Ag Foam Research Articles

Nitrate reduction catalyzed by bimetallic silver‐copper macroporous foams

IIn this work we describe the use of bimetallic silver‐copper macroporous foams for electrochemical nitrate reduction in acidic conditions (pH 2, 0.1 M NaClO4). By carefully selecting the composition of the electrodeposition bath, we have successfully prepared foams with atomic percentage varying from Ag dominant to Cu dominant. Also, we have succeeded to obtain morphologies that vary between the one specific to pure Ag foam to the one specific to pure Cu foam. We have shown that these foams contain a pure silver phase and also a silver‐copper alloy. The electrochemical active surface area of the foams depends both on the morphology as well as on the atomic composition. These materials were used for the first time as catalysts for nitrate electrochemical reaction (NO3RR). Both liquid and gaseous products were quantified with several analytical techniques. It was shown that bimetallic foams present superior faradaic efficiency (FE) towards liquid products in comparisons with pure silver and copper foams, suggesting a synergetic contribution from both metals. The Ag94Cu6 (AgCu10) foam shows a FE as high as 92% towards liquid products and the lowest FE (3%) towards the undesired product, nitrous acid. Also, this material shows a better stability than pure copper materials.

Spongy Ag Foam for Soft and Stretchable Strain Gauges.

Strain gauges, particularly for wearable sensing applications, require a high degree of stretchability, softness, sensitivity, selectivity, and linearity. They must also steer clear of challenges such as mechanical and electrical hysteresis, overshoot behavior, and slow response/recovery times. However, current strain gauges face challenges in satisfying all of these requirements at once due to the inevitable trade-offs between these properties. Here, we present an innovative method for creating strain gauges from spongy Ag foam through a steam-etching process. This method simplifies the traditional, more complex, and costly manufacturing techniques, presenting an eco-friendly alternative. Uniquely, the strain gauges crafted from this method achieve an unparalleled gauge factor greater than 8 × 103 at strains exceeding 100%, successfully meeting all required attributes without notable trade-offs. Our work includes systematic investigations that reveal the intricate structure-property-performance relationship of the spongy Ag foam with practical demonstrations in areas such as human motion monitoring and human-robot interaction. These breakthroughs pave the way for highly sensitive and selective strain gauges, showing immediate applicability across a wide range of wearable sensing applications.

Nitrous acid electroreduction on macroporous silver foam

In this paper, silver 3D foams have been synthesized using dynamic hydrogen bubble template and thiocyanate-based deposition bath. The material was used as electrocatalyst for nitrous acid (HNO2) reduction. On this material, we found that overpotential of nitrous acid reduction is decreased by at least 300 mV and the in situ formed nitric oxide (NO) reduction becomes the predominant step when the potential is decreased even further, comparing to flat silver polycrystalline electrode. Another difference between this material and the silver polycrystalline electrode concerns the influence of the nature of supporting electrolyte on the preferred reaction. Precisely, while Ag polycrystalline is preferentially reducing HNO2 into NO in low concentration of perchlorate electrolyte, Ag foam preferentially reduces the in situ formed NO into N2O, in all tested electrolytes, if the same potential range is considered. The initial reduction of HNO2 into NO is better evidenced after the partial removal of thiocyanate species. Finally, the use of isotope 15N in the nitrite salt and of a flow thin layer cell enabled the detection of nitrogen among other gaseous products for both silver foam and flat silver electrode.

Supercooling degree decrease of barium hydroxide octahydrate employing 3D porous silver foam as supporting material

Inorganic hydrated salts possess high latent heat of phase transition and are promising phase change materials (PCMs). However, the issues of supercooling, low thermal conductivity, susceptibility to leakage, and phase separation significantly impediment the practical applications of inorganic hydrated salts. In this study, it is proposed to decrease the inorganic hydrated salt supercooling degree by increasing the surface roughness of the porous material and to load the nucleating agent silver (Ag) onto polydopamine (PDA) modified melamine foam (MF) by electroless plating to obtain 3D porous Ag foams, which are then utilized as support materials. The results demonstrated that the 3D porous Ag foam compounded with barium hydroxide octahydrate (BHO) can ameliorate the shortcomings of leakage and reduce the supercooling degree in the cooling process. The composite not only exhibits high enthalpy of over 248.5 J/g and high thermal conductivity of 1.82 W·m−1·K−1 but also has a low supercooling degree of 0.21 ℃. Furthermore, the composites exhibited superior shape stability and thermal cycling stability. This study provides an effective method for reducing the supercooling degree of inorganic hydration salts.

