Metals Ag Research Articles

A theoretical equation of state to formulate the melting curve of metals with varying pressure

The objective of this study has been formulate mathematical equations for the melting temperature of metallic solids using various thermodynamics equation of state, specifically those proposed by Modified generalized Lennard – Jones(mGL-J) equation of state (EOS) and Usual-Tait EOS. The derived equations of state establish the relation between pressure, volume, melting temperature, bulk modulus and first-order pressure derivative at zero pressure. These equations of state are used to calculate melting curves for the metallic elements Pd, Cd, Pt, Mn, Au, Al, Zn and Ag up to 30 GPa. The obtained results from Modified generalized Lennard – Jones(mGL-J) equation of state display a significant rise in the melting curve because of a large increase in bulk modulus. The results of mGL-J EOS is the most consistent with the experimental data. The outcomes obtained from Usual-Tait equation of state diverges to a great extent with the experimental melting temperature. The study contributes to a better understanding of the quantitative effect of pressure on the melting temperature of various solids. The derived equations of state are useful to calculate melting temperature at larger pressures.

Nonthermal Plasma-Stimulated C-N Coupling from CH4 and N2 Depends on the Presence of Surface CHx and Plasma-Phase CN Species.

Formation of C-N containing compounds from plasma-catalytic coupling of CH4 and N2 over various transition metals (Ni, Pd, Cu, Ag, and Au) is investigated using a multimodal spectroscopic approach, combining polarization-modulation infrared reflection-absorption spectroscopy (PM-IRAS) and optical emission spectroscopy (OES). Through sequential experiments utilizing CH4 and N2 nonthermal plasmas, we minimize plasma-phase reactions and identify key intermediates for C-N coupling on metal surfaces. Results show that simultaneous CH4 and N2 exposure with plasma stimulation produces surface C-N species. However, N2-CH4 sequential exposure does not lead to C-N species formation, while CH4-N2 sequential exposure reveals the presence of CHx surface species and CN radical species as key precursors to C-N species formation. From further analysis using X-ray photoelectron spectroscopy and liquid chromatography-mass spectrometry, the influence of exposure conditions on the degree of nitrogen incorporation and the nature of C-N species formed were revealed. The work highlights the importance of surface chemistry and exposure conditions in surface C-N coupling with plasma stimulation.

Polydopamine-assisted immobilization of metallic nanoparticles confined regionally in bamboo microchannels as continuous-flow microreactors for enhanced catalysis

In contrast to conventional plant-based microreactors where the nanocatalyst is anchored on the inner walls of microchannel structures, this study presents a bamboo-based flow microreactor in which the metallic nanocatalyst is immobilized within polydopamine (PDA) region-modified bamboo microchannels. This novel design facilitates a large surface area for nanocatalyst loading, enhances mass transfer, and reduces nanocatalyst leaching. Firstly, the hierarchical PDA architecture was fabricated on the wall surface of required bamboo microchannels through an ammoniation-induced self-assembly process to serve as a nanocatalyst support layer. The thickness of PDA architectures was modulated by adjusting the flow duration. Secondly, the metallic nanoparticles (NPs), including Pd, Au, and Ag, were effectively immobilized within the hierarchical PDA architectures as highly efficient catalysts using a flow-assisted method with minimal chemical usage and low catalyst loading (Pd content: 0.011 wt%). The catalytic performances of the proposed Pd-PDA/bamboo microreactor were evaluated for the continuous hydrogenation of nitroaromatics under flow conditions, encompassing variations in Pd content, nitroaromatic concentration, and liquid flow rate. The optimized Pd-PDA/bamboo microreactor exhibited high average conversion (>97 %) of nitroaromatics during 20 days of continuous operation without any noticeable deactivation or loss in activity due to its excellent stability resulting from firm immobilization of active metallic NPs within hierarchical PDA architectures. Additionally, this bamboo microreactor demonstrated potential applicability in environmental pollution treatment through azo dye hydrogenation.

