Reduction Of Metal Precursors Research Articles

Influence of different morphologies on the catalytic activity of Pt-Pd nanostructures for methanol oxidation

Developing efficient and durable catalysts for methanol oxidation in acidic media remains a significant challenge in electrochemical energy conversion. This study addresses this issue by synthesizing Pt-Pd bimetallic electrocatalysts with different morphologies, including nanowires, core-shell nanoparticles, and core-shell nanowires, and evaluating their catalytic activities. The electrocatalysts were prepared via chemical reduction of metal precursors using formic acid as a reducing agent. X-ray diffraction analysis revealed distortions in the lattice parameters of the nanostructured bimetallic catalysts, and STEM/EDX analysis confirmed the formation of the different morphologies on the carbon support. Electrochemical assessments showed that the bimetallic catalysts exhibited superior catalytic activities to nanostructured Pt/C catalysts. The Pd@Pt/C core-shell nanowires displayed the highest catalytic efficiency, with the lowest methanol oxidation onset potential (468 mV) and the highest mass and specific activities. Electrochemical impedance measurements revealed the lowest charge transfer resistance value for the Pd@Pt/C core-shell nanowires. Chronoamperometric tests further indicated that the Pd@Pt/C core-shell nanowires catalyst exhibited superior tolerance to inactivation by reaction intermediates, achieving mass and specific activities approximately twice as high as those of the Pt/C catalyst. The enhanced catalytic performance of the Pd@Pt/C core-shell nanowires was attributed to the synergistic effects of the two morphologies that alter the electronic and geometric structures of the Pt within the catalyst.

The Effect of SnO<sub>2</sub> and Rh on Pt Nanowire Catalysts for Ethanol Oxidation

In this study, we synthesized Pt-Rh nanowires (NWs) through chemical reduction of metallic precursors using formic acid at room temperature, excluding the use of surfactants, templates, or stabilizing agents. These NWs were supported on two substrates: carbon (Vulcan XC-72R) and carbon modified with tin oxide (SnO<sub>2</sub>) via the sol-gel method (10 wt.% SnO<sub>2</sub>). We explored the electroactivity of Pt/SnO<sub>2</sub>/C, Pt-Rh/C, Pt-Rh/SnO<sub>2(commercial)</sub>/C (commercial SnO<sub>2</sub>), and Pt-Rh/SnO<sub>2</sub>/C NWs toward electrochemical oxidation of ethanol in acidic media using various techniques, including CO-stripping, cyclic voltammetry, derivative voltammetry, chronoamperometry, and steady-state polarization curves. Physical characterization involved X-ray diffraction and transmission electron microscopy. The synthesized NWs exhibit higher ethanol oxidation activity than the commercial Pt/C (Johnson Matthey™) catalyst. Rh atoms are hypothesized to enhance complete ethanol oxidation, while the NW morphology improves ethanol adsorption at the catalyst surface for subsequent oxidation. Additionally, the choice of support material plays a significant role in influencing the catalytic activity. The superior catalytic activity of Pt-Rh/SnO<sub>2</sub>/C NWs may be attributed to the facile dissociation of the C-C bond, low CO adsorption (electronic effect due to Rh presence), and the bifunctional mechanism facilitated by the oxophilic nature of the SnO<sub>2</sub> support.

Effect of pH, Amount of Metal Precursor, and Reduction Time on The Optical Properties and Size of Zinc Oxide Nanoparticles Synthesized Using Aqueous Extract of Rhizomes of Acorus calamus

Nanoparticles possess various unique characteristics compared to the corresponding bulk materials. Large band gap, non-toxic nature, and multi-applicability are the worthwhile characteristics of zinc oxide to be synthesized and studied. The size of nanoparticles can be controlled by varying the different experimental conditions. This paper reports the synthesis of zinc oxide nanoparticles by using an aqueous extract of rhizomes of Acorus calamus, where the bio-components present in aqueous extract acted as reducing agents. The size and band gap energy of zinc oxide nanoparticles were studied by varying different parameters such as pH, concentration of the metal precursor, and reduction time. The variations in the size of nanoparticles were studied by UV-visible spectroscopy. FTIR showed phenolic compounds, primary amines, and amides (proteins/enzymes) as the functional groups responsible for the reduction of metal precursors to form nanoparticles. The surface morphology of nanoparticles was studied by FE-SEM image. The FE-SEM image displayed the formation of various shapes and agglomeration of the nanoparticles. XRD pattern revealed that the average size of zinc nanoparticles is 10 nm. In vitro antibacterial activity of ZnO nanoparticles has been assayed against gram-positive and gram-negative bacteria. The growth inhibitory activity of nanoparticles against different bacterial pathogens has also been determined

Wearable Plasmonic Sensors Engineered via Active-Site Maximization of TiVC MXene for Universal Physiological Monitoring at the Molecular Level.