Highly selective Ag foam gas diffusion electrodes for CO2 electroreduction by pulsed hydrogen bubble templation

The manuscript presents a novel approach for polymer-based Ag-DHBT-GDE fabrication, enabling highly efficient CO2 electrolysis to CO with remarkable performance and selectivity.

Exploring the role of Ag foam interlayer in alleviating the brittleness of G018 glass sealant for joining YSZ to Mn–Co spinel coated Crofer 22 H

Glass/Glass-ceramic sealing is always accompanied by issues of high porosity and brittle joints. To migrate these problems, an Ag foam was innovatively induced as an interlayer in the process of glass sealing the yttria-stabilized zirconia (YSZ) ceramic to Mn–Co spinel-coated Crofer 22 H stainless steel. Interlayer-added joints showed a significant reduction in porosity, and the shear strength was improved to 52.3 MPa, with an enhancement of 37.8 %. The influence of interlayer on the microstructure of the joint has been investigated and the formation process of the joint is illustrated. The Ag interlayer expels gases from the sealant material through expansion at high temperatures and promotes finer nucleation grains of crystallites integrating with the interlayer, reducing the porosity and alleviating the brittleness as well.

CO2 Electroreduction on Silver Foams Modified by Ionic Liquids with Different Cation Side Chain Length.

Ionic liquids (ILs) are capable of tuning the kinetics of electroreduction processes by modifying a catalyst interface. In this work, a group of hydrophobic imidazolium-based ILs were immobilized on Ag foams by using a procedure known as "solid catalyst with ionic liquid layer" (SCILL). The derived electrocatalysts demonstrated altered selectivity and CO production rates for the electrochemical reduction of CO2 compared to the unmodified Ag foam. The activity change caused by the IL was dependent on the length of the N-alkyl substituent. The rate of CO production is optimized at moderate chain length and IL loadings. The observed trends are attributed to a local enrichment of CO2-based species in the proximity of the catalyst and a modification of the environment of its active sites. On the contrary, high loadings or long IL chains render the surface inaccessible and favor the hydrogen evolution reaction.

Ag-MOF-derived 3D Ag dendrites used for the efficient electrocatalytic reduction of CO2 to CO

Ag-based electrodes have emerged as important candidates for the industrial electrochemical CO2 reduction reaction (eCO2RR) to form CO. Herein, an intrinsic versatile Ag electrode has been derived in situ from Ag-MOF on Ag foam (denoted as ER-AF), which exhibits the highest current density (57.2 mA cm−2) at a potential of −1.15 V vs. RHE reported to date for the formation of CO in a commonly used H-type cell. ER-AF has multiple-roles: The 3D dendrite structure promotes mass diffusion; the rich edges sites favor CO2 adsorption and conversion, and the highly exposed (111) facet facilitates the desorption of CO. Their cooperating functions result in the remarkable performance of ER-AF in the eCO2RR to form CO. This work offers an effective strategy to achieve high eCO2RR activity and selectivity by assembling the active and stable sites together on the MOF-derived materials.

Cascade Electrochemical Reduction of Carbon Dioxide with Bimetallic Nanowire and Foam Electrodes

AbstractCascade electrochemical reduction of CO2 has been investigated on nanostructured bimetallic gold‐copper and silver‐copper catalyst nanowire and foam electrode arrays. The bimetallic electrocatalysts allow for the overall carbon dioxide reduction reaction (CO2RR) to be performed, where CO2 to CO conversion occurring at silver (Ag) or gold (Au) is decoupled from conversion to multicarbon species at Cu. The catalyst fabrication methods permit the catalyst orientation to be controlled and thus investigation of catalyst order on the cascade process. Segmentation of bimetallic electrodes is most versatile for nanofoam arrays. Placement of an Ag foam beneath a Cu foam, where CO produced at Ag must pass through the Cu foam, results in an enhancement in methane, ethanol, and propanol production as compared to the reverse electrocatalyst ordering.

