordination number of Ag nanoclusters and gas-sensitive activity emerges, with a summit at a moderate coordination of Ag 5. Mechanistic studies show that the efficient adsorption of activated *C 2 H 6 O on electron-rich Ag 5 clusters is a key factor for the Sabatier phenomenon (adsorption energy from −0.322 eV to −0.663 eV), which leads to highly selective sensing. We found that the catalyst electron-rich surface layer induced by Ag 5 clusters serves as a descriptor to explain the structure–activity relationship. Furthermore, due to the well-defined geometric and electronic structures in the Ag 5 clusters, the optimized catalyst achieves both maximum activity and selectivity in chemoselective sensing reactions. This study reveals the Sabatier principle and provides insightful guidance for the rational design of more efficient and practical nanocluster catalysts for heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Abstract: Pyrolysis of herb residue was investigated in a fixed-bed to determine the effects of pyrolysis temperature and catalysts (ZSM-5, Al-SBA-15 and alumina) on the products yields and the qualities of bio-oils. The results indicated that the maximum bio-oil yield of 34.26% was obtained at 450°C with 10wt.% alumina catalyst loaded. The pyrolytic oils were examined by ultimate analysis and calorific values determination, and the results indicated that the presence of all catalysts decreased the oxygen content of bio-oils and increased the calorific values. The order of the catalytic effect for upgrading the pyrolytic oil was Al2O3 >Al-SBA-15>ZSM-5. The bio-oil with the lowest oxygen content (26.71%) and the highest calorific value (25.94MJkg−1) was obtained with 20wt.% alumina catalyst loaded. Furthermore, the gas chromatography/mass spectrometry (GC/MS) was used in order to investigate the components of obtained pyrolytic oils. It was found that the alumina catalyst could clearly enhance the formation of aliphatics and aromatics. [Copyright &y& Elsevier]

Acidity and redox properties of the catalyst are two crucial factors affecting the performance of NH 3 -SCR. Herein, we design a novel WO x /Cu-CeO 2 oxide catalyst in which the WO x species are highly dispersed on the {111}/{100}-terminated surface of Cu-doped CeO 2 nanospheres, which exhibits great deNO x activity advantage and wide operating temperature window (200–400 °C, over 85% NO x conversion with a gas hourly space velocity (GHSV) of 60,000 h−1), as well as good sulfur resistance and N 2 selectivity. The relationship among the composition, acidity and redox properties of the WO x /Cu-CeO 2 catalyst is established in the NH 3 -SCR reaction. The combined experimental studies and spectroscopic characterization reveal that the introduction of Cu into the lattice of CeO 2 not only increases the surface Ce3+ and oxygen vacancy concentration but also provides more sites for capture and dispersion of WO x species, thus mediating and improving the Lewis and Brønsted acid sites and reducibility of catalyst. XPS and DFT calculations further demonstrate that electronic interaction between WO x and Cu-doped CeO 2 is enhanced duo to the existence of interactions of short-range Ce-O-Cu and Ce-O-W. Moreover, the NH 3 -SCR reaction over WO x /Cu-CeO 2 may follow both Langmuir-Hinshelwood and Eley-Rideal reaction pathway according to the in situ DRIFTS. [Display omitted] • The addition of Cu and W significantly increased the NO conversion of CeO 2. • Cu doping CeO 2 increased the Ce3+, O vacancy and enhanced the Lewis acid site. • WO x improved Brønsted acidity and facilitated Langmuir-Hinshelwood mechanism. • Existence of strong electronic interaction between WO x species and Cu-CeO 2. [ABSTRACT FROM AUTHOR]

Although the electro-Fenton (EF) process is effective for wastewater treatment, recycling spent catalysts remain a major challenge. Therefore, we introduce a reuse strategy for spent catalysts where an iron hydroxyphosphate [Fe 5 (PO 4) 4 (OH) 3 ·2H 2 O] catalyst is utilized. Fe 5 (PO 4) 4 (OH) 3 ·2H 2 O obtained •OH and •O 2 − by activating in-situ produced H 2 O 2 , and the degradation rate of sulfamethoxazole reached 94.5% after 120 min and showed excellent stability (maintained above 90%) for 10 cycles. Finally, the used catalyst was converted into slow-release ammonium ferrous phosphate (NH 4 FePO 4 ·H 2 O) fertiliser at a conversion rate of 85.6%. NH 4 FePO 4 ·H 2 O significantly promoted plant and seed growth within 6 days, highlighting the contribution of the resource recycling of the spent catalyst. This study serves as a valuable reference for the efficient utilization of spent catalysts. This study successfully applied EF catalysts and explored the recycling of spent catalysts. • The investigation of electro-catalyst recovery and the utilization of EF process have been conducted. • The catalyst Fe 5 (PO 4) 4 (OH) 3 ·2H 2 O showed good degradation performance of the recalcitrant pollutant sulfamethoxazole. • The catalyst promoted the production of.•OH and •O 2 − during the EF process. • The catalyst was converted into a slow-release fertilizer NH 4 FePO 4 for plant growth. [ABSTRACT FROM AUTHOR]

