Ag Loading Research Articles

Study on Effect of Calcination and Ag Loading on Ag/TiO2 Catalyst for Low-Temperature Selective Catalytic Oxidation of Ammonia

Study on Effect of Calcination and Ag Loading on Ag/TiO2 Catalyst for Low-Temperature Selective Catalytic Oxidation of Ammonia

Gas‐Phase Photocatalytic Degradation of a Mixture of VOCs on Ag NPs Decorated ZnO

AbstractIn this research, silver was loaded onto ZnO using the photoreduction method to enhance the photocatalytic activity of ZnO in the visible region. The photocatalytic activity of ZnO and Ag/ZnO was investigated for the gas‐phase degradation of volatile organic compounds such as ethyl acetate, ethanol, and toluene under visible light irradiation. The Ag/ZnO effectively decomposed ethyl acetate, toluene, and ethanol separately and in a mixed state. The characteristics of Ag/ZnO and ZnO were studied using XRD, SEM, EDAX, XPS, BET, UV–vis DRS, and PL analyses. The XRD pattern confirmed the formation of metallic silver in the Ag/ZnO photocatalyst. The PL results showed that the loading of Ag on the ZnO significantly reduces the photoelectron‐hole pairs recombination in Ag/ZnO.

Enhanced CO2-to-CH4 conversion via grain boundary oxidation effect in CuAg systems

The authentic active sites of oxide-derived copper (OD-Cu), namely grain boundaries (GBs) and oxidized Cuδ+ species, is still debatable, and their role in governing CH4 conversion remains unclear. Herein, this study answers these questions using bimetallic catalysts by novel electro-shock strategy with controllable GBs for the oxidization of Cuδ+ species by modulating Ag loading. The Ag enrichment at the GBs facilitates the bonding of oxygen with the uncoordinated Cu atoms, resulting in GB oxidation effect. The obtained CH4 selectivity is twice that of GBs or nanoalloy effect. The enhanced performance is attributed to the stable Cuδ+ species and unique electron transfer mechanism from GB oxidation structure. Operando attenuated-total-reflection Fourier-transform-infrared-spectroscopy unveils the reaction pathway of CO2-to-CH4 and the sluggish reversible quenching processes of intermediates. Theoretical calculations indicate that the weak *CO adsorption on GB oxidation structure facilitates *CO hydrogenation, promoting CO2-to-CH4 conversion.

Solar Light Elimination of Bacteria, Yeast and Organic Pollutants by Effective Photocatalysts Based on Ag/Cr-TiO2 and Pd/Cr-TiO2.

This study focused on searching for more effective nanomaterials for environmental remediation and health protection; thus, coliform bacteria, yeast and the organic food dye sunset yellow were selected as target pollutants to be eliminated under solar light by Ag/Cr-TiO2 and Pd/Cr-TiO2. Firstly, Cr3+ was in situ incorporated into the anatase crystalline lattice by the sol-gel method; then, Ag or Pd nanoparticles were deposited on Cr-TiO2 by chemical photoreduction. The scientific challenge addressed by the development of these composites was to analyse the recovery of Cr, to be employed in photocatalyst formulation and the enhancement of the TiO2 photocatalytic activity by addition of other noble metals. By extensive characterization, it was found that after TiO2 doping with chromium, the parameters of the crystal lattice slightly increased, due to the incorporation of Cr ions into the lattice. The TiO2 band gap decreased after Cr addition, but an increase in the optical absorptions towards the visible region after noble metals deposition was also observed, which was dependent of the Ag or Pd loading. Generally, it was observed that the noble metals type is a factor that strongly influenced the effectiveness of the photocatalysts concerning each substrate studied. Thus, by using Ag(0.1%)/Cr-TiO2, the complete elimination of E. coli from samples of water coming from a highly polluted river was achieved. Pd(0.5%)/Cr-TiO2 showed the highest efficiency in the elimination of S. cerevisiae from a lab prepared strain. On the other hand, the Pd(0.1%)/Cr-TiO2 sample shows the highest dye degradation rate, achieving 92% of TOC removal after 180 min.

