Nickel Oxide Catalyst Research Articles

Bipolar electrodeposition of gradient polypyrrole films as a catalyst matrix for anodic ethanol oxidation

Lateral gradient coatings displaying various compositions and microstructures along a single surface are desirable for material screening. Here we report a successful application of bipolar electrochemistry to deposit lateral gradient polypyrrole films on a graphite strip substrate. The gradient film shows varying morphologies and a wettability gradient along the length of the bipolar electrode, with superabsorbent property in the middle portion of the film. The film was use as a catalyst matrix for ethanol oxidation in alkaline electrolyte. Aqueous Ni(NO3)2 solution as the catalyst precursor was absorbed into the film. Area-step cyclic voltammetry was used to evaluate the electrocatalytic activity of various local parts along the gradient film to ethanol oxidation. The local surface with the highest catalytic activity was screened out and the excellent catalytic activity is attributed to the outstanding properties of this zone in both water absorption and electrical conductivity. The nickel oxide catalyst can be highly dispersed in the nanoporous network polymer matrix, due to the uniform penetration of the aqueous precursor solution into the superabsorbent film. XPS and EIS analyses support the catalytic mechanism based on the redox transition between NiOOH and Ni(OH)2. This work indicates that loading aqueous catalyst precursors into superabsorbent conducting polymer films may be a promising method for the preparation of electrocatalysts.

The Development of Fine Surface Roughness of FeCrAl Substrate by Gamma Alumina Coating Material Through Nickel Oxide Catalyst

The most commonly used method for protecting atmospherically exposed steel against corrosion, is the application of protective organic coating systems. It is widely recognized that the stability of the coating-substrate interface is related to the interfacial adhesion forces and electrochemical properties of this region. This study aim to develop fine surface roughness by ultrasonic and electroplating coating methods that applied for FeCrAl catalytic converter. This method consists of thwo methods which are ultrasonic bath that carried out by frequency of 35 kHz and various ultrasonic times of 1, 1.5, 2, 2.5 and 3 hours is imposed and the electroplating was conducted for several variation times of 15, 30, 45, 60 and 75 minutes, current density of 8 A/dm2. The result shows that the surface roughness of UB samples in between 0.11 to 0.21 µm, UBdEL samples of 0.81 to 2.17 µm, UB+EL samples of 0.64 to 1.63 µm and EL samples of 0.69 to 1.11 µm. The finest surface of each techniques are located at UB 1.5 h, UBdEL 45 minutes, UB 1.5 h+EL 30 minutes and UB 30 minutes. That data is supported by coating thickness of coated FeCrAl substrate where UB samples in between 2 -2.8 µm, UBdEL samples of 4.1 to 5 µm, UB+EL samples of 9.1 to 12 µm and EL samples of 6.2 to 11.3 µm.

Kinetics and thermodynamics study for photodegradation of Brown HT dye by MnO and NiO as catalysis

The photo-catalyzed oxidation process of Brown HT dye was studied in the aqueous solution of the dye, using an irradiation source (ultraviolet rays UV) with the use of manganese oxide (MnO) and nickel oxide (NiO) catalysts, where the effect of increasing the weight of the catalyst in the range of 0.05–0.8 g was studied using a fixed concentration of dye 20 ppm, The best weight gave the highest dissociation rate of the dye 0.1 g from MnO and 0.075 g from NiO, and at the best weight the effect of many factors on it was studied, including pH, change of initial dye concentration, and temperature. The effect of changing the pH in the range (2–10) was studied, and the best pH gave the highest rate of dissociation of the dye at pH = 2 in the presence of MnO and pH = 4 in the presence NiO when using UV as an irradiation source. The effect of changing the initial concentration of the dye in the range of 10–50 ppm was studied, as the higher the concentration, the lower the dissociation rate. Accordingly, there is an inverse relationship between the initial concentration and the dissociation rate. The effect of changing the temperature in the range (298–323) K was studied. It was found that the higher the temperature, the greater the dissociation rate. Accordingly, the relationship is direct between temperature and reaction speed, and the activation energy for each reaction was calculated using the Arrhenius equation.

