Formation Of Metal Nanoparticles Research Articles

FORMATION OF NICKEL NANOPARTICLES IN SOLUTIONS OF A HYDROPHILIC GRAFT COPOLYMER

A graft copolymer of poly(vinyl alcohol) and polyacrylamide (PVA-g-PAAm) with interacting main and grafted chains was synthesized by radical matrix polymerization of PAAm from the PVA backbone in an aqueous medium. Its basic molecular parameters including the number and length (molecular weight) of grafts were determined using elemental analysis, DTGA and viscometry. The copolymer macromolecules formed special monomolecular micelles of elipsoidal shape and length ~18-64 nm in aqueous solutions due to the formation of intramolecular polycomplexes between the main and grafted chains. This copolymer was used as a hydrophilic matrix for the in situ synthesis of nickel nanoparticles (NiNPs) in aqueous solutions.On the basis of UV-Vis spectroscopy, an original and simple method for monitoring the kinetics of the formation and yield of metal nanoparticles in systems in which a surface plasmon resonance band does not appear has been proposed and implemented. Using this approach, the kinetics of borohydride reduction of Ni-salt to NiNPs in pure water and PVA-g-PAAm solutions was studied depending on the concentrations of Ni-salt and copolymer matrices. An increase in the initial rate of accumulation and yield of NiNPs with an increase in the concentration of Ni-salt and a decrease in both parameters in copolymer solutions in comparison with pure water was established. At the same time, the accumulation rate and NiNP yield in a complex way was depended on the matrix concentration that was determined by the ratio of such factors as a decrease in the diffusion rate of NaBH4 molecules in copolymer solutions and the accumulation of Ni2+-ions in matrix particles due to complexation with active chemical groups at the first stage of reduction process. The morphology and main structural elements of the NiNPs/PVA-g-PAAm composition were revealed using TEM. It was shown that the in situ synthesis of NiNPs in copolymer matrices was accompanied by the “detachment” of PAAm grafts from the main PVA chains and led to the appearance of two new structures, such as “hairy coils” and “hairy rods”, containing small spherical NiNPs (d~0,5–12,0 nm) in isolated and chain states, respectively. The appearance of the latter structures was explained by the formation of coordination complexes of Ni2+-ions with active groups of both PVA and PAAm chains at the first stage of the reduction reaction.

New concept of radiolytic synthesis of gold nanoparticles in continuous flow

Radiolytic synthesis has been used to produce a plethora of unsupported and supported metallic nanoparticles in batch. As proof of a new concept, we evaluated the formation of gold nanoparticles by radiolytic synthesis in continuous flow using a millifluidic reactor. A mixture of gold ions solution, branched polyethyleneimine, and ethylene glycol yielded gold nanoparticles with a mean size of 3.4 ± 1.0 nm after irradiation with an X-ray irradiator (127 Gy/min) at an absorbed dose of 5.1 kGy. The morphology and size distribution of gold nanoparticles was influenced by AgNO3, where its absence resulted in a mean size of 20.9 ± 15.8 nm. The radiolytic synthesis of gold nanoparticles in continuous flow was achieved in short reaction times (<60 min), at room temperature, and with low concentrations of both stabilizing and reducing agents. These results demonstrate the potential of radiolytic synthesis in continuous flow for high-throughput formation of metallic nanoparticles with controlled specifications in size and distribution.