Degradation of Nile Blue by Photocatalytic, Ultrasonic, Fenton, and Fenton-like Oxidation Processes

The aim of this study is to investigate new catalytic systems for the degradation of a dye that has been classified as first-degree toxic pollutant. Advanced oxidation process such as photocatalytic oxidation, ultrasonic oxidation, Fenton, and Fenton-like constitute a promising technology for the treatment of wastewater containing organic compounds. Waste effluents from textile industries are a major source of water pollution. These wastewaters contain dyes, which have high toxicity and low biodegradability. In this study, degradation of Nile Blue (NB), an azo dye, was studied using the photocatalytic oxidation (TiO2 and silver-loaded TiO2 (Ag-TiO2) as catalyst), ultrasonic oxidation, Fenton (Fe(II)/H2O2), and Fenton-like (Cu(II)/H2O2, V(IV)/H2O2) processes. It was found that the photocatalytic degradation of NB increased with decreasing pH, and the degradation rate also increased in the presence of TiO2/UV compared to UV irradiation alone. In addition, Ag loading on TiO2 dramatically reduced the degradation time. The ultrasonic degradation of NB was also studied using different initial dye concentrations at different pH values and amplitudes. Concentrations of Fe(II), Cu(II), V(IV) and H2O2 on degradation ratio were investigated. It is found that Fe(II) ion is more effective than Cu(II) and V(IV) ions in the degradation of NB.

Impact of plasmonic silver on the perovskite Bi9Ti6FeO27: Removal of tetracycline and antimicrobial activity

The synthesis, characterization, photocatalytic, and antibacterial analysis of plasmonic Ag- loaded Bi9Ti6FeO27 at various concentrations of Ag are presented in this study. The synthesis of Ag/Bi9Ti6FeO27 is based on the impregnation of different weight percentages of Ag (20, 50, and 80) on Bi9Ti6FeO27. The XRD and HRTEM result shows that the perovskite Bi9Ti6FeO27 maintained orthorhombic crystallinity having space group Pnm (No.62). Upon addition of Ag, do not disturb the crystallinity of Bi9Ti6FeO27. XPS analysis displays the valence states and surface chemical composition of the as-prepared Ag/Bi9Ti6FeO27. All the composites exhibit good UV–visible absorbance in the range of 200–800 nm, and the band-gap energy gradually decreases from 3.30 eV to 2.73 eV with an increase in silver content. The photocatalytic degradation of 40 ppm tetracycline is examined at 120 min at neutral pH (7). Loading of Ag on Bi9Ti6FeO27 significantly promoted the photocatalytic degradation efficiency of tetracycline (84 %). Furthermore, the antibacterial activity of Ag/Bi9Ti6FeO27 was investigated against “Escherichia coli”, Klebsiella pneumoniae”, and “Acinetobacter baumannii” bacteria. Higher loading of Ag on Bi9Ti6FeO27 exhibited the most potent antibacterial activity by effectively inhibiting the growth of both bacterial strains through reactive oxidative species and the presence of silver nanoparticles. The composite has proved its stability through the five repeated cycles. This work provides an emerging strategy to finely design the nanocomposites and highlight their potential for environmental remediation and healthcare industries.

Enhanced ethanol gas sensing performance of Ag/SnO2 composites

A simple hydrothermal method was adopted to synthesize rectangular block-shaped SnO2 nanomaterials loaded with different amounts of Ag. The structural composition, morphology and chemical state of the nanomaterials were systematically investigated using XRD, SEM, TEM and XPS analysis. The gas sensing performance to ethanol was comprehensively evaluated by testing key parameters including gas response, optimal operating temperature, response-recovery time, and selectivity. The result demonstrates that the Ag/SnO2 composite, compared to pure SnO2, exhibits enhanced efficiency in detecting ethanol. The gas sensor fabricated by the sample Ag/SnO2-2 had a response of up to 80 for 200 ppm ethanol at 300℃. Moreover, the response time (reduced from 52 s to 29 s) and the selectivity were significantly improved. The superior gas sensing performance of Ag/SnO2 is attributed to the generation of highly active sites from Ag ion loading, accelerated electron transfer processes, and modulation of Schottky heterojunctions. In summary, this work demonstrates an effective strategy to improve the gas sensing performance of SnO2-based sensors by Ag loading.

