Silver Nanoparticle Catalyst Research Articles

Kinetics of 4-Nitrophenol Reduction with Black Tea Extract Conjugated Silver Nanoparticle Catalyst

Kinetics of 4-Nitrophenol Reduction with Black Tea Extract Conjugated Silver Nanoparticle Catalyst

Atomic Cobalt-Silver Dual-Metal Sites Confined on Carbon Nitride with Synergistic Ag Nanoparticles for Enhanced CO2 Photoreduction.

Photocatalytic reduction of CO2 to value-added solar fuels is of great significance to alleviate the severe environmental and energy crisis. Herein, we report the construction of a synergistic silver nanoparticle catalyst with adjacent atomic cobalt-silver dual-metal sites on P-doped carbon nitride (Co1Ag(1+n)-PCN) for photocatalytic CO2 reduction. The optimized photocatalyst achieves a high CO formation rate of 46.82 μmol gcat-1 with 70.1% selectivity in solid-liquid mode without sacrificial agents, which is 2.68 and 2.18-fold compared to that of exclusive silver single-atom (Ag1-CN) and cobalt-silver dual-metal site (Co1Ag1-PCN) photocatalysts, respectively. The closely integrated in situ experiments and density functional theory calculations unravel that the electronic metal-support interactions (EMSIs) of Ag nanoparticles with adjacent Ag-N2C2 and Co-N6-P single-atom sites promote the adsorption of CO2* and COOH* intermediates to form CO and CH4, as well as boost the enrichment and transfer of photoexcited electrons. Moreover, the atomically dispersed dual-metal Co-Ag SA sites serve as the fast-electron-transfer channel while Ag nanoparticles act as the electron acceptor to enrich and separate more photogenerated electrons. This work provides a general platform to delicately design high-performance synergistic catalysts for highly efficient solar energy conversion.

Highly Tunable Syngas Product Ratios Enabled by Novel Nanoscale Hybrid Electrolytes Designed for Combined CO2 Capture and Electrochemical Conversion

AbstractCoupling renewable energy with the electrochemical conversion of CO2 to chemicals and fuels has been proposed as a strategy to achieve a new circular carbon economy and help mitigate the effects of anthropogenic CO2 emissions. Liquid‐like Nanoparticle Organic Hybrid Materials (NOHMs) are composed of polymers tethered to nanoparticles and are previously explored as CO2 capture materials and electrolyte additives. In this study, two types of aqueous NOHM‐based electrolytes are prepared to explore the effect of CO2 binding energy (i.e., chemisorption versus physisorption) on CO2 electroreduction over a silver nanoparticle catalyst for syngas production. Poly(ethylenimine) (PEI) and Jeffamine M2070 (HPE) are ionically tethered to SiO2 nanoparticles to form the amine‐containing NOHM‐I‐PEI and ether‐containing NOHM‐I‐HPE, respectively. At less negative cathode potentials, PEI and NOHM‐I‐PEI‐based electrolytes produce CO at higher rates than 0.1 molal. KHCO3 due to favorable catalyst‐electrolyte interactions. Whereas at more negative potentials, H2 production is favored because of the carbamate electrochemical inactivity. Conversely, HPE and NOHM‐I‐HPE‐based electrolytes display poor CO2 reduction performance at less negative potentials. At more negative potentials, their performance approached that of 0.1 molal. KHCO3, highlighting how the polymer functional groups of NOHMs can be strategically selected to produce value‐added products from CO2 with highly tunable compositions.

Amorphous carbon coating enhances activity of high rate CO2electroreduction to CO

The amorphous carbon coated silver nanoparticle (Ag/C) catalyst can achieve the maximum current density up to 800 mA cm−2with FECOup to 95% through carbon shell promoting the adsorption of CO2.

Selective Electroless Copper Plating of Ink-Jet Printed Textiles Using a Copper-Silver Nanoparticle Catalyst.