Investigation of the catalytic activity of Ag(0) nanoparticles supported into anionic hydrogel networks for hydrogen production process

In the presented study, the hydrogen production from the hydrolysis of the morpholine-borane (MB) with hydrogel supported Ag(0) nanoparticle catalyst system was reported. For this purpose, nanosized p(sulfopropyl acrylate potassium salt-co-itaconic acid)@Ag composite material, (p-SIH@Ag), was prepared and used as catalyst. In this study, the effects of base, catalyst amount, MB substrate concentration and temperature were investigated for the MB hydrolysis reaction. p-SIH@Ag catalyzed MB hydrolysis reaction at 30 °C, the activation energy (Ea) was determined as 24.3 kjmol−1 and the turn over frequency (TOF) as 37.52 mol H2(mol Ag(0).h)−1. In reusability studies, the catalyst preserved 72% of its activity even after the 5th catalytic cycle despite the sensitivity of Ag metal to oxidation. Our study is the first in the literature to use hydrogel supported Ag metal catalyst system in hydrogen production via MB hydrolysis.

Selective Photocatalytic CO2 Reduction Through Plasmonic Z‐Scheme Ag‐Bi2O3‐ZnO Heterostructures

AbstractCombination of plasmonic noble metal with semiconductors offers a promising and potential solar energy harvesting and conversion route. Herein, plasmonic Z‐scheme Ag‐Bi2O3‐ZnO (AgBZ) heterostructure is designed and synthesized via solution combustion and photo‐deposition method. Metallic Ag nanoparticles (NPs) were deposited over Bi2O3‐ZnO heterostructure; thus, they exhibit strong visible light absorption owing to surface plasmon resonance (SPR). The photocatalytic efficiency of the synthesized catalysts is investigated by the photocatalytic CO2 reduction to fuels under simulated solar light irradiation. The present system has shown an outstanding photocatalytic CO2 reduction and excellent selectivity of CO. The evolved rate of CO fuel, the amount of CO produced per unit time, over optimized Ag‐Bi2O3‐ZnO (3AgBZ) heterostructures was (96.74 μmol g−1/h) which was approximately 12 times larger than that of Bi2O3‐ZnO (0AgBZ) and 49‐fold than the quantity of evolved CO fuels over pure ZnO photocatalyst. The percentage of evolved CO to CH4 fuels over optimized Ag‐Bi2O3‐ZnO (3AgBZ) heterostructures was about 50 : 1compared to that of 2 : 3 over Bi2O3‐ZnO (0AgBZ). The great improvement and the high selectivity would be ascribed to the synergistic effect of metallic surface plasmon resonance and the Z‐scheme charges transfer system. This work would open a window to construct a single photocatalyst with different charge separation systems and excellent CO2 reduction selectivity. Finally, the mechanism for the enhanced photocatalytic performance by the synergistic effect was described and discussed.

Catalytic post-treatment of homogeneous Ag–S2O8 and Cu–H2O2 advanced oxidation processes: Revealing the importance of capacitive-Faradaic electrochemical structure of Pt/AC

