Ag Species Research Articles

Sustainable in situ synthesis of silver/titanium dioxide/organofunctional trialkoxysilane nanocomposite coatings on cotton fabric to tailor superior multifunctional protective properties

Multifunctional properties are crucial for the production of high-quality technical textiles. In this study, a cotton fabric with simultaneously superior UV-protection, self-sterilisation, photocatalytic self-cleaning and flame retardant properties was produced using a sol–gel/hydrothermal process, in which titanium(IV) isopropoxide (TTIP) as a titanium dioxide (TiO2) precursor was combined for the first time with mixtures of organofunctional trialkoxysiloxanes, i.e., 3-(trihydroxysilyl)propyl methylphosphonate (TPMP) as a P-based flame retardant and dimethyloctadecyl [3-(trimethoxysilyl)propyl]ammonium chloride (SiQAC) or aminopropyltriethoxysilane (APTES) as the antimicrobial, biobarrier-forming precursors. The latter was used in two increased concentrations of APTES1 and APTES2. A sol–gel/hydrothermal approach was employed with a small amount of silver nitrate (AgNO3) added during the hydrothermal treatment to produce Ag-loaded TiO2. The results of scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS), X-ray diffraction spectroscopy (XRD), inductively coupled plasma mass spectroscopy (ICP MS) and Fourier-transform infrared spectroscopy (FT-IR) confirmed the successful functionalisation of TiO2 by TPMP, SiQAC and APTES through the formation of Si–O–Ti bonds and the well-dispersed Ag/TiO2/TPMP/SiQAC, Ag/TiO2/TPMP/APTES1 and Ag/TiO2/TPMP/APTES2 coatings on the surface of the cotton fabric. The type of biobarrier-forming precursor significantly influenced the formation of the Ag species after the Ag loading of TiO2. The presence of SiQAC induced the formation of AgCl crystals, while APTES controlled the formation of silver nanoparticles (Ag NPs), which was more pronounced at the lower APTES1 concentration. The interactions between the coating components significantly influenced the functional protection performance, with the highest level of cooperation achieved in the Ag/TiO2/TPMP/SiQAC and Ag/TiO2/TPMP/APTES1 coatings, which exhibited the best overall multifunctionality, albeit with certain drawbacks. While the Ag/TiO2/TPMP/APTES1 coating provided excellent UV protection for the cotton, this was only improved by the Ag/TiO2/TPMP/SiQAC coating. At the same time, the Ag/TiO2/TPMP/APTES1 coating impaired the development of the char barrier by TPMP, which is due to the formation of Ag NPs. Nevertheless, both coatings showed high photocatalytic self-cleaning performance, complete self-sterilisation activity and improved burning behaviour.

Temperature-driven dynamic evolution process of Ag species on silver-loaded Zr0.2Sn0.8O2 catalyst for selective catalytic oxidation of ammonia

Silver-based catalysts are extensively utilized in the selective catalytic oxidation of ammonia (NH3-SCO). However, enhancing low-temperature activity often causes a decline in N2 selectivity, presenting a substantial challenge in balancing activity and N2 selectivity. In this work, we introduced zirconium into the SnO2 support, resulting in a significant enhancement of low-temperature activity by 200 °C for the Ag/Zr0.2Sn0.8O2 catalyst; yet, this also led to the formation of N2O at low temperatures and NOx at high temperatures. Characterizations such as XPS and in situ DRIFTS revealed that the dynamic changes of silver species driven by temperature had a profound impact on the reaction mechanism and guided the formation of different products. Below 200 °C, the predominance of Ag+ directed the imide mechanism, with the –HNO species being the key intermediate leading to the production of N2O. Above 300 °C, Ag0 became dominant, favoring the internal selective catalytic reduction (i-SCR) mechanism and the production of NOx. This work provides novel insights into improving N2 selectivity of Ag-based catalysts and contributes to a deeper understanding of the reaction mechanisms.