The electroless copper plating of textiles, which have been previously printed with a catalyst, is a promising method to selectively metallise them to produce high-reliability e-textiles, sensors and wearable electronics with wide-ranging applications in high-value sectors such as healthcare, sport, and the military. In this study, polyester textiles were ink-jet printed using differing numbers of printing cycles and printing directions with a functionalised copper–silver nanoparticle catalyst, followed by electroless copper plating. The catalyst was characterised using Transmission Electron Microscopy (TEM) and Ultraviolet/Visible (UV/Vis) spectroscopy. The electroless copper coatings were characterised by copper mass gain, visual appearance and electrical resistance in addition to their morphology and the plating coverage of the fibres using Scanning Electron Microscopy (SEM). Stiffness, laundering durability and colour fastness of the textiles were also analysed using a stiffness tester and Launder Ometer, respectively. The results indicated that in order to provide a metallised pattern with the desired conductivity, stiffness and laundering durability for e-textiles, the printing design, printing direction and the number of printing cycles of the catalyst should be carefully optimised considering the textile’s structure. Achieving a highly conductive complete copper coating, together with an almost identical and sufficiently low stiffness on both sides of the textile can be considered as useful indicators to judge the suitability of the process.

Effects of microporous layer on electrolyte flooding in gas diffusion electrodes and selectivity of CO2 electrolysis to CO

Understanding the relationship between gas diffusion electrode (GDE) structures and the performance of electrochemical CO2 reduction reaction (CO2RR) is crucial to developing industrial-scale technologies to convert CO2 to valuable products. We studied how the microporous layer (MPL) on GDE's coated with silver nanoparticle catalysts affects the electrochemical CO2 conversion to CO in a flow cell electrolyser. We demonstrate a convenient method to measure the rate of catholyte seepage through a GDE during CO2RR experiments and used this method to show how the MPL thickness affects flooding of the GDE. We found the GDE with the thickest MPL (39BB) had the best selectivity for CO and stability at current densities above 100 mA cm−2 as the thick MPL minimized flooding. However, at low current densities the 39BB electrode achieved a lower CO selectivity than the GDE with thinner MPL. These results suggest opportunities to improve CO2 electrolyser performances at high current by optimisation of the MPL structure and wettability.

One-Pot Facile Synthesis of Noble Metal Nanoparticles Supported on rGO with Enhanced Catalytic Performance for 4-Nitrophenol Reduction.

In this study, reduced graphene oxide (rGO)-supported noble metal (gold, silver, and platinum) nanoparticle catalysts were prepared via the one-pot facile co-reduction technique. Various measurement techniques were used to investigate the structures and properties of the catalysts. The relative intensity ratios of ID/IG in rGO/Au, rGO/Ag, rGO/Pt, and GO were 1.106, 1.078, 1.047, and 0.863, respectively. The results showed the formation of rGO and that noble metal nanoparticles were decorated on rGO. Furthermore, the catalytic activities of the designed nanocomposites were investigated via 4-nitrophenol. The catalysts were used in 4-nitrophenol reduction. The catalytic performance of the catalysts was evaluated using the apparent rate constant k values. The k value of rGO/Au was 0.618 min−1, which was higher than those of rGO/Ag (0.55 min−1) and rGO/Pt (0.038 min−1). The result proved that the rGO/Au catalyst exhibited a higher catalytic performance than the rGO/Ag catalyst and the rGO/Pt catalyst. The results provide a facile method for the synthesis of rGO-supported nanomaterials in catalysis.

Statistical optimization of bio-mediated silver nanoparticles synthesis for use in catalytic degradation of some azo dyes

The present study deals with optimization of process parameters for the synthesis of silver nanoparticles from outer shell extract of Eucalyptus globulus fruit and maximization of nanoparticles yield. The statistical tool of design of experiments (DOE), following response surface methodology (RSM), was, thus, employed. The synthesized silver nanoparticles were characterized by UV–Vis, FTIR, Raman, DLS, SEM-EDX, FESEM and TEM analyses. The nanoparticle, as catalyst, was utilized for reductive degradation of three azo dyes such as methyl orange, methyl red and congo red in aqueous medium at room temperature. Reductive degradation pathway of the said dyes using NaBH4 and silver nanoparticle catalyst was followed under visible light. More than 90% degradation of the dyes was observed within 10 min for methyl orange, and 20 min for both methyl red and congo red. The mechanism of the degradation process and the kinetic parameters were evaluated. The degradation pathway was found to follow a pseudo first-order kinetic model and the activation energy was evaluated to be 244, 204 and 104 kJ mol−1 for methyl orange, methyl red and congo red respectively. The role of common ions on the degradation efficiency was determined and the process was found effective in the river water system.

