Presence Of NiO Research Articles

Transparent (Ni,Au)/ZnO:Al-Based Ohmic Contacts to p-Type GaN as an Insight into the Role of Ni and Au in Standard p-Type GaN Contacts.

In this work, Ni/ZnO:Al and Au/ZnO:Al structures are proposed as efficient ohmic contacts to p-GaN. Through a careful selection of deposition parameters and annealing environment, we not only achieve the formation of high-quality ohmic contacts but also gain insights into the interfacial reactions, enhancing the understanding of conventional Ni/Au contact formation on p-GaN. In particular, the notion that the presence of NiO at the interface is enough for an ohmic contact to form is challenged by showing that in fact it has to be NiO formed at the interface from metallic Ni and additional oxygen. An Au-based ohmic contact is also presented, and its formation mechanism is explained, contrary to popular knowledge that Au does not form an ohmic contact with p-GaN. The obtained contacts are low resistivity, with contact resistances of 4.77 × 10-3 Ω·cm2 and 3.34 × 10-3 Ω·cm2 for Au-based and Ni-based ones, respectively. What is also important is that we show these oxide-based contacts with metallic interlayers give lower series resistances in simplified diode structures than a standard Ni/Au-based contact, making them promising for optoelectronic devices.

Manufacturing of heavy tungsten alloys from nano-sized metal oxides via simultaneous reduction-sintering powder treatments

Heavy tungsten alloys are of great importance in the engineering and mining industries as well as the military and medical applications because of their stability at high temperatures, high strength and dense structures. The present study develops a novel technology for the production of heavy tungsten alloys via thermal treatment of nano-sized metal oxides based on simultaneous reduction and sintering processes. Heavy tungsten alloy (95W-3Ni-2Fe) was produced from the reduction of mixed nano-sized metal oxides precursor in H2 at 1000 o C followed by sintering at 1350–1450 o C for 30–90 min. The reduced and sintered samples were characterized by XRD to follow up the crystallinity, total porosity measurement was used to find out the densification properties, the grain structure and morphology were examined by RLM and SEM attached with EDAX. Micro-hardness tester was also used to investigate the influence of sintering conditions on the grain densification. A fundamental study on the kinetics of reduction of mixed nano-sized metal oxides precursor was performed by isothermal and non-isothermal techniques. Both results from isothermal and non-isothermal tests were used to calculate the activation energy which was correlated with macro- and micro-structures to predict the corresponding reduction mechanism. However, the influence of sintering temperature and time on the crystallinity of the produced phases, grain structure, morphology, total porosity, pore-size distribution, bulk and apparent densities, and the hardness of sintered compacts was extensively investigated. The results revealed that the presence of NiO and/or Fe2O3 in the mixed metal oxides precursor was very important to ease the reducibility of WO3 as the metallic phases of Ni and/or Fe act as a catalyst for the reduction of WO3. The rate of reduction proceeds faster in the following order: NiO > Fe2O3 > mixed oxide > WO3. In non-isothermal experiments, it was found that the heating rate has a considerable effect on the reduction of precursor, i.e., the lower the heating rate, the higher the degree of reduction. It might be reported that the use of nano-sized metal oxides particles in the fabrication of heavy tungsten alloys greatly affects the main properties of the produced alloy. With the increase in sintering time, larger sizes of dense grains were developed, and the matrix became denser as a result of sintering and re-crystallization effects. The higher the sintering time, the higher the grain densification and the less pores formed in the matrix. On the other hand, with the increase in the sintering temperature, the grain boundaries were well defined in which the grains were composed of tungsten metal and surrounded by inter-metallics. The higher the temperature, the higher the XRD peak intensities of metallic tungsten and intermetallics as a result of sintering and re-crystallization.

Transformation of Graphite Recovered from Batteries into Functionalized Graphene-Based Sorbents and Application to Gas Desulfurization.