Modulating the anchoring states of Ag on TiO2 by SiO2 to boost the NH3-SCO activity over Ag-based catalysts

Ag-based catalysts show high activity in NH3-selective catalytic oxidation (NH3-SCO). The anchoring states of Ag species determines its valence and dispersion, thereby influencing the performance of Ag-based catalysts. Herein, we elucidated that the content and anchoring strength of the hydroxyl (OH) groups on support together affect the anchoring states of Ag. TiO2 has few OH groups but high anchoring strength, the anchored Ag is in a highly dispersed oxidized state, while the unanchored Ag is aggregated in a metallic state (Ag0), so it presents an unevenly sized dispersion and mainly in oxidized state. SiO2 has abundant OH groups but weak anchoring, and can excessively agglomerate into large Ag0 nanoparticles (Ag0 NPs). Therefore, the introduction of SiO2 can regulate the anchoring states of Ag on the TiO2 support, making Ag presents highly dispersed Ag0 NPs, thus following a reaction mechanism with lower energy barriers and significantly improving the NH3-SCO performance.

MOF-based Ag NPs/Co3O4 nanozyme for colorimetric detection of thiophanate-methyl based on analyte-enhanced sensing mechanism.

Silver nanoparticles supported on metal-organic framework (ZIF-67)-derived Co3O4 nanostructures (Ag NPs/Co3O4) were synthesized via a facile in situ reduction strategy. The resulting materials exhibited pH-switchable peroxidase/catalase-like catalytic activity. Ag NP doping greatly enhanced the catalytic activity of Ag NPs/Co3O4 towards 3,3',5,5'-tetramethylbenzidine (TMB) oxidation and H2O2 decomposition which were 59 times (A652 of oxTMB) and 3 times (A240 of H2O2) higher than that of ZIF-67, respectively. Excitingly, thiophanate-methyl (TM) further enhanced the peroxidase-like activity of Ag NPs/Co3O4 nanozyme due to the formation of Ag(I) species in TM-Ag NPs/Co3O4 and generation of more radicals resulting from strong interaction between Ag NPs and TM. The TM-Ag NPs/Co3O4 nanozyme exhibited lower Km and higher Vmax values towards H2O2 when compared with Ag NPs/Co3O4 nanozyme. A simple, bioelement-free colorimetric TM detection method based on Ag NPs/Co3O4 nanozyme via analyte-enhanced sensing strategy was successfully established with high sensitivity and selectivity. Our study demonstrated that hybrid noble metal NPs/MOF-based nanozyme can be a class of promising artificial nanozyme in environmental and food safety applications.

Ionic Liquid‐Silver Catalysts For Acetylene Acetoxylation At Tow‐Temperature

It was crucial to develop a catalyst with high catalytic activity at iow temperatures, as the zinc‐based catalysts were prone to deactivation in the high‐temperature reaction of acetylene acetoxylation, and ionic liquid (IL)‐silver (Ag) catalysts were synthesized and applied in acetylene acetoxylation. The X‐ray diffraction, transmission electron microscopy, and X‐ray photoelectron spectroscopy characterizations displayed that Ag species were stabilized in the state of Ag+, and the dispersion of the Ag active species was effectively improved in supported‐ionic‐liquid‐phase (SILP) system. Furthermore, we prepared Ag‐IL liquid phase catalysts for catalyzing acetylene acetoxylation in liquid phase systems. It was demonstrated that the presence of ILs could effectively stabilize the Ag+ active site. The catalytic performance of the Ag‐IL/AC catalyst prepared in this article at a low temperature of 180 °C was 2.5 times that of the traditional Zn/AC catalyst. The development of low‐temperature catalysts would play a driving role in the development of acetylene acetoxylation.