Smart hydrogel-microsphere embedded silver nanoparticle catalyst with high activity and selectivity for the reduction of 4-nitrophenol and azo dyes

A simple method is reported for the preparation of silver nanoparticle (AgNP) embedded pH-responsive hydrogel microparticle catalyst via Michael addition gelation and in-situ silver nitrate (AgNO3) reduction. The AgNP-hydrogel microsphere exhibited an efficient reduction of pollutants like 4-Nitrophenol (4-NP) and Congo red (CR) under acidic medium with turn over frequency (TOF) of ~170 h–1 and ~124 h–1 respectively. Interestingly, the activity of the catalysts was turned-OFF under a basic medium (≥ pH 12) due to the deswelling pH-responsive matrix surrounding the AgNPs. On the contrary, turning-OFF the hydrogenation of a cationic pollutant like methylene blue (MB) using high pH (≥ 12) was not possible, due to ionic interaction of MB molecules with the negatively charged catalyst at this pH. This feature was used to demonstrate selective hydrogenation of only MB from a mixture of 4-NP and MB. Finally, five recycling steps confirmed the reusability and practical application potential of the catalyst.

(Keynote) Electrolyzer Development and Process Optimization: Paving the Road for Industrial Carbon-Dioxide Electroreduction

Electrochemical reduction of CO2 is a promising method for converting a greenhouse gas into value-added products, utilizing renewable energy. Novel catalysts, electrode assemblies, and cell configurations are all necessary to achieve economically appealing performance. In this talk, I am going to present a zero gap electrolyzer cell, which converts gas phase CO2 to products without the need for any liquid catholyte. I will show how to optimize the cell components, to simultaneously provide industrially relevant performance, such as high partial current density (up to 800 mA cm-2), low cell voltage (−2.8-3.2 V), high conversion efficiency (up to 45 %), and high selectivity for CO production (over 95%).I will also demonstrate our CO2 electrolyzer cell, where multiple layers are connected into an electrolyzer stack, thus scaling up the electrolysis process. The operation of the cell was validated using both silver nanoparticle and copper nanocube catalysts. Evenly distributing the CO2 gas among the layers (parallel connection), the operation of the cell stack was identical to the sum of multiple single-layer cells. When passing the CO2 gas through the layers one after the other (serial gas connection), the CO2 conversion efficiency was increased remarkably.Finally, I will show how the cell can operate with pure water feed on the anode side, therefore avoiding the use of alkaline anolyte. A carefully designed activation protocol will be presented, which allows the cell to operate at high current density, using pure water feed. The effect of temperature and flow rate on the operation will also be presented. Finally, the nature of ion-transport through the anion exchange membrane as a function of the operational conditions will be discussed.

(Invited) Electrolyzer Development and Process Optimization: Paving the Road for Industrial Carbon-Dioxide Electroreduction