The recycling and recovery of value-added secondary raw materials such as spent Zn/C batteries is crucial to reduce the environmental impact of wastes and to achieve cost-effective and sustainable processing technologies. The aim of this work is to fabricate reduced graphene oxide (rGO)-based sorbents with a desulfurization capability using recycled graphite from spent Zn/C batteries as raw material. Recycled graphite was obtained from a black mass recovered from the dismantling of spent batteries by a hydrometallurgical process. Graphene oxide (GO) obtained by the Tour's method was comparable to that obtained from pure graphite. rGO-based sorbents were prepared by doping obtained GO with NiO and ZnO precursors by a hydrothermal route with a final annealing step. Recycled graphite along with the obtained GO, intermediate (rGO-NiO-ZnO) and final composites (rGO-NiO-ZnO-400) were characterized by Wavelength Dispersive X-ray Fluorescence (WDXRF) and X-ray diffraction (XRD) that corroborated the removal of metal impurities from the starting material as well as the presence of NiO- and ZnO-doped reduced graphene oxide. The performance of the prepared composites was evaluated by sulfidation tests under different conditions. The results revealed that the proposed rGO-NiO-ZnO composite present a desulfurization capability similar to that of commercial sorbents which constitutes a competitive alternative to syngas cleaning.

Interdiffusion at electrochemical interfaces between yttria-stabilized zirconia and doped ceria

Integration of doped ceria into fuel electrode-supported solid oxide cells is challenging due to high sintering temperatures leading to undesirable interdiffusion between the layers. We investigate the influence of the dopant in ceria X0.1Ce0.9O1.95 (10XDC, X = Y, Gd or Sm) on the interdiffusion with yttria-stabilized zirconia (8YSZ). Powder mixtures of 8YSZ and 10XDC were sintered at temperatures between 1000–1400 °C to quantify the phase formation. Interdiffusion in layered systems sintered at 1400 °C was investigated by SEM. Symmetrical Ni-10XDC cells with an 8YSZ electrolyte were analyzed using impedance spectroscopy. Despite small differences in the interdiffusion behavior, different dopants do not lead to significant changes in the cell impedance. Notably, the presence of NiO in the fuel electrode leads to enhanced interdiffusion kinetics of 10XDC with 8YSZ and the formation of porosity at the electrolyte interface. The detrimental influence of these microstructural changes on the electrode performance was investigated.

Performance optimization of Ca2Fe2O5 oxygen carrier by doping different metals for coproduction syngas and hydrogen with chemical looping gasification and water splitting

This work focused on the potential effects of different metals (Co/Al/Ni/Ce) on the chemical looping performance of brownmillerite-structured Ca2Fe2O5 for syngas and hydrogen production. Oxygen carriers (OC) were prepared by the sol-gel method. The presence of NiO and CeO2 phases in fresh Ca2Fe2O5 samples indicated that Ni and Ce were not fully doped into the brownmillerite structure. The oxides of Al and Co were not detected in the fresh Ca2Fe2O5 sample, indicating that the Al and Co were doped into the brownmillerite structure. The introduction of Ni and Co decreased the reduction temperature and increased the reduction rate of OC. However, the increase in reactivity with Ni-modified OC is mainly due to the high reactivity of the NiO phase. The presence of Al and Ce inhibited the reduction of Ca2Fe2O5 and decreased the oxygen transport capacity, which is beneficial for syngas production but leads to a lower H2 production in the steam reactor (SR). The Co-modified Ca2Fe2O5 exhibited better resistance to carbon deposition and increased the H2 production in SR. When the ratio of Ca:Fe:Co equals 2:1.5:0.5, the formation of Ca2Co0.5Fe1.5O5 exhibited the highest hydrogen yield and purity of 10.92 mmol/g OC and 99.32%, respectively. In addition, the Ca2Co0.5Fe1.5O5 showed almost stable reactivity over the 5 reaction cycles.