Catalytic deoxygenation of waste cooking oil utilizing nickel oxide catalysts over various supports to produce renewable diesel fuel

The development of renewable diesel fuel from the deoxygenation of non-edible oil is an alternative to non-renewable fuels. Herein, the evaluation of catalytic deoxygenation of waste cooking oil (WCO) over supported Ni-based catalysts was investigated. A series of Ni-based catalysts supported on activated carbon (AC), reduced graphene oxide (rGO), and beta zeolite (Zeo) were prepared via the wet-impregnation method and later carbonised under N2 flow at 550 °C for 4 h. Addition of Ni to AC improves the good physicochemical properties of the catalyst, owing to the high number of acid-base sites, high surface area, smaller crystallite size, and high pore volume of the catalyst. From the catalytic results, Ni20/AC was the most active catalyst by giving 90% hydrocarbon yield and 89% selectivity towards n-(C15 + C17) under H2-free and solvent-free conditions for 3 h at 350 °C and 300 rpm. Furthermore, it was stable up to the fourth cycle with consistent hydrocarbon yield (85–87%) and 66–77% selectively towards n-(C15 + C17). Overall, Ni20/AC shows highly promising catalytic performance due to its good physiochemical properties and high catalyst stability.

Oxidation of VOCs on a highly stabilized furfuryl alcohol-based activated carbon supported nickel oxide catalyst

Conversion of volatile organic compounds (VOCs) such as toluene and xylene to less harmful CO2 and H2O via catalytic oxidation over the metal oxide-impregnated activated carbon beads is a viable solution for controlling emission of the pollutants. The poly(furfuryl) alcohol (PFA) precursor-based carbon beads (∼0.8 mm) were synthesized via suspension polymerization. The metal-salt was in situ dispersed in the polymerization reaction mixture, and PFA-supported Ni was carbonized (C) and steam activated (A). Decomposition of toluene (∼2000 ppm) and xylene (∼400 ppm) at 500 °C over the supported metal oxide catalysts followed the trend: NiO > CoO > CuO > FeO. Approximately 8.5% (w/w) NiO loading showed the highest VOC decomposition rate. The present results revealed that NiO-PFA/C/A was stable under the experimental VOC oxidation reaction conditions, and is an efficient oxidation catalyst for controlling VOC emissions under a continuous operation.

Co-Pyrolysis of Southern Pine and Micronized Rubber Powder with Nickel Oxide and Sodium Carbonate Catalysts

Co-Pyrolysis of Southern Pine and Micronized Rubber Powder with Nickel Oxide and Sodium Carbonate Catalysts

Study on catalytic performance of supported transition metal oxide catalyst for ozone decomposition

In this paper, γ-Al2O3 supported nickel, manganese, cobalt, and other metal oxide catalysts were prepared by the impregnation method respectively, and its ozone catalytic decomposition performance was studied at 25°C under a WHSV of 200000 mL/(gcat·h). The results showed that 10% NiO/γ-Al2O3 catalyst demonstrates superior catalytic activity, and the ozone conversion rate is higher than 96% within 20 h. According to the characterizations of XRD, XPS, TEM, SEM-EDS and H2-TPR, its excellent ozone may be attributed to the formation of NiAl2O4 spinel on the surface of NiO/γ-Al2O3 catalyst. Furthermore, the mechanism of ozone decomposition on different transition metal oxide catalysts is divergent. The related study sheds new light on the reaction mechanism of ozone catalytic decomposition over transition metal oxides such as nickel and manganese, it also provides the guidelines for the development of efficient ozone decomposition catalysts.

Oxidation of Cyclohexane using Copper–Nickel Catalyst

The copper–nickel oxide catalyst was prepared by the incipient wetness impregnation method for the selective oxidation of cyclohexane. The catalysts 25Cu100−xNix/Al2O3 were characterized by surface area, XRD, H2-TPR, FE-SEM, and Raman spectra analysis. The investigation revealed that an optimum ratio of copper to nickel, calcination temperature of the catalyst, and the suitable support play a crucial role in converting cyclohexane, and yield of product (KA oil). The catalyst 25Cu50Ni50/Al2O3 showed a significantly higher conversion of cyclohexane compared to a single-metal oxide catalyst. The enhancements of conversion by the bimetallic oxides catalyst were due to the synergistic effect of copper–nickel bimetallic oxides. The support also plays a significant role in the increase in conversion of cyclohexane, and the order of KA oil selectivity followed as 25Cu50Ni50/Al2O3 > 25Cu50Ni50/SiO2 > 25Cu50Ni50/MgO.