Electrochemical reduction of CO2 is a promising method for converting a greenhouse gas into value-added products, utilizing renewable energy. Novel catalysts, electrode assemblies, and cell configurations are all necessary to achieve economically appealing performance. In this talk, I am going to present a zero gap electrolyzer cell, which converts gas phase CO2 to products without the need for any liquid catholyte. This is the first report of a CO2 electrolyzer cell, where multiple stacks are connected, thus scaling up the electrolysis process. The operation of the cell was validated using both silver nanoparticle and copper nanocube catalysts, and the first was employed for the optimization of the electrolysis conditions. Upon this, CO formation with partial current densities above 250 mA cm−2 were achieved routinely, which was further increased to 300 mA cm−2 (with ~95 % Faradaic efficiency) by pressurizing the CO2 inlet. Evenly distributing the CO2 gas among the stacks (parallel connection), the operation of the multi-stack cell was identical to the sum of multiple single-stack cells. When passing the CO2 gas through the stacks one after the other (serial gas connection), the CO2 conversion efficiency was increased remarkably. Importantly, the presented electrolyzer simultaneously provides high partial current density, low cell voltage (−3.0 V), high conversion efficiency (up to 40 %), and high selectivity for CO production; while operating at up to 10 bar differential pressure.In the second part of the talk I will show how the cell can operate with pure water feed on the anode side, therefore avoiding the use of alkaline anolyte. A carefully designed activation protocol will be presented, which allows the cell to operate at high current density, using pure water feed. The effect of temperature and flow rate on the operation will also be presented. Finally, the nature of ion-transport through the anion exchange membrane as a function of the operational conditions will be discussed.

Dual-atom Ag2/graphene catalyst for efficient electroreduction of CO2 to CO

Electrochemical reduction of CO2 into value-added carbon compounds offers a promising strategy to mitigate global warming, but present challenges for chemistry due to the poor selectivity and stability of electrocatalysts. In this work, we report a dual-atom Ag2/graphene catalyst featuring well-defined AgN3-AgN3 active site for CO2 electrochemical reduction. This dual-atom catalyst can drive CO2 reduction reaction at a potential as high as -0.25 V, and exhibit excellent CO Faradic efficiency up to 93.4 % with a current density of 11.87 mA cm−2 at -0.7 V and long-term stability, far surpassing the single-atom Ag1/graphene and the traditional silver nanoparticle catalysts. DFT calculations reveal that the dual-atom Ag site lowers the barrier for the formation of *COOH by stabilizing the *CO2 through the concomitant interactions with the C and an O atom of CO2, resulting in excellent catalytic performance.

Electrolytic Conversion of Bicarbonate into CO in a Flow Cell

Electrochemical CO2 reduction offers a method to use renewable electricity to convert CO2 into CO and other carbon-based chemical building blocks. While nearly all studies rely on a CO2 feed, we show herein that aqueous bicarbonate solutions can also be electrochemically converted into CO gas at meaningful rates in a flow cell. We achieved this result in a flow cell containing a bipolar membrane (BPM) and a silver nanoparticle catalyst on a porous carbon support. Electrolysis upon a N2-saturated 3.0-M potassium bicarbonate electrolyte solution yields CO with a faradaic efficiency (F.E.CO) of 81% at 25 mA cm-2 and 37% at 100 mA cm-2. This output is comparable to the analogous experiment where the electrolyte is saturated with gaseous CO2 (faradaic efficiency for CO is 78% at 25 mA cm-2 and 35% at 100 mA cm-2). The H+ flux from the BPM is critical to this chemistry in that it reacts with the bicarbonate feed to generate CO2, which is then reduced to CO at the gas diffusion electrode. These results are important in that they show that the addition of gaseous CO2 to bicarbonate electrolytes is not necessary in order to obtain reduced carbon products with a flow cell architecture. This process offers a means of using electrolysis to bypass the thermally-intensive step of extracting CO2 from bicarbonate solutions generated in carbon capture schemes.

Visible-light-driven reduction of nitrostyrene utilizing plasmonic silver nanoparticle catalysts immobilized on oxide supports

Abstract The localized surface plasmon resonance (LSPR) mediated enhanced chemical activity can be entitled as a promising strategy for efficient solar to chemical energy conversion. To tune the selectivity of a desired product in a chemical reaction is of paramount importance yet a great challenge. In this paper, a new strategy to effectively enhance the selectivity of the product formation under visible light irradiation is reported. A series of Ag catalysts deposited on metal oxide support materials (TiO2, ZrO2, Al2O3 and CeO2) along with their preparative techniques, optimum metal content ratio and effect of different wavelength of light is explored for the chemoselective reduction of p-nitrostyrene to p-aminostyrene under visible light irradiation. The prepared catalysts were characterized by a range of physicochemical techniques including UV–vis, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The reduction reaction was carried out in ethanolic suspension at room temperature and pressure utilizing ammonia borane (AB) as an in-situ source of H2. The reaction results displayed 100% conversion with a maximum chemoselectivity of 81% shown by Ag/TiO2 under light irradiation conditions. The high chemoselectivity could be attributed to the preferential alignment of polar nitro group on the surface of plasmonic silver under light irradiation conditions.