Enhancing Biofuel Production Through Nanoparticle-assisted Fermentation: A Comparative Study

Nanoparticles have many applications in various fields, including biofuel technology, and rising demands for energy and increased harmful environmental impacts of fossil fuel have increasing interest towards biofuel as an alternative eco-friendly source of energy and ethanol blended petrol. The production of ethanol from agricultural waste (rice straw) and banana plant residue with biological approach is an important step toward energy sustainability and in minimizing greenhouse gases emissions. A promising approach, the use of nanoparticles to assist fermentation. The process enhances biofuel production by incorporation of nanoparticles in fermentation process. The purpose of this research paper is to explore the application of nanoparticle-assisted fermentation for enhanced biofuel production. This study explains the process of ethanol production by Saccharomyces cerevisiae in the presence of NiO and Fe3O4 nanoparticles. This study investigates the Comparative analysis of cost and yield production of ethanol production through the fermentation with and without Nanoparticles. The outcomes of this research offer valuable insights into how employing nanoparticles to assist fermentation can strengthen the process and potentially drive advancements in biofuel technologies.

Effects of NiO, SnO2, and Ni-doped SnO2 semiconductor metal oxides on the oxygen sensing capacity of H2TPP

Improving the performance of optical oxygen sensors can be accomplished by adding metal oxide semiconductors (MOSs) additives to the composition comprising an oxygen-sensing agent immobilized in a polymeric thin film. For several decades, MOSs have attracted great interest in gas sensors due to their high sensitivity to many target gasses. Herein, meso-tetraphenylporphyrin (H2TPP) dye was immobilized into the poly(1-trimethylsilyl-1-propyne) (poly(TMSP)) silicone rubber in the presence of NiO, SnO2, Ni:SnO2 metal oxide particles as additives, and their thin films were prepared to investigate oxygen-sensitive optical chemical sensor properties. The characterizations of the synthesized metal oxide powders were carried out through XPS, XRD, FT-IR, PL spectroscopy and SEM methods. Intensity-based spectra and decay kinetics of H2TPP-based thin films were investigated for the concentration range of 0%–100% [O2]. The oxygen sensitivity (I0/I100) of the porphyrin was calculated as 70%. Whereas the relative signal intensity values of H2TPP-based sensor slides were measured as 75%, 80%, and 88% in the presence of NiO, SnO2, Ni:SnO2 additives, respectively. The H2TPP in combination with Ni:SnO2 semiconductor provided a higher I0/I100 value, larger response range, higher Stern-Volmer constant (KSV) value, and faster response time compared to the undoped form, and also NiO and SnO2 additive-doped forms of H2TPP. The response and the recovery times of the porphyrin-based sensing slide along with Ni:SnO2 additives have been measured as 12 and 50 s. These results make the H2TPP along with the MOSs promising candidates as oxygen probes.

Fabrication of a YSZ electrolyte layer via co-pressing/co-sintering for tubular NiO-YSZ anode-supported SOFCs

• A simple and effective method to fabricated semi-cells of tubular Ni-YSZ anode-supported electrolyte film is proposed. • The method is the combination of centrifugal deposition, co-pressing and co-sintering techniques. • The YSZ films are dense with the thickness of 21.4∼27.3 μm. A simple and effective method to fabricated semi-cells of tubular NiO-YSZ anode-supported electrolyte film is proposed. This method is the combination of centrifugal deposition technique, cold isostatic co-pressing and co-sintering. The X-ray diffraction patterns showed that the presence of NiO and YSZ, and YSZ grains of electrolyte film grow preferentially on (2 2 0), (3 1 1), (2 2 2), (4 0 0). The YSZ films are dense with the thickness of 21.4∼27.3 μm. At 1400℃, the YSZ crystallite size in the electrolyte film is largest with the size of ∼4.6 μm, which confirms the crystallite growth during co-sintering. The EDX mapping at the same location of EDS further reveals the presence of O, Ni, Y and Zr in the calcined powders.