Spectroelectrochemical Experiment for Studying Water Oxidation with a Nickel Oxide Catalyst

Electrochemical and spectroelectrochemical techniques are very important for characterizing energy materials. In the search for new sources of renewable energy, water splitting for hydrogen production and CO2 reduction is attracting significant attention. These applications require efficient and durable catalysts and a detailed understanding of the underlying catalytic mechanism. Here, we experimentally study electrodeposited nickel oxide as a catalyst for electrochemical water oxidation by combining UV–vis and electrochemical techniques, with emphasis on revealing the interplay between catalytic activity and physical changes in the catalyst. Specifically, the spectroelectrochemical characterization of the catalyst at different pH enables students to establish correlations between catalytic activity, pH, and physical changes in the catalyst. Students are also introduced to fundamental principles of electrocatalysis such as Tafel plots, TOF (turnover frequency), and midpoint potential. Moreover, they are guided toward the reliable interpretation of optical absorption and electrochemical data, along with the conceptual aspects behind these techniques.

Synthesis and characterization of nickel oxide and evaluation of its catalytic activities for degradation of methyl orange in aqueous medium

This study focuses on synthesis of nickel oxide catalyst and exploration of its catalytic activities for degradation of methyl orange in aqueous medium. Nickel oxide was prepared sole-gel method using nickel nitrate haxahydrate and citric acid as precursor materials. X-ray diffractometry and scanning electron microscopy were used for characterization of prepared nickel oxide particles. The prepared particles were used as the catalysts for the degradation of Methyl Orange in aqueous medium. The effects of different parameters on degradation of methyl orange were investigated. The degradation of methyl orange followed the Eley-Rideal (E-R) mechanism. The apparent activation energies for degradation of methyl orange determined was found as 36.4 kJ/mol.

DFT исследование гомолитического разрыва C–H связей алканов и реакции дегидрирования пропиленгликоля на кластерах Fe4O7, NiFe3O7 и их протонированных и гидроксилированных формах

The results of a DFT study of elementary acts, both catalytic transformations of alkanes on hydride-hydroxyl forms of Fe4O7 and NiFe3O7 clusters, and processes of hydrocarbons transformation on iron and nickel-oxide clusters without initially hydride-hydroxyl filling are presented. Homolytic scission of the C–H bonds of alkanes on the hydride-hydroxyl form of the Fe4O7 cluster is accompanied by the formation of alkyl radicals capable of biradicals recombination according to the singlet type. There is also an additional reaction direction, which is represented by a singlet intra-associative rearrangement generating alcohols chemisorbed with the iron atom of the Fe4O6 cluster. This reaction is irreversible, proceeds with a large exothermic effect of 45.90 kcal∙mol-1, sufficient to overcome the chemisorption bond and diffuse into the volume of the supercritical fluid. The calculated characteristics of the interaction of alkanes with an iron-positioned hydroxyl group indicate that the activation energies of the forward direction of elementary acts in the homologous series: primary and secondary C–H bonds, lie in the range of 30.91-32.74 kcal∙mol-1, that is, these reactions are not very selective and strongly endothermic, since the activation energies of the reverse directions of the corresponding elementary acts are in the range of 1.40-3.27 kcal∙mol-1. The transition in the homologous series from the primary and secondary C–H bonds of propane to the tertiary C–H bonds of isobutane significantly changes the activation specificity of the homolytic scission of C–H bonds. The relative activation energy of the forward direction of the reaction decreases by about 8.00 kcal∙mol-1. A reaction system with the participation of the nickel-iron-oxide cluster NiFe3O7 and propane has been studied quantum-chemically. The result of the interaction of these reagents is the formation of isopropyl alcohol (propan-2-ol), which is chemisorbed with the nickel atom of the NiFe3O6 cluster. This reaction is irreversible and proceeds with a large exothermic effect of 50.95 kcal∙mol-1. The energetics of this process qualitatively coincides with the activation characteristics of the second stage of methane transformation on the Fe4O6 cluster; however, in this case, the reaction is a one-stage. It is noted that when carrying out various SCF extraction processes, for example, during the purification and regeneration of nickel and iron oxide catalysts, it should be borne in mind that the use of a propane-butane mixture as a supercritical fluid can be accompanied by its saturation with heavier hydrocarbons of linear and branched structure and alcohols. However, in real technological SCF processes, it is realistic to select the optimal temperature and flow regime that minimizes this effect. In the presence of a pre-reaction complex involving the hydrogen bond of the hydroxyl group of the initial propylene glycol and the interstitial oxygen atom (Fe–O–Fe) of the Fe4O7 cluster, a one-stage reaction with the oxidation product 1-hydroxypropan-2-ol becomes possible. The Fe4O6 iron oxide cluster with four coordinated iron centers having a hydroxyl group bound to each of them interacts with propylene glycol to form 1-hydroxypropan-2-ol, and the Fe–OH and Fe–O–Fe cluster substructures are the oxidative centers. In this case, the product of the reaction is a water molecule chemisorbed on the iron center and a hydrogen atom chemisorbed on the Fe–O–Fe substructure. This reaction is extremely exothermic (Q = 62.55 kcal∙mol-1) and has a very low activation energy for the forward direction of the reaction. By the example of the described heterogeneous hydrate-dissociative effects involving metal oxide surfaces and simple or functionalized alkanes, it can be seen that it is the protonated and hydroxylated forms of metal oxide surfaces that are responsible for elementary acts related to supercritical water oxidation.

