Dispersed Ni Particles Research Articles

Ultrasound-assisted synthesis of highly dispersed nickel nanoclusters on MXene for efficient dehydrogenation of hydrazine borane

Hydrazine borane (N2H4BH3), recognized as an excellent hydrogen source, has received widespread attention due to its good chemical stability and superior gravimetric hydrogen storage capacity. However, developing monodispersed and ultrafine noble-metal-free nanocatalysts to enhance hydrogen generation from N2H4BH3 is vital yet challenging. In this work, we proposed an ultrasound-assisted synthesis approach to prepare highly dispersed Ni nanoclusters (NCs, ∼1.9 nm) on Ti3C2Tx MXene. The ultrasound-induced oxygen-containing functional groups on the Ti3C2Tx MXene surface can regulate the size and dispersion of Ni particles. The as-prepared Ni/Ti3C2Tx exerts superior catalytic performance and 100% H2 selectivity toward hydrogen production from the aqueous solution of N2H4BH3. Its turnover frequency (TOF) value reaches 302 h−1 at 323 K, which is 6 times higher than that of Ni/Ti3C2Tx prepared without ultrasound treatment and even exceeds almost all previously reported monometallic noble-metal-free catalysts. The superior catalytic efficiency of Ni/Ti3C2Tx is attributed to the highly dispersed and electron-rich Ni NCs, as well as the electronic metal-support interaction (EMSI) between the Ti3C2Tx MXene support and the Ni NCs. Highly active and affordable catalysts provide an effective approach to boost N2H4BH3 as a promising hydrogen storage material in practical application.

Reversible Solid Oxide Cells: Durability of Co-Impregnated Fuel Electrodes

1.Introduction The use of renewable energy is essential to realize a decarbonized society, but solar power generation, for example, is affected by weather conditions. Reversible Solid Oxide Cells (r-SOC)1,2 have been attracting attention because they can perform both power generation (SOFC) and electrolysis (SOEC) in a single cell and can adjust the supply and demand of electricity. The conventional cermet fuel electrodes used in r-SOCs, such as Ni-YSZ, have technical issues such as Ni particle agglomeration and Ni sublimation under high partial pressure of water vapor3,4. Therefore, our research group has developed an alternative fuel electrode with highly dispersed catalytic Ni particles and GDC on the surface of conductive backbone (La-Sr-Ti oxide (LST) and Gd-doped ceria (GDC)), denoted here as Ni-GDC co-impregnated fuel electrode. This is fabricated by highly dispersing catalytic Ni particles and GDCs on the surface of LST and GDC to achieve higher durability5. Here in this study, we apply various Ni-GDC co-impregnated fuel electrodes with different Ni and GDC loadings and evaluate their initial electrochemical performance and long-term durability especially in SOEC mode. 2.Experimental Four types of Ni-GDC co-impregnated fuel electrodes, LST-GDC-only fuel electrodes as the backbone, Ni-YSZ and Ni-GDC cermet fuel electrodes as cermet-based fuel electrodes for comparison were used in this study. The Ni-GDC co-impregnated fuel electrode consists of LST and GDC porous composite electrode framework, which was co-impregnated with Ni and GDC as catalysts. Details of the cell with the Ni-GDC co-impregnated fuel electrode are compiled in Fig. 1(a). Each cell was fabricated using LSCF/GDC for the air electrode and YSZ for the supporting electrolyte plate. The structure of the Ni-GDC co-impregnation cell is shown in Fig. 1(b). Initial performance tests and SOEC 1000-hour durability tests were conducted at an operating temperature of 800°C and 50%-humidified hydrogen. 3.Results and discussion Figure 1(c) shows the results of SOEC 1000-hour durability tests for the Ni-YSZ cermet fuel electrode, the Ni-GDC cermet fuel electrode, and the Ni-GDC co-impregnated fuel electrode. The Ni-GDC co-impregnated fuel electrode exhibited less degradation than the cermet fuel electrode. Since the backbone of the co-impregnated fuel electrode, LST-GDC consists of stable oxides, it is considered to be more durable than the conventional cermet fuel electrodes which have Ni-based backbone structure. The Ni-GDC co-impregnated fuel electrode is also considered to suppress Ni aggregation by highly-dispersing Ni and GDC catalysts on its stable framework.FIB-SEM micrographs of the Ni-GDC co-impregnation fuel electrode before and after the SOEC 1000-hour durability test is shown in Fig. 1(d). Growth of the co-impregnated Ni particles was observed, but the Ni particles were small relative to the entire fuel electrode and the amount of Ni loaded was low, leading to a longer overall durability of the fuel electrode due to such a co-impregnated microstructure. Acknowledgements A part of this research was supported by JST's Adopting Sustainable Partnerships for Innovative Research Ecosystem (ASPIRE) (Grant No. JPMJAP2307). An initial part of this study was supported by NEDO (JPNP20005). We thank all the parties concerned. References N. Q. Minh, M. B. Mogensen, Electrochem. Soc. Interface, 22, 55 (2013).M. B .Mogensen, M. Chen, H. L. Frandsen, C. Graves, J. B. Hansen, K. V. Hansen, A. Hauch, T. Jacobsen, S. H. Jensen, T. L. Skafte, and X. Sun, Clean Energy, 3, 175 (2019).M. B. Mogensen, M. Chen, H. L. Frandsen, C. Graves, A. Hauch, P. V. Hendriksen, T. Jacobsen, S. H. Jensen, T. L. Skafte, and X, Sun, Fuel Cells, 21, 415 (2021).M. Hubert, J. Laurencin, P. Cloetens, B. Montinaro, and F. Lefebvre-Joud, J Power Sources, 397, 240 (2018).S. Futamura, Y. Tachikawa, J. Masuda, S. M. Lyth, Y. Shiratori, S. Taniguchi, and K. Sasaki, ECS Trans., 78 (1), 1179 (2017) Figure 1