Oxygen vacancy-enrich Ag/brookite TiO2 Schottky junction for enhanced photocatalytic CO2 reduction

Insufficient surface catalytic sites and charge kinetics constrains the progress of CO2 photoreduction reaction. In this work, oxygen vacancy-enriched Ag/brookite TiO2 hybrid by anchoring Ag nanoparticles on brookite TiO2 has been synthesized through the transformation of Ti-glycerol precursor with simultaneous reduction of Ag+ in the diethylene glycol (DEG)-H2O solution. In particular, the involving of oxygen vacancy and Ag species could extend light absorption range, facilitate charge separation and transfer, and accumulate the electrons on Ag center. As a result, the Ag/brookite TiO2 with formed Schottky junction reveals enhanced CO2 photoreduction performance compare with pristine TiO2 and solvothermal treated TiO2 (TiO2-sol). Particularly, the oxygen vacancy-enriched Ag/TiO2 hybrid shows the highest catalytic activity with CH4 and CO yields. This work offers an approach to modify brookite phase TiO2 with metallic sites and oxygen vacancy for improved CO2 photoreduction.

Boosting the activity for organic pollutants removal of In2O3 by loading Ag particles under natural sunlight irradiation

A novel photocatalyst In2O3 with loading Ag particles is prepared via a facile one-step annealing method in air atmosphere. The Ag/In2O3 exhibits considerable photoactivity for decomposing sulfisoxazole (SOX), tetracycline hydrochloride (TC), and rhodamine B (RhB) under natural sunlight irradiation, which is much higher than that of pristine In2O3 and Ag species. After natural sunlight irradiation for 100 min, 70.6% of SOX, 65.6% of TC, and 81.9% of RhB are degraded over Ag/In2O3, and their corresponding chemical oxygen demand (COD) removal ratio achieve 95.4%, 38.4%, and 93.6%, respectively. A batch of experiments for degrading SOX with adjusting pollutant solution pH and adding coexisting anions over Ag/In2O3 are carried out to estimate its practical application prospect. Particularly, the as-prepared Ag/In2O3 possesses a superior stability, which exhibits no noticeable deactivation in decomposing SOX after eight cycles’ reactions. In addition, the Ag/In2O3 coated on a frosted glass plate, also possesses a superior activity and stability for SOX removal, which solve the possible second pollution of residual powdered catalyst in water. Ag particles on In2O3 working as electron accepter improve charge separation and transfer efficiency, as well as the photo-absorption and organic pollutants affinity, leading to the boosted photoactivity of Ag/In2O3. The photocatalytic mechanism for degrading SOX and degradation process over Ag/In2O3 has been systemically investigated and proposed. This work offers an archetype for the rational design of highly efficient photocatalysts by metal loading.

NMR Spectroscopic Signatures of Cationic Surface Sites from Supported Coinage Metals Interacting with N-Heterocyclic Carbenes.

N-heterocyclic carbenes (NHCs) have been extensively studied to modulate the reactivity of molecular catalysts, colloids, and their supported analogues, being isolated sites, clusters, or nanoparticles. While the interaction of NHCs on metal surfaces has been discussed in great detail, showing specific coordination chemistry depending on the type of NHC ligands, much less is known when the metal is dispersed on oxide supports, as in heterogeneous catalysts. Herein, we study the interaction of NHC ligands with Au surface sites dispersed on silica, a nonreducible oxide support. We identify the easy formation of bis-NHC ligated Au(I) surface sites parallel to what is found on metallic Au surfaces. These species display a specific 13C NMR spectroscopic signature that clearly distinguishes them from the mono-NHC Au(I) surface sites or supported imidazoliums. We find that bis-ligated surface species are not unique to supported Au(I) species and are found for the corresponding Ag(I) and Cu(I) species, as well as for the isolobal surface silanols. Furthermore, the interaction of NHC ligand with silica-supported Au nanoparticles also yields bis-NHC ligated Au(I) surface sites, indicating that metal atoms can also be easily extracted from nanoparticles, further illustrating the dynamics of these systems and the overall favorable formation of such bis-ligated species across a range of systems, besides what has been found on crystalline metal facets.