Signal-Boosted Electrochemical Lateral Flow Immunoassay for Early Point-of-Care Detection of Liver Cancer Biomarker.

The early diagnosis of cancer in a point-of-need manner is of great significance, yet it remains challenging to achieve the necessary sensitivity and speed. Traditional lateral flow immunoassay (LFIA) methods are limited in accuracy and quantification, restricting their suitability for home-based applications. Thus, we explored a new and user-friendly electrochemical LFIA (e-LFIA) test strip to detect α-fetoprotein (AFP), a diagnostic marker for liver cancer. The specific electrochemical immunoprobe utilized in this e-LFIA test strip is characterized by significant signal boosting, resulted from the loading Ag shell into a gold nanoparticle (AuNP)-coated dendritic mesoporous silica nanoscaffold (DMSN). Leveraging the distinct electrochemical characteristics of Ag anodic stripping and the high volume-to-surface area ratio of DMSNs, the developed DMSNs/AuNPs@Ag-based e-LFIA test strip is capable of detecting AFP at a low concentration of 0.85 ng/mL within a rapid 20 min timespan, both of these values are smaller than those in current clinical testing. Furthermore, we utilized homemade screen-printed electrodes in this sensing prototype and demonstrated the high versatility and reliability of this e-LFIA device. We envision that this DMSNs/AuNPs@Ag-based e-LFIA holds substantial potential for the early diagnosis of liver cancer and household health monitoring.

Characterization of exopolysaccharide/potato starch nanocomposite films loading g-C3N4 and Ag and their potential applications in food packaging

The interest in nanocomposite films incorporating edible ingredients and active nanoparticles has surged due to their potential to enhance food quality and prolong shelf-life. This research focused on developing innovative exopolysaccharides (EPS)/potato starch (PS) nanocomposite films integrated with g-C3N4 and AgNO3. Extensive analysis was conducted to assess the microstructure, physical attributes and antimicrobial properties of these films. Fourier transform infrared (FT-IR) analysis revealed electrostatic and hydrogen bonding interactions within the film components. X-ray diffraction (XRD) and X-ray photoelectron spectrometer (XPS) data indicated a high level of compatibility among EPS, PS, g-C3N4, and AgNO3, with no new absorption peaks or characteristic signals of C3N4 and Ag appearing in the nanocomposite films patterns. The thickness, water solubility and water vapor permeability (WVP) of the EPS-PS-C3N4-Ag nanocomposite film increased due to the addition of g-C3N4, reached 0.31 ± 0.03 nm, 36.61 ± 1.76 % and 1.42 ± 0.34 × 10−10 g−1 s−1 Pa−1, respectively. While transparency, swelling degree, and oxygen permeability (OP) significantly decreased, reached 26.18 ± 2.38 %, 63.01 ± 2.51 % and 41.98 ± 1.28 %, respectively. Scanning electron microscopy (SEM) and atomic force microscope (AFM) images depicted an augmented roughness and porosity on the film surface upon integration of g-C3N4 and AgNO3. Moreover, the EPS-PS-C3N4-Ag nanocomposite film displayed enhanced mechanical strength due to the presence of g-C3N4. The melting temperature (Tm) of EPS-PS-C3N4-Ag nanocomposite film was 313.3 °C, the removal rates of DPPH and ABTS was 66.11 ± 2.87 % and 45.09 ± 1.23 % respectively. Significant inhibition of microbial growth was observed in film containing g-C3N4 and AgNO3, which demonstrated no toxicity towards NIH-33 cells, suggesting their potential application as promising active packaging material for food preservation.