Rapid fabrication of Ni supported MgO-ZrO2 catalysts via solution combustion synthesis for steam reforming of methane for hydrogen production

In this study, we introduced a solution combustion as a simple, efficient, and rapid technique for synthesis of a nanostructured Ni catalyst supported on MgO-ZrO2 for hydrogen production by steam reforming of methane. A series of Ni/MgO-ZrO2 catalysts with different Ni contents were prepared and investigated to observe a suitable Ni loading content. The evaluation of catalytic performance of the as-prepared catalysts was performed in a packed-bed reactor at 700 °C and atmospheric pressure at steam to carbon ratio (S/C) of 2. As a result, the 20Ni/20MgO-ZrO2 catalyst exhibited not only outstanding catalytic performances, but also minimized coke deposits, attributed to the presence of oxygen vacancies of MgO-ZrO2 solid solution. In addition, combustion synthesis could result in formation of NiO-MgO solid solution, boosting uniform dispersion of Ni particles. A durability test of the optimized 20Ni/20MgO-ZrO2 catalyst was conducted at 700 °C for 50 h, revealing a near constant methane conversion of approximately 92.9%. Although filamentous carbon and carbon encapsulation were observed on the surface of spent catalyst, there is no significant negative impact on the steam reforming performance. In conclusion, this present work highlights the efficacy of the solution combustion method for synthesis of nanostructured Ni/MgO-ZrO2 catalysts with superior catalytic performance and less coke deposits for hydrogen production from methane steam reforming.

Unveiling the potential of desert sand-derived mesoporous silica supported nickel-based catalysts for co-production of H2 and carbon nanomaterials via methane cracking

This study investigates the replacement of a costly commercial silicate source with locally abundant desert sand in the United Arab Emirates (UAE), for synthesizing mesoporous silica. Hydrothermal synthesis methods were employed to develop various mesoporous materials having different pore geometries, namely MCM41-S, SBA15-S and MCF-S, using desert sand as a silica source. These materials were then impregnated with 15 wt% NiO (∼13 wt% Ni) by sono-wet impregnation technique. All Ni-based silica supported catalyst demonstrated enhanced stability at 550 °C during the reaction. It was observed that the synthesized MCF-S proves to be a highly efficient catalyst support, as Ni/MCF-S, for the catalytic decomposition of methane (CDM), exhibiting the highest methane conversion (60 %), which is 1.4–2.1 times higher than the Ni-based classic-structured mesoporous siliceous supported catalysts, such as SBA15-S and MCM41-S. In particular, the H2 yield (62 %) of the Ni/MCF-S catalyst was 1.40 and 2.38 times higher than that of the Ni/SBA15-S and Ni/MCM41-S catalysts, respectively. To understand the observed differences, a detailed characterization of the physicochemical properties of these materials was conducted. The results revealed that the macro/mesopores size (4–60 nm) and bimodal sinusoidal pore geometry of MCF-S, played a critical role in enhancing Ni particle dispersion, resulting in the highest active Ni metal surface area (7.66 m2/gcat) and contributing to the improved catalytic activity of Ni catalysts in methane cracking.

Preparation of Ni-B/MgAl2O4 catalysts for hydrogen production via steam reforming of methane

In this paper, a series of B doped Ni/MgAl2O4 catalysts for hydrogen production via steam reforming of methane (SRM) were prepared, and their catalytic activities and stability were evaluated. The characterization of XRD, XPS, TPR, BET, TPO, and TEM revealed that the addition of B could promote Ni dispersion, which lead to the reduce of Ni particle size. 0.5 wt% B was incorporated into Ni/MgAl2O4 would increase Ni particle dispersion rate from 11.2% to 14.8%, which caused Ni particle average size was decreased from 8.78 to 6.96 nm. At the same time, 0.5% B doped would increase the chemisorbed oxygen content of the catalyst, and more oxygen vacancies were formed. Thus, Ni particles sintering and carbon deposition during SRM was suppressed, and the catalytic activity and stability were promoted. Ni-B0.5/MgAl2O4 could achieve 90.2% methane conversion rate and 85% H2 yield under 700 °C with a WHSV of 36,000 mL·(gh)−1 during SRM process, and only a marginal reduction (2%) of methane conversion rate was observed after 48 h reaction. The total carbon content on the used Ni-B0.5/MgAl2O4 catalyst was approximately 0.031 gc∙gcat−1, which was three times lower than that of Ni/MgAl2O4. However, the excess B doping into Ni/MgAl2O4 had a negative effect on the catalytic activity and stability.