Efficient and stable immobilization of TiO2-based composite photocatalytic system for separation and purification of organic pollutants in wastewater under solar light

Photocatalytic removal of organic pollutants emerging from untreated industrial and aquaculture wastewater are still limited by catalytic efficiency and stability in practical application. In this study, we report the development of a silicone-immobilized, PEG-assisted Ag-doped TiO2 composite for efficient and sustainable removal of organic pollutants under solar irradiation. Firstly, a silicone-immobilized pristine TiO2 (S-TiO2) photocatalytic system was developed, demonstrating superior and stable removal of the organic pollutant Rhodamine B (Rh B) compared to PVA-TiO2 and dip-coated TiO2. Subsequently, pristine TiO2 was modified with the surfactant PEG, Ag species (Ag2O, Ag3PO4), and synthesized using the hydrothermal method, immobilized on silicone (S-H-PEG/PAgT). The S-H-PEG/PAgT, characterized by SEM, XRD, UV–Vis, and WCA revealed surface roughness, crystalline phase, excellent light absorption in the visible region, a narrow band gap, and hydrophobicity. The S-H-PEG/PAgT showed enhanced catalytic performance than S-TiO2 (Control) in the removal of tetracycline, a representative emerging organic contaminant. Furthermore, it displayed remarkable stability over 10 cycles and practicability in environmental conditions. Mechanism analysis revealed •O2– and h+ as the dominant active species involved in the catalytic reaction. Notably, a synergistic effect of surface hydrophobicity, roughness, and photocatalytic activity contributed to the reduction of pollutants. Therefore, the developed novel solar light driven S-H-PEG/PAgT photocatalytic system shows great promise for practical purification of organics pollutants in wastewater.

Ruthenium And Silver Synergetic Regulation NiFe LDH Boosting Long‐Duration Industrial Seawater Electrolysis

AbstractThe chloride ions in seawater result in corrosion, low catalytic efficiency, and poor stability of the electrocatalysts in direct seawater electrolysis, which limits the use of large‐scale seawater electrolysis technology. Herein, a corrosion‐resistant Ag/NiFeRu layered double hydroxide (LDH) electrocatalyst for seawater electrolysis at industrial current density, in which Ru and Ag species in the catalyst can have a corrosion‐resistance of chloride ions from the anode surface and enhance its robustness in seawater is designed. The catalyst requires the overpotentials of 256 and 287 mV to obtain a current density of 1 A cm−2 in 1 m KOH and 1 m KOH + seawater, respectively. More importantly, it works stably for over 1000 h at 1 A cm−2 in alkaline seawater. Further quasi‐industrial conditions measurement (6 m KOH + seawater, 60 °C) shows a markedly low overpotential of 174 mV at 1 A cm−2 on Ag/NiFeRu LDH, obtaining over 140 h under harsh industrial conditions. Theoretical calculations demonstrate that the Ru species can effectively regulate the local electronic structure of NiFe LDH, and enhance the intrinsic activity of NiFe LDH. The transformation of Ag2O from Ag during OER stabilizes the Fe site in NiFe LDH, which improves the overall stability of the electrocatalyst.

Photocatalytic oxidation of methane to methanol over zinc titanate supported silver catalysts

The direct activation of methane under mild condition to achieve highly selective of oxygenates is a challenging project. In this study, a well dispersed silver supported ZnTiO3 catalyst was prepared to achieve selective preparation of methanol from methane and water under mild condition. X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy characterizations demonstrate that silver species are uniformly dispersed on ZnTiO3 surface in the form of metallic silver nanoparticles. The photoelectric characterizations reveal that the addition of silver species enhances light absorption and promotes charge separation of the catalysts. Under the reaction conditions of 50 °C and 3 MPa, the methanol is obtained as the only liquid product over the designed Ag/ZnTiO3 catalyst under light irradiation. In this photocatalytic process, the holes generated by ZnTiO3 activate water to produce intermediate ·OH, which further reacts with methane to synthesize methanol. The silver species as co-catalysts extend the light absorption range of ZnTiO3 as well as promote charge separation.