Two-dimensional transition metal carbon/nitrides (MXenes) are promising candidates to revolutionize next-generation wearable sensors as high-performance surface-enhanced Raman scattering (SERS) substrates. However, low sensitivity of pure MXene nanosheets and weak binding force or uncontrolled in situ growth of plasmonic nanoparticles on hybrid MXene composites limit their progress toward universal and reliable sensors. Herein, we designed and manufactured a highly sensitive, structurally stable wearable SERS sensor by in situ fabrication of plasmonic nanostructures on the flexible TiVC membranes via the maximization of chemically reducing sites using alkaline treatment. DFT calculations and experimental characterization demonstrated that the hydroxyl functional groups on the surface of MXenes can facilitate the reduction of metal precursors and the nucleation of gold nanoparticles (AuNPs) and can be covalently attached to AuNPs. Thus, the fabricated flexible TiVC-OH-Au sensor satisfied the rigorous mechanical requirements for wearable sensors. In addition, combining the electromagnetic (EM) enhancement from dense AuNPs formed by the activation of nucleation sites and charge transfer (CT) between target molecule and substrate induced by the abundant DOS near the Fermi level of TiVC, the fabricated sensor exhibits ultrasensitivity, long-term stability, good signal repeatability, and excellent mechanical durability. Moreover, the proof-of-concept application of the wearable SERS sensor in sweat sensing was demonstrated to monitor the content of nicotine, methotrexate, nikethamide, and 6-acetylmorphine in sweat at the molecular level, which was an important step toward the universality and practicality of the wearable sensing technology.

Synthesis of metallic high-entropy alloy nanoparticles.

The theoretically infinite compositional space of high-entropy alloys (HEAs) and their novel properties and applications have attracted significant attention from a broader research community. The successful synthesis of high-quality single-phase HEA nanoparticles represents a crucial step in fully unlocking the potential of this new class of materials to drive innovations. This review analyzes the various methods reported in the literature to identify their commonalities and dissimilarities, which allows categorizing these methods into five general strategies. Physical minimization of HEA metals into HEA nanoparticles through cryo-milling represents the typical top-down strategy. The counter bottom-up strategy requires the simultaneous generation and precipitation of metal atoms of different elements on growing nanoparticles. Depending on the metal atom generation process, there are four synthesis strategies: vaporization of metals, burst reduction of metal precursors, thermal shock-induced reduction of metal precursors, and solvothermal reduction of metal precursors. Comparisons among the methods within each strategy, along with discussions, provide insights and guidance for achieving the robust synthesis of HEA nanoparticles.

EFFECT OF HEAT TREATMENT ON THE STRUCTURE AND FUNCTIONAL CHARACTERISTICS OF A PtCo/C CATALYST

The PtCo/C electrocatalyst obtained by the method of simultaneous reduction of metal precursors using sodium borohydride was treated at a temperature of 350 ˚C in an argon atmosphere for 1 hour. The results of X-ray phase analysis and transmission electron microscopy indicate an increase in the average size of crystallites and the formation of nanoparticle agglomerates after heat treatment. The shift in the reflection of Pt (111) after treatment indicates the possible segregation of metal components during the heating of the sample. An increase in the catalyst activity after heat treatment is shown, both mass activity and specific activity. The stability of the sample after heat treatment, according to the results of the stress test in the potential range of 0.6–1.4 V, showed a higher value than the material in the “as prepared” state.