Synergistically boosting highly selective CO2–to–CO photoreduction over BiOCl nanosheets via in-situ formation of surface defects and non-precious metal nanoparticles

Hollow hierarchical BiOCl (BOC) assembled by nanosheets with highly exposed (001) facet is synthesized via a gas-bubble-template strategy. The as-synthesized BOC is further modified by thermal treatment in N2 to in-situ introduce oxygen vacancies (OVs) and metallic bismuth (Bi0) nanoparticles from the BOC lattice (Bi0/OVs-BOC). Thermal treatment in N2 enables an intimate contact between OVs-BOC and Bi0 nanoparticles, which is conducive to the transfer of photogenerated charge carriers. In CO2 photoreduction test, the Bi0/OVs-BOCs exhibit almost 100 % selectivity towards CO, and some of the samples also have a significant increase in yield. For instance, BOC-250 shows about 24.82 μmol∙g–1 h–1 CO2-to−CO photoreduction efficiency which is nearly four times higher than that of the BOC with high stability. It is found that suitable energy band structure and desirable intrinsic carrier mobility account for the substantial enhancement of CO2-to−CO photoreduction activity due to the in-situ introduction of OVs and Bi0 nanoparticles. Density functional theory (DFT) calculations unveil that the decreased reaction energy, the weakened adsorption energy for CO, and suitable adsorption energy for H and OH of Bi0/OVs-BOC lead to high selectivity. This work sheds light on the synergistic effect of in-situ formed OVs and metal nanoparticles on enhancing the photocatalytic activity and selectivity of solar energy materials.

(Invited) N-Doped Carbon-Based Materials: Improved Fundamental Understanding through Comprehensive Characterization

N-doped carbon materials are used across a wide range of energy applications including fuel cell catalysts, CO2 electroreduction, catalyst supports, and energy storage materials. They are often integrated with metals in the form of either metal nanoparticles or atomically-dispersed sites to tune their performance for specific catalytic reactions. In general, these materials are very heterogeneous, containing a multitude of nitrogen functionalities and therefore, they are intrinsically challenging to understand, requiring a wide range of characterization techniques.This talk will discuss a family of N-doped catalysts derived from a series of N-doped carbon nanospheres. N-doped nanospheres, produced solvothermally, are synthesized with the ability to control size, shape, concentration of nitrogen dopants, and their nitrogen functionalities. The tunability of these spheres allows for systematic studies that help to identify trends with different N functionalities and densities. Platinum and non-platinum metals were incorporated using various synthetic routes, targeting formation of either metal nanoparticles or atomically-dispersed species. Understanding the surface and bulk chemistry of these materials is essential for elucidating the effects of nitrogen dopants on nucleation and stability of metals across the periodic table. Trends observed experimentally will be compared with metal adsorption computations with the goal of extending beyond experimental data to make predictions for more efficient catalyst development. Within a catalyst layer, the surface chemistry also affects interactions with ionomer, and both the nature of the metal and its morphology, as well as the functionality of nitrogen impacts these interactions.

Continuous Preparation of Precious Metal Nanoparticles from Plant Biomass and CFD Simulation

Precious metal nanomaterials have broad application prospects in many fields. However, most of the existing synthesis processes of precious metal nanomaterials are carried out in a batch reactor. Recently, the technology of batch preparation of noble metal nanoparticles by chemical method has become mature, but with the increase of reactor volume, the problems of heat and mass transfer of the system are prominent. In this paper, the technology of reducing plant biomass with green characteristics to prepare precious metal nanoparticles was introduced into the continuous operation of micro channel reactor and reactor to investigate the influence of reactor structure parameters and reaction conditions on the formation and particle size distribution of precious metal nanoparticles, and combined with computational fluid dynamics (CFD) simulation technology to explore its influence mechanism. In this paper, it is found that the AgNPs (4.7 ± 1.9 nm) prepared by ETFE tube has a larger average particle size and a wider particle size distribution than the AgNPs (4.24 ± 0.9 nm) prepared by PTFE tube.