The impact of heat treatment on the luminescence properties of Dy/Ag co-doped sodium alumina borate glasses

The sodium alumina borate glasses were synthesized by conventional melt-quenching method and heat treated with different durations to ensure the formation and growth of Ag nanoparticles. Transmission electron microscope measurements revealed that the average nanoparticle size increases with the heat treatment duration. The bonding nature between Dy3+ ions and surrounding ligands was getting more covalent with HT. Judd-Ofelt intensity parameters proved the asymmetric nature around Dy3+. The most intense emission and excitation bands of Dy3+ ions were observed for 6 h heat-treated glass (HT-6h). Intense blue (483 nm) and yellow (572 nm) emissions were obtained in which the yellow one has the highest radiative parameters approving the suitability of glasses for yellow laser applications. Based on colorimetric results emission closest to white light can be generated by HT-6h under 426 nm excitation. The decay time of 4F9/2 → 6H13/2 transition increases with heat treatment attributed to the combined effect of the enhanced local electric field induced by the Ag nanoparticles and energy transfer from Ag species to Dy3+ ions. The findings show that Dy3+/Ag+ co-doped sodium alumina borate glasses are potential materials for photonic applications.

How Physicians and Nursing Staff Perceive Effectiveness and Tolerability of Bryophyllum Preparations: An Online Survey in an Anthroposophic Hospital

Background: Bryophyllum preparations are widely used in anthroposophic medicine, most often for mental and behavioural disorders. Three prospective studies have revealed positive effects of Bryophyllum pinnatum on sleep quality, and various trials have shown very good tolerability. Results from animal models have indicated CNS depressant and anxiolytic effects. This survey was conducted at the hospital “Klinik Arlesheim” in Switzerland to find out how the physicians and the nursing staff perceive the effectiveness and the tolerability of the Bryophyllum preparations they most frequently use. Design: Internal, anonymous online survey of healthcare professionals (April 8–May 31, 2022). The questionnaire comprised 105 multiple-choice questions. Answering the questions was taken as consent to participate in the survey. Participants and Methods: All physicians and nursing staff with a valid email address at the hospital “Klinik Arlesheim AG” were invited via email to participate in this REDCap survey. The data were analysed descriptively. Results: Out of 266 invited participants, 48 answered some and 36 answered all questions (response rate between 18.0% and 13.5%). The participants had long experience with Bryophyllum preparations and were comprised approximately equal numbers of physicians and nursing staff. Various Bryophyllum preparations from the hospital’s own production and Wala Heilmittel GmbH (in both cases produced from the species B. daigremontianum) and from Weleda AG (species B. pinnatum) were used. The indications for which most participants had prescribed or administered Bryophyllum preparations “very frequently” were anxiety, sleep disorders, crisis situations in oncology, posttraumatic stress disorder, benzodiazepine dependence/withdrawal, and depression. Improvements such as relief from restlessness, decreased anxiety, balance, easier falling asleep, better sleeping through, increased resilience, mood elevation, and less urge to move one’s legs were reported “frequently” or “very frequently.” Almost all participants agreed that Bryophyllum can be used to reduce the intake of synthetic sedatives or psychotropic drugs, but only approximately half believed that it could replace them. The majority of participants mentioned good tolerability of the various products, but a few reported occasional stomach or intestinal irritation, daytime fatigue, drowsiness, diarrhoea, and nausea. Conclusion: Bryophyllum preparations are perceived as helpful in the treatment of various mental disorders, particularly anxiety, and are generally well tolerated. Most of these preparations are used for indications that have not yet been clinically investigated.

From Mono- to Polynuclear 2-(Diphenylphosphino)pyridine-Based Cu(I) and Ag(I) Complexes: Synthesis, Structural Characterization, and DFT Calculations.

A series of monometallic Ag(I) and Cu(I) halide complexes bearing 2-(diphenylphosphino)pyridine (PyrPhos, L) as a ligand were synthesized and spectroscopically characterized. The structure of most of the derivatives was unambiguously established by X-ray diffraction analysis, revealing the formation of mono-, di-, and tetranuclear complexes having general formulas MXL3 (M = Cu, X = Cl, Br; M = Ag, X = Cl, Br, I), Ag2X2L3 (X = Cl, Br), and Ag4X4L4 (X = Cl, Br, I). The Ag(I) species were compared to the corresponding Cu(I) analogues from a structural point of view. The formation of Cu(I)/Ag(I) heterobimetallic complexes MM'X2L3 (M/M' = Cu, Ag; X = Cl, Br, I) was also investigated. The X-ray structure of the bromo-derivatives revealed the formation of two possible MM'Br2L3 complexes with Cu/Ag ratios, respectively, of 7:1 and 1:7. The ratio between Cu and Ag was studied by scanning electron microscopy-energy-dispersive X-ray analysis (SEM-EDX) measurements. The structure of the binuclear homo- and heterometallic derivatives was investigated using density functional theory (DFT) calculations, revealing the tendency of the PyrPhos ligands not to maintain the bridging motif in the presence of Ag(I) as the metal center.