Dimensionally stable anodes for the oxygen evolution reaction: Ruthenium dioxide on a nickel metal substrate

Dimensionally stable anodes (DSA) for the oxygen evolution reaction (OER) gradually passivate under operating conditions due to the formation of insulating TiO2 at the interface of the Ti-metal substrate and the catalytically active metal oxide layer (typically a mixture of ruthenium and iridium oxides). The incorporation of a catalytically active, yet stable, interfacial buffer layer or substrate is a potential means of promoting the overall performance. Here, we prepared DSA-like RuO2 on Ni films by the thermal decomposition method and contrast their OER activity with an analogous RuO2 on Ti-metal film. The fabrication process resulted in the presence of NiO and Ni oxides/(oxy)hydroxides at the surface of the rutile RuO2 layer. Along with RuO2, the former species were active in the water splitting reaction under the testing conditions. Ni–RuO2 films showed lower OER overpotentials relative to Ti–RuO2 suggesting a synergistic effect between Ni- and Ru-oxides and the Ni layer between Ti and RuO2 to improve overall performance. Further studies should optimize the NiO–RuO2 loading levels, understand the NiO–RuO2 synergy toward catalytic performance and determine the stability under accelerated testing conditions.

Bio-waste eggshell membrane assisted synthesis of NiO/ZnO nanocomposite and its characterization: Evaluation of antibacterial and antifungal activity

This paper presents the synthesis of NiO/ZnO nanocomposite using a bio-waste eggshell membrane as a template, which is used to control the particle size. It is a two-step process, soaking followed by the calcination method. The synthesized NiO/ZnO nanocomposite was characterized by the following techniques: Powdered X-ray diffraction analysis (PXRD), Ultra-Violet Visible spectroscopy (UV–Visible), Fourier transformed infra-red spectroscopy (FT-IR), Raman spectroscopy, Dynamic Light Scattering analysis (Zeta potential & particle size), Field Emission Scanning Electron Microscope (FE-SEM) with Energy Dispersive X-ray Analysis (EDX), and Hi-ResolutionTransmission electron microscope (HR-TEM) respectively. The NiO/ZnO nanocomposite exists in both face-centered cubic (NiO) and hexagonal wurtzite (ZnO) structures, according to PXRD results. The crystallite size was equal to 14.12 nm (NiO) and 14.70 nm (ZnO). The UV–Visible spectrum showed the wavelength at 302 nm and 372 nm, which indicates the presence of NiO and ZnO. The peaks at 449 cm−1 and 550 cm−1 are due to the stretching vibration of (Ni-O) NiO2 octohedral in the cubic NiO and the stretching vibration of ZnO. A Raman vibrational mode confirms the formation of the NiO/ZnO nanocomposite. The zeta potential analysis of the NiO/ZnO nanocomposite was equal to −42.7 mV, which indicates good stability, and the particle size distribution was equal to be 205.8 nm with a polydispersity index value of 0.5940. The SEM images of the NiO/ZnO nanocomposite appeared aggregated with small rods. The EDX spectra confirmed the presence of nickel, oxygen, and zinc, respectively. TEM images of the NiO/ZnO nanocomposite showed the particle size is less than 50 nm. The synthesized NiO/ZnO nanocomposite was subjected to antibacterial and antifungal activity by the agar-well diffusion method. The results demonstrated that the zone of inhibition of NiO/ZnO nanocomposite was high in Bacillus subtilis (30 ± 0.88 mm) for bacterial pathogens and Aspergillus terreus (30 ± 0.0 mm) for fungal pathogens, respectively. The minimum inhibition concentration (MIC) of NiO/ZnO nanocomposite was tested for bacterial pathogens. The results showed that the synthesized NiO/ZnO nanocomposite inhibited cell growth even at the lowest concentration (9.37 μg/mL). So it is inferred that the NiO/ZnO nanocomposite could act as an antifungal and antibacterial agent for a wide range of diseases.

Enhanced Self-Assembled Monolayer Surface Coverage by ALD NiO in p-i-n Perovskite Solar Cells.