Implementation of homogeneous advanced oxidation processes (HAOPs) catalysed by Cu and Ag metals is limited due to high residual concentrations of oxidants and dissolved metals. The proposed post-treatment process starts with recirculation of H2-enriched HAOP-treated water through the Pt-loaded activated carbon (AC). Hydrogen oxidation reaction (HOR) on Pt results in degradation of oxidants while silver and/or copper ions are reduced and deposited on the catalytic media. The subsequent aeration of the catalyst results in oxygen reduction reaction (ORR) and oxidation of the metals back into ionic forms. This allows the homogeneous metal catalysts to be reused in multiple HAOP cycles.The capacitive-Faradaic electrochemical structure of the Pt/AC catalyst with Pt acting as a Faradaic electrode and AC as a capacitive electrode plays an important role in the process. The HOR on Pt/AC results in accumulation of electrons in electrical double layer of AC. These electrons can be effectively used in a subsequent H2-free reduction of metal ions and oxidants. Thus, the degradation of H2O2 and S2O82− and reduction of Cu2+ and Ag + ions proceed much faster if the H2-step of the process is split into two sub-processes: (i) hydrogenation of Pt/AC catalyst in an inert Na2SO4 solution to pre-charge the Pt/AC with electrons originating at HOR, followed by (ii) catalytic reduction of oxidants and metal ions by the capacitively stored electrons.The process was investigated using Ag–S2O82− ([S2O82−]0 = 25 mM; [Ag+]0 = 50 mg/L) and Cu–H2O2 ([H2O2]0 = 100 mM, [Cu]0 = 635 mg/L) solutions. Total degradation of oxidants was achieved within <2 h and complete metals’ recovery was obtained. Several cycles of HAOP experiments were performed for the degradation of 1,4-dioxane (10 mg/L) and phenol (25 mg/L) using Ag– S2O82− and Cu–H2O2 HAOPs, respectively. The residual oxidants were completely degraded in all experiments. The reactivation of Pt/AC catalysts inhibited by phenol derivatives was achieved by hydrogenation in Na2SO4 solution (i.e., using the pre-charge approach).

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

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

High-performance Schottky-barrier field-effect transistors based on two-dimensional GaN with Ag or Au contacts

The performance of two-dimensional (2D) monolayer GaN Schottky barrier field effect transistors (SBFETs) with four different metals (Ag, Au, Al, and Pt) as electrodes were studied by using ab initio simulations. The N-type Schottky contact is formed on Ag-GaN, Au-GaN, and Pt-GaN, characterized by electron Schottky barrier heights (SBH) of 0.6, 0.5, and 0.38 eV, respectively. Whereas, Al-GaN contact formed P-type Schottky contact with hole SBH of 1.42 eV. The 5.1 nm GaN SBFETs with four metal electrodes all could overcome the short-channel effect. Additionally, GaN SBFETs with Ag and Au electrodes have excellent performance, whose ON-currents are 1151.1 μA/μm and 1258.9 μA/μm, respectively. They could satisfy the demands of International Technology Roadmap for Semiconductors for high-performance transistor. Furthermore, research indicates that the device's current increases with increasing temperature. Notably, under the constant bias and gate voltage, the current is unaffected by temperature variations between the left and right electrodes.

Graphene tunable dual-band nonreciprocal thermal emitter under TE polarization

Nonreciprocal thermal radiation is an emerging research direction, which can be achieved by adding anisotropic magneto-optical materials to some optical components. At present, most of the research focuses on nonreciprocal thermal radiation under TM polarization. In this paper, we propose a nonreciprocal emitter under TE polarization, which is a dual-band nonreciprocal emitter. There are twice guided mode resonances (GMRs) between 13 μm and 16 μm. It is a grating composed of a metal Ag and a magneto-optical material InAs. When the applied magnetic field is 3T, more than 90 % nonreciprocity is achieved at the incident wavelengths of 13.845 μm and 15.32 μm. In addition, we add a layer of graphene to the grating ridge to tune the peak position. It has a wide range of applications for the study of nonreciprocal thermal radiation, which can improve the energy conversion efficiency.

Structural and optical properties of highly Ag-doped TiO2 thin films prepared by flash thermal evaporation

The present study investigates the structural and optical properties of silver (Ag)-doped titanium dioxide (TiO2) thin films prepared via flash thermal evaporation using TiO2 and Ag powders mixture at various mass ratios. The crystallinity and surface morphology of the films were studied by varying the percentage of Ag content. Structural properties were characterized using X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM), while optical properties were assessed through optical transmission spectra analysis. Results indicate that Ag doping enhances crystallinity, as evidenced by XRD and Raman spectroscopy, and induces surface plasmon resonance (SPR) absorption attributed to Ag nanoparticles. SEM micrographs reveal agglomerated silver particles on the film surface, confirming Ag diffusion during annealing. Surface analysis through Secondary Ion Mass Spectrometry (SIMS) measurements illustrated the diffusion of Ag within the TiO2 samples and its subsequent accumulation at the surface. We have suggested that the crystallization observed in the evaporated TiO2-Ag thin films may primarily result from the thermal diffusion of Ag metal rather than the annealing process alone. Optical transmission spectra demonstrate a shift in the absorption edge towards the visible region with increasing Ag concentration, indicating enhanced light absorption properties.