Novel activated carbon supported trimetallic PdCoAg nanoparticles as efficient catalysts for the hydrolytic dehydrogenation of ammonia borane

Activated carbon (AC) supported palladium, cobalt and silver nanoparticle (PdCoAg/AC) catalysts were prepared by in situ reduction of sodium borohydride (NaBH4) and characterized by various techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX), Transmission electron microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The PdCoAg/AC catalyst is active in the hydrolysis of ammonia-borane (AB) even at low temperatures. Compared with mono- (Pd) and bi-metallic (PdCo) nanoparticles, this trimetallic (PdCoAg) structure showed greatly increased catalytic activity for AB hydrolysis. Their hydrolysis completion time was 50 s. This study also included full experimental details of kinetic data to determine the activation parameters (Ea, ΔH and ΔS) for the rate law and the catalytic hydrolysis of AB. In addition, the PdCoAg/AC catalysts had favorable catalytic activity also after seven runs. Hydrogen generation rate (HG), Ea, ΔH and ΔS were obtained at 25 °C as 4666.66 mL min−1g−1 (2 mmol AB and 50 mg PdCoAg/AC), 26.836 kJ mol-1, 29.416 kJ mol−1and –108.42 J mol−1K−1, respectively. In addition, the study showed that Pd0.6Co0.2CAg0.2/AC (Pd:Co:Ag atomic ratio = 6:2:2) showed the total turnover frequency (TOF) value of 6624 h−1. These results demonstrate that the PdCoAg/AC catalyst is a promising alternative in search of the practical application of AB as a hydrogen storage material for fuel cell applications.

Facile synthesis of poly (benzylamine) brushes stabilized silver nanoparticle catalyst for the abatement of environmental pollutant methylene blue

Abstract A novel type of polymer brushes as a stabilizing agent was synthesized by benzylamine at room temperature. The synthesized polymer brushes can act as an excellent stabilizing agent and the method of synthesis is also a simple one. Three different types of magnetically recoverable nano-catalysts were prepared through individual immobilization of silver nanoparticles (Ag NPs) onto the surface of Fe3O4 NPs, Fe3O4-OA NPs and Fe3O4-PBA NPs viz., Fe3O4-Ag NPs, Fe3O4-OA-Ag NPs, Fe3O4-PBA-Ag NPs catalysts, respectively. The synthesized catalysts were characterized by XRD, 1H NMR, GPC, Raman, FT-IR, UV-vis, VSM, SEM and HR-TEM. The catalytic potential of the newly prepared catalyst was examined through the reduction/degradation of methylene blue by NaBH4 under pseudo-first order reaction condition. The apparent rate constant (Kapp) and TOF of Fe3O4-Ag NPs, Fe3O4-OA-Ag NPs, Fe3O4-PBA-Ag NPs are 2.0 × 10−2 s−1, 3.3 × 10−2 s−1, 15.6 × 10−2 s−1 and 5.0 × 10−3 s−1, 83.3 × 10−3 s−1, 285.7 × 10−3 s−1 respectively. Among the catalysts, based on Kapp value, catalytic activity of Fe3O4-PBA-Ag NPs (15.6 × 10−2 s−1) is eight times higher than Fe3O4-Ag NPs (2.0 × 10−2 s−1). The Fe3O4-PBA-Ag NPs catalyst was tested to estimate the material stability up to seven runs without losing catalytic activity by recovery catalysts. This new method of prepared catalysts is expanded for the application of magnetic recoverable nano-catalysts in various industrially important reactions because of its simple preparation method along with its recyclable capacity and high activity.