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.

Construction of 0-dimensional silver quantum dot/MoSe2@MXene/3-dimensional porous copper foam composite electrodes with heterogeneous interfaces for synergistic electrocatalytic degradation of antibiotics

This study proposes a novel and efficient Ag quantum dots (QDs)/MoSe2@two-dimensional transition metal carbide/nitride (MXene)/copper foam (CF) composite electrode to address the challenge of electrocatalytic degradation of antibiotics in water. The electrode formed a unique electron donor–acceptor system by loading Ag QDs and heterostructured nanosheets on CF, significantly facilitating charge transfer and segregation at the interface. The catalytically active sites at the edges and defective locations of MoSe2 in conjunction with the two-dimensional MXene structure, which formed an efficient electron transfer channel, promoted the electron transfer from the interior to the surface and accelerated the hydrogen adsorption and reduction reactions. Moreover, the charge redistribution at the interface of Ag QDs and MoSe2@MXene formed interfacial dipoles, increasing the active sites on the catalyst surface and promoting the generation of cathodic atomic hydrogen (H*). Under optimal conditions, the degradation rate of tigecycline (TGC) reached as high as 90.1 % ± 2.4 % within 60 min. The anode-generated OH and HClO, along with the cathode-generated H, further promoted the degradation of TGC through co-catalysis. The degradation pathways were analyzed using density-functional theory (DFT) calculations and liquid chromatography-mass spectrometry (LC-MS) techniques. Moreover, toxicity analysis of the degradation products was carried out to ensure the safety of the treated wastewater discharge. A reflux continuous effluent reactor was also designed to achieve high degradation efficiency and low energy consumption after stable operation, laying the foundation for industrial applications. This technology provides new ideas for the design of green, efficient, stable, and low-consumption electrocatalytic reactors and contributes to a sustainable future environment.

Photochemical Fabrication of Ag‐Modified Hierarchical Cu@Cu2O/CuO Nanocomposite Toward Room Temperature NO2 Detection

Developing room temperature (RT) gas sensor based on metal oxide semiconductor material has long been challenging. Herein, a 1D hierarchical Ag‐modified Cu@Cu2O/CuO nanocomposite has been designed by low‐temperature etching self‐assembly combined with photochemical deposition method based on Cu nanowires (NWs). After a step of alkaline solution etching, the surface of Cu NWs is self‐assembled to form a hierarchical Cu@Cu2O/CuO, and then Ag nanoparticles are modified on its surface by photochemical deposition to obtain the desired material. All the preparation processes are carried out at RT and have good controllability. When applied as sensing material, the optimal Cu@Cu2O/CuO/Ag nanocomposite exhibits high response of ≈337.0 to 10 ppm NO2 with excellent selectivity and fast response/recovery (60/400 s) at 25 °C. It is worth noting that such a strategy of loading Ag nanoparticles improves its gas sensitivity by about 42.4 times, and the resulting sensor shows good sensitivity and screening ability to NO2 in the low concentration range. Finally, the nanostructure of the material is characterized systematically and the sensing mechanism is discussed.

Trace silver doping improved the efficiency of copper-based Fenton-like catalysts cathode for wastewater treatment