Electrochemical Regeneration of Free Chlorine Treated Nickel Oxide Catalysts for Oxidation of Aqueous Pollutants

Nickel oxide upon free chlorine treatment has been used as a heterogeneous oxidant to eliminate aqueous organic pollutants, where oxygenation or chlorination could regenerate the oxidation capacity. In order to overcome problems associated with low regeneration efficiency and undesirable chloride ion generation, we herein investigate electrochemical regeneration for sustainable catalytic usage of the free chlorine treated nickel oxide, obviating a dosage of chemicals. Scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) characterized drop-casted catalysts with thermal decomposition to be NiO nanoparticles with amorphous nickel oxyhydroxide shells generated by free chlorine treatment. Along with an elevated open circuit potential of the active sites (NiOx(OH)y) near 0.75 V NHE (at pH 14), the chlorination was found to enhance the electrical conductivity of the catalysts. Galvanostatic anodization at current density < 4 mA/cm2 effectively restored the oxidizing power for repetitive degradations of 4-chlorophenol (4-CP). Despite greater conversion under the continuous anodization, periodic regeneration (10/60 on/off) showed far lower energy consumption (44.6 ± 3.0 kW h/kg 4-CP) for 4-CP removal. The changes in XPS and X-ray absorption near edge structure (XANES) spectra, coupled with kinetic and electrochemical analyses, demonstrated that electron transfer towards Ni3+ with H abstraction would be the primary degradation mechanism. The stability and versatility were assessed by sequencing batch cycles and degradation of 2,4-dichlorophenol, carbofuran, and oxalic acid. Application in a real phenolic wastewater matrix noted 98% and 79% removal of chemical oxygen demand and total organic carbon after 12 h.

Triple layered Ga2O3/Cu2O/Au photoanodes with enhanced photoactivity and stability prepared using iron nickel oxide catalysts

In this study, the photoelectrochemical performance of Cu2O-based photoanodes is evaluated in terms of photoactivity and stability.

Non-Enzymatic Electrooxidation of Urea with a Disposable Paper-Based Sensor Using Hierarchical NiO Hollow Sphere