Management of skin graft donor site in pediatric patients with tumescent technique and AQUACEL® Ag foam dressing

Split thickness skin graft donor sites are challenging to manage in children because of patient fear and anxiety. Therefore, strategies that minimize the frequency of dressing change are beneficial. This paper describes a technique to simplify wound care for split thickness skin graft donor sites. A tumescent solution of saline containing 0.25% bupivacaine with epinephrine is infiltrated into the graft donor site. Skin grafts are harvested with an electric dermatome. The donor sites are dressed with AQUACEL® Ag Foam, which is a sodium carboxymethylcellulose hydrofiber dressing that contains silver ions. A total of 17 split thickness skin grafts were performed with this technique. Patient age ranged from 2.4 year to 16.9 years (average 12 years). The AQUACEL® Ag Foam dressings were removed at an average of 23 days (range 11 to 31 days) at which time complete donor site epithelialization was seen in 13/17 (76.5%) patients. The remaining 4 patients had < 5% of the donor site that had not epithelialized; these went on to heal uneventfully with a brief period of petrolatum gauze dressing changes. Two patients had foul smelling discharge under the dressing that resolved promptly with dressing removal. The above technique allows the primary dressing to stay in place long enough for epithelialization to take place. The obviation of dressing changes in the early post-operative period results in patient comfort and care giver convenience.

Preparation of Ag foam catalyst based on in-situ thermally induced redox reaction between polyvinyl alcohol and silver nitrate with supercritical CO2 foaming technology

The preparation process of a traditional metal foam catalyst is cumbersome, energy-intensive, and difficult to scale production, which restricts its development. In this work, the potential of polyvinyl alcohol (PVA) as a polyhydroxy reductant was explored. We used the thermally induced redox reaction between PVA and silver nitrate (AgNO3), combining with supercritical carbon dioxide (ScCO2) foaming technology, proposing an innovative idea for preparing the micron-sized Ag foam catalyst. Firstly, through the compound plasticizing effect of H2O and AgNO3, using CO2 as foam agent, the PVA/AgNO3 composite foams with uniform structure could be prepared below 100 °C. The maximum cell density could reach 5.39*109 cells/cm3 and the average cell size could reach 8.27 μm. Then, using the PVA matrix as a reductant and self-sacrifice template, silver ions could be quickly in-situ reduced at lower temperature (160–210 °C), the resulting silver particles could self-assemble into a foam-like skeleton structure. The Ag foams have an adjustable porous structure with a cell size of 4.01–16.30 μm and a ligament size of 1.08–2.82 μm. Applying it as a catalyst to promote the reduction of 4-nitrophenol (4-NP), the catalytic reaction rate constant is 10 times that of existing commercial Ag foam. The prepared Ag foam catalyst has the advantages of less dosage, easy recovery and good stability. Also, it has great application potential in the sensing, biomedicine, heat conduction and other fields.

What Is the Best Approach to Prevent Advanced-Stage Pressure Injuries After Pediatric Tracheotomy?

What Is the Best Approach to Prevent Advanced-Stage Pressure Injuries After Pediatric Tracheotomy?

(Invited) Electrochemical Tuning Sensing and Catalytic Performance of Catalytic Materials -from Nanoscale to Atomic Scale

In this talk, we will introduce two facile methods for the preparation of a nanoporous Ag foam and a promising electrocatalyst for the oxygen reduction reaction (ORR). Ag has a high electrical and thermal conductivity, low cost, and is relatively abundant in the earth compared to other Pt-group metals. Unlike Pt-related noble metals, the poor hydrogen evolution reaction (HER) activity of Ag in acidic environments makes it rarely considered as a potential HER electrocatalyst. We demonstrate a spongy-like highly nanoporous Ag foam obtained using a simple Ag surface treatment through the repetitively electrochemical anodic formation of AgBr/cathodic reduction back to Ag exhibited Pt-like high HER activities. Bimetallic Pt-Ni with Pt on the outermost layer and an innermost layer enriched in Ni, referred to as (Pt3Ni(Pt-skin), is a promising configuration of electrocatalyst for the ORR in fuel cells. We prepare a core (Pd)/shell (Pt3Ni(Pt-skin)) catalyst (Pt3Ni(Pt-skin)/Pd/C) from Zn underpotential deposition (UPD) on a Ni UPD modified Pd/C catalyst, facilitating Pt atomic layer-by-layer growth on the Ni surface through the galvanic replacement process. The Pt3Ni(Pt-skin) thin layer with ultra-low Pt loading presents not only a breakthrough in Pt specific activity and Pt mass activity, both of which were superior to state-of-the-art Pt-Ni catalysts, but also in high durability owing to the perfect Pt3Ni(Pt-skin) construction