Optimizing electrochemical power generation: Harnessing synergies and surface innovation in NiTe-modified MOF nanoarchitectures

Metal-organic frameworks (MOFs) are considered potential electrocatalysts due to their high specific surface area (SSA) and the facilitation of efficient synergistic interactions. In this work, we have implemented a simple and cost-effective surface modification approach to design an efficient electrocatalyst for energy-conversion technologies, specifically water splitting. This work focuses on engineering a novel NiTe functionalized MOF structure wherein NiTe within the MOF channels is the core material, intricately intertwined with highly dispersed Ni particles enveloped by Ni MOF. This fusion of MOFs and NiTe within a designed configuration produces an efficient electrocatalyst with synergistic and surface interface effects and demonstrates bifunctional activity for water splitting. Among the prepared catalysts, one of the resulting catalysts (named Ni MOF/Ni/Ni10Te8) exhibits a low overpotential of 99 mV for the hydrogen evolution reaction (HER) and 180 mV for the oxygen evolution reaction (OER), both benchmarked against RHE @10 mA cm−2. This performance remains steady, with a stability of 99 % after 15 h of continuous operation. Furthermore, the Ni MOF/Ni/Ni10Te8 catalyst also operates in seawater electrocatalysis, requiring a low overpotential of 440 mV at 10 mA cm−2 to produce 70 mL of hydrogen and 34 mL of oxygen. Equally noteworthy are the Faradaic efficiencies achieved, with hydrogen production at 95.7 % and oxygen production at 92.9 %. Developing efficient and economically viable electrocatalysts like the Ni MOF/Ni/NiTe catalyst will advance a cleaner and more sustainable future.

Tuning of the acid sites in the zeolite-alumina composite Ni catalysts and their impact on the palm oil hydrodeoxygenation reaction

The hydrodeoxygenation (HDO) of bio-oil is one of the potential approaches to produce green diesel. However, HDO catalyst requires the development of bifunctionality which translates to the simultaneous presence of acidic and metal sites for desired catalytic activity and selectivity. Zeolites and their composites are attractive candidates for the conversion of biomass to fuels. In the present work, a series of Ni-incorporated Al2O3-zeolite beta bifunctional composite catalysts with distinct Al2O3 (25–75 wt%) and Ni contents (5–15 wt%) were synthesized via a facile one-pot method directly from nickel acetate, nano-boehmite (γ-AlO(OH)) and the NH4+ form of beta zeolite (NH4+-BZ). The nano-boehmite particles, due to the positive charges on their surface, electrostatically attract negatively charged beta zeolite crystals, which leads to the assembly of a hierarchical pore structure upon calcination. Interestingly, the composite catalysts synthesized were quite homogeneous with uniform dispersion of Ni particles. All composite catalysts were thoroughly characterized using XRD, SEM-EDX, SEM-mapping, HR-TEM, H2-TPR, H2-TPD, NH3-TPD, XPS, 31P MAS NMR, 27Al MAS NMR and N2 sorption analysis. The synthesized composite catalysts with distinct Al2O3 contents showed diverse textural properties, distinct nature of acid sites and improved performance in hydrodeoxygenation of palm oil. Particularly, the Ni/BZ-Al50 (with BZ:Al2O3 = 50:50) composite catalyst significantly enhanced the conversion of palm oil (up to 90%) and yield of n-C15-C18 hydrocarbons (up to 69%) at moderate temperature of 375 °C as compared to 10Ni/BZ catalyst (Conv. = 75%, yield of n-C15-C18 = 52%). The higher catalytic performance realized with composite catalysts can be ascribed to its hierarchical pore structure, moderate acidity (chemisorption studies), tuned acid sites nature (solid state NMR) and homogeneous distribution of active Ni sites (H2 chemisorption) which helps to improve product selectivity by minimizing side reactions. The time-on-stream (TOS) experiments were carried out up to 20 h which clearly showed that composite catalysts are more stable suggesting the lower amount of coke deposition (TPO studies) and suppression of metal sintering.

A Novel Method for Preparation of Al–Ni Reactive Coatings by Incorporation of Ni Nanoparticles into an Al Matrix Fabricated by Electrodeposition in AlCl3:1‐Eethyl‐3‐Methylimidazolium Chloride (1.5:1) Ionic Liquid Containing Ni Nanoparticles

Al/Ni reactive coatings are fabricated via electrochemical deposition (ECD) at different applied voltages for reactive bonding application. :1‐ethyl‐3‐methylimidazolium chloride ([EMIm]Cl) (1.5:1) ionic liquid electrolyte is used as source of Al, whereas Ni is in the bath and incorporated into final coatings as nanoparticles (NPs). Scanning electron microscopy and Auger electron spectroscopy reveal a homogeneous Ni particle dