NiO Catalysts Research Articles

Ethane oxydehydrogenation over TiP2O7-supported NiO catalysts

Titanium pyrophosphate-supported NiO catalysts with different Ni loadings in the range from 10 to 26 wt. % were prepared by wet impregnation, characterized by nitrogen adsorption at −196 °C, ICP-OES, XRD, CO2-TPD and H2-TPR techniques and tested in ethane oxydehydrogenation (ODH) in the temperature range from 350 to 450 °C. With increasing the Ni loading, the surface area of the catalysts decreased while the NiO particle size, the basicity and the reducibility increased strongly influencing their catalytic performance. Increasing the Ni loading boosted ethane conversion that reached 36 and 50 % at 425 and 450 °C, respectively, for the highest nickel loading catalyst. Ethylene was the main reaction product for all the catalysts. The ethylene selectivity at isoconversion increases with increasing the Ni loading. The stability of the catalysts was studied at a temperature as high as their calcination temperature, i.e. 450 °C, and at lower temperature.

Carbon doping switching on the hydrogen adsorption activity of NiO for hydrogen evolution reaction

Hydrogen evolution reaction (HER) is more sluggish in alkaline than in acidic media because of the additional energy required for water dissociation. Numerous catalysts, including NiO, that offer active sites for water dissociation have been extensively investigated. Yet, the overall HER performance of NiO is still limited by lacking favorable H adsorption sites. Here we show a strategy to activate NiO through carbon doping, which creates under-coordinated Ni sites favorable for H adsorption. DFT calculations reveal that carbon dopant decreases the energy barrier of Heyrovsky step from 1.17 eV to 0.81 eV, suggesting the carbon also serves as a hot-spot for the dissociation of water molecules in water-alkali HER. As a result, the carbon doped NiO catalyst achieves an ultralow overpotential of 27 mV at 10 mA cm−2, and a low Tafel slope of 36 mV dec−1, representing the best performance among the state-of-the-art NiO catalysts.

In situ X-ray emission and high-resolution X-ray absorption spectroscopy applied to Ni-based bimetallic dry methane reforming catalysts.

The promoting effect of cobalt on the catalytic activity of a NiCoO Dry Methane Reforming (DMR) catalyst was studied by a combination of in situ Kβ X-ray Emission Spectroscopy (XES) and Kβ-detected High Energy Resolution Fluorescence Detected X-ray absorption spectroscopy (HERFD XAS). Following the calcination process, Ni XES and Kβ-detected HERFD XAS data revealed that the NiO coordination in the NiCoO catalyst has a higher degree of symmetry and is different than that of pure NiO/γ-Al2O3. Following the reductive activation, it was found that the NiCoO/γ-Al2O3 catalyst required a relatively higher temperature compared to the monometallic NiO/γ-Al2O3 catalyst. This finding suggests that Co is hampering the reduction of Ni in the NiCoO catalyst by modulation of its electronic structure. It has also been previously shown that the addition of Co enhances the DMR activity. Further, the Kβ XES spectrum of the partly reduced catalysts at 450 °C reveals that the Ni sites in the NiCoO catalyst are electronically different from the NiO catalyst. The in situ X-ray spectroscopic study demonstrates that reduced metallic Co and Ni are the primary species present after reduction and are preserved under DMR conditions. However, the NiCo catalyst appears to always be somewhat more oxidized than the Ni-only species, suggesting that the presence of cobalt modulates the Ni electronic structure. The electronic structural modulations resulting from the presence of Co may be the key to the increased activity of the NiCo catalyst relative to the Ni-only catalyst. This study emphasizes the potential of in situ X-ray spectroscopy experiments for probing the electronic structure of catalytic materials during activation and under operating conditions.

Performance of nickel catalyst toward photocatalytic degradation of methyl orange

In this study, the EGNiO1000 that generated using new green electrolyte Nephelium lappaceum extract via electrochemical system shows excellent photoactivity toward MO degradation up to 96.8% under visible light irradiation compared to EGNiO0, EGNiO50, commercial NiO, and commercial TiO2 catalyst. The presence of bioactive compound such as polyphenols, alkaloids, flavanoids and vitamins. The active component that presence in Nephelium lappaceum such as polyphenols, alkaloids, flavanoids and vitamins, are highly responsible for improving the structural, morphological and optical properties of EGNiO1000, thus lead to the enhancement on the photodegradation activity. Green approach with simple electrochemical system display a great potential to generate of other novel metal catalyst with excellent photoreaction.