Catalytic oxidation of ammonia: A pre-occupied-anchoring-site strategy for enlarging Ag nanoparticles at low Ag loading and achieving enhanced activity and selectivity on Ag-CuOx/Al2O3 catalyst

The Ag nanoparticles (AgNPs) in Ag/Al2O3 catalysts play a crucial role in the selective catalytic oxidation of NH3 (NH3-SCO). To enhance NH3-SCO activity, Cu, which has stronger anchoring ability than Ag, is introduced onto Al2O3, reducing available anchoring sites for Ag. As Ag cannot displace anchored Cu species, Ag species agglomerate into larger AgNPs even with low Ag loading. Consequently, these enlarged AgNPs become more active centers for NH3-SCO. The optimal Ag:Cu molar ratio is confirmed as 2:3. This 'pre-occupied-anchoring-site’ strategy decreases Ag loading to 1/5 of the original, reducing catalyst costs while maintaining activity. In situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) studies reveal that NH3-SCO on 2Ag1.8Cu/Al (weight ratio) catalyst follows the hydrazine mechanism below 200 °C, coexisting with the imide mechanism from 200–250 °C, and solely the imide mechanism beyond 250 °C. This strategy is applicable to various transition metals, including Mn, Co, Ni, and Fe, promoting cost-effective AgNPs formation.

Smart and responsive zeolite catalysts for toluene “storage-oxidation” cycling removal

“Storage - oxidation” cycling provides a novel and efficient route for VOCs’ removal. Herein, Cu and Ag modified β zeolite with different SiO2/Al2O3 ratio were prepared as smart and responsive materials for toluene removal. The storage strength for toluene on the metal sites (ion-exchange sites, metallic clusters and nanoparticles) and zeolite substrate (acid sites and channels) were discriminated, and the corresponding regeneration either by in-situ thermal oxidation or plasma assisted oxidation was coupled to fulfill the “storage-oxidation” cycle. By virtue of the collaboration of identified Cu2+ and Ag+ for toluene storage, a Cu2.0Ag3.0/β-25 catalyst was designed with high storage capacity (0.41 mmol/g) and adequate strength for trapping toluene, being available for in-situ thermal regeneration. In this study, the location of Cu and Ag species in β zeolite has been modulated to enable such smart and responsive materials available for toluene “storage and in-situ oxidation” cycling, which provides a general guidance for BTEX elimination.

Surface reorganization of oxide-derived Cu-M (M = Zn, Ag) bimetallic catalysts in CO2 electroreduction environment

As the oxide-derived copper-based electrodes gain continuously more recognition for their great performance in catalyzing CO2 reduction reaction (CO2RR), it is important to define which surface features stand behind their catalytic properties. The presented research explores the surface reorganization of Cu, CuAg10, and CuZn37 passivated materials caused by the reductive environment of CO2RR. It is shown that the presence of Ag constituent has a marginate influence on the mechanism of passive layer growth on copper, whereas Zn changes it in a significant manner. Therefore, the synthesis parameters need to be adjusted differently for both bimetallic systems. The passivation of both Cu and CuAg surfaces provided the best surface area development in the most concentrated electrolyte (3 M NaOH) and CuZn in the least concentrated solution (1 M NaOH). Additionally, after subjecting the selected passivated electrodes to CO2RR conditions, a thorough surface analysis was performed to inspect the influence of Ag and Zn on the characteristic features of the oxide-derived electrodes identified in the modified surfaces. It was found that the more noble Ag component slightly lowers the mixed valance nature of the Cu electrode, however, it provides Ag species that are beneficial for CO2RR selectivity. On the other hand, the CuZn material indicates lower resistance to reduction by suppressed surface area development which leads to a decrease in oxygen vacancies and the amount of oxidized Cu species.

