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•The Ag@NiV0.2Co0.2 is fabricated by a simple spontaneous redox reaction.•A highly active layer is formed due to the surface reconstruction and V leaching.•The oxygen-deficient ...(oxy)hydroxide layer is key to the enhanced OER activity.•In-situ Raman provide direct observation of surface reconstruction and active species.•Our findings provide valuable guidance to design novel electrocatalysts.
The transition-metal (oxy)hydroxides have been considered as one of the promising electrocatalysts for oxygen evolution reaction (OER). Therefore, it is necessary to have in-depth study on the origin behind their favorable inherent OER activity and further improve their catalytic performance. Herein, nickel–cobalt-vanadium trimetallic (oxy)hydroxide nanosheets decorated with silver nanoparticles (Ag NPs) (Ag@NiV0.2Co0.2) are fabricated for OER by a simple spontaneous redox reaction. The Ag@NiV0.2Co0.2 can deliver an overpotential of only 255 mV at 10 mA cm−2 and a small Tafel slope of 38.3 mV dec-1 in alkaline solution. We accredit the outstanding catalytic performance to the following aspects: (1) the active (oxy)hydroxide layer on the surface of Ag@NiV0.2Co0.2 generated through the surface reconstruction, (2) the optimal local coordination induced by the interaction between Ag NPs and trimetallic system, (3) the extensively exposed active sites, and (4) the significantly improved charge-transfer ability due to the incorporation of Ag NPs. Our findings may provide deep understanding on the mechanism of OER and offers a novel strategy to design electrocatalysts with superior OER activity.
Abstract
The first-principles density functional theory method has been employed to comprehensively investigate adsorption configurations, adsorption energies, electronic properties, and gas sensing ...characteristics of pure and transition metal (TM = Sc, Pd, and Cu) decorated holey graphyne (HGY) monolayer for the detection of ammonia (NH
3
). The calculations reveal that the NH
3
molecule weakly interacts with the pristine HGY surface with an adsorption energy of −0.146 eV. The expedited charge transfer and strong orbital hybridization between the NH
3
molecule and the decorated TM (except Pd) resulted in the strong adsorption of the NH
3
on the TM-decorated system. Among the three metals, it is found that the Sc decorated HGY can be regarded as the potential NH
3
sensor owing to its reasonable adsorption energy of −1.49 eV, a large charge transfer of 0.113
e
, and an attainable recovery time of 3.2 s at 600 K. Furthermore, the stability of the Sc decorated HGY structure at ambient temperature is also validated using the
ab initio
molecular dynamic simulations. The results of the current study mirror the probable application of 2D HGY-based gas sensors for the detection of ammonia.
Al‐doped ZnO nanotubes (NTs) decorated with Cu2O particles (Al‐ZnO/Cu2O NTs) are prepared by a two‐step hydrothermal method, and the photocatalytic properties are examined by the degradation of ...methyl orange (MO) solution under simulated solar light at room temperature. Compared with the Al‐doped ZnO nanorods (Al‐ZnO NRs) and the Al‐doped ZnO NTs (Al‐ZnO NTs), the Al‐ZnO/Cu2O NTs exhibit better photocatalytic properties. The improvement of photocatalytic performance of Al‐ZnO/Cu2O NTs is attributed to both Cu2O particle decoration and NT structures. In the samples, the decoration of Cu2O particles can prolong the exciton lifetimes, and the NT structures increase specific area. Therefore, both of these two conditions contribute to improved photocatalytic efficiency.
The Al‐doped ZnO nanotubes (NTs) decorated with Cu2O particles are prepared on an Al‐doped ZnO seed layer via a two‐step hydrothermal method. The enhancement of photocatalytic performance originates not only from the high specific surface area of NT structures, but also from the decoration of Cu2O particles.
•Two kinds of silane coupling agents (r-aminopropyl triethoxy silane, KH550; and trimethoxy vinyl silane, A171) and dicumyl peroxide were used to bond the wood fiber/high-density polyethylene ...(WF/HDPE) composite and wood veneer.•Samples treated with A171 had higher bonding strength than those treated with KH550.•The greater the volume of wood fiber in the WF/HDPE, the poorer the bonding strength of the veneer and the lower its water resistance.