Effective photocatalytic degradation of remazol brilliant blue using nickel catalyst

In this study, Nephelium lappaceum extract was used as new electrolyte medium in electrochemical method to generate electro-nickel under two different type of concentrations, which are 50 ppm and 1000 ppm, later will denoted as EGNiO50 and EGNiO1000. Excellent photoactivity of EGNiO1000 toward the photocatalytic degradation of remazol brilliant dye (RBB) was obtained under visible light irradiation compared to EGNiO0, EGNiO50, commercial NiO, and commercial TiO2 catalyst. The presence of bioactive compound in crude extract is believed to activate and improve the structural and morphological properties of catalyst, thus enhance the photodegradation activity. Green system of electrochemical method that only use crude extract as electrolyte displays great potential to generate of other novel metal catalyst with excellent photoreaction.

A highly efficient and stable Ni/SBA-15 catalyst for hydrogen production by ethanol steam reforming

The production of hydrogen by steam reforming of ethanol was carried out on SBA-15-supported nano NiO catalyst synthesized by the equivalent-volume impregnation method with two different Ni sources (nickel nitrate and nickel sulfamate). The catalyst was characterized by N2 adsorption–desorption, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy to examine the physical and chemical properties. The activity tests were performed with the steam, with water/ethanol molar ratio ranging from 2:1 to 15:1, the N2 flow rate from 20 to 120 mL min−1 to determine the space-time, and the temperature range from 623 to 923 K on the two different Ni source catalysts. A favorable operating condition was established at 823 K using water/ethanol = 6 molar ratio and carrier gas (N2) flow of more than 50 mL min−1 for nickel nitrate source, but for nickel sulfamate source, the optimum temperature changed to 773 K and other conditions were the same as for the nickel nitrate source. After eliminating the influence of internal and external diffusion factors, an empirical power-law kinetic rate equation was derived from the experimental data. The non-linear regression method was used to estimate the kinetic parameter. The activation energy of the catalyst was then calculated, and the supported nickel nitrate and nickel sulfamate catalysts were 25.345 and 41.449 kJ mol−1, respectively, which was in agreement with the experimental and model-predicted results.

The effect of NiO catalyst on reduction, synthesis and binder content of TiC-Ni nanocomposite

In the present study, synthesis of TiC-Ni nanocomposite via magnesiothermic method was investigated. The effects of catalyst content on the mechanisms of TiO2 reduction and synthesis of TiC-Ni nanocomposite were evaluated. For this purpose, the powder mixture was milled at different NiO content. By adding 0.1–0.3 at.% NiO to the mixture and milling after combustion, it was found that the synthesis did not completely occur. In 0.4 at.% NiO to the mixture, the synthesis was completed and after leaching pure TiC was synthesis. Additionally, the effect of NiO on the binder content composite synthesis was examined. It was observed by increasing NiO content, combustion time decreased and Ni content in nanocomposite increased. TEM observations confirmed for 0.4 at.% NiO at initial powder pour TiC with spherical morphology and for >0.5 at.% NiO at initial powder TiC-Ni nanocomposite with semi- spherical morphology was synthesis.

Optimum Band Gap Energy of ((Ag),Cu)(InGa)Se2 Materials for Combination with NiMo–NiO Catalysts for Thermally Integrated Solar-Driven Water Splitting Applications

