Ag Species Research Articles

Bio-inspired synthesis of Ag-g-C3N4 nanocomposites and their application for photocatalytic degradation of para-nitrophenol

Nanocomposites are promising in advanced materials for environmental applications due to their ability to boost functionality through synergistic effects. Graphitic carbon nitride (g-C3N4) is renowned for its exceptional characteristics in photocatalysis. This work examines the preparation of g-C3N4 from different precursors, and how the presence of silver nanoparticles (Ag NPs) and silver ions (Ag+) in g-C3N4 matrices improve their combined effect on photocatalytic activity, specifically in the degradation of para-nitrophenol (PNP), a persistent organic pollutant. From urea and melamine precursors for the preparation of g-C3N4, the latter provided a much higher yield. Using an easy synthesis approach, Ag NPs were evenly distributed in the g-C3N4 framework, whereas Ag+ ions were incorporated by an apparent physical procedure. A bio-inspired, environmentally friendly method was also applied to prepare Ag NPs. The nanocomposites showed improved light absorption and separation of charge carriers due to the synergistic interaction between g-C3N4 and Ag species. Using UV and Vis LED light sources, we investigated both pure g-C3N4 and Ag-g-C3N4 catalysts. For breaking down para-nitrophenol, the silver-modified catalysts performed significantly better than pure g-C3N4 in both UV and Vis. The study clarified the functions of Ag NPs and Ag+ ions in enhancing photocatalytic activity by examining their involvement in generating reactive oxygen species and degrading pollutants. This work highlights the capability of g-C3N4-based nanocomposites as effective photocatalysts for environmental remediation. It also explores the benefits of adding silver species to improve performance in degrading pollutants.

Study on the effect and mechanism of support structure and characteristic on Ag-based catalysts for low-temperature selective catalytic oxidation of ammonia

Herein, the influence of support type and properties on the catalytic activity and selectivity of Ag-based NH3-SCO catalyst was studied through the evaluation of NH3-SCO performance, the physicochemical characterization of H2-TPR, NH3-TPD, N2 isothermal adsorption–desorption, XPR and XPS, and the mechanism study of 1H MAS NMR, In-situ DRIFTS and DFT calculations. Ag/nano-TiO2, Ag/Al2O3, and Ag/MnO2 all showed better NH3-SCO activity because of more abundant Brønsted and Lewis acid sites of Al2O3 and TiO2 and more actual Ag loading amount due to the larger specific surface area and suitable surface chemistry. The N2 selectivity of Ag/nano-TiO2 is significantly better, which may be due to the highly dispersed Ag species and the abundant Brønsted acid sites with higher N2 selectivity. The mechanism study showed that the terminal hydroxyl was the preferred consumption target of Ag species, and this consumption promoted the effective dispersion and stable anchoring of Ag on the TiO2 surface.

Ag-modified CuO-Fe2O3 composite catalysts for low-temperature NH3-SCO

A series of CuFe and Ag-modified CuFe composite catalysts were prepared for low-temperature selective catalytic oxidation of ammonia (NH3-SCO). Significant synergistic effects existed between Cu and Fe oxides in the CuFe(7:12) catalyst for catalyzing NH3 oxidation. Loading 6 wt.% Ag over CuFe(7:12) further enhanced NH3 conversion and N2 selectivity. At 200 °C, NH3 conversion and N2 selectivity reached 97.1 % and 79.3 %, respectively, over 6Ag/CuFe(7:12). Besides the exceptional catalytic effects of Ag species, the increased surface area, formation of CuFe2O4, improved reducibility of Cu and Fe oxides, and increased acid sites due to the composite of Cu and Fe and modification with Ag contributed to the superior performance of the 6Ag/CuFe(7:12) catalyst in NH3-SCO. In-situ DRIFTS results showed that NH3 oxidation might follow the internal selective catalytic reduction mechanism: NH3 was dehydrogenated and oxidized to NOx and nitrate species, and the formed NOx and nitrate species were reduced by the remaining NH3, −NH2 and −NH species to N2 and H2O. Loading Ag over CuFe(7:12) suppressed the formation of NO and NO2 but promoted that of N2O during NH3 oxidation, which could be attributed to the enhanced formation and decomposition of NH4NO3 in the presence of Ag.