Electrochemical detection of acetaminophen and caffeine using Ag nanoparticles doped metal-organic framework (ZIF-67) composites

The combination of metal organic framework (MOFs) with metal nanoparticles has great prospects for improving the electrochemical property of sensors. In this paper, silver (Ag) nanoparticles doping Co-based zeolitic imidazolate framework (ZIF-67) composites (Ag-ZIF-67) were prepared by ultrasonic treatment of ZIF-67 and reduction of metal precursor (AgNO3) in ZIF-67 material. Ag-ZIF-67 nanosheet material was obtained and characterized by transmission electron microscopy and electrochemical impedance spectroscopy. Due to the synergistic effect of high porosity and large specific surface area of ZIF-67, as well as the high electrical conductivity and prominent catalytic activity of Ag nanoparticles, Ag-ZIF-67 modified glassy carbon electrode showed excellent electrocatalytic activity for the detection of acetaminophen (AP) and caffeine (CAFF), including wide linear range (0.1–70.0 μM) for AP and (0.5–300.0 μM) for CAFF, high anti-interference ability. Additionally, the prepared Ag-ZIF-67 sensor also exhibited excellent selectivity for two compounds detection and prospective results in pharmaceutical formulations samples.

Noteworthy biocompatibility of effective microorganisms (EM) like microbial beneficial culture formulation with metal and metal oxide nanoparticles

The present study evaluates the biocompatibility of silver and zinc oxide nanoparticles with various effective microorganisms (EM), like beneficial microbial formulations. The respective nanoparticle was synthesised by chemical reduction of metal precursor with reducer via simple route green technology principles. The synthesised nanoparticles were characterised by UV visible spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) studies, revealing highly stable, nanoscale particles with marked crystallinity. EM-like beneficial cultures composed of viable cells of Lactobacillus lactis, Streptomyces sp, Candida lipolytica, and Aspergillus oryzae were formulated with rice bran, sugarcane syrup, and groundnut cake. The respective formulation was inoculated into the nanoparticles amalgamated pots raised with green gram seedlings. Biocompatibility was determined by measuring plant growth parameters of a green gram at pre-determined periods associated with enzymatic antioxidants like catalase (CAT), superoxide dismutase (SOD), and glutathione S transferase (GST) levels. Most significantly, the expression level of these enzymatic antioxidants level was also investigated by quantitative real-time polymerase chain reaction (qRT-PCR). The impact of the soil conditioning effect on soil nutrients like nitrogen, phosphorous, potassium, organic carbon, soil enzymes glucosidases, and β-xylosidases activity was also studied. Among the formulation, rice bran-groundnut cake-sugar syrup formulation recorded the best biocompatibility. This formulation showed high growth promotion, soil conditioning effect and no impact on the oxidative stress enzymes genes that revealed the best compatibility of nanoparticles. This study concluded that biocompatible, eco-friendly formulations of microbial inoculants could be used for the desirable agro active properties that show extreme tolerance or biocompatibility to the nanoparticles. This present study also suggests the utilisation of the above said beneficial microbial formulation and metal-based nanoparticles with desirable agro active properties in a synergistic manner due to their high tolerance or compatibility towards the metal or metal oxide nanoparticles.

Examining Silver Deposition Pathways onto Gold Nanorods with Liquid-Phase Transmission Electron Microscopy

Liquid-phase transmission electron microscopy (LP-TEM) enables one to directly visualize the formation of plasmonic nanoparticles and their postsynthetic modification, but the relative contributions of plasmonic hot electrons and radiolysis to metal precursor reduction remain unclear. Here we show silver deposition onto plasmonic gold nanorods (AuNRs) during LP-TEM is dominated by water radiolysis-induced chemical reduction. Silver was observed with LP-TEM to form bipyramidal shells at higher surfactant coverage and tip-preferential lobes at lower surfactant coverage. Ex situ silver photodeposition formed nanometer-thick shells on AuNRs with preferential deposition in inter-rod gaps, while chemical reduction deposited silver at AuNR tips at low surfactant coverage and formed pyramidal shells at higher surfactant coverage, consistent with LP-TEM. Silver deposition locations during LP-TEM were inconsistent with simulated near-field enhancement and hot electron generation hot spots. Collectively, the results indicate chemical reduction dominated during LP-TEM, indicating observation of plasmonic hot electron-induced photoreduction will necessitate suppression of radiolysis.

Greenery method for Synthesis of some alkali and alkaline earth metallic nanoparticles and its antibacterial screening activity

In the presence study of science and technology has greater significance for the development of nanoparticles and its physicochemical properties. Alkali and alkaline earth metalic nanoparticle has synthesized by using various plant extract and metalic solution. However, biogenic reduction of metal precursors to produce corresponding metalic nanoparticle is eco-friendly, low cost, free of chemical contaminants for medical and biological applications. The synthesized Metallic nanoparticle is found to be more susceptible towards the bacterial strains.