Enhanced electrocatalytic CO formation from CO2 on nanostructured silver foam electrodes in ionic liquid/water mixtures

We employ a novel type of nanostructured silver foam electrocatalyst to the electrochemical CO2 reduction reaction (CO2RR) in 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) ionic liquid. The Ag catalyst is prepared from an aqueous electroplating bath by means of an additive-assisted electrodeposition approach, yielding macro-porous Ag foams. The pore sidewalls are composed of Ag nanoneedles having diameters of ∼50–100 nm and lengths that can exceed 1 μm. We demonstrate that, when combined with the [Bmim][BF4] electrolyte, this Ag electrocatalyst significantly shifts the onset of CO2 electroreduction by ∼220 mV to less negative potentials as compared to a polished Ag foil electrode. The addition of moderate amounts of water (optimum water mole fraction of 20%) to the pure [Bmim][BF4] electrolyte leads to a further ∼120 mV decrease in the CO2RR overpotential. The combination of the Ag foam catalyst with the [Bmim][BF4]/water mixture results in a ∼300 mV wide potential window where CO is selectively produced with Faraday efficiencies >94%. The structural stability of the catalyst is supported by identical location scanning electron microscopy.

Enhanced Electroreduction of Carbon Dioxide to Methanol Using Zinc Dendrites Pulse‐Deposited on Silver Foam

AbstractThe electrocatalytic CO2 reduction reaction (CO2RR) can dynamise the carbon cycle by lowering anthropogenic CO2 emissions and sustainably producing valuable fuels and chemical feedstocks. Methanol is arguably the most desirable C1 product of CO2RR, although it typically forms in negligible amounts. In our search for efficient methanol‐producing CO2RR catalysts, we have engineered Ag‐Zn catalysts by pulse‐depositing Zn dendrites onto Ag foams (PD‐Zn/Ag foam). By themselves, Zn and Ag cannot effectively reduce CO2 to CH3OH, while their alloys produce CH3OH with Faradaic efficiencies of approximately 1 %. Interestingly, with nanostructuring PD‐Zn/Ag foam reduces CO2 to CH3OH with Faradaic efficiency and current density values reaching as high as 10.5 % and −2.7 mA cm−2, respectively. Control experiments and DFT calculations pinpoint strained undercoordinated Zn atoms as the active sites for CO2RR to CH3OH in a reaction pathway mediated by adsorbed CO and formaldehyde. Surprisingly, the stability of the *CHO intermediate does not influence the activity.

Comparative Study between Pristine Ag and Ag Foam for Electrochemical Synthesis of Syngas with Carbon Dioxide and Water

The electrosynthesis of syngas (H2 + CO) from CO2 and H2O can reduce greenhouse gas emissions and address the energy crisis. In the present work, silver (Ag) foam was employed as a catalytic electrode for the electrochemical reduction of CO2 in aqueous solution to design different syngas ratios (H2:CO). In addition to H2 and CO, a small amount of formic acid was found in the liquid phase. By contrast, the planar polycrystalline Ag yields CO, formic acid, methane and methanol as the carbon-containing products. During the potential-controlled electrolysis, the Ag foam displayed a relatively higher activity and selectivity in the electroreduction of aqueous CO2 to CO compared with its smooth surface counterpart, as evidenced by the lower onset potential, higher partial current density and Faradic efficiency at the same bias voltage. Moreover, the electrode remained stable after three successive cycles. Based on the characterization using X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, potential step determination and density functional theory calculations, superior performance was credited to the three-dimensional structure of Ag foam constructed with coral-like Ag particles, in which the numerous edge sites are beneficial for the stabilization of the surface adsorbed COOH species and the exposed {111} facets favor the desorption of adsorbed CO species.