Because of the smooth, dense, and nonpolar surface of wood-plastic composites (WPCs), it is challenging to form an efficient bonding interface between the WPC and the material of the wood veneer by using traditional adhesives. In this study, two kinds of silane coupling agents (r-aminopropyl triethoxy silane, production number KH550; and trimethoxy vinyl silane, production number A171) and dicumyl peroxide were used to improve the bond between the wood fiber/high-density polyethylene (WF/HDPE) composite and the wood veneer. The attenuated total reflection-Fourier transform infrared spectroscopy curve shows that the two kinds of silane coupling agents were grafted to the surface of the wood veneer, and the contact angle between distilled water and the veneer surface increased from 46° to greater than 120° after treatment. The bonding strength between the treated veneer and the WF/HDPE composite was significantly enhanced, and samples treated with A171 had higher bonding strength than those treated with KH550. The greater the volume of wood fiber in the WF/HDPE, the poorer the bonding strength of the veneer and the lower its water resistance. Images from a scanning electron microscope show that the silane coupling agent A171 can induce a denser interface between the wood veneer and the WF/HDPE composite.
This paper gives an overview of recent progress in microstructure-specific hydrogen mapping techniques. The challenging nature of mapping hydrogen with high spatial resolution, i.e. at the scale of ...finest microstructural features, led to the development of various methodologies: thermal desorption spectrometry, silver decoration, the hydrogen microprint technique, secondary ion mass spectroscopy, atom probe tomography, neutron radiography, and the scanning Kelvin probe. These techniques have different characteristics regarding spatial and temporal resolution associated with microstructure-sensitive hydrogen detection. Employing these techniques in a site-specific manner together with other microstructure probing methods enables multi-scale, quantitative, three-dimensional, high spatial, and kinetic resolution hydrogen mapping, depending on the specific multi-probe approaches used. Here, we present a brief overview of the specific characteristics of each method and the progress resulting from their combined application to the field of hydrogen embrittlement.
This paper is part of a thematic issue on Hydrogen in Metallic Alloys
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The body against the wall is a reading of the representations of the human body in the graffiti image with the lenses of the history of art, aesthetics, sociology and literature; Explored with the ...purpose of trying to understand something of the contemporary social and cultural universe. Within the wide spectrum of the graffiti image stands a prolific slope in which the motive of primordial representation is the human body. Painted, stenciled, adhered on the walls, these images are ephemeral tattoos in urban skin; In them the body becomes a form of language through which they range from advertising messages to diatribes on the status quo, and from individual opinions and desires to collective imaginaries.
We have applied density functional calculations to study the structure, stability and hydrogen storage properties of Li-coated C70 fullerenes. Our results show that among different possibilities for ...the geometry of Li-coated C70 fullerenes, Li atoms prefer to occupy exohedral and endohedral positions on top of the pentagons. Among isomers of Li2C70 and Li6C70, those in which one of the Li atoms occupy the endohedral position of one of the polar pentagonal rings and the other ones situate on the top of the pentagons around the opposite polar pentagon, have higher binding energies. Charge transfer is occurred from Li to C70, putting extra electrons in the vicinity of the Li atom. This results in the binding of hydrogen in atomic form to the on-top C site that is nearest to the Li atom in the preferred configuration of hydrogenated Li-coated C70 fullerene. Therefore, there are two types of hydrogen binding in Li6C70. One group of hydrogen bind to Li atoms in quasi-molecular form, which will desorb at a lower temperature, and the other group of H atoms bind to C in atomic form, which will desorb at higher temperatures.
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•LiC70: pentagonal rings > hexagonal rings.•LiC70: endohedral position > hexagonal rings.•Li2C70: one Li endohedral polar P1 and other exohedral of P2.•Li6C70: endohedral positions polar P1 rings and other exohedral of P2 pentagonal rings.•Two types of H bonding; H binds to Li in quasi-molecular and bind to C in atomic form.