Silica supported biosynthesized silver nanoparticles as effective adsorbent and photocatalyst for removal of methylene blue from water

The silica supported silver nanoparticles (Ag@SG) were prepared by wet impregnation of silica gel (SG) using different concentrations of biogenic silver nanoparticles (AgNPs; 0.25–5 mM) solution, prepared from Cicer arientinum pod extract. Among them, the Ag@SG composite prepared by using 1.25 mM AgNPs solution (Ag1.25@SG) was found to contain only Ag0 species as nanoparticles, whereas the samples prepared by higher concentrations contained Ag0 as well as Ag+ (silver oxide) species. All the Ag@SG composites including SG, exhibited good adsorption capacity for a cationic dye (methylene blue; MB) in water. However, Ag1.25@SG having only Ag0 species exhibited higher photocatalytic activity for degradation of MB under visible light irradiation as compared to other composites. The study reveals that the plasmonic Ag0 species supported on silica are catalytically more active than Ag+ species. Furthermore, the AgNPs (Ag0) in supported form exhibits much higher (∼5-fold) photocatalytic activity than unsupported AgNPs. The synergistic effect of adsorption property of silica surface and plasmonic photocatalytic activity of AgNPs in the synthesized composites was found to be effective for the removal of MB. In addition, the fine dispersion of AgNPs on internal surface of silica provides better activity for photocatalysis. The study shows that this material is a promising adsorbent as well as photocatalyst for the removal of dyes from water.

Ag–N–C single atom catalyst with resistance for Ag loss in acetylene hydrochlorination

Ag–N–C catalyst was synthesized by the calcination process with AgNO3 as precursors, active carbon as support, and melamine as an N source. Series of characterizations showed that Ag was transferred into AgCl during the active phase by HCl, and pyridinic structure in the support was bonded with Ag components. Then, Ag–N–C single atom catalyst (SAC) was obtained by washing Ag–N–C with acid, aberration-correction high-angle-annular-dark-field scanning transmission electron microscopy showed that Ag presented in single atoms form, and Ag coordinated with the nitrogen atom in the support. Ag loss rate for Ag–N–C SAC was only 0.09% after running 10 h in acetylene hydrochlorination process, which was much smaller than Ag–N–C (57%), indicating that the presence of the Ag–N bond could be inhibiting Ag species loss.

Enhanced CO oxidation performance over hierarchical flower-like Co3O4 based nanosheets via optimizing oxygen activation and CO chemisorption

Enhancing low-temperature activity is a focus for carbon monoxide (CO) elimination by catalytic oxidation. In this work, the hierarchical flower-like silver (Ag) modified cobalt oxides (Co3O4) nanosheets were prepared by solvothermal method and applied into catalytic CO oxidation. The doped Ag species in the form of AgCoO2 induced the prolongated surface Co–O bond and weaker bond intensity. Consequently, the oxygen activation/migration ability and redox capacity of Ag0.02Co were enhanced with more oxygen vacancies. The chemisorbed CO was preferentially converted to CO2 but not carbonates. The inhibited carbonates accumulation could avoid the coverage of active sites. According to Density functional theory (DFT) calculations, the electron transfer from AgCoO2 to Co3O4 promote electron donation ability of Co3O4 layer, benefiting for oxygen activation. Moreover, the longer Co–C and C–O bond length suggest the weakened chemisorption strength and higher active of CO molecule. The Ag modified Co3O4 exhibited more satisfactory activity at lower temperature. Typically, it realized 100% CO conversion at 90 °C, and displayed 6.3-fold higher reaction rate than pristine Co3O4 at 40 °C. Moreover, the Ag0.02Co exhibited outstanding long-term stability and water resistance. In summary, the optimized oxygen activation, CO chemisorption and interfacial electron transfer synergistically boosted the CO oxidation activity on Ag modified Co3O4.