Two Routes for Sonochemical Synthesis of Pt-Nanoparticles

To improve the performance of electrochemical hydrogen conversion devices such as electrolyzers and fuel cells, more efficient catalyst materials must be developed. As the available surface area is key to the performance of a catalyst, high surface area nanoparticles are required. The synthesis of such nanostructured catalysts is predominantly based on chemical reduction with a strong reducing agent like sodium borohydride. However, it is difficult to achieve the desired particle properties without the use of additives such as surfactants or stabilizers.In order to achieve more control over the nucleation and growth stage of the nanoparticles, we can replace the chemical reduction route by sonochemical reduction. In sonochemistry, high power ultrasound is used to generate reducing radicals which allow for controlled reduction of metal precursors. The radical generation rate is strongly linked to the nucleation and growth of the resulting nanoparticles and can easily be tuned by adjusting the ultrasonic frequency and power. Ultrasound therefore offers an easy and reproducible way of tuning the size of nanoparticles.In our work we have compared the size, shape, and morphology of Pt-nanoparticles synthesized sonochemically and with chemical reduction to see if the sonochemical route indeed offers better control during nucleation and growth. TEM-images along with X-ray diffractograms revealed that the sonochemical route gives smaller and more monodisperse particles compared to chemical reduction. In addition, the particle shape was found to be spherical with the sonochemical route, whereas chemical reduction resulted in many different shapes. The better and easier control over synthesis parameters exhibited by the sonochemical route can therefore be utilized to produce nanoparticles of very similar physical properties. We also showed that the catalytic properties of these nanoparticles towards hydrogen evolution were very similar further strengthening the sonochemical route when it comes to development of catalyst materials.A comparison between high frequency (408 kHz) and low frequency (20 kHz) ultrasound was also made to determine the impact of the higher mechanical effects expected at lower frequencies. No significant differences in particle size and morphology were found, but agglomerate sizes were found to decrease at lower frequencies. In addition, it was found that extensive probe erosion occurs at 20 kHz resulting in contamination of the nanoparticle solution. In fact, it was shown that the eroded particles act as nucleation sites for Pt-nanoparticles and increased reduction rates were observed. No such particle erosion happened at higher frequencies which led us to conclude that direct sonication at low ultrasonic frequencies in general must be avoided to prevent contamination of your system. This is important in all applications of low frequency (20 kHz) ultrasound, whether it be sonochemistry, dispersion of colloids, or ink preparation for electrochemical characterization.

Enhanced hydrogen evolution by using ternary nanocomposites of mesoporous carbon nitride/black phosphorous/transition metal nanoparticles (m-gCN/BP-M; M = Co, Ni, and Cu) as photocatalysts under visible light: A comparative experimental and theoretical study

The effect of first-row transition metal nanoparticles as co-catalysts on the activity of mesoporous graphitic carbon nitride (m-gCN) and black phosphorous (BP) heterojunctions (m-gCN/BP) in the photocatalytic hydrogen evolution reaction (HER) is investigated comparatively. Three m-gCN/BP-M (M: Co, Ni, and Cu) ternary nanocomposites were prepared via wetness impregnation and chemical reduction of metal precursors on as-prepared m-gCN/BP binary heterojunctions. The photocatalytic HER activities of m-gCN, m-gCN/BP, m-gCN/BP-Ni, m-gCN/BP-Co, and m-gCN/BP-Cu nanocomposites were determined to be 0.233, 0.330, 0.442, 0.326, and 0.223 mmol g−1 h−1, respectively, under visible light illumination. These results revealed that type of transition metal NPs as co-catalysts have considerable effect on the activity of m-gCN/BP heterojunctions in the photocatalytic HER, among which m-gCN/BP-Ni is the best one. The DFT calculations performed on the nanocomposites revealed that m-gCN/BP-Ni possesses the lowest band gap and the highest visible light absorption resulting in the highest photocatalytic activity in HER.

Recent Advances of Magnetic Gold Hybrids and Nanocomposites, and Their Potential Biological Applications

Magnetic gold nanoparticles (mGNP) have become a great interest of research for nanomaterial scientists because of their significant magnetic and plasmonic properties applicable in biomedical applications. Various synthetic approaches and surface modification techniques have been used for mGNP including the most common being the coprecipitation, thermal decomposition, and microemulsion methods in addition to the Brust Schiffrin technique, which involves the reduction of metal precursors in a two-phase system (water and toluene) in the presence of alkanethiol. The hybrid magnetic–plasmonic nanoparticles based on iron core and gold shell are being considered as potential theranostic agents. In this critical review, in addition to future works, we have summarized recent developments for synthesis and surface modification of mGNP with their applications in modern biomedical science such as drug and gene delivery, bioimaging, biosensing, and neuro-regeneration, neuro-degenerative and arthritic disorders. This review includes techniques and biological applications of mGNP majorly based on research from the previous six years.