Mechanical characterization of nanocrystalline Cu-Ag alloys subjected to shear deformation

ABSTRACT This study investigates the mechanical behaviour of nanocrystalline Cu-Ag alloys using molecular dynamics simulations combined with detailed analyses of dislocation densities, atomic populations, and deformation characteristics. Shear tests were conducted across three different atomic compositions at temperatures ranging from 10 K to 500 K. The influence of temperature and Ag impurities on the mechanical properties of nanocrystalline Cu is explored. Elevated temperatures are found to promote plastic deformation by increasing atomic mobility, resulting in reduced dislocation densities and flow stresses. Increasing Ag content correlates with lower dislocation densities, highlighting enhanced plastic activity between grain and grain boundaries. Structural population analysis underscores the significant impact of Ag species on the mechanical response of nanocrystalline Cu. Further investigations are warranted to explore additional deformation mechanisms. These findings contribute to a deeper understanding of nanocrystalline Cu-Ag alloys, informing the design of novel materials with tailored mechanical properties.

Improving the NH3 oxidation and removing NOx during ammonia-rich fuel catalytic combustion using the Ag/CuOx@SiO2 catalyst with high-temperature catalytic activity

Ammonia, as a carbon-free, hydrogen-rich and renewable fuel, is of great significance for building the zero-carbon emission energy supply system in the word. However, the drawbacks of high ignition energy and high NOx emissions limit its widespread application. Catalytic combustion provides a reliable option for NH3 combustion. In the study, the catalyst of Ag/CuOx@SiO2 catalyst with high-temperature catalytic activity was prepared, and the catalytic flow reactor was employed to evaluate the ability of the catalyst in enhancing NH3 oxidation and removal NOx during NH3-rich combustion with high temperature region (900 K∼1400 K) and wide equivalence ratio range (0.4 ∼ 1.2). The high-temperature catalytic activity of the catalyst was proved by XPS spectrogram that the valence states of Ag and CuOx species in the catalyst have not been changed after the catalytic combustion. The results of catalytic combustion indicated that the catalyst enhanced the NH3 oxidation significantly. Compared to NH3 combustion, the temperature of 100 %NH3 conversion (T100) was decreased by over 500 K during NH3 catalytic combustion. Moreover, catalytic combustion performed higher efficiency on enhancing NH3 oxidation than the approach of co-firing NH3 with higher reactive gas fuels. The T100 of NH3 catalytic combustion was lower by 200 K∼220 K than that of NH3/H2 and NH3/CH4 combustion. Furthermore, the catalyst reduced the NOx effectively during NH3/H2 and NH3/CH4 combustion. At 1400 K, NO selectivity during NH3/H2 and NH3/CH4 catalytic combustion reduced by 86.80 %∼90.42 % and 43.61 %∼61.42 % compared to the combustion, respectively. Additionally, the peak of N2O selectivity moved to lower temperature range during catalytic combustion. Especially in stoichiometric and fuel rich conditions, the peak temperature reduced by 100 K∼200 K. The study provided references for the development of catalysts in ammonia-rich fuel catalytic combustion.

ZIF-8 derived Ag/ZnO photocatalyst with enriched Ag-ZnO interface for effective oxidation of methane to liquid oxygenates with simultaneous mmol-scale productivity and ∼100 % selectivity

Achieving a high yield of oxygenates and inhibiting overoxidation remain challenging for CH4 photooxidation. Here, we report a catalyst with enriched Ag-ZnO interfaces by using ZIF-8 as the precursor. The resulting Ag/Z-450 photocatalysts show extraordinary efficiency in the photocatalytic oxidation of CH4, a high liquid oxygenate yield of 57.88 mmol·gcat−1 (28.94 mmol·gcat−1·h−1) and a selectivity of ∼100 % were obtained over 3.0Ag/Z-450, with HCHO as the major product (41.04 mmol·gcat−1, ∼71 % selectivity). Mechanistic studies revealed that ZnO and Ag species acted as electron donors and acceptors, respectively, which enhanced charge carriers transfer and separation. CH4 and O2 can be effectively activated to generate •CH3 and reactive oxygen species (ROS), their following reaction led to formation of CH3OOH, which can be further converted to CH3OH and HCHO. This work contributes to the development of a “two-in-one” CH4 photooxidation catalyst system that simultaneously achieves unparallel productivity and selectivity.