The treatment of highly concentrated and recalcitrant organic pollutants in industrial wastewater has garnered significant attention, with Fenton oxidation emerging as a promising approach. However, traditional iron-based Fenton reagents present certain limitations, and copper-based Fenton systems are often less efficient. Thus, it is necessary to develop innovative copper-based Fenton catalytic materials. In this study, Cu₂O and Ag-modified activated carbon fibers (Cu₂O-Ag@ACF) were synthesized via liquid-phase reduction. The composition, structure, and morphology of Cu₂O-Ag@ACF were systematically characterized. The Cu₂O-Ag@ACF was employed as a functionalized cathode in the electro-Fenton process to degrade a highly concentrated organic pollutant solution, with methylene blue serving as a model contaminant. The loading of Cu₂O and Ag not only enhances the electrochemical performance of ACF but also improves its Fenton oxidation efficiency. Cu₂O-Ag@ACF exhibited less than 1 % performance degradation after five cycles of use, highlighting its potential for industrial applications under simulated realistic conditions. Moreover, the electro-Fenton system parameters, including current density, pH, electrode spacing, and solution temperature, were optimized. Under the optimal conditions, the degradation rate of methylene blue by Cu₂O-Ag@ACF reached 92.8 % within 120 minutes. Kinetic analysis indicated that the reaction followed a first-order kinetic model, with a rate constant of 0.253 min⁻¹. Furthermore, this study revealed that trace silver doping significantly accelerated the generation of reactive oxygen species, thereby enhancing the efficiency of the Cu-based Fenton-like catalysts. In conclusion, this work presents a convenient strategy for the sustainable and efficient purification of industrial wastewater, contributing to the improvement of human life quality.

Improved electrochemical performance of Ag-modified Bi0.7Sr0.3FeO3 cathodes by electroless plating for intermediate-temperature solid oxide fuel cells

The Bi0.7Sr0.3FeO3-δ (BSFO)-Ag composite cathode is prepared by modifying BSFO with in-situ chemical plating of Ag. The plated Ag effectively reduces the polarization resistance (Rp) of BSFO. At the Ag loading of 20 wt.%, the optimized Rp of BSFO at 650oC in air condition is 0.35 Ω cm2, which is only 18.6% of that of BSFO cathode (1.88 Ω cm2). The electrochemical performance improvement is primarily attributed to the low oxygen adsorption energy (Eads) domain at the interfaces of BSFO-Ag, as indicated by the first-principles calculations (Eads, -0.81eV). Thus, the addition of Ag changes the cathodic reaction rate control step from the molecular oxygen on the cathode surface adsorption and diffusion to charge transfer on the cathode. The maximum power density (Pmax) of the prepared single cell at 650oC is 450.98 mW cm-2 using H2 (∼3 vol.% H2O) as fuels. The open-circuit voltage (OCV) does not decay significantly (around 0.66 V) after 50 h at the current density of 400 mA cm-2, showing good long-term stability.

Visible-light-driven photocatalytic oxidation of furfural to furoic acid over Ag/g-C3N4

Furoic acid (FA) is a useful bio-chemicals, which can be used in the production of pharmaceuticals, food additives, flavors, industrial chemicals, biofuels, etc. Oxidation of furfural to FA has been carried out by a thermal catalytic method, but photocatalytic oxidation protocol has not been reported yet. Here, g-C3N4-supported Ag nanoparticles (Ag NPs) catalysts with different Ag loading were synthesized and used for the photocatalytic oxidation of furfural to FA under visible light irradiation. The physicochemical and photoelectrochemical properties of the catalysts were systematically investigated by XRD, TEM, XPS, UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS), photoluminescence, etc. Compared with the pristine g-C3N4, Ag-CN(N2 + H2) was found to have better photocatalytic performances in the aerobic oxidation of furfural under visible light irradiation, and the conversion can reach 82 % with a FA yield of 30 %. Importantly, the loading of Ag NPs has a significant effect on the photoelectrochemical properties. Specifically, 0.5 % Ag NPs loading maximized the photocurrent response, indicating that the loading of Ag NPs enhances charge separation and migration under visible light excitation. The introduction of Ag NPs also led to a significant decrease in electrochemical impedance, which promoted the rate of electron transfer at the interface, further confirming the improved photocatalytic efficiency. The addition of Ag NPs broadens the solar absorption and promotes the separation/transport of photo-generated carriers to form “hot electrons”, and provides the active species for furfural oxidation. The reasonable reaction mechanism of the photocatalytic oxidation of furfural to FA was elucidated. This work offers a novel method for the oxidation of furfural to FA in a mild and green way.