Solar-driven water splitting is considered one of the promising future routes to generate fuel in a sustainable way. A carbon-free solar fuel, molecular hydrogen, can here be produced along two different but intimately related routes, photoelectrochemical (PEC) water splitting or photovoltaic electrolysis (PV-electrolysis), where the latter builds on well-established solar cell and electrolysis materials with high efficiency. The PV-electrolysis approach is also possible to construct from an integrated PEC/PV-system avoiding dc–dc converters and enabling heat exchange between the PV and electrolyzer part, to a conventionally wired PV-electrolysis system. In either case, the operating voltage at a certain current needs to be matched with the catalyst system in the electrolysis part. Here, we investigate ((Ag),Cu)(In,Ga)Se2 ((A)CIGS)-materials with varying Ga-content modules for combination with NiMo–NiO catalysts in alkaline water splitting. The use of (A)CIGS is attractive because of the low cost-to-performance ratio and the possibility to optimize the performance of the system by tuning the band gap of (A)CIGS in contrast to Si technology. The band gap tuning is possible by changing the Ga/(Ga + In) ratio. Optoelectronic properties of the (A)CIGS materials with Ga/(Ga + In) ratios between 0.23 and 0.47 and the voltage and power output from the resulting water splitting modules are reported. Electrolysis is quantified at temperatures between 25 and 60 °C, an interval obtainable by varying the thermal heat exchange form a 1-sun illuminated PV module and an electrolyte system. The band gaps of the (A)CIGS thin films were between 1.08 to 1.25 eV and the three-cell module power conversion efficiencies (PCE) ranged from 16.44% with 1.08 eV band gap and 19.04% with 1.17 eV band gap. The highest solar-to-hydrogen (STH) efficiency was 13.33% for the (A)CIGS–NiMo–NiO system with 17.97% module efficiency and electrolysis at 60 °C compared to a STH efficiency of 12.98% at 25 °C. The increase in STH efficiency with increasing temperature was more notable for lower band gaps as these are closer to the overpotential threshold for performing efficient solar-driven catalysis, while only a modest improvement can be obtained by utilizing thermal exchange for a band gap matched PV-catalysts system. The results show that usage of cost-effective and stable thin film PV materials and earth abundant catalysts can provide STH efficiencies beyond 13% even with PV modules with modest efficiency.

Catalytic Fast Pyrolysis of Forestry Wood Waste for Bio-Energy Recovery Using Nano-Catalysts

Fast pyrolysis is envisioned as a promising technology for the utilization of forestry wood waste (e.g., widely available from tree logging) as resources. In this study, the potential of an innovative approach was explored to convert forestry wood waste of Vernicia fordii (VF) into energy products based on fast pyrolysis combined with nano-catalysts. The results from fast pyrolysis using three types of nano-catalysts showed that the distribution and composition of the pyrolytic product were affected greatly by the type of nano-catalyst employed. The use of nano-Fe2O3 and nano-NiO resulted in yields of light hydrocarbons (alkanes and olefins) as 38.7% and 33.2%, respectively. Compared to the VF sample, the use of VF-NiO and VF-Fe2O3 led to significant increases in the formation of alkanes (e.g., from 14% to 26% and 31%, respectively). In addition, the use of nano-NiO and nano-Fe2O3 catalysts was found to promote the formation of acid, aromatics, and phenols that can be used as chemical feedstocks. The NiO catalyst affected the bio-oil composition by promoting lignin decomposition for the formation of aromatics and phenolics, which were increased from 9.52% to 14.40% and from 1.65% to 4.02%, respectively. Accordingly, the combined use of nano-catalysts and fast pyrolysis can be a promising technique for bio-energy applications to allow efficient recovery of fuel products from forestry wood waste.

Solvent Effect on the Solvothermal Synthesis of Mesoporous NiO Catalysts for Activation of Peroxymonosulfate to Degrade Organic Dyes.

In this work, we successfully prepared three different mesoporous NiO nanostructures with preferential (111) planes using three different solvents–water, a water–ethanol mixture, and a water–ethylene glycol mixture. The NiO nanosheets prepared from the water–ethylene glycol mixture and denoted as NiO-EG showed a nanosheet morphology thinner than 10 nm, whereas the water–ethanol and water samples were 30–40 nm and above 100 nm thick, respectively. The NiO-EG catalyst was found to exhibit a high catalyzing ability to activate peroxymonosulfate (PMS) for decoloring dyes, by which 94.4% of acid orange 7 (AO7) was degraded under the following reaction conditions: AO7 = 50 mg/L, catalyst = 0.2 g/L, PMS = 0.8 g/L, pH = 7, and 30 min reaction time. The dye degradation rate was investigated as a function of the catalyst dosage, pH, and dye concentration. According to quenching experiments, it was found that SO4•–, HO•, and O2•– were the dominant radicals for AO7 degradation, and oxygen vacancies played a significant role in the generation of radicals. High surface area, thin flaky structure, rich oxygen vacancies, fast charge transport, and low diffusion impedance all enhanced the catalytic activity of NiO-EG, which exhibited the highest degradation ability due to its abundant accessible active sites for both adsorption and catalysis.

The effects of doping alumina with silica in alumina-supported NiO catalysts for oxidative dehydrogenation of ethane

Abstract The production of ethylene via the oxidative dehydrogenation of ethane is well-documented as an energy efficient process. Alumina-supported NiO catalysts make the oxidative dehydrogenation of ethane more selective to ethylene and operate at low reaction temperatures ( × 10−2 μmolethylene/s·m2 at 500 °C.