Metal halide perovskites have attracted tremendous attention due to their excellent electronic properties. Recent advancements in device performance and stability of perovskite solar cells (PSCs) have been achieved with the application of self-assembled monolayers (SAMs), serving as stand-alone hole transport layers in the p-i-n architecture. Specifically, phosphonic acid SAMs, directly functionalizing indium–tin oxide (ITO), are presently adopted for highly efficient devices. Despite their successes, so far, little is known about the surface coverage of SAMs on ITO used in PSCs application, which can affect the device performance, as non-covered areas can result in shunting or low open-circuit voltage. In this study, we investigate the surface coverage of SAMs on ITO and observe that the SAM of MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid) inhomogeneously covers the ITO substrate. Instead, when adopting an intermediate layer of NiO between ITO and the SAM, the homogeneity, and hence the surface coverage of the SAM, improve. In this work, NiO is processed by plasma-assisted atomic layer deposition (ALD) with Ni(MeCp)2 as the precursor and O2 plasma as the co-reactant. Specifically, the presence of ALD NiO leads to a homogeneous distribution of SAM molecules on the metal oxide area, accompanied by a high shunt resistance in the devices with respect to those with SAM directly processed on ITO. At the same time, the SAM is key to the improvement of the open-circuit voltage of NiO + MeO-2PACz devices compared to those with NiO alone. Thus, the combination of NiO and SAM results in a narrower distribution of device performance reaching a more than 20% efficient champion device. The enhancement of SAM coverage in the presence of NiO is corroborated by several characterization techniques including advanced imaging by transmission electron microscopy (TEM), elemental composition quantification by Rutherford backscattering spectrometry (RBS), and conductive atomic force microscopy (c-AFM) mapping. We believe this finding will further promote the usage of phosphonic acid based SAM molecules in perovskite PV.

Albemarle catalysts reports 1Q 2021 sales growth

The speciation of Ni in spent Fluid Catalytic Cracking catalysts is studied. Carefully performed XRD analyses with NiO/SiO2 samples used as calibration standards, demonstrate that the presence of NiO as a separate phase is reliably detected also for NiO concentration close to 0.1 wt% (1000 ppmw). Actually, both on real spent FCC catalysts (ECAT's) and on artificially contaminated industrial FCC catalysts, NiO is not detectable as a separate phase, even after contamination of the order of 15,000 ppmw of Ni. SEM–EDS experiments provide evidence of a largely preferential location of Ni on alumina particles present in the FCC catalyst mixture, thus acting as “nickel traps”. XRD, UV–vis and TPR data confirm that Ni deposits on alumina particles forming a hardly reducible surface and subsurface layer, giving rise to a solid whose composition is NixAl2O3+x with x << 0.25. As a result of this, the formation of extended Ni metal particles in the raiser reactor is avoided, being their unwanted dehydrogenation activity essentially eliminated. The absence of bulk NiO in the spent FCC catalysts (at least when Ni content is in the range 2000–10,000 ppmw) allows the classification of this material as a non-hazardous waste.

Synthesis of MnO/C/NiO-Doped Porous Multiphasic Composites for Lithium-Ion Batteries by Biomineralized Mn Oxides from Engineered Pseudomonas putida Cells.

A biotemplated cation-incoporating method based on bacterial cell-surface display technology and biogenic Mn oxide mineralization process was developed to fabricate Mn-based multiphasic composites as anodes for Li-ion batteries. The engineered Pseudomonas putida MB285 cells with surface-immobilized multicopper oxidase serve as nucleation centers in the Mn oxide biomineralization process, and the Mn oxides act as a settler for incorporating Ni ions to form aggregates in this process. The assays using X-ray photoelectron spectroscopy, phase compositions, and fine structures verified that the resulting material MnO/C/NiO (CMB-Ni) was porous multiphasic composites with spherical and porous nanostructures. The electrochemical properties of materials were improved in the presence of NiO. The reversible discharge capacity of CMB-Ni remained at 352.92 mAh g−1 after 200 cycles at 0.1 A g−1 current density. In particular, the coulombic efficiency was approximately 100% after the second cycle for CMB-Ni.