Cost-Effective Microfabricated Silver-Based Paper Cathodes for High-Discharge-Rate Aluminum-Air Batteries

We report a cost-effective microfabricated silver-based air-cathode for high-discharge-rate aluminum-air batteries which are suitable for micro-drone applications. A challenge for batteries for aerial drones is that both high gravimetric energy density and power density are required for extended operation. While air batteries can address the energy density issue, achieving high power density necessitates high loadings of expensive catalytic materials such as platinum (Pt), which can constitute over 99% of the cost in commercial air batteries. [1] Building upon prior research that studied the power performance of an aluminum-air battery (AAB) system with a silver-based cathode, this study further explores the influence of silver (Ag) sputtering conditions and Ag loadings on AAB power performance. [2]The power performance of AAB is significantly influenced by both air flux through the air cathode and electrochemically active catalyst surface area ratio (ECSA). The ECSA is the ratio of the electrochemically active catalyst surface area to its cathode area. Sputtered Ag cathodes with catalyst loadings ranging from 0.03 mg-Ag/cm2 to 0.3 mg-Ag/cm2 consistently show high porosity, indicating good air flux for the microfabricated cathode. Increasing the loading of the sputtered Ag catalyst further can lead to particle agglomeration. To improve power performance and ECSA, a silver-copper (AgCu) co-sputtering technique has been developed, significantly increasing the surface area and power performance.Figure 1 shows cathodes with Ag loadings ranging from 0.038 mg-Ag/cm2 to 0.267 mg-Ag/cm2 under two silver sputtering conditions: 400W+5mTorr and 100W+10mTorr. Within the examined range, the latter sputtering condition shows superior power performance compared to the former. For Ag loadings exceeding 0.1 mg-Ag/cm2, both conditions show decreasing power performance as Ag loading increases, and the 100W+10mTorr curve shows a maximum power at 0.088 mg-Ag/cm2. Figure 2 shows SEM images of 0.038 mg-Ag/cm2, 0.088 mg-Ag/cm2, and 0.19 mg-Ag/cm2 films, using the 100W+10mTorr sputtering condition. Ag particle size increases with higher Ag loading, which can result from particle agglomeration. Figure 3 shows the catalyst layer porosity and the ECSA calculated from the SEM images. All samples show porosity over 90%, indicating good air flux for the microfabricated Ag cathode. The trend of ECSA for different Ag loading correlates well with the power performance, suggesting that the power performance of the microfabricated Ag cathode primarily depends on the ECSA.Further enhancement of the ECSA through AgCu co-deposition is investigated, involving two parent alloy compositions (at%): Ag28Cu72 and Ag16Cu84. Following the co-sputtering, the parent alloy undergoes selective etching of Cu using hydrochloric acid (HCl). Figure 4 compares power performance between Ag28Cu72 and Ag16Cu84. Both curves exhibit an upward trend as the silver loading increases from 0.09 mg-Ag/cm2 to 0.4 mg-Ag/cm2, with Ag28Cu72 samples showing superior power performance. Figure 5 shows an SEM image of Ag28Cu72 parent alloy with 0.32 mg-Ag/cm2 loading after Cu etching, demonstrating that the ECSA increased to 47.52 while maintaining a high porosity of 90.2%. The peak power of Ag28Cu72 0.32 mg-Ag/cm2 sample is increased to 200 mW/cm2. By comparison, a 4mg-Pt/cm2 commercial cathode shows a peak power of 280 mW/cm2.Figure 6 compares the discharge performance of the 0.088 mg-Ag/cm2 cathode with a commercial 4 mg-Pt/cm2 cathode. Both cells can discharge under 1.1 Amp with a power density exceeding 500 W/kgbattery, a threshold sufficient to lift a quadrotor drone. [3] Battery weight encompasses anode, cathode, electrolyte and battery packaging. The 0.088 mg-Ag/cm2 cathode shows a discharge power plateau above 600 W/kgbattery (86% of the 4 mg-Pt/cm2) and an energy density of 228 Wh/kgbattery when discharge power density exceeding 500 W/kgbattery (95% of the 4 mg-Pt/cm2). Remarkably, the material cost of the 0.088 mg-Ag/cm2 cathode is 5000 times less than the 4 mg-Pt/cm2 cathode.