Decoration of Ag Species into Reduced Graphene Oxide Foam as a Superelastic and Robust Host toward Stable Zn Metal Anodes under Dwell-Fatigue Condition.

Deep-sea equipment usually operates under dwell-fatigue condition, which means the equipped energy storage devices must survive under the changing pressure. Special mechanical designs should be considered to maintain the electrochemical performance of electrodes under this extreme condition. In this work, an effective assembly strategy is proposed to accommodate the dwell-fatigue loading using Ag decorated reduced graphene oxide (rGO) foam (denoted as AGF) as a superelastic and robust Zn host. The wet-press assembly process enables the formation of highly porous and robust framework. The strong synergetic effect between rGO and Ag further guarantees AGF's superelasticity and ultrahigh mechanical strength. Meanwhile, the homogeneously distributed Ag species on the rGO sheets act as zincophilic sites to effectively facilitate Zn plating. Furthermore, AGF offers enough space to address the expansion during the charge and discharge cycles. As expected, the symmetrical cell using this AGF@Zn host demonstrates a long lifespan over 400h at a depth-of-discharge of 50%. It is worth mentioning that the superelastic AGF host realizes stable Zn plating/stripping under varying pressures.

Highly selective oxidation of 5-HMF to HMFCA via a facile Pt-Ag co-catalytic strategy

5-Hydroxymethyl-2-furancarboxylic acid (HMFCA) is an important feedstock in chemical and pharmaceutical industries. Its production through aerobic conversion of 5-hydroxymethylfurfural (5-HMF) has promising prospects but is challenged by the over-oxidation. In this work, we develop a refined Pt-Ag co-catalytic strategy to tailor the selectivity of 5-HMF’s aerobic oxidation. By simple in situ addition of AgNO3 to the thermal catalytic system of Pt nanoparticles, the main products of 5-HMF oxidation could be shifted from 2,5-furandicarboxylic acid (FDCA) to HMFCA with an ultrahigh selectivity of over 99 %. Density functional theory calculations demonstrate that such strategy could alter the HMFCA adsorption sites from Pt to Ag sites and prevent the oxidation of hydroxymethyl group. In addition, this strategy can be extended to other Ag species, such as AgCl, Ag2O and AgO. This work provides insights into the Pt-Ag synergistic catalysis and opens up a simple avenue to control the product selectivity for biomass refinement.

Hybrid Ethylcellulose Polymeric Films: Ag(I)-Based Components and Curcumin as Reinforcing Ingredients for Enhanced Food Packaging Properties.

Bio-active ethylcellulose (EC) polymeric films have been obtained by incorporating curcumin (curc) and Ag(I)-based compounds, known for their antioxidant and antimicrobial activity, respectively, within the polymeric matrix. The recently reported Ag(I) coordination polymer, in both its structural forms (α-[(bpy)Ag(OTf)]∞ and β-{[(bpy)Ag][OTf]}∞), and the [(bpy)Ag(OTf)]∞-curc polymeric co-crystal (bpy=2,2'-bipyridine; OTf=trifluoromethanesulfonate) have been selected as Ag(I) species. The hybrid composite films have been prepared through the simple solvent casting method and characterized through Powder X-Ray Diffraction (PXRD), Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscope (SEM), UV-vis spectroscopy. The deep investigation of the film samples highlighted the non-inert behaviour of EC towards these specific active ingredients. Antimicrobial tests showed that EC films embedding the Ag(I)-based compounds present good antimicrobial performance, in particular against Staphylococcus aureus, used as a model of Gram-positive bacteria. In addition, Silver migration tests, performed on the Ag(I)-incorporating EC films, evidenced low values of silver release particularly in the case of the EC films incorporating [(bpy)Ag(OTf)]∞-curc.