Influence of Heat Treatment on the Microstructure and Functional Characteristics of PtCu/C Catalysts

PtCu/C electrocatalysts with different compositions, obtained by the method of the combined reduction of metal precursors, are heat treated at a temperature of 350°C in an argon atmosphere. The study by X-ray powder diffraction and transmission electron microscopy shows an increase in the average size of nanoparticles after heat treatment, which explains a decrease in the value of the electrochemically active surface area of the catalysts. An increase in the specific activity of the catalysts in the reaction of oxygen electroreduction after heat treatment is shown. The study by stress testing in the potential range of 0.6–1.4 V shows an increase in the stability of the heat-treated catalyst in comparison with the material in the “as prepared” state. A decrease in the amount of dissolved copper from the catalyst nanoparticles after heat treatment during electrochemical activation is shown, which also indicates an increase in catalyst stability.

Recyclable 2D Colloid Surfactants with High Catalytic Activities at Pickering Emulsion Interfaces

AbstractThis study introduces a novel 2D colloid surfactant system that exhibits catalytic activity at the interface of a reactant‐containing water‐in‐oil Pickering emulsion microreactor. To this end, amphiphilic nanoplatelets (ANPLs) are fabricated with hydrophobic poly (n‐butyl methacrylate) brushes on one face, and hydrophilic poly (2‐aminoethyl methacrylate) brushes on the other face via surface‐induced activators regenerated by electron transfer atom transfer radical polymerization (SI‐ARGET ATRP) on zirconium hydrogen phosphate (ZrHP) nanoplatelets. Subsequently, in situ reduction of metal precursors on the primary amine reaction sites on the hydrophilic face of ANPLs is conducted, thus enabling the production of ANPL catalysts (ANPLcat): ANPLAg, ANPLPd, and ANPLAu. Owing to the platelet geometry and catalytic functionalization, the ANPLcat demonstrates excellent ability to stabilize the Pickering emulsion reactant drops, while exhibiting its own catalytic activity at the interface. It is demonstrated that this ANPLcat system has a high catalytic activity that requires a short reduction reaction time with the speed of which is 750% higher compared with the spherical colloidal surfactant catalyst. In addition, ANPLcat is easily recoverable and recyclable. These results highlight that the ANPLcat‐based emulsion microreactor system is expected to be widely applied as a high‐performance catalyst for various organic chemical reactions.

Sustainable synthesis of silver nanoparticles using fruit waste and its antibacterial activity

Herein we have employed efficient, inexpensive and eco-friendly green synthesis process to produce well-defined geometries of silver nanoparticles at room temperature by utilizing fruit extracts (Punica granatum and Artocarpus heterophyllus) having unique optical, antibacterial and catalytic property. Reducing or anti-oxidant properties of phytochemicals present in fruit waste are typically responsible for reduction of metal precursor into their respective nanoparticles.Occurrence of surface plasmon resonance (SPR) peak in visible region (around 420 nm) as characterized by UV–Vis spectroscopy indicates formation of silver nanoparticles further confirmed via Transmission electron microscopy (TEM) measurements. The average size and stability are detected by dynamic light scattering (DLS), zeta potential analysis and TEM measurements. Crystallinity and face-centered cubic (fcc) structure of formed silver nanoparticles are examined via selected electron area diffraction (SEAD) pattern. Antibacterial sensitivity of formed silver nanoparticles against the bacteria E Coli is also determined.

Origin of luminescence properties and synthetic methods for gold- and bimetallic gold-based nanomaterials

This review covers the mechanistic origin of luminescent mono- and bimetallic gold-based nanomaterials and their syntheses by the chemical reduction of metal precursors in the presence of surface capping agents.

Effect of the Synthetic Method on the Properties of Ni-Based Hydrogen Oxidation Catalysts.