MODERN TECHNIQUES FOR FACE AND NECK PHLEGMONS TREATMENT

Aim. In the course of this study we carried out the analysis of clinical course features and assessment of microbiological structure of the wound surface in patients with face and neck phlegmons. The etiologic cause of the disease may be hemolytic streptococcus, different types of staphylococcus, mixed flora and anaerobic bacteria.Materials and methods. All patients required urgent surgical intervention: wide opening, drainage of cellular spaces with the subsequent irrigation with antiseptic solutions with the application of a combination of wound coverings "Aquacel Ag + Hydrofiber dressing", "Aquacel Ag Foam Hydrofiber dressing" and "Granuflex" (ConvaTec, the USA) with proper antibacterial therapy.Results. Comparison of clinical observations (favorable course of inflammatory process) and obtained microbiological assessment (quicker decrease of microbial content in the wound) confirms validity, high efficiency of wound covering application and clear advantage in comparison with traditional gauze bandages.Conclusion. The analysis of the causes of phlegmon on the face and neck over the past 5 years has shown a significant increase in the number of patients with traumatic, tonsilogenous and odontogenic phlegmons of the face and neck. The modern high-efficient method of local treatment with the use of wound coverings combinations makes it possible to suppress the purulent-inflammatory process at the early stage, to put the secondary stitches and shorten the period of treatment of patients.

Beyond Copper in CO2 Electrolysis: Effective Hydrocarbon Production on Silver-Nanofoam Catalysts

Ag-foam catalysts have been developed for the electrochemical CO2 reduction reaction (ec-CO2RR) based on a concerted additive- and template-assisted metal-deposition process. In aqueous media (CO2-saturated 0.5 M KHCO3 electrolyte), these Ag foams show high activity and selectivity toward CO production at low and moderate over-potentials. Faradaic efficiencies for CO (FECO) never fell below 90% within an extremely broad potential window of ∼900 mV, starting at −0.3 V and reaching up to −1.2 V versus a reversible hydrogen electrode (RHE). An increased adsorption energy of CO on the Ag foam is discussed as the origin of the efficient suppression of the competing hydrogen-evolution reaction (HER) in this potential range. At potentials of <−1.1 V versus RHE, the FEH2 values significantly increase at the expense of FECO. Superimposed on this anti-correlated change in the CO and H2 efficiencies is the rise in the CH4 efficiency to the maximum of FECH4 = 51% at −1.5 V versus RHE. As a minor byproduct, even C–C-c...

Making Ag Present Pt-like Activity for Hydrogen Evolution Reaction

Silver (Ag) has a high electrical and thermal conductivity, low cost, and is relatively abundant in the earth compared to other Pt-group metals. Unlike Pt-related noble metals, the poor hydrogen evolution reaction (HER) activity of Ag in acidic environments makes it rarely considered as a potential HER electrocatalyst. We demonstrate a spongy-like highly nanoporous Ag foam obtained using a simple Ag surface treatment through the repetitively electrochemical anodic formation of AgBr/cathodic reduction back to Ag exhibited Pt-like high HER activities. The spongy-like nanoporous Ag foam effectively increases the number of surface active sites and lowers the Gibbs free energy of adsorbed atomic hydrogen (Had) on catalysts (ΔGM-H) from multiple Ag grains constructing nanoarchitecture branches.

IMPROVED LOCAL TREATMENT WITH WOUND COVERING IN PATIENTS WITH FACE AND NECK PHLEGMONS REGARDING WOUND PROCESS PHASE

Clinical and microbiological analysis of «Aquacel Ag + Hydrofiber dressing», «Aquacel Ag Foam dressing Hydrofiber» and «Granulex» (ConvaTec, USA; wound covering efficiency in complex treatment of patients with face and neck phlegmons was carried out. We proved positive influence and potent action of the wound dressing on reparative processes in postoperative purulent wounds in patients with face and neck phlegmons. Application of «Aquacel Ag + Hydrofiber dressing», «Aquacel AgFoam Hydrofiber dressing» and «Granuflex» wound covering in a complex therapy allowed to improve wound condition in earlier terms, put secondary sutures and reduce terms of patient hospital stay.