Trace Metal Loading of B‐N‐Co‐doped Graphitic Carbon for Active and Stable Bifunctional Oxygen Reduction and Oxygen Evolution Electrocatalysts

AbstractUnderstanding the structure‐property relations of non‐precious metal heteroatom co‐doped carbon electrocatalysts exhibiting high activity as well as long‐term durability for both ORR and OER remains challenging but is indispensable for the development of bifunctional ORR/OER electrocatalysts. We propose B‐N‐co‐doped graphitic 2D carbon nanostructures impregnated with controlled amount of transition metals (M‐BCN; M=Co, Ni, Fe, Cu) as bifunctional ORR/OER electrocatalysts. Co‐BCN outperformed the Ni‐, Fe‐, Cu‐based BCN catalysts exhibiting potential values of 0.87 V and 1.62 V at −1 mA/cm2 and 10 mA/cm2 during ORR and OER, respectively. Importantly, Co‐BCN shows bifunctional cyclic stability (Δη; EOER−EORR=0.75 V) of up to 300 cycles in 1 M KOH for a duration of 20 h with total activity loss of only 10.2 % (ORR) and 6.2 % (OER), respectively. A low loading of the metal precursors was used to preserve porosity and to facilitate the formation of metal nanoparticles or M−NxB/C type species embedded in the graphitic carbon layers. The B‐N‐co‐doped graphitic layers also protect the embedded metal nanoparticles explaining the observed long‐term stability.

Chemisorbed Superoxide Species Enhanced the High Catalytic Performance of Ag/Co3O4 Nanocubes for Soot Oxidation.

The respective action mode between surface-adsorbed oxygen and bulk lattice oxygen during catalytic soot oxidation is still not fully recognized. Herein, a series of Ag-loaded Co3O4 catalysts with different Ag loading amounts were prepared by the impregnation method, and 5% Ag/Co3O4 presented competitive catalytic activity toward soot combustion with a T50 below 290 °C in 10% O2/N2. This remarkable improvement in catalytic performance could be primarily attributed to the enhanced Ag-Co3O4 metal-support interaction induced by the formation of uniform, dispersive, and suitable size metallic Ag nanoparticles. The activation, activity, consumption-regeneration, identification, and reaction of surface-adsorbed oxygen along with the activity of bulk lattice oxygen were characterized by various designed and in situ techniques. The results demonstrated that the chemisorbed superoxide species (O2-) play the potentially responsible role for boosting soot combustion, while the bulk lattice oxygen is much less active within the tested temperatures, inducing a negligible activity contribution. Moreover, soot-temperature programmed reduction, isothermal kinetic study, and density functional theory calculation provided supplementary support for the enhancement effect of Ag-Co3O4 combination in the activation and utilization of surface-adsorbed oxygen. The overall objective of this work is to identify the role of surface-adsorbed oxygen and bulk lattice oxygen for soot oxidation over Ag/Co3O4 catalysts.

Bundle-Type Columnar Cu2O Photoabsorbers with Vertical Grain Boundaries Fabricated Using Instant Strike-Processed Metallic Seeds and Their Enhanced Photoelectrochemical Efficiency

The design to control grain boundaries (GBs) causing recombination losses as planar defects in the absorbing layers is an essential strategy for the development of highly efficient photoelectrochemical (PEC) reaction systems. We propose a method to design a progressive bundle-type columnar structure as an alternative to single crystals with the least defects, where the GBs are parallel to the charge transport movement and the electric field direction. An instant strike bias (0.01 s and −1 V vs Ag/AgCl) in the same electrolytes induces the formation of island-shaped metallic Cu nanoparticles in the initial stage. These act as seed crystals for controlling Cu₂O growth evolution, resulting in dramatically high-density Cu₂O nuclei. This is followed by the deposition of bundle-type columnar Cu₂O with longitudinal GBs, contrary to the typical randomly crystallized Cu₂O. Metallic Cu seeds with a stronger electric field than that of the exposed indium tin oxide (ITO) region provide selective crystallization sites for Cu₂O growth along the ⟨111⟩ ionic bonding. Despite the instant strike interval, the p-type Cu₂O photoelectrodes retained an outstanding photocurrent density of 5.2 mA cm–² at 0 VRHE and an onset potential of 0.7 VRHE because of the highly improved charge transport and transfer efficiencies inside Cu₂O induced by effectively suppressing charge scattering in the GBs. The impedance measurements depict the overall decrease in the total resistance, charge-transfer resistance, and the photoabsorber/electrode interface resistance of the PEC systems with the introduction of the instant strike process.