Urea in the urine, protein metabolism, is present in the final product of human. The level of urea is a crucial biomarker that can assess the metabolic activity of humans such as the liver and renal function. [1] A high level of urea in the urine can result in kidney failure, dehydration, and gastrointestinal bleeding, while a low level can lead to nephritic syndrome, hepatic failure, etc. [2] Therefore, accurate and rapid sensing of urea is essential in a diagnostic clinic. Recently, paper-based analytical devices (PAD) are gaining its popularity as a manageable device for point-of-care equipment due to its inexpensive, portable, disposable, and environmentally-friendly qualities.[3] The majority of electrochemical biosensors rely on enzymes, such as urease; yet, utilization of enzyme is limited due to its high cost, poor reproducibility, and most of all, thermal and chemical instability which can influence the duration of sensor that depends on storage conditions such as temperature, pH, and humidity.[4] In addition, non-enzymatic biosensors has been attracted with the advantage of simplicity, redox flexibility, stability, and low cost. As a non-enzymatic metal-based material, Ni-based nanomaterials exhibited excellent catalytic activity over urea originated from catalytic effect for the formation of the redox couple of Ni(II) and Ni(III) on the surface. [5] When compared to enzymatic-based sensors, non-enzymatic catalysts tend to present lower sensitivity and higher limit of detection corresponding to lower performances of urea biosensor. To address this limit, there have been efforts to modify nanostructures with various shapes such as nanofiber, nanoparticle, and nanoflake arrays. Here we investigated a hollow sphere structure with nanosheet building block by using a hydrothermal method. The hollow sphere structure can increase the selectivity and sensitivity for urea biosensor by providing facile transport channels through electrolyte that exploits its inner and outer surfaces as the active site with maintaining the structural stability of the catalyst. Integration of non-enzymatic hierarchical catalyst on disposable PAD will lead to a high potential for the development of point-of-care testing devices. In this study, a non-enzymatic electrochemical paper-based sensor using hollow structure NiO was developed and demonstrated for the determination of urea. PADs were fabricated by sputtering on cotton paper, and hollow NiO was synthesized by hydrothermal method. Structure and morphologies of hierarchical NiO on PAD were characterized by XRD and SEM. Electrochemical properties such as selectivity and LOD were conducted by using a potentiostat with urea solution. A detailed description of the fabrication process and discussion of structure formation and sensing performances of hollow nickel oxide catalyst will be presented.

Nanoporous nickel oxide catalyst with uniform Ni dispersion for enhanced hydrogen production from organic waste

In this report, we propose magnetically separable porous nickel oxide nanostructure with uniform Ni distribution having the large surface area and atomically dispersed Si sites for enhanced hydrogen production from organic waste. The catalyst showed ten times higher production rate from volatiles during carbonization of organic waste and coal than that in the absence of the catalyst. The reduced Ni/NiO catalyst yielded two times higher hydrogen production compared to the traditional Ni/Al2O3 catalyst. The highest yield of hydrogen over reduced Ni/NiO was 32 g/kgfeed at 600 °C in fixed bed reactor via pyrolysis-reforming of bagasse. The Ni/NiO showed far more efficient recyclability compared to traditional Ni/Al2O3. The economic aspect of the Ni/NiO catalyst was compared with the Ni/Al2O3 catalyst based on H2 yield. TGA and TPO analysis confirmed the presence of amorphous coke.

Oxidative dehydrogenation of ethane on diluted or promoted nickel oxide catalysts: Influence of the promoter/diluter

Ti- and Nb- containing NiO catalysts have been synthesized by two different preparation methods: i) by precipitation (Me-Ni-O oxides, Me = Nb or Ti), in order to prepare promoted NiO catalysts; and ii) by wet impregnation on TiO2 or NbOx supports, in order to prepare diluted/supported NiO catalysts. The catalysts have been also characterized and tested in the oxidative dehydrogenation of ethane. The catalytic performance of Ti- and Nb-promoted catalysts strongly depends on the composition, although in both cases the optimal one is found at similar Ti or Nb loadings (ca. 90 wt% NiO), showing similar ethylene selectivity in the ODH of ethane (ca. 90% at 10–20% ethane conversion). However, in the case of diluted catalysts, the catalytic behavior of Ti- and Nb-containing catalysts is drastically different. Then, over TiO2-diluted NiO catalyst, the highest selectivity to ethylene (ca. 90% selectivity) is achieved at NiO loading of 20 wt.%. However, over Nb2O5-diluted NiO catalyst, selectivity to ethylene was lower than 70%. A discussion on the characteristics of selective catalysts is done. In this case, the best catalysts must present a low concentration of free NiO and TiO2 or Nb2O5 phases, maximizing the Ni-O-Ti or Ni-O-Nb interaction. Interestingly, this takes place at different NiO loading depending on the preparation method and the nature of promoted/diluter. The low selectivity to ethylene achieved by NiO diluted with Nb2O5 has been related to the low interaction of NiO with the surface of Nb2O5, which hinders the elimination of unselective electrophilic O species.