Fluorescent nanocomposites of Ag nanoclusters grown in anionic polymer layers grafted to plastic substrate: Preparation, characterization and evaluation in Hg2+ sensing and white light generation

AbstractFluorescent noble metal nanoclusters (NCs) are emerging optical nanomaterials with properties similar to those of quantum dots. Their applications can be expanded by combining them with polymer matrices to obtain flexible and transparent light‐emitting nanocomposites. However, achieving highly fluorescent nanocomposites of this type remains challenging due to phase separation and aggregation of NCs in polymer hosts leading to a strong reduction in fluorescence efficiency. We address this key issue by covalently grafting a layer of a specifically selected matrix polymer onto a transparent plastic film and photochemically synthesizing the fluorescent metal NCs directly in the grafted layer. The surface‐grafted matrix polymer effectively captures the noble metal (Ag) ions, photo‐reduces them to atoms, acts as a capping ligand for the growing Ag NCs, and immobilizes them on the substrate surface. The Ag NCs were produced by both wet and dry synthesis, and effects of synthesis method, reaction time, and matrix polymer layer thickness on the fluorescence properties of the resulting nanocomposites were investigated and discussed. Importantly, the fluorescence intensity of these nanocomposite films is sensitive to submicromolar concentrations of aqueous Hg2+ that makes them useful as fluorescent sensing materials for selective and ultrasensitive detection of Hg2+ ions in water. Besides, the nanocomposite films obtained by the dry synthesis of NCs exhibit an intensive emission covering the whole green to red range of the visible spectrum and, hence, produce bright white light under illumination with a blue LED that makes them attractive as down‐conversion materials in one‐phosphor‐converted white LEDs.

The photocatalytic potential of single-atom Ag with tungsten-based two-dimensional transition metal dichalcogenides substrate for harmful gas removal

Tungsten-based two-dimensional transition metal dichalcogenides (TMDs) is a promising non-precious metal catalyst that can be applied to drive photocatalytic removal of harmful gases. However, the photocatalytic performance of these promising tungsten-based TMDs is limited by low carrier separation efficiency. In order to promote the separation efficiency of photogenerated carriers, it is a useful strategy to introduce a trace amount of precious metal Ag into tungsten-based TMDs. Due to the presence of precious metal Ag, the separation efficiency of photogenerated carrier is significantly improved. The photocatalytic removal potential of single-atom Ag with tungsten-based TMDs substrate for harmful gases was demonstrated in this work. Specifically, the effects of trace Ag atom and its load on the light absorption spectra, work function, band structure and density of states of tungsten-based TMDs were discussed by first principles calculations, among which tungsten-based TMDs substrate included 2 H-WS2, 2 H-WSe2 and 2 H-WTe2. It was found that Ag@2 H-WS2 and Ag@2 H-WSe2 possess strong light absorption capacity, low electron escape work and suitable band structure for photocatalysis. Through cohesive energy, formation energy and molecular dynamics, it was found that Ag@2 H-WSe2 possesses excellent stability, while Ag@2 H-WS2 may be unstable. Thus, Ag@2 H-WSe2 was identified as a new photocatalyst with broad application prospects. Finally, taking NH3, H2S, NO2 and SO2 as model harmful gases, it was proved that Ag@2 H-WSe2 can effectively photocatalyze the removal of harmful gases by differential charge density, projected density of states and energy barrier calculations. The above calculations indicates that Ag@2 H-WSe2 exhibits excellent photocatalytic activity and stability, and is a promising photocatalyst.