Mechanochemical Preparation of Magnetically Separable Fe and Cu-Based Bimetallic Nanocatalysts for Vanillin Production

A highly sustainable method for the preparation of supported iron oxide and copper nanoparticles (NPs) on a biomass-derived carbon by solvent-free mechanochemical process is reported. In-situ mechanochemically obtained extracts from orange peel could behave as a green reducing agent, allowing the formation of Cu metal nanoparticles as well as generating a magnetic phase (magnetite) in the systems via partial Fe3+ reduction. At the same time, orange peel residues also served as template and carbon source, adding oxygen functionalities, which were found to benefit the catalytic performance of mechanochemically synthesized nanomaterials. The series of magnetic Cu-Fe@OP were tested in the oxidation of trans-ferulic acid towards vanillin, remarkably revealing a maximum vanillin yield of 82% for the sample treated at 200 °C.

Large scale synthesis of copper nickel alloy nanoparticles with reduced compressibility using arc thermal plasma process

Among the various methods employed in the synthesis of nanostructures, those involving high operating temperature and sharp thermal gradients often lead to the establishment of new exotic properties. Herein, we report on the formation of Cu-Ni metallic alloy nanoparticles with greatly enhanced stiffness achieved through direct-current transferred arc-thermal plasma assisted vapour-phase condensation. High pressure synchrotron X-ray powder diffraction (XRPD) at ambient temperature as well as XRPD in the temperature range 180 to 920 K, show that the thermal arc-plasma route resulted in alloy nanoparticles with much enhanced bulk modulus compared to their bulk counterparts. Such a behaviour may find an explanation in the sudden quenching assisted by the retention of a large amount of local strain due to alloying, combined with the perfect miscibility of the elemental components during the thermal plasma synthesis process.

Sustainable electricity production from seawater using Spirulina platensis microbial fuel cell catalyzed by silver nanoparticles-activated carbon composite prepared by a new modified photolysis method

A new and innovative microbial fuel cell of high energy conversion efficiency (with no heat emission or corrosion problems) was formulated using nanoparticles of dry biomass Spirulina platensis microalgae. High cell potential up to 1.0 V was obtained from this microbial fuel cell. The Spirulina platensis nanoparticles have been prepared using the top-down approach, then were sonicated to facilitate their digestion as a feedstock for the microorganisms in the seawater. The microorganisms in the polluted seawater at the deaerated anode chamber oxidized the organic matter producing electrons that transfer to the anode surface inside the microbial fuel cell via the microbial nanowires. These electrons (electric current) passed in the external circuit from the anode surface to the cathode surface. The microstructure of the bacterial biofilm on the anode surface was confirmed using the scanning electron microscope. The promising catalyst silver nanoparticles-activated carbon composite was prepared by a new modified photolysis method. The transmitting electron microscope micrograph of silver nanoparticles showed an average particle size of about 10 nm homogeneously loaded on the activated carbon matrix. The powder X-ray diffraction pattern of silver nanoparticles-activated carbon composite confirmed the formation of zero-valent metallic silver nanoparticles via the photoreduction of silver nitrate using low cost modified photolysis method. The composite efficiently catalyzed the slow oxygen reduction reaction at the cathode surface. The open cell potential of microbial fuel cell was 500 mV and 1000 mV and the corresponding power density up to 1.0 and 2.5 W. m−2 in the absence and the presence of silver nanoparticles-activated carbon composite, respectively. Both open-cell potential and the closed-cell potential were maximized in the presence of silver nanoparticles-activated carbon composite and remained unchanged for nearly one month of the cell operation.