Synthesis of porous and homogeneous Ni/Al2O3 cryogel for CO2 reforming of CH4

Nickel–alumina cryogel was prepared from aluminium sec-butoxide and nickel acetate by one-pot sol–gel processing and subsequent freeze drying. Catalysis for CO2 reforming of CH4 and carbon formation during the reforming were examined on the cryogel by comparison to those on the corresponding xerogel catalyst prepared by employing normal drying in order to evaluate the utility of the freeze drying. While the catalytic activity was not different significantly between the two sol–gel catalysts, carbon formation was suppressed more markedly on the cryogel than on the xerogel. The surface area and pore volume of the catalyst after the calcination and after the subsequent high-temperature reduction were larger for the cryogel than for the xerogel. XRD, UV-visible, FT-IR, and Raman spectra suggested the principal formation of NiAl2O4 after the calcination for both catalysts, whereas the presence of NiO, leading finally to large nickel particle, was suggested for the xerogel although it may be a small portion. Mean diameter of nickel particles estimated from TEM and XRD showed smaller size for the cryogel than for the xerogel. These results suggested that role of the freeze drying was to improve structural and textual properties of alumina gel as well as to give finer nickel particles throughout the gel.

Surface treatment of titanium by in-situ anodizination and NiO photodeposition: enhancement of photoelectrochemical properties for water splitting and photocathodic protection of stainless steel

Chromium-doped TiO2 nanotubes (CT) film on titanium substrates was prepared by an in-situ electrochemical anodizing method and then a wide range time was used for photodeposition of NiO on the surface of CT to optimize the condition for the fabrication of NiO-chromium-doped TiO2 nanotubes (NCT). Various techniques were used to characterization which confirms the anatase form of TiO2 as well as the presence of NiO. The UV–Vis spectra exhibit that deposited of NiO on the surface of CT progressively enhances visible light absorption. Photoelectrochemical performance of as-prepared samples was studied in the presence and absence of light which showed that NCT samples are markedly beneficial for reducing photo generated charges recombination. NCT2 sample effectively increased photocurrent density four times more than the bare CT sample and showed the maximum amount of H2 evolution during water splitting after 60 min. In addition, Tafel tests are performed to investigate the photocathodic protection of as-prepared samples for 403 stainless steel. It was observed that the photocathodic protection performance is achieved for NCT2 which prepared at a photodeposition time of 20 min.

TiO2-supported Ni-Sn as an effective hydrogenation catalyst for aqueous acetic acid to ethanol

Various Ni and Ni-Sn catalysts supported on TiO2 were prepared and the catalytic activities were evaluated for ethanol formation from aqueous acetic acid. Although catalytic activities of the Ni/TiO2 catalysts were limited, the addition of Sn improved the activity dramatically, and the optimum Ni/Sn ratio was approximately 1:1 (w/w). SnO2, the precursor of Sn, could not be reduced into metal Sn in pure form but did reduce into Ni-Sn alloys in the presence of NiO, the precursor of Ni. Analyses with XRD and SEM-EDS revealed that the Ni-Sn alloys were homogeneously dispersed on the TiO2 surface. Furthermore, IR analysis indicated that the Ti atoms in the catalyst act as a Lewis acid, which coordinates to the oxygen atoms of acetic acid, enhancing the attack of hydrogens activated on neighboring Ni-Sn alloys. Based on these results, Ni-Sn/TiO2 is proposed as an effective hydrogenation catalyst for converting aqueous acetic acid into ethanol.

Prediction of foaming temperature of glass in the presence of various oxidizers via thermodynamics route

Oxidation of silicon carbide in a molten glass is a known method for the production of foam glasses. In this process, oxidation of SiC particles directly by the ion oxygen in the glass and/or by gaseous oxygen released from the reduction of various multi-valence oxides leads to foaming of the glass. In the latter case, the foaming temperature depends clearly on the nature of these additives. The choice of these oxidizers and/or heat treatment temperature of the glass-SiC-oxidizer are made through try and error. However, in the present work the authors have tried to predict the foaming temperature of a mixture of soda-lime glass, SiC particle, and oxidizers NiO, CoO, SnO2, and Fe2O3 through the thermodynamics of reactions involving condensed phases. According to our predictions, the foaming temperature of the glass in the presence of NiO, CoO, SnO2, and Fe2O3 was 705 °C, 780 °C, 893 °C, and (790 °C and 986 °C) respectively, which were compatible with the experimentally obtained results.

Toxic Effects of Metal Oxide Nanoparticles Based on the Enzymatic Activity and Biosynthesis of β-Galactosidase Using a Mutant Strain of E. coli.