A new water−soluble naphthalene diimide as a highly selective fluorescent chemosensor for Cu(II) ion: Synthesis, DFT calculations, photophysical and electrochemical properties

The highly selective, sensitive, and water-soluble fluorescent sensors are desideratum for optoelectronic, environmental, biological, and biomedical applications. An innovative fluorescence chemosensor, naphthalene diimide (3) with metal binding sites, was designed, synthesized and characterized. The chemosensor's optical, electrochemical, spectroelectrochemical, and morphological properties were investigated, and then the density functional theory (DFT) simulations were conducted. The selectivity of 3 for the metals Cu(II), Ag(I), Hg(II), Mg(II), Fe(III), Ca(II), Co(II), Zn(II), Pb(II) and Cd(II) were investigated through UV–visible and fluorescence spectroscopy techniques. 3 was highly selective and sensitive toward Cu(II) metal ions. The chemosensor can detect Cu(II) in water with a detection limit of 1.11 μM, which is lower than the WHO standard and has good repeatability. Further investigations through the IR, DPV, AFM, UV–visible and fluorescence spectroscopies, SEM, EDX and TEM techniques confirmed the binding capabilities of the 3 with Cu(II).

Applications of Ni and Ag metallizations at the solder/Cu interfaces in advanced high-power automobile interconnects: An electromigration study

An advanced Pb-free solder interconnect, Cu line/Cu pillar/Ni/Sn1.8Ag/Ag/Cu lead frame/Sn3Ag0.5Cu/Au/Ni(P)/Cu trace, using the flip-chip quad flat no‑lead (FCQFN) packaging technology was designed for high-power automobile applications. An electromigration study revealing the Ni and Ag metallization effects on the interfacial reaction was investigated. Current stressing was conducted at a 2 A direct current at 160 °C until the defined 200 %-electrical-resistance-rise failure occurrence. Electromigration induced a two-stage electrical resistance increase mode in the advanced automobile test vehicle with a mechanism transition time of 585 h, as evidenced by the in situ resistance monitoring. Phase transformation from the constituent phases into the predominant (Cu,Ni)6Sn5 and Cu3Sn intermetallic compounds (IMCs) at the interfaces was proposed to explain the rapid resistance rise in the early-stage electromigration. Void formation and coalescence due to the Kirkendall effect and volume shrinkage during the phase transformation were proposed to explain the following steady resistance increase after the critical current stressing time. Furthermore, the phase transformation and growth of the IMCs behaved divergently at different interfaces and electron flow directions. The rapid phase transformation occurred in the downstream Sn1.8Ag solder interconnect due to the accelerated Ni metallization dissolution and formed a complete IMC joint. The anisotropic diffusion driven by the competitive or synergetic effect between the electron wind force and chemical potential gradient was proposed to explain the asymmetric microstructures after the electromigration experiment. The application of Ag metallization benefited the flip-chip soldering process, and the layer-type Ag3Sn IMC served as a diffusion barrier against Sn/Cu interdiffusion at the solder/Cu lead frame interface during the solid-state electromigration. In contrast, the Ni metallization was designed as a diffusion barrier to hinder interdiffusion and the undesirable Cu3Sn growth at the solder/Cu interface. The findings presented in this study could benefit the solder interconnect design with an appropriate metallization combination against undesirable electromigration failure.

In‐situ elemental reaction‐regulated Ag2S films enable the best thermoelectric performances

AbstractSilver sulfide thin film, with excellent thermoelectric properties, is few reported due to the complex and time‐consuming high‐temperature or high‐pressure synthesis process. Here, a fast ionic conductor n‐type Ag2S film with good crystallinity and uniform density is prepared by sputtering metal Ag films of different thicknesses on glass and then reacting in S precursor solution at low temperature. At 450 K, β‐Ag2S films can be obtained and underwent a phase transition from α‐Ag2S monoclinic, which had a significant effect on their electrical and thermal properties. The grain size of Ag2S films increases with the increase of film thickness. Before and after the phase transition, the carrier concentration and mobility cause obvious changes in the electrical properties of Ag2S. The carrier concentration of body‐centered cubic phase β‐Ag2S is about three orders of magnitude higher than that of monoclinic phase α‐Ag2S, and the mobility is also 2–3 times that of the latter. Especially, after the phase transition, the conductivity of β‐Ag2S rises exponentially from the zero conductivity of α‐Ag2S and increases with the increase of temperature. The Ag2S film shows the highest figure of merit of 0.83 ± 0.30 at 600 K from the sample with ∼1600 nm thickness, which is the highest record among Ag2S‐based thermoelectric materials reported so far.