Resource utilization of waste deNOx catalyst for continuous-flow catalysis by supported metal reactors

Resource utilization of waste deNOx catalysts has become a major demand. A new resource path for continuous-flow catalysis using the waste deNOx catalysts (V2O5-WO3/TiO2, CeO2-WO3/TiO2 and MnO2-CeO2/TiO2) as carriers was proposed. The waste deNOx catalysts supported NiO catalysts prepared by an in-situ preparation method were used to investigate continuous-flow nanocatalysis of p-nitrophenol reduction. The result showed that the MnO2-CeO2/TiO2 supported NiO (Ni/TMC) exhibited excellent catalytic performance in the catalytic reduction of p-nitrophenol (4-NP). The conversion of 4-NP (2.5 mM) reached nearly 100% at the injection speed of 1.5 mL·min−1. It maintained 100% conversion after 10 recycling time since waste deNOx catalysts could reduce aggregation for NiNPs. Furthermore, high oxygen vacancy, chemisorbed oxygen, and the strong interaction between Ni and waste deNOx catalyst resulted in a highly efficient, recoverable and cost-effective multifunctional reactor. All of these advantages present the opportunity to be implemented in the field of wastewater treatment and environmental toxicology.

Resource utilization of waste V2O5-based deNOx catalysts for hydrogen production from formaldehyde and water via steam reforming

The harmless disposal of abandoned and toxic V2O5(WO3)/TiO2 (VWT) deNOx catalysts has become a worldwide great demand, a new resource path for hydrogen production from steam reforming of formaldehyde and water using the waste VWT deNOx catalysts as catalyst carriers was proposed. The waste V2O5-based catalysts supported NiO (N/VWT) catalysts prepared by impregnation method were comparatively studied for hydrogen production. The H2 and CO selectivity of the optimum N/VWT separately reached 100% and 72.5%, and the formaldehyde conversion of the N/VWT reached 86.3% at 400 ℃ and higher than 93.0% at 450–600 ℃. Analysis showed that the hydroxyl species played the most important role, and its richness determined the catalytic performance directly. The high acid sites and excellent redox properties were beneficial to enhance the catalytic performance. The in situ DRIFT study verified that the hydrogen bonds between formate species and hydroxyl groups reduced reaction steps, which accelerated the progress of the reaction. The adsorbed formaldehyde transformed to formate species firstly, and then produced H2 and CO2 (or CO) by dehydrogenation. Ultimately, the resource utilization path not only completely solved the harmless problems of the waste V2O5-based deNOx catalysts and formaldehyde, but also contributed to the hydrogen production.

Study on the fast pyrolysis of oil sludge by PY-GC/MS

Oil sludge is an organic solid waste produced in oilfield exploitation, transportation, and petroleum refineries. Pyrolysis is one of the most effective ways to reduce oil sludge and realize energy re-utilization. In the present work, the amounts and distributions of pyrolysis products at different reaction time and with different amounts of NiO catalyst were investigated with PY-GC/MS. The results suggest that the degree of the pyrolysis reaction increased and more macromolecules were degraded into smaller hydrocarbons as the reaction time prolonged. The addition of NiO catalyst effectively promoted the conversion of aromatic and paraffin products, and increased the production of small molecule olefins.

High surface area SiC(O)‐based ceramic by pyrolysis of poly (ethylene glycol) methacrylate‐modified polycarbosilane

AbstractIn the present work, a high surface area SiC(O)‐based ceramic powder was synthesized upon thermal transformation of a polymer‐derived macromolecular precursor, which was obtained by the chemical modification of a allylhyldrido polycarbosilane with poly(ethylene glycol) methaacrylate under argon environment. The pyrolysis of developed precursor led to the formation of amorphous and high surface area SiC(O)‐based ceramic powder with in situ generated micro/meso‐porosity. The specific surface area of the obtained powders depends on the processing temperature. It decreases from 363 to 122 m2/g as the pyrolysis temperature increases from 600 to 1200°C, respectively. Furthermore the promising samples were fabricated using pressing technique, which led to crack‐free SiC(O) monoliths on subsquent heat treatment. The present study also emphasizes the potential of produced SiC(O) ceramic powder to support NiO catalyst. The impregnation method were used to produce high surface area NiO@SiC(O) ceramic powder (NiO as a catalyst; SiC(O) as a catalyst support) for further catalytic applications. Interestingly, the distribution of the NiO was shown to strongly depend on the oxygen content present in the SiC(O) matrix. Thus, larger oxygen contents induce homogeneously distributed flower‐like NiO catalyst onto SiC(O).