With the increasing demands of indoor air quality monitoring, highly sensitive and selective gas sensor arrays consisting of metal oxide semiconductors have been increasingly studied. As an effective ...strategy to obtain the desired performance, noble metal functionalization is frequently chosen owing to its target-specific sensing mechanisms. However, the lack of a comprehensive analysis on the sensing mechanisms of different combinations of metal oxides and noble metals limit the versatility of these sensor arrays for use in selective gas sensor arrays. In this study, we fabricate a 3 × 3 gas sensor array to obtain a reliable comparison of the sensing mechanism through the use of three metal oxides—WO3, SnO2 and NiO—in three different nanostructure forms: a thin film and dome-like nanostructures with and without Au nanoparticle (NP) decoration. The responses of the sensor arrays to four target gases (CH3COCH3, C6H5CH3, NH3, and H2S) are generally enhanced by the dome-like nanostructure and show distinctively enhanced responses when the sensors are decorated with Au NPs. Moreover, the dome-like SnO2 with Au NPs shows an increase of up to 121 times for C6H5CH3 compared with the pristine SnO2 thin film. Additionally, the sensitization effects of Au NPs depend on the types of metal oxides and gases, which improve the gas discrimination capability by diversifying the gas selectivity of the sensor units in the array. The prepared sensor array can distinguish four target gases by principal component analysis (PCA). The contributions of different enhancement mechanisms, which are dependent on the gases and metal oxides, are investigated by comparing the activation energy of each gas response with and without Au. The comparison among the chosen gases reveals that the decoration of Au NPs is effective for C6H5CH3 and NH3 regardless of the type of metal oxide. Among the metal oxides, the effects of Au NPs on gas responses are in the order of SnO2, NiO, and WO3, in which the energy level difference between the Au NPs and metal oxide are 0.2, 0.1, and −0.6 eV, respectively. These results confirm that the dominant enhancement mechanism of Au NPs for each combination of gases and metal oxide is a decrease in activation energy. Therefore, this study provides a systematic understanding of the sensitization mechanism of Au NPs on metal oxides toward gases for the fabrication of selective gas sensor arrays.
•A simple electrostatic attraction method synthesis Z-Scheme ternary heterojunction.•Formed Schottky junction make electrons and holes can be maximal separation.•Optimized degradation performance on ...MB and TC under visible-light irradiation.•Discussed the path of charge transfer and the mechanism of pollutant degradation.
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The discharge of industrial wastewater poses serious concerns to the environment and human health. Therefore, urgent development of simple and efficient catalysts for removal of pollutants is required. In this study, a novel ternary nanocomposite Ag/g-C3N4/LaFeO3 (A/CN/LFO) was synthesized for the degradation of dye and pharmaceutical wastewater. The catalyst was prepared by decorating Ag nanoparticles (NPs) on g-C3N4/LaFeO3 (CN/LFO) Z-scheme heterojunction and formation of Schottky junctions with LaFeO3 (LFO) and g-C3N4 (CN). The formed hybrid structure between metal and Z-scheme heterojunction induced directional transfer of electrons or holes from the Z-scheme heterojunction to metal, providing maximum separation between electrons and holes for more efficient redox reactions. Consequently, the ternary nanocomposite displayed optimized efficiencies toward the photocatalytic degradation of methylene blue (MB) and tetracycline hydrochloride (TC) under visible-light irradiation, estimated to 98.97% (90 min) and 94.93% (120 min), respectively. These values were almost 4.81 times and 3.88 times higher than those of pristine LaFeO3, respectively. The charge transfer mechanism and pollutant degradation pathway were also studied. The data revealed that Ag decorated Z-scheme heterojunction showed efficient light absorption and separation of photogenerated carriers, which might be useful for large-scale practical applications related to wastewater treatment and pollution control.
Stabilizing atomically dispersed single atoms (SAs) on silicon photoanodes for photoelectrochemical-oxygen evolution reaction is still challenging due to the scarcity of anchoring sites. Here, we ...elaborately demonstrate the decoration of iridium SAs on silicon photoanodes and assess the role of SAs on the separation and transfer of photogenerated charge carriers. NiO/Ni thin film, an active and highly stable catalyst, is capable of embedding the iridium SAs in its lattices by locally modifying the electronic structure. The isolated iridium SAs enable the effective photogenerated charge transport by suppressing the charge recombination and lower the thermodynamic energy barrier in the potential-determining step. The Ir SAs/NiO/Ni/ZrO
/n-Si photoanode exhibits a benchmarking photoelectrochemical performance with a high photocurrent density of 27.7 mA cm
at 1.23 V vs. reversible hydrogen electrode and 130 h stability. This study proposes the rational design of SAs on silicon photoelectrodes and reveals the potential of the iridium SAs to boost photogenerated charge carrier kinetics.
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