Ag Intercalation in Layered Cs3Bi2Br9 Perovskite for Enhanced Light Emission with Bound Interlayer Excitons.

Cesium bismuth bromide (CBB) has garnered considerable attention as a vacancy-ordered layered perovskite with notable optoelectronic applications. However, its use as a light source has been limited due to its weak photoluminescence (PL). Here, we demonstrate metal intercalation as a novel approach to engineer the room-temperature PL of CBB using experimental and computational methods. Ag, when introduced into CBB, occupies vacant sites in the spacer region, forming octahedral coordination with surrounding Br anions. First-principles density functional theory calculations reveal that intercalated Ag represents the most energetically stable Ag species compared to other potential forms, such as Ag substituting Bi. The intercalated Ag forms a strong polaronic trap state close to the conduction band minimum and quickly captures photoexcited electrons with holes remaining in CBB layers, leading to the formation of a bound interlayer exciton, or BIE. The radiative recombination of this BIE exhibits bright room-temperature PL at 600 nm and a decay time of 38.6 ns, 35 times greater than that of free excitons, originating from the spatial separation of photocarriers by half a unit cell separation distance. The BIE as a new form of interlayer exciton is expected to inspire new research directions for vacancy-ordered perovskites.

Zwitterionic Thiolate-Protected Ag22(0/I) and Ag20(I) Clusters: Assembly, Structural Characterization, and Antibacterial Activity.

Zwitterionic thiolate ligands have the potential to introduce novel assembly modes and functions for noble metal clusters. However, their utilization in the synthesis of silver clusters remains understudied, particularly for the clusters containing reductive Ag(0) species. In this article, we report the first synthesis of a mixed-valence silver(0/I) cluster protected by zwitterionic Tab as thiolate ligands (Tab = 4-(trimethylammonio)benzenethiolate), denoted as [Ag22(Tab)24](PF6)20·16CH3OH·6Et2O (Ag22·16CH3OH·6Et2O), alongside an Ag(I) cluster [Ag20(Tab)12(PhCOO)10(MeCN)2(H2O)](PF6)10·11MeCN (Ag20·11MeCN). Ag22 has a distinct hierarchical supratetrahedral structure with a central {Ag6} kernel surrounded by four [Ag4(Tab)6]4+ units. High-resolution electrospray ionization mass spectra demonstrate that Ag22 has two free electrons, indicating a superatomic core. Ag20 has a drum-like [Ag12(Tab)6(PhCOO)6(H2O)]6+ inner core capped by two tetrahedral-like [Ag4(Tab)3(PhCOO)2(MeCN)]2+ units. Ag20 can be transformed into Ag22 after its reaction with NaBH4 in solution. Antibacterial measurements reveal that Ag22 has a significantly lower minimum inhibitory concentration than that of the Ag20 cluster. This work not only extends the stabilization of silver(0/I) clusters to neutral thiol ligands but also offers new materials for the development of novel antibacterial materials.

Ni-Ag Catalysts for Hydrogen Production through Dry Reforming of Methane: Characterization and Performance Evaluation

To investigate the influence of Ag and the loading of Ni species, Ni-Ag type catalysts were synthesized with varying Ni/Ag ratios (1, 1.5 and 2) using the coprecipitation method. The catalysts were extensively characterized using various techniques such as TG-DSC-SM, XRD, ICP, BET, SEM-EDX and TPR and subsequently tested in the CH4/CO2 reaction without any pretreatment. Regardless of the ratio employed, a phase mixture containing NiO and Ag was observed after calcination under air between 600 °C and 1200 °C. SEM analysis confirmed the presence of a close interface between Ag and NiO. The specific surface area was found to be significantly higher for the catalyst with lower Ni content (R = 1). TPR analysis demonstrated that the inclusion of Ag facilitated the reduction of Ni at lower temperatures. XRD analyses of the spent catalyst confirmed catalyst reduction during the reaction. Among the samples, a catalyst with Ni/Ag = 1 exhibited superior catalytic activity without any pretreatment under a reduction atmosphere, in which case the conversions of methane and CO2 at 650 °C amounted to 38 and 45 mol%, respectively, with H2/CO = 0.7 and 71 mol% of H2. The presence of Ag species enhances the stability of the Ni catalyst and improves catalytic performance in the dry reforming of methane.