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.

Efficient nonthermal plasma degradation of toluene over NiO catalyst with limited NOx generation

A problem encountered during nonthermal plasma destruction of pollutants in gas streams containing air is that high levels of nitrogen oxides may also be formed as a consequence of the complex processing conditions. In the work presented herein, a post nonthermal plasma catalytic system was evaluated for removal of toluene gas. NiO/γ-Al2O3 catalysts with different NiO loadings were prepared via the traditional impregnation method and their activity determined under certain conditions. The effects of the specific input energy (SIE), catalyst calcination temperature, and NiO loading on the toluene degradation were investigated. The catalyst prepared by calcination at 450 °C showed the highest activity. The catalytic activity of the catalysts first increased then decreased with increasing NiO loading, with the maximum toluene conversion of 93 % being achieved by 1.25 wt% NiO/γ-Al2O3 at 200 ppm. Meanwhile, the amount of NOx produced during the reaction was investigated. In the reaction process, a very small amount of NOx was produced, indicating that the catalyst is green and efficient.

Development of Supported NiO Nanocluster for Aerobic Oxidation of 1-Phenylethanol and Elucidation of Reaction Mechanism via X-ray Analysis

Abstract Supported NiO nanocluster catalysts were synthesized by using Ni colloid as a precursor and applied to the aerobic oxidation of 1-phenylethanol. Obtained catalysts were characterized through X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS) and in situ X-ray diffraction (XRD). Activated carbon (AC) supported NiO nanocluster catalyst showed catalytic activity toward the aerobic oxidation of 1-phenylethanol without any additives. Only the AC support allowed the NiO catalyst to be active although other supports did not. XAFS and in situ XRD revealed that NiO nanocluster was fixed on the supports successfully. XAFS and XPS gave information about differences in the local structure, chemical state and electronic state of Ni among the different supports. The obtained catalyst showed activity more effectively compared to conventional nickel-based catalysts.

Pinpointing the active sites and reaction mechanism of CO oxidation on NiO.

Exploring the active sites and reaction mechanisms of CO oxidation on metal oxides is of great significance in the field of heterogeneous catalysis. NiO has been attracting increasing attention in this field due to its high performance and low cost. Nevertheless, the active sites and reaction mechanism of NiO still remain controversial due to the complexity of the experiments involved, the limitations of characterization techniques, and the difficulty in searching for the global reaction pathway in theory. In this work, terraced and stepped NiO(100) surfaces, with and without oxygen vacancies, were established based on the Wulff construction, and the active sites and reaction mechanism were revealed at the atomic level using a novel global pathway searching method. Theoretical results indicate that the coordination-unsaturated Ni ions are the active sites for CO oxidation; O2 interacts with the low-coordinated Ni ions to form reactive oxygen species; then they react with CO to form CO2; oxygen species on stepped NiO(100) have a low barrier and sustain a catalytic cycle. The present work reveals that the best direction for the design and development of NiO-based catalysts with high performance is to prepare NiO catalysts with more defects and low-coordinated Ni ions. We anticipate that the approach adopted in this work can be applied to a wide range of heterogeneous catalysts for exploring the active sites and mechanisms.

Effect of chemical vapor deposition parameters on the diameter of multi-walled carbon nanotubes

The multi-walled carbon nanotubes (MWCNTs) with controlled diameter distribution are useful in the fabrication of composite materials as reinforcement, due to their superior strength and toughness. Chemical vapor deposition (CVD) is a viable process to synthesize MWCNTs. In this investigation, an attempt has been made to study the effect of CVD process parameters (reaction temperature, flow rate of precursor gas, process time) on the mean diameter of MWCNTs. The MWCNTs of controlled diameter distribution was selectively grown on NiO catalyst supported by Al2O3 nano particles. The argon and acetylene were used as carrier and carbon precursor gas, respectively. The catalyst and carbon samples were characterized using field emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy and thermogravimetric/differential thermal analysis. From this investigation, it is understood that the increase in reaction temperature and flow rate of precursor gas increased the mean diameter of MWCNTs but increase in process time decreased the diameter. The diameter distribution and quality of MWCNTs are strongly influenced by the diameter of the catalyst particles.