Performance of Transition Metals in Imidazolium‐Assisted CO2 Reduction in Acetonitrile

AbstractThis study explores the electrochemical reduction of CO2 in dry acetonitrile containing 1,3‐dimethyl imidazolium cations, utilizing late‐transition metals (Au, Ag, Zn, Cu, and Ni). All metals exhibit remarkable selectivity, nearing 100 %, for CO formation. Particularly noteworthy is Au, which manifests the lowest (−2.37 V vs. Ag/Ag+) overpotential in chronopotentiometry experiments. We propose that, for metals with lower CO binding energies compared to Au (Ag and Zn electrodes) – calculated by DFT, the rate‐determining step is the adsorption of CO2. This distinction in CO2 adsorption is reinforced by the examination of partial charge transfer from negatively charged slabs to CO2 (−0.241 a.u with the Au electrode and +0.002 a.u with the Zn electrode). Conversely, the greater CO binding energy calculated for Cu and Ni likely diminishes electrocatalytic activity relative to the Au electrode. Our results unveil a volcano trend in catalyst activity, albeit with smaller performance disparities between the late‐transition metals and Au than previously observed in aqueous conditions, possibly due to the co‐catalytic influence of imidazolium cations. This study suggests that metals unsuitable for aqueous environments hold promise for cost‐effective and viable electrochemical conversion of CO2 to CO in non‐aqueous media containing imidazolium compounds.

Amphiphilic Dendronized Copolymer-Encapsulated Au, Ag and Pd Nanoparticles for Catalysis in the 4-Nitrophenol Reduction and Suzuki-Miyaura Reactions.

The branched structures of dendronized polymers can provide good steric stabilization for metal nanoparticle catalysts. In this work, an amphiphilic dendronized copolymer containing hydrophilic branched triethylene glycol moieties and hydrophobic branched ferrocenyl moieties is designed and prepared by one-pot ring-opening metathesis polymerization, and is used as the stabilizer for metal (Au, Ag and Pd) nanoparticles. These metal nanoparticles (Au nanoparticles: 3.5 ± 3.0 nm; Ag nanoparticles: 7.2 ± 4.0 nm; Pd nanoparticles: 2.5 ± 1.0 nm) are found to be highly active in both the 4-nitrophenol reduction and Suzuki-Miyaura reactions. In the 4-nitrophenol reduction, Pd nanoparticles have the highest catalytic ability (TOF: 2060 h-1). In addition, Pd nanoparticles are also an efficient catalyst for Suzuki-Miyaura reactions (TOF: 1980 h-1) and possess good applicability for diverse substrates. The amphiphilic dendronized copolymer will open a new door for the development of efficient metal nanoparticle catalysts.

Synthesis and characterization of Ag@M-BTC (M = Zn & Cd) Nanocomposites for efficient removal of methylene blue and indigo carmine

Two MOF based composite materials decorated with Ag NPs viz. Ag@M-BTC (BTC= 1,3,5-benzenetricarboxylate; M=Zn & Cd) were synthesised and characterized using various physicochemical techniques, including FT-IR, PXRD, FE-SEM, EDX, HR-TEM, BET and XPS. The FT-IR spectra of the nanocomposites (NCs) and the pristine MOFs suggest retention of the MOF structure in the resulting composite materials and the PXRD patterns confirm the presence of metallic Ag within the crystalline phase of the MOFs. The observed rough surfaces on the NCs as evidenced from FE-SEM micrographs, indicates the deposition of Ag NPs on the surface of the MOFs. Furthermore, HR-TEM images reveal the presence of nanosized Ag aggregates of spherical shape inside the MOF matrix as well as on the surface. The adsorption activity of the synthesised NCs have been assessed for Methylene Blue (MB) and Indigo Carmine (IC). It is observed that the NCs, Ag@Zn-BTC (1a) and Ag@Cd-BTC (2a) performs better degradation as compared to that of pristine MOFs. These NCs can degrade MB completely (100 %) after 50 min treatment time, while maximum 91 % degradation was recorded for the IC dye. Here, the degradation process can be thought of as operating via chemisorption phenomena, supported by theoretical calculations. Additionally, these NCs can be reused up-to three times for the effective degradation of dyes.