Chemical vapor deposition-based synthesis of cost-effective binder-free nanostructured Ag/MoS2/Ni–F electrode material for portable energy storage devices

The synthesis of novel electrode materials (E-Ms) is the demand of scientific community to overcome the energy crisis in developing countries. Hereon, the molybdenum disulfide (MoS2) and silver-wrapped MoS2 (Ag/MoS2) E-Ms are synthesized on hierarchical-nickel foam (Ni–F) via a cost-effective chemical vapor deposition technique. The synthesized E-Ms are characterized in terms of structure, chemical bonding, surface morphology, weight percentage of elements, porosity and energy storage capability. The X-ray diffraction analysis is indicated that by wrapping of Ag species, the diffraction peaks associated with MoS2 material not only moved to higher Bragg's angles but their peaks intensities are also lowered which showed the existence of structural defects in the synthesized E-Ms. The surface area of cauliflower like Ag/MoS2/Ni–F E-Ms (170 m2g-1) is higher than the surface area (60 m2g-1) of MoS2/Ni–F E-Ms. The cauliflowers based Ag/MoS2/Ni–F E-Ms is presented supreme specific capacitance of 4200 Fg-1 as compared to MoS2/Ni–F E-Ms (2518 Fg-1) at 1Ag-1. The implementation of power law and Dunn's model is demonstrated that the synthesized E-Ms can behave like a battery and supercapacitor (0.67 < b < 0.92) nature. The diffusive-controlled contribution for cauliflower-based synthesized E-Ms is 97 % at 5 mVs−1 and became 88 % at 70 mVs−1. The assembled asymmetric supercapacitor (ASC) device is exhibited the specific capacitance of 957 Fg-1, energy density of 366–284 Whkg−1 and power density of 1494–14110 Wkg-1. The ASC device could sustain the capacitance retention of 94 %, Coulombic efficiency of 99 % even for 20000 cycles in contrast to capacitance retention of 95 % and Coulombic efficiency of 97.89 % of the synthesized E-Ms.

Silver nanoparticles composited co-dopped polypyrrole/zinc coating for enhancing anti-corrosion and antibacterial properties of ZK60 magnesium alloy in Hank’s solution

For the biodegradable implant applications, silver nanoparticles (Ag NPs) are incorporated in polypyrrole (PPy) co-dopped with tartrate (TA) and salicylate (SA) anions to obtain multi-functional Ag NPs-PPy(TA + SA)/Zn bilayer coating on ZK60 magnesium alloy with high protective and antibacterial properties. The effects of Ag NPs on the composition, structure, and antibacterial and protective properties of Ag NPs-PPy(TA + SA)/Zn bilayer coating are studied. Incorporating Ag NPs influences the electrochemical growth conditions of PPy(TA + SA), possibly increasing the defects in PPy chains. Its surface morphology and film thickness are similar to PPy(TA + SA). However, Ag species (Ag+/Ag0 ≈ 0.1) are only distributed in the PPy surface layer (hundreds of nm), containing some adsorbed and agglomerated Ag NPs on its surface. In Hank’s solution at 37 °C, Ag NPs-PPy(TA + SA) experiences slow degradation, and the Ag content loses slowly to zero. Its protection time is significantly improved to 113 ± 2.6 days, much more prolonged than PPy(TA + SA) (54 ± 1.5 d), suggesting the crucial role of Ag NPs. After Ag NPs-PPy(TA + SA) is broken due to its local destruction, ZK60 displays typical local corrosion. Ag NPs-PPy(TA + SA) exhibited excellent cytocompatibility and antibacterial properties. The corresponding mechanism involved is thoroughly discussed.