Design of experiment for optimization of nitrophenol reduction by green synthesized silver nanocatalyst

Phenol derived molecules are considered as critical pollutants in the environment and need to be decontaminated to safeguard our mother Earth. This may sometimes be achieved by degradation using nanomaterials. Plant mediated biosynthesis of nanoparticles is truly encouraging for environmental safety as well as easy availability of precursor materials.The present report demonstrates the catalytic reduction of 4-nitrophenol using silver nanoparticle, synthesized from rhizome of Cyperus Rotundus. It is characterized by UV–vis and FTIR spectra, DLS, SEM-EDS, AFM, FESEM and TEM. The size of the particle is estimated to be in the range of 10–40 nm. Degradation pathway using NaBH4 and silver nanoparticle catalyst is followed under visible light. The influence of variables such as time, dose of NaBH4, 4-nitrophenol (4-NP) and silver nanoparticle was investigated following response surface methodology. A mathematical model is built up to correlate the interactive influences of the significant variables and the reduction. The mutual interactions of these variables are mapped in the design space by response surface and contour plots. The process follows a pseudo first-order kinetic model and the activation energy was evaluated to be 53.3 kJ mol−1. The conversion of 4-NP–4-AP was confirmed from NMR studies.

Preparation of Nickel Nanoparticles by Direct Current Arc Discharge Method and Their Catalytic Application in Hybrid Na-Air Battery

Nickel nanoparticles were prepared by the arc discharge method. Argon and argon/hydrogen mixtures were used as plasma gas; the evaporation of anode material chiefly resulted in the formation of different arc-anode attachments at different hydrogen concentrations. The concentration of hydrogen was fixed at 0, 30, and 50 vol% in argon arc, corresponding to diffuse, multiple, and constricted arc-anode attachments, respectively, which were observed by using a high-speed camera. The images of the cathode and anode jets were observed with a suitable band-pass filter. The relationship between the area change of the cathode/anode jet and the synchronous voltage/current waveform was studied. By investigating diverse arc-anode attachments, the effect of hydrogen concentration on the features of nickel nanoparticles were investigated, finding that 50 vol% H2 concentration has high productivity, fine crystallinity, and appropriate size distribution. The synthesized nickel nanoparticles were then used as catalysts in a hybrid sodium–air battery. Compared with commercial a silver nanoparticle catalyst and carbon black, nickel nanoparticles have better electrocatalytic performance. The promising electrocatalytic activity of nickel nanoparticles can be ascribed to their good crystallinity, effective activation sites, and Ni/NiO composite structures. Nickel nanoparticles prepared by the direct current (DC) arc discharge method have the potential to be applied as catalysts on a large scale.

Silica‐Supported Silver as a Green and Sustainable Catalyst for the [3+2]‐Cycloaddition Reaction of Azomethine Ylides with 2′‐Hydroxychalcone Derivatives

AbstractA reusable heterogeneous silver nanoparticle catalyst supported on silica was used for the [3+2]‐cycloaddition reaction of azomethine ylides with 2′‐hydroxychalcone derivatives. The green and sustainable catalytic protocol afforded highly functionalized pyrrolidines, indolizidines, and pyrrolizidines in good yields with high regio‐ and diastereoselectivities.

Highly selective detection of sulfide through poisoning silver nanoparticle catalysts

Catalyst poisoning often occurs in a variety of catalytic reactions, which is undesirable as it leads to a loss of catalytic activity and durability. From the viewpoint of catalyst poisoning, we herein successfully develop a facile and highly selective method for the detection of sulfide in aqueous solution, using Ag nanoparticles (AgNPs) as probes. With the addition of different amounts of sulfide into the reaction system, a series of different kinetics for catalytic reduction of 4-nitrophenol can be obtained. Mechanism studies demonstrate that the slowing down of reaction rate is owing to the surface poisoning of AgNPs, namely, the formation of a thin layer of Ag2S on the surface of AgNPs. Based on the linear relationship between the rate constant and concentration of sulfide, the quantitative determination of sulfide in a range of 500nM − 7.5μM has been achieved. Moreover, this analytical method shows high selectivity for sulfide beside other anions, and thus has been successfully applied in the determination of sulfide in real samples.