Defects engineering in nanomaterials can be used to precisely and effectively modulate catalysts' reactivity. Here we report a highly efficient NH 3 -SCR catalyst constructed with in-situ formation of carbon-doped CeZrO 2−x with dual defects, in which O atoms are substituted by C atoms to generate surface oxygen vacancies and subsurface oxygen substitutions. The carbon-doped CeZrO 2−x exhibit superior activity and better SO 2 /H 2 O resistance compared with traditional bulk CeZrO x and V 2 O 5 -WO 3 /TiO 2. The related characterization results reveal that the surface oxygen vacancy and subsurface oxygen substitution resulted in the formation of a large number of unsaturated coordination Ce and Zr species on catalyst's surface, which contributed to the adsorption and activation of NH 3 , thus promoting the catalytic activity. Meanwhile, the abundant oxygen vacancy also stimulated the E-R reaction pathway over carbon-doped CeZrO 2−x. In addition, it was proved that more zirconium sulfate and unstable ammonium sulfate species were exposed over carbon-doped CeZrO 2−x , benifiting the better SO 2 -tolerance. [Display omitted] • Carbon-doped CeZrO 2−x with dual defects was constructed for NH 3 -SCR. • The carbon-doped CeZrO 2−x exhibits superior activity and better SO 2 /H 2 O resistance. • Oxygen vacancy and oxygen substitution enhanced the Lewis acid site. • Zirconium sulfate and unstable ammonium sulfate contributed to SO 2 -tolerance. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Sn doped CeMoO x fibers with hollow structure have been successfully synthesized. • Sn doped CeMoO x fibers exhibit good SO 2 tolerance. • Higher Brønsted acid sites and chemisorbed oxygen species responsible for SO 2 tolerance. Abstract A series of novel Sn modified CeMoO x electrospun fibers were fabricated using a combination method of sol-gel process and electrospinning technique for the selective catalytic reduction (SCR) of NO with NH 3. The performances of fresh and sulfated Sn modified CeMoO x catalysts in the presence of different amount of SO 2 at low temperature were investigated. Characterization of these catalysts aimed at elucidating the effect of additive. The catalyst had a Sn/(Sn + Ce + Mo) = 0.2 M ratio showed the widest SCR activity improvement with near 100% NO x conversion at 225–450 °C with a gas hourly space velocity of 100 000 h−1. X-ray photoelectron spectroscopy (XPS) indicated that Sn modification significantly increases the chemisorbed oxygen species that may facilitate NO oxidation to NO 2. H 2 -TPR and NH 3 -TPD characterization showed that the catalysts have better redox ability and higher Brønsted acid sites, which is also enhanced by Sn modification. Combined with the adsorption and transient reaction studied from in situ DRIFTs spectra suggested a "fast SCR" reaction route, i.e., the more active NH 4 + ions react with gaseous NO 2 molecules, which primarily occurred on the surface of either the fresh or sulfated Sn/0.2-CeMoO x. Furthermore, as compared to CeMoO x , the sulfated Sn/0.2-CeMoO x sample obtained even smaller grain size, better redox ability, higher Brønsted acid sites and more chemisorbed oxygen species, which were contributed to the excellent SO 2 resistance. [ABSTRACT FROM AUTHOR]

• Mn-NPs loaded N-doped RGO (Mn-NRGO) was used for PMS activation to degrade BPA. • A selectivity toward different aromatic compounds in Mn-NRGO/PMS system was found. • Mn-NRGO/PMS system degraded BPA by mediated electron transfer pathway. • The electron transfer pathway was achieved by outer-sphere catalyst-PMS complex. • The crucial role of synergistic effect between Mn-NPs and doped N was elucidated. A family of graphene-based activators including reduced graphene oxide (RGO), nitrogen doped reduced graphene oxide (NRGO), zero-valent manganese loaded reduced graphene oxide (Mn-RGO) and zero-valent manganese loaded N-doped reduced graphene oxide (Mn-NRGO) were fabricated to activate peroxymonosulfate (PMS) for bisphenol A (BPA) degradation. A significant synergistic effect between loaded manganese nano-particles (Mn-NPs) and doped N was revealed by comparing the apparent reaction rate constants with about 12.4, 7.6 and 10.5-folds enhancement when compared Mn-NRGO with RGO, NRGO, Mn-RGO, respectively. By integrating the results of chemical scavenger experiment, electron paramagnetic resonance test, galvanic oxidation process, PMS stoichiometric efficiency, linear sweep voltammetry and in-situ Raman spectrum, a predominant outer-sphere catalyst-PMS complexes mediated electron transfer pathway was uncovered. Based on kinetic studies, the specific contribution of synergistic effect was quantified to be at least 70%. The calculated Fermi level advanced by 0.03 eV in Mn-NG compared with that in NG, demonstrating that Mn-NG is more liable to donate electrons to PMS. The E ads and l O-O results pointed out that synergistic effect between Mn-NPs and doped N relied on the intimate affinity between Mn-NPs and HSO 5 – which triggered more uneven distribution of charge on the whole carbon sheets, and more adsorption of HSO 5 – on carbon framework. These newly created adsorption consequently reinforcing the formation of catalyst-PMS complexes and the elevation of mediated electron transfer pathway. Overall, this study firstly provides a comprehensive and definite insight of the synergistic effect between loaded Mn-NPs and doped-N on carbon materials for promoting PMS activation to degrade organics. [ABSTRACT FROM AUTHOR]