Low-nuclearity CuZn ensembles on ZnZrOx catalyze methanol synthesis from CO2

Metal promotion could unlock high performance in zinc-zirconium catalysts, ZnZrOx, for CO2 hydrogenation to methanol. Still, with most efforts devoted to costly palladium, the optimal metal choice and necessary atomic-level architecture remain unclear. Herein, we investigate the promotion of ZnZrOx catalysts with small amounts (0.5 mol%) of diverse hydrogenation metals (Re, Co, Au, Ni, Rh, Ag, Ir, Ru, Pt, Pd, and Cu) prepared via a standardized flame spray pyrolysis approach. Cu emerges as the most effective promoter, doubling methanol productivity. Operando X-ray absorption, infrared, and electron paramagnetic resonance spectroscopic analyses and density functional theory simulations reveal that Cu0 species form Zn-rich low-nuclearity CuZn clusters on the ZrO2 surface during reaction, which correlates with the generation of oxygen vacancies in their vicinity. Mechanistic studies demonstrate that this catalytic ensemble promotes the rapid hydrogenation of intermediate formate into methanol while effectively suppressing CO production, showcasing the potential of low-nuclearity metal ensembles in CO2-based methanol synthesis.

Eggshell waste bioprocessing for sustainable acid phosphatase production and minimizing environmental hazards

BackgroundThe Environmental Protection Agency has listed eggshell waste as the 15th most significant food industry pollution hazard. Using eggshell waste as a renewable energy source has been a hot topic recently. Therefore, finding a sustainable solution for the recycling and valorization of eggshell waste by investigating its potential to produce acid phosphatase (ACP) and organic acids by the newly-discovered B. sonorensis was the target of the current investigation.ResultsDrawing on both molecular and morphological characterizations, the most potent ACP-producing B. sonorensis strain ACP2, was identified as a local bacterial strain obtained from the effluent of the paper and pulp industries. The use of consecutive statistical experimental approaches of Plackett–Burman Design (PBD) and Orthogonal Central Composite Design (OCCD), followed by pH-uncontrolled cultivation conditions in a 7 L bench-top bioreactor, revealed an innovative medium formulation that substantially improved ACP production, reaching 216 U L−1 with an ACP yield coefficient Yp/x of 18.2 and a specific growth rate (µ) of 0.1 h−1. The metals Ag+, Sn+, and Cr+ were the most efficiently released from eggshells during the solubilization process by B. sonorensis. The uncontrolled pH culture condition is the most suitable and favoured setting for improving ACP and organic acids production. Quantitative and qualitative analyses of the produced organic acids were carried out using liquid chromatography-tandem mass spectrometry (LC–MS/MS). Lactic acid, citric acid, and hydroxybenzoic acid isomer were the most common organic acids produced throughout the cultivation process. The findings of TGA, DSC, SEM, EDS, FTIR, and XRD analysis emphasize the significant influence of organic acids and ACP activity on the solubilization of eggshell particles.ConclusionsThis study emphasized robust microbial engineering approaches for the large-scale production of a newly discovered acid phosphatase, accompanied by organic acids production from B. sonorensis. The biovalorization of the eggshell waste and the production of cost-effective ACP and organic acids were integrated into the current study, and this was done through the implementation of a unique and innovative medium formulation design for eggshell waste management, as well as scaling up ACP production on a bench-top scale.