Monitoring the Dynamics of the Galvanic Replacement Reaction to Develop Free-Standing Electrocatalysts

Hydrogen (H2) is well-known for its potential to become the future fuel and bring a more sustainable energy system [1]. The selective electrooxidation of organic compounds from biomass appears to be a possible substitute for the kinetically slow oxygen evolution reaction (OER) at the anode, which increases the electrical energy input for a conventional water electrolysis in alkaline media [2]. However, this approach is currently impeded by limited fundamental knowledge of the different active sites of electrocatalysts. The latter can be used to control selectivity at low potential and high current density to co-generate value-added products at the anode instead of CO2 by complete oxidation. Nanostructured gold-based multi-metal electrocatalysts can meet such objectives. Particularly in the electro-valorization of cellulosic biomass at electrode potentials unfavorable to C-C bond breaking and high overall cell voltage.To develop such electrocatalysts, we have initiated a multivariate methodology to study the dynamics of galvanic replacement between silver and gold. This procedure allows us to control nanoporosity and nanoalloying in the resulting gas diffusion electrode (GDE): GDE-Ag1-xAux. GDE-Ag represents the electrode upon which Ag particles were electrochemically grown prior to reaction with Au(III). Thermodynamically, silver with E°(Ag+/Ag) = 0.8 V vs SHE (standard hydrogen electrode) can be replaced by gold with E°(AuCl4 –/Au) = 1.0 V vs SHE according to: 3Ag + xKAuCl4(aq) → 3xAgCl + xKCl + Ag3-3xAux.[2,3] From a kinetic point of view, the challenge is to capture in real time the formation of metal cages of Ag-Au alloys after a '3by1' atomic exchange that introduces nanoporosity and electronic strain as silver and gold have a similar atomic radius. To interrogate the driving force behind this redox process, we have also established an electrochemical methodology to extract quantitative data, allowing detailed capture of the mixed electrochemical and mass transport (diffusion) kinetics. As the precipitation product AgCl leads to pore fouling, we have developed an efficient methodology to trigger its instant dissolution as soon as it is formed, thus promoting the production of a high-quality alloy. As shown in Figure 1, upon injection of a KAuCl4 solution into a degassed solution in contact with the GDE-Ag electrode, the open circuit potential (OCP) begins to change. This evolution is due to the modification of the electrochemical interface as silver atoms are progressively replaced by gold atoms. Thereby, leading to a regulated potential defined either by the Ag(I)/Ag redox couple, or by the Au(III)/Au pair. Interestingly, we found that the OCP variation logically depends on initial conditions such as Ag loading on the GDE, KAuCl4 concentration, Ag particle size, etc. This fundamental knowledge has led to the synthesis of efficient electrocatalysts for the oxidation of cellulose subunits in alkaline media with an onset electrode potential much lower than OER (E < 1 V vs RHE (reversible hydrogen electrode)). Indeed, the formation of an alloy phase, the creation of nanoporosity within it and the free-standing nature amplify, through synergistic and electronic effects, the electrocatalytic efficiency. Acknowledgments This work was funded by French National Research Agency (ANR-22-CE43-0004).