Molecular modeling of Ag4 cluster formation

Nucleation is the main process which affects on the characteristics of the formed metal nanoparticles. At the same time the mechanism of homogeneous nucleation of metal particles in solutions are still debatable. There are two contrary points of view which briefly may be presented as “Instantaneous” and “Continuous”. Instantaneous nucleation postulated by classical nucleation theory (CNT) means formation of nuclei as a result of supersaturation of solution via set of equilibrium reactions (on the whole nA⇔An) but Continuous nucleation implies step-by-step irreversible addition of monomer to formation of nuclei and/or nanoparticle (A→A2→…→An). Using DFT calculations the thermodynamic parameters of all possible reactions leading to formation of Ag4 cluster which may be considered as intermediate in the nucleation process have been estimated. It was found that formation of Ag4 is thermodynamically possible via both of mechanisms. At the same time it was noted that addition of Ag+ to silver cluster is more preferred than association of uncharged particles. Taking into account the much higher concentration of silver ions compared to silver atoms this fact may indicate on the preference of stepwise mechanism of nucleation of metal nanoparticles in real solutions.

Gum Tragacanth (GT): A Versatile Biocompatible Material beyond Borders.

The use of naturally occurring materials in biomedicine has been increasingly attracting the researchers’ interest and, in this regard, gum tragacanth (GT) is recently showing great promise as a therapeutic substance in tissue engineering and regenerative medicine. As a polysaccharide, GT can be easily extracted from the stems and branches of various species of Astragalus. This anionic polymer is known to be a biodegradable, non-allergenic, non-toxic, and non-carcinogenic material. The stability against microbial, heat and acid degradation has made GT an attractive material not only in industrial settings (e.g., food packaging) but also in biomedical approaches (e.g., drug delivery). Over time, GT has been shown to be a useful reagent in the formation and stabilization of metal nanoparticles in the context of green chemistry. With the advent of tissue engineering, GT has also been utilized for the fabrication of three-dimensional (3D) scaffolds applied for both hard and soft tissue healing strategies. However, more research is needed for defining GT applicability in the future of biomedical engineering. On this object, the present review aims to provide a state-of-the-art overview of GT in biomedicine and tries to open new horizons in the field based on its inherent characteristics.

Tuning the optical and electrical properties of magnetron-sputtered Cu–ZnO thin films using low energy Ar ion irradiation

Cu doped ZnO (Cu–ZnO) nanocomposite thin films were successfully synthesized at room temperature by RF magnetron sputtering. The signature of Cu in pristine ZnO thin films was confirmed by Rutherford Backscattering Spectroscopy (RBS) with atomic concentration of ~10%. The Cu–ZnO thin films were irradiated with 800 keV Ar ion beam at three different ion fluences viz. 5 × 1015, 7 × 1015 and 9 × 1015 ions/cm2. As characterized by X-ray diffraction, the pristine and irradiated films show a hexagonal wurtzite structure with remarkable intensities of (100), (002) and (101) orientations. The surface morphology of the pristine and irradiated films was recorded using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The images clearly show the grain growth near the surface of films with increasing the ion fluences. The surface plasmon absorption (380 nm onwards) indicating the formation of metal nanoparticles in oxide matrices was confirmed by UV–visible spectroscopy of ion irradiated films. The electrical properties of the pristine and irradiated films were deduced by current voltage (I–V) and Hall measurements. The conductivity of the film increases as irradiation proceeds, achieves a maxima and then decreases with further processing of the ion beam. This study explores ion beam irradiation as a versatile tool to tailor the physical properties of nanocomposite thin films. Further, the properties can be precisely controlled by optimizing ion fluences and incident ion energy as well.