The latest progress in alkaline anion-exchange membranes has led to the expectation that less costly catalysts than those of the platinum-group metals may be used in anion-exchange membrane fuel cell devices. In this work, we compare structural properties and the catalytic activity for the hydrogen-oxidation reaction (HOR) for carbon-supported nanoparticles of Ni, Ni3Co, Ni3Cu, and Ni3Fe, synthesized by chemical and solvothermal reduction of metal precursors. The catalysts are well dispersed on the carbon support, with particle diameter in the order of 10 nm, and covered by a layer of oxides and hydroxides. The activity for the HOR was assessed by voltammetry in hydrogen-saturated aqueous solutions of 0.1 mol dm–1 KOH. A substantial activation by potential cycling of the pristine catalysts synthesized by solvothermal reduction is necessary before these become active for the HOR; in situ Raman spectroscopy shows that after activation the surface of the Ni/C, Ni3Fe, and Ni3Co catalysts is fully reduced at 0 V, whereas the surface of the Ni3Cu catalyst is not. The activation procedure had a smaller but negative impact on the catalysts synthesized by chemical reduction. After activation, the exchange-current densities normalized with respect to the ECSA (electrochemically active surface area) were approximately independent of composition but relatively high compared to catalysts of larger particle diameter.

An Eco-approach synthesis of undoped and Mn doped ZnO nano-photocatalyst for prompt decoloration of methylene blue dye

The present work reports the synthesis of nano pure ZnO and Mn-doped ZnO in an Eco-approach using seed extract of Cassia angustifolia for the removal of methylene blue. The aqueous Phyto-molecules helps in the reduction of metal precursor to nano-photocatalyst zinc oxide and the changes in absorbance was noted in UV-DRS for varying the parameters to get optimized. Different concentrated dopant material manganese sulphate (0.001 M, 0.003 M, and 0.005 M) was introduced on ZnO to enhance the optical absorption and to generate a new Fermi level. The XRD data exhibit the same wurtzite pattern for pure ZnO and Mn-doped ZnO samples. The slight shift in peak positions was noted in Mn-doped ZnO samples compared to pure ZnO without additional peaks determines the incorporation of Mn2+ ions in the lattice of ZnO NPs. The peak appearance in FT-IR denotes the bond formation among functional groups and metal oxide. The structural morphology of ZnO and Mn-doped ZnO was observed in Field Emission Scanning Electron microscopy. The elemental composition of Mn in ZnO was predicted in the EDAX. The High-resolution transmission electron microscopy (HRTEM) denotes the reduced size and altered the crystallinity of ZnO when Mn was introduced as the dopant in the green route. The effective photocatalytic activity of nano ZnO, Mn-doped ZnO achieves 84 and 95% decoloration of water pollutant Methylene blue (MB) dye with H2O2 and UV radiation by changing parameters like dye concentration, amount of catalyst, and pH. Results from this study suggest that the nano- Mn-doped ZnO photocatalyst can be advantageous for dye removal compared to pure ZnO. The green synthesized Mn-doped ZnO using Cassia angustifolia seed might considerable for treating dye contaminated water and supports in water remediation.

Formation of Active Centers of Nickel–Zinc Catalysts Deposited on the Nanodiamond for the Selective Hydrogenation of Phenylacetylene

A study is performed of bimetallic catalysts NiZn/ND with ratios Ni : Zn = 1 : 1 and 1 : 3 prepared by impregnation using detonation nanodiamond (ND) as a support. They were compared with monometallic Ni/ND and Zn/ND. It is shown by nitrogen adsorption/desorption, scanning and transmission electron microscopy that metal deposition does not affect the porous structure or morphology of a support. Coordination of metal precursors on a nanodiamond surface proceeds with the participation of functional groups, as is confirmed by a change in the electrokinetic charge of the surface. The reduction of metal precursors is studied by temperature-programmed reduction and in situ XAFS spectroscopy. In Ni-containing samples, two forms of Ni2+ are found that are bonded differently with the support. ZnO is not reduced in the samples upon treatment with hydrogen at temperatures up to 400°C. The fraction of reduced nickel is determined by analyzing XANES spectra. Virtually full reduction of nickel is observed in a catalyst with a Ni : Zn ratio of 1 : 1 after 4 h of in situ treatment with hydrogen inside a spectrometer cell at 400°C, but not at a Ni : Zn ratio of 1 : 3 under the same conditions. The highest selectivity of styrene formation in the reaction of phenylacetylene hydrogenation throughout the investigated range of temperatures (100–350°С) is ensured by NiZn/ND; NiZn3/ND is less active and selective, since ZnO closes the active nickel centers and prevents the adsorption of phenylacetylene.