Insight into the performance-boosting mechanism of Ag/MgAlOx for NH3 selective catalytic oxidation: Perspective from the support crystalline phase structures

Arranging an ammonia oxidation process after the selective catalytic reduction of NOx by NH3 (NH3-SCR) system is an effective way for ensuring the DeNOx efficiency and controlling the slip ammonia. To improve operability and reduce operating costs in ammonia selective catalytic oxidation (NH3-SCO), developing feasible and efficient catalysts becomes meaningful. Herein, focusing on the dilemma of Ag/Al2O3 catalysts in NH3-SCO applications, Ag/MgAlOx catalysts with different support different crystalline phase structures (5 %Ag/MgAl-LDO and 5 %Ag/MgAl2O4) were innovatively synthesized and systematically evaluated application potential in NH3-SCO. Results indicated that the introduction of Mg apparently broadened reaction temperature window and catalytic performance of 5 %Ag/MgAl2O4 was higher than 5 %Ag/MgAl-LDO, while the N2 selectivity was completely opposite. The combination of series characterization and density functional theory (DFT) calculations revealed that 5 %Ag/MgAl2O4 surface has more Ag0 species with small particle size, which is favorable for ammonia adsorption and activated dehydrogenation to further promote reaction of NOx species, resulting in a higher NH3-SCO activity. In contrast, 5 %Ag/MgAl-LDO readily induces oxidized Ag species and Ag0 is more inclined to be present in large particle sizes, which is more conducive to dissociation of O2 to produce reactive O species (O*) leading to the peroxidation of ammonia to nitrate and thus, positively affects the improvement of N2 selectivity. Model catalyst 5 %Ag/MgAl-650 (mixed-phase) was prepared by controlling the roasting conditions and exhibited excellent catalytic performance in NH3-SCO with almost 93 % of NH3 oxidized at 250 °C (N2 selectivity up to 71 %). This work could afford theoretical support for the optimization and application of catalysts with high performance at low temperatures in selective catalytic oxidation of slip ammonia.

Advancing highly selective low-temperature ammonia oxidation: Hydrophobic silicalite-1 shell confining silver nanoparticles on Cu/ZSM-5 core

A judiciously devised core–shell NH3-SCO catalyst featuring a Cu/ZSM-5 core enveloped by an Ag/silicalite-1 shell (Cu/ZSM-5@Ag/S-1) was rationally constructed. Integrating the silicalite-1 shell effectively suppresses the migration of Ag into Cu/ZSM-5 core, conserving the active Cu2+ sites for the catalytical conversion of byproducts NOx. Concurrently, the shell averts the formation of positively charged Ag species, facilitating the generation of abundant Ag0 nanoparticles encapsulated in the S-1 shell. Comprehensive characterizations reveal abundant Ag0 species within the core–shell Cu/ZSM-5@Ag/S-1 catalyst, boosting O2 activation and NH3 dehydrogenation and thereby contributing to superior low-temperature activity in NH3-SCO reactions. Furthermore, the hydrophobic S-1 shell effectively reinforces the hydrothermal stability of the core–shell Cu/ZSM-5@Ag/S-1. DRIFTS coupled with DFT studies elucidate that the core–shell sample follows the imide mechanism, while the shell-free sample adheres to the hydrazine mechanism. This work advances our understanding of catalyst design and presents a promising solution with practical implications for ammonia oxidation processes.

Adjusting Ag0 on oxygen-deficient Ag/MnO2 through electronic metal-support interaction to enhance mineralization of toluene in post-plasma catalytic system