Activating peroxydisulfate by morphology-dependent NiO catalysts: Structural origin of different catalytic properties

Understanding how the morphology of a nanocatalyst tailors its catalytic performance is a crucial issue for the rational design and fabrication of active heterogeneous catalysts at the nanometer level. Herein, we demonstrate novel findings of peroxydisulfate (S2O82−; PDS) activation catalyzed by nickel oxide (NiO) nanocatalysts of different morphologies, in which oxygen vacancies (VO) were the defective sites that facilitated the chemical bonding with PDS molecules and promoted the reactivity of VO-connected nickel ions for PDS activation, thus elucidating the structural origin of its catalytic activities. The morphologically tunable NiO with various VO concentrations exhibited different catalytic performance for the removal of phenol (a model organic pollutant). Based on an electron paramagnetic resonance (EPR) study, radical competition reactions, and quenching tests, the main reactive species was revealed to be the non-radical PDS-NiO complex, which can effectively attack C6H5O− to yield intermediates attached to NiO surface. This work not only improves the fundamental understanding of active sites in morphologically tunable transition metal oxides, but also provides valuable guidelines for the rational design and synthesis of high-performance, morphology-dependent nanocatalysts.

REDUCTION OF p-NITROPHENOL TO p-AMINOPHENOL BY USING NiO CATALYSTS: A COMPARATIVE STUDY

Different nickel oxide catalysts have been prepared by simple precipitation method using different nickel precursors and using surfactant sodium dodecyl sulfate (SDS) or without surfactant. The prepared catalysts have been characterized by using XRD and FT-IR. The particle sizes have been calculated by using the Scherrer equation. The nickel oxide catalyst prepared by using nickel acetate as precursor and surfactant SDS has shown less particle size as compared to other catalysts prepared by using other precursors. Also, nickel oxide catalyst prepared using nickel acetate precursor and surfactant SDS has shown higher catalytic activity for reduction of p-nitrophenol (PNP) to p-aminophenol (PAP) using sodium borohydride (NaBH 4 ). Also, for the said reaction effect of concentration of p-nitrophenol on catalytic efficiency has been studied.

Nickel oxide-silica core-shell catalyst for acetylene hydroxycarbonylation

Acrylic acid and its ester derivatives are important chemicals utilized to synthesize numerous end products. Acrylic acid is industrially produced via propylene oxidation. We report in this study a nickel oxide-silica core-shell catalyst (NiO@SiO2) for acetylene hydroxycarbonylation as an alternative way to synthesize acrylic acid. NiO@SiO2 catalyst provided the higher turnover frequency and yield than commercial nickel oxide catalyst on acetylene hydroxycarbonylation. The carbon monoxide/acetylene ratio influenced more significantly to initial reaction rate than final acrylic acid yield. The silica shell protected the nickel oxide from sintering during reaction, however, the catalyst was deactivated by coke formation, attributed to acetylene decomposition.

Nitrogen-doped Nickel Oxide Catalysts for Oxygen-Evolution Reactions

알칼라인 조건에서의 산소발생 반응(oxygen-evolution reaction: OER)은 다양한 에너지 시스템에 중요한 반응으로 여겨지고 있다. 큰 overpotential을 감소시키기 위해 다양한 촉매들이 개발되고 있으며, 그 중 NiO는 높은 활성도에 대한 가능성으로 인해 연구가 활발하게 진행되고 있다. 촉매의 표면에서 OER에 대한 메커니즘은 정확하게 규명되지는 않았지만, 산화물 촉매에서 Ni 또는 O vacancy와 같은 결함들은 많은 전기화학반응에서 활성점으로 여겨진다. 따라서, 본 연구에서는 nitrogen을 ethylenediamine을 이용하여 NiO의 O위치에 치환하여 Ni vacancy를 형성하고 그로 인해서 OER의 activity와 내구성에 어떠한 영향을 미치는지에 대해 분석해 보았다.