Biosynthesis of metallic nanoparticles from waste Passiflora edulis peels for their antibacterial effect and catalytic activity

Recently, the waste agricultural materials have been widely considerable for green synthesis of noble metallic nanoparticles (MNPs) due to cost efficiency and environmental protection. This study has presented a simple method for the preparation of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) utilizing aqueous extract of waste Passiflora edulis peel (PEP) as reducing and stabilizing agents. The formation of MNPs was optimized reaction conditions to obtain the best colloidal solutions. The characterizations of the biosynthesized MNPs were performed by analysis techniques such as Fourier transmission infrared spectroscopy (FTIR), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED). The TEM data confirmed PEP-AgNPs and PEP-AuNPs in the spherical shape with mean size of 25 nm and 7 nm, respectively. The XRD and SAED patterns showed the synthesized nanoparticles existing in crystalline nature. Antibacterial and catalytic activities have been investigated for their applications. The PEP-AgNPs exhibited a strong antibacterial activity against three strains including Escherichia coli, Bacillus subtilis, and Staphylococcus aureus. The excellently catalytic activity of both the biosynthesized nanoparticles has been demonstrated for reduction of nitrophenols and degradation of toxic organic dyes via study on their kinetics.

Optimization of accurate controlled formation of Au MNPs via non-thermal microplasma continuous glow discharge within aqueous electrochemical (GDE) method

In this work, micro plasma-induced non-equilibrium liquid chemistry was utilized to synthesize and controlled formation of gold metallic nanoparticles (Au MNPs) by governing the concentration of (HAuCl4). These new approaches based on both plasma and liquid electrolytes contain charged species, and the interactions between the two phases represent a unique combination of physics, chemistry, and materials science. Continuous and stable DC glow discharge was done in home–made cavity to synthesize the definite sizes of (Au MNPs) by means of (3 kV) discharge voltage and (2 mA) discharge current for a period of (7 min) in aqueous solution of HAuCl4 with four different concentrations of about 1 mM, 5 mM, 10 mM and 20 mM at room temperature. The atmospheric pressure plasma discharge between stainless steel capillary tube cathode electrode over the (HAuCl4) solution and platinum plate as an anode dipped in solution for rapid formation of colloidal Au MNPs. Morphology aspects of the synthesized Au MNPs layer were studied by examining the (FE-SEM), HR-TEM images and X-ray difraction (XRD) pattern. Optical features of (Au MNPs) were considered via a UV–Vis beam spectrophotometer. These measurements showed that Au MNPs were organized by governing the concentration of HAuCl4, and uniform Au MNPs with specific exclusive sizes were acquired. Grain size, specific surface area and optical stability of Au MNPs strongly be affected by the HAuCl4 concentrations.

Simultaneous Decomposition and Dewetting of Nanoscale Alloys: A Comparison of Experiment and Theory.

We consider the coupled process of phase separation and dewetting of metal alloys of nanoscale thickness deposited on solid substrates. The experiments involve applying nanosecond laser pulses that melt the Ag40Ni60 alloy films in two setups: either on thin supporting membranes or on bulk substrates. These two setups allow for extracting both temporal and spatial scales on which the considered processes occur. The theoretical model involves a longwave version of the Cahn-Hilliard formulation used to describe spinodal decomposition, coupled with an asymptotically consistent longwave-based description of dewetting that occurs due to destabilizing interactions between the alloy and the substrate, modeled using the disjoining pressure approach. Careful modeling, combined with linear stability analysis and fully nonlinear simulations, leads to results consistent with the experiments. In particular, we find that the two instability mechanisms occur concurrently, with the phase separation occurring faster and on shorter temporal scales. The modeling results show a strong influence of the temperature dependence of relevant material properties, implying that such a dependence is crucial for the understanding of the experimental findings. The agreement between theory and experiment suggests the utility of the proposed theoretical approach in helping to develop further experiments directed toward formation of metallic alloy nanoparticles of desired properties.

Probing Kinetics and Mechanism of Formation of Mixed Metallic Nanoparticles in a Polymer Membrane by Galvanic Replacement between Two Immiscible Metals: Case Study of Nickel/Silver Nanoparticle Synthesis.