The effects of six metal oxide nanoparticles (MO-NPs) on the activity and biosynthesis of an enzyme (β-galactosidase) were examined using a mutant strain of E. coli. Different sensitivities were observed according to the type of NP and metabolic process. The toxic effects on enzyme activity were significantly greater than on biosynthesis (p < 0.011), except in the presence of NiO. In both cases, ZnO NP caused the greatest inhibition among the tested NPs, followed by CuO. The EC50s for ZnO were 0.19 and 3.68 mg/L for enzyme activity and biosynthesis, respectively. Similar orders of toxicity were observed as follows: ZnO > CuO > NiO > Co₃O₄ > TiO₂, Al₂O₃ for enzyme activity; and ZnO > CuO > NiO ≫ Al₂O₃, TiO₂, Co₃O₄ for the biosynthetic process. More systematic research, including in-depth studies like investigation of the molecular mechanisms, is necessary to elucidate the detailed mechanisms of inhibition involved in both metabolic processes.

LaNiO3 as a precursor of Ni/La2O3 for reverse water-gas shift in DBD plasma: Effect of calcination temperature

Reverse water–gas shift (RWGS) is considered as a promising reaction to convert CO2 into CO, which together with H2, can be used for the synthesis of Fisher-Tropsch chemicals. In this study, a hybrid dielectric barrier discharge (DBD) plasma-catalysis system was developed for RWGS at room temperature. LaNiO3 perovskite catalysts calcined at 600, 700, 800 and 900 °C (denoted as LNO-600, LNO-700, LNO-800 and LNO-900) were synthesized and tested for RWGS in DBD plasma reactor. Different methods including XRD, N2 adsorption-desorption, H2-TPR, TEM, CO2-TPD, O2-TPD, XPS, XANES, EXAFS and TG-DTA were employed for the characterization of fresh, reduced and spent catalysts. The results showed that a fully crystallized LaNiO3 perovskite structure could be formed only at temperatures of >800 °C, and lower calcination temperatures resulted in the presence of NiO and amorphous La2O3. Ni was extracted from the LaNiO3 perovskite structure to form Ni supported on La2O3 support (Ni/La2O3) after reduction for all catalysts. The CO2 conversion did not show obvious difference over different catalysts. However, the maximum CO selectivity and the minimum CH4 selectivity were achieved over LNO-600. The higher catalytic activity of LNO-600 should be attributed to its higher Ni dispersion, smaller Ni particle size and stronger metal-support interaction. It should be noted LNO-800 showed the highest coke resistance ability, due to the highest ratio of surface adsorption oxygen and largest oxygen storage capacity evidenced by the XPS and O2-TPD results. In addition, the effect of H2/CO2 ratio on the performance of RWGS was studied and a H2/CO2 ratio of 2:1 was confirmed to be the optimum for the simultaneous achievement of higher CO2 conversion and CO selectivity.

Catalytic pyrolysis of Napier grass with nickel-copper core-shell bi-functional catalyst

Nickel-copper (Ni-Cu) core-shell catalysts supported on phosphorus-modified carbon microspheres (mCMs) were prepared at three Ni/Cu mass ratios, and applied to the catalytic pyrolysis of Napier grass (Pennisetum purpureum) under atmospheric pressure. The catalytic pyrolysis was carried out inside a custom-built one-shot two-stage fixed-bed reactor. The catalyst structure was confirmed by X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. Remarkably, the Ni-Cu/mCM catalysts increased the produced alkyl-phenols by up to fourfold, and these products are an excellent gasoline blend stock due to their high blending octane number. At the same time, the mass of undesired compounds in the bio-oil including alcohols, ketones, and furan were markedly decreased compared to the case without a catalyst. The oxygen content of the bio-oil was reduced by up to 24 % compared to the non-catalytic case. The hydrogen/carbon and oxygen/carbon molar ratios were also improved after all catalytic treatments. Finally, a reaction mechanism was proposed, including the pathways of oxygen removal through dehydration, decarbonylation, and dealkoxylation. The presence of NiO in the Ni-Cu/mCM catalyst promoted the alkylation reaction to yield more alkyl-phenols.