While nonthermal plasma (NTP) technology exhibits notable efficacy in removing volatile organic compounds (VOCs), its practical application is impeded by a restricted carbon dioxide (CO2) selectivity. In this work, Ag-loaded α-MnO2 nanorods with strong electronic metal-support interaction (EMSI) were synthesized to enhance the mineralization of toluene in post-plasma system (PPC). EMSI was constructed between Ag species and MnO2 by anchoring Ag on hydroxyl groups. Increasing Ag loading facilitated the generation of oxygen vacancies, which promoted electron transfer from MnO2 to Ag sites, reinforcing EMSI and favoring the formation of Ag0. The results showed that the 3% Ag-loaded α-MnO2 nanorods exhibited better activity than bare MnO2, with a remarkable boost in CO2 selectivity to 77.5%, far exceeding the 33% CO2 selectivity of MnO2. It was concluded that both oxygen vacancies and Ag0 affected the toluene conversion by enhancing the conversion of ozone (O3) to reactive oxygen species (ROS). Through in-situ DRIFTS, it was found that Ag0 transformed O3 to a higher concentration of atomic oxygen (O*), capable of degrading organic intermediates to CO2. Additionally, Ag0 facilitated the direct ring-opening of adsorbed toluene. This research introduces a novel method for designing catalysts with EMSI to improve the mineralization of VOCs.

Nanosilver-based materials as feed additives: Evaluation of their transformations along in vitro gastrointestinal digestion in pigs and chickens by using an ICP-MS based analytical platform

The use of a new nanomaterial in the feed chain requires a risk assessment that involves in vitro gastrointestinal digestions to predict its degradation and oral exposure to nanoparticles. In this study, a nanosilver-based material was incorporated into pig and chicken feed as a growth-promoting additive and subjected to the corresponding in vitro gastrointestinal digestions. An inductively coupled plasma mass spectroscopy (ICP-MS) analytical platform was used to obtain information about the silver released in the different digestion phases. It included conventional ICP-MS for total silver determination, but also single particle ICP-MS and coupling to hydrodynamic chromatography for detection of dissolved and particulate silver. The bioaccessible fraction in the intestinal phase accounted for 8–13% of the total silver, mainly in the form of dissolved Ag(I) species, with less than 0.1% as silver-containing particles. Despite the additive behaving differently in pig and chicken digestions, the feed matrix played a relevant role in the fate of the silver.

Unexpected strong toluene chemisorption over Ag/CeO2 catalysts for total toluene oxidation

The effect of Ag content on the sorption properties and toluene removal activity over Ag/CeO2 catalysts is studied. In this paper, the series of Ag/CeO2 catalysts with Ag content from 1 to 10 wt% are prepared by impregnation method and characterized using a complex of methods: low-temperature N2 adsorption, XRD analysis, TPR-H2, and TEM-HR. For the first time, the strong toluene chemisorption over Ag-containing species accompanied by total oxidation into CO2 is observed. The correlation between the amount of chemisorbed toluene and Ag loading in the catalysts confirms the toluene chemisorption over Ag species and/or Ag-CeO2 interface. The active surface oxygen of ceria oxidizes chemisorbed toluene. The cooperation of active sites on silver and ceria provides both enhanced chemisorption of toluene and its total oxidation. The total removal of toluene (2000 ppm) was achieved at ∼140 °C over 5Ag/CeO2 and 10Ag/CeO2 catalysts due to both chemisorption and total oxidation of toluene.

Capture of single Ag atoms through high-temperature-induced crystal plane reconstruction

The “terminal hydroxyl group anchoring mechanism” has been studied on metal oxides (Al2O3, CeO2) as well as a variety of noble and transition metals (Ag, Pt, Pd, Cu, Ni, Fe, Mn, and Co) in a number of generalized studies, but there is still a gap in how to regulate the content of terminal hydroxyl groups to influence the dispersion of the active species and thus to achieve optimal catalytic performance. Herein, we utilized AlOOH as a precursor for γ-Al2O3 and induced the transformation of the exposed crystal face of γ-Al2O3 from (110) to (100) by controlling the calcination temperature to generate more terminal hydroxyl groups to anchor Ag species. Experimental results combined with AIMD and DFT show that temperature can drive the atomic rearrangement on the (110) crystal face, thereby forming a structure similar to the atomic arrangement of the (100) crystal face. This resulted in the formation of more terminal hydroxyl groups during the high-temperature calcination of the support (Al-900), which can capture Ag species to form single-atom dispersions, and ultimately develop a stable and efficient single-atom Ag-based catalyst.