Galvanic replacement between metals has received notable research interest for the synthesis of heterometallic nanostructures. The growth pattern of the nanostructures depends on several factors such as extent of lattice mismatch, adhesive interaction between the metals, cohesive forces of the individual metals, etc. Due to the difficulties in probing ultrafast kinetics of the galvanic replacement reaction and particle growth in solution, real-time mechanistic investigations are often limited. As a result, the growth mechanism of one metal on the surface of another metal at the nanoscale is poorly understood so far. In the present work, we could successfully probe the galvanic replacement of silver ions with nickel nanoparticles, stabilized in a polymer membrane, using two complementary methods, namely, small-angle X-ray scattering (SAXS) and radiolabeling, and the results are supported by density functional theory (DFT) computations. The silver-nickel system has been chosen for the present investigation because of the high degree of bulk immiscibility caused by the large lattice mismatch (15.9%) and the weak adhesive interaction, which makes it a perfect model system for immiscible metal pairs. Membrane, as a host medium, plays a crucial role in retarding the kinetics of atomic and particle rearrangements (nucleation and growth) due to slower mobility of the atoms (monomers) and particles within the polymer network. This allowed us to examine the real-time concentration of silver monomers during galvanic replacement of silver ions with nickel nanoparticles and evolution of Ni/Ag nanoparticles. From combined experiment and DFT computations, it has been demonstrated, for the first time to the best of our knowledge, that the majority of silver atoms, which are produced on the nickel nanoparticle surface by galvanic reactions, do not form traditional core-shell nanostructures with nickel and undergo a self-governing sequential nucleation and growth of silver nanoparticles via formation of intermediate prenucleation silver clusters, leading to the formation of mixed metallic nanoparticles in the membrane. The surface of NiNPs has a heterogeneous effect on the silver nucleation pathway, which is evident from the reduced critical free energy barrier of nucleation (ΔGcrit). The present work establishes an original mechanistic pathway based on a sequential nucleation model for formation of mixed metallic nanoparticles by the galvanic replacement route, which opens up future possibilities for size-controlled synthesis in mixed systems.

Iridium and Ruthenium Modified Polyaniline Polymer Leads to Nanostructured Electrocatalysts with High Performance Regarding Water Splitting.

The breakthrough in water electrolysis technology for the sustainable production of H2, considered as a future fuel, is currently hampered by the development of tough electrocatalytic materials. We report a new strategy of fabricating conducting polymer-derived nanostructured materials to accelerate the electrocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and water splitting. Extended physical (XRD, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX)) and electrochemical (cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS)) methods were merged to precisely characterize the as-synthesized iridium and ruthenium modified polyaniline (PANI) materials and interrogate their efficiency. The presence of Ir(+III) cations during polymerization leads to the formation of Ir metal nanoparticles, while Ru(+III) induces the formation of RuO2 oxide nanoparticles by thermal treatment; they are therefore methods for the on-demand production of oxide or metal nanostructured electrocatalysts. The findings from using 0.5 M H2SO4 highlight an ultrafast electrochemical kinetic of the material PANI-Ir for HER (36 − 0 = 36 mV overpotential to reach 10 mA cm−2 at 21 mV dec−1), and of PANI-Ru for OER (1.47 − 1.23 = 240 mV overpotential to reach 10 mA cm−2 at 47 mV dec−1), resulting in an efficient water splitting exactly at its thermoneutral cell voltage of 1.45 V, and satisfactory durability (96 h).

Electron-beam-induced degradation of halide-perovskite-related semiconductor nanomaterials

The instability of lead halide perovskites in various application-related conditions is a key challenge to be resolved. We investigated the formation of metal nanoparticles during transmission electron microscopy (TEM) imaging of perovskite-related metal halide compounds. The metal nanoparticle formation on these materials originates from stimulated desorption of halogen under electron beams and subsequent aggregation of metal atoms. Based on shared mechanisms, the TEM-based degradation test can help to evaluate the material stability against light irradiation.