Ag/CNT Catalyst Synthesized by Plasma-Enhanced Atomic Layer Deposition for Anion Exchange Membrane Fuel Cells

Anion exchange membrane fuel cells (AEMFCs) have recently gained attention as a viable alternative to proton exchange membrane fuel cells (PEMFC), offering the potential for high output without relying on expensive platinum (Pt) catalysts. PEMFCs operate in an acidic environment characterized by a high concentration of H+, necessitating the use of platinum-based catalysts to ensure both performance and stability in such conditions. In contrast, AEMFCs operate in an alkaline environment (OH-), affording the use of high-performance catalysts like silver (Ag), which is sensitive to acidity. Moreover, the cost of Ag is approximately 1/50 of Pt, offering significant cost advantages for fuel cell commercialization. Atomic layer deposition (ALD) has garnered substantial attention as a valuable technique for crafting high-performance nano-catalysts. ALD's self-limiting nature, based on the sequential exposure of vaporized precursors and reactants, enables precise control over catalyst size and composition. In this study, we employed plasma-enhanced ALD (PEALD) to fabricate cutting-edge AEMFC cathodes comprised of carbon nanotubes (CNTs) adorned with Ag. This approach yielded impressive results, achieving an AEMFC output exceeding 300 mW cm-2 or more than 2 W mgAg -1 at 65 °C with a CNT cathode featuring an exceedingly low Ag loading of less than 0.15 mg cm-2. Notably, this represents the world's highest reported Ag-AEMFC performance to date. The Ag-decorated cathode created through ALD played a pivotal role in significantly reducing resistance in the polarization region, a major contributor to overall energy losses in AEMFCs. Additionally, when evaluating the durability of the Ag-decorated CNT anode in an alkaline environment, we observed excellent long-term stability. In this presentation, we will discuss a more detailed exploration of the relationship between AEMFC performance, featuring ALD-fabricated Ag-CNT catalysts, and the intricate catalyst structure.

Antimicrobial silver loading onto reused high-density polyethylene matrices grafted with poly(4-vinylpyridine)

High-density polyethylene HDPE is a highly polluting plastic, and its reuse, reprocessing and modification are subjects of current research to mitigate environmental pollution. In recent times, it has been modified for specialized purposes as a harmless and resistant polymer. The present work details the modification of HDPE (obtained from Bonafont, Coke, and Gatorade caps) with the monomer 4-vinylpyridine (4VP) via radiation-induced grafting copolymerization initiated by gamma rays from a Co-60 source and with the subsequent Ag(I) loading using the reagent AgNO3 in aqueous medium. Poly(4VP) is widely used to retain metals and manufacture pH-responsive polymers, while Ag(I) is a recognized bactericide harmless to humans at therapeutic concentrations; therefore, both poly4VP and Ag(I) can work in a synergistic system against pathologic bacteria as is here proposed. We advance a favorable antimicrobial activity of the Ag-loaded graft copolymers evaluated in vitro with Kirby-Bauer tests against Pseudomonas aeruginosa and Staphylococcus aureus. Additionally, FTIR-ATR, TGA, contact angle, swelling, and pH response were carried out to complete the characterization.

ZIF-8 loaded Ag/ZnO electrospun nanofibers enabling high-performance H2 gas sensing for battery safety early warning

Safety issues triggered by battery thermal runaway have become the most crucial obstacle to the future development of the high-energy-density energy storage systems. As hydrogen (H2) will be inevitably generated along with heat release caused by the side reactions in the early stages of battery thermal runaway, rapid monitoring of trace H2 is considered as an effective measure enabling the battery safety early warning. Herein, to develop high-performance H2 sensing materials to monitor of low-concentration H2 leakage, ZIF-8 loaded Ag/ZnO electrospun nanofibers (ZAZ NFs) were designed by electrospinning and self-sacrificial template methods. Benefiting from all the enrichment and sieving effects of ZIF-8 shell, the catalytic and sensitization effects of Ag and abundant active sites provided by Ag and ZIF-8 loading, the ZAZ sensor enables ppb-level limit of detection toward H2, fast response (9 s), high selectivity and excellent humidity resistance. Furthermore, this ZAZ sensor can also realize the safety early warning (67.79 s before battery bulge) for practical pouch lithium cells, highlighting its great application potential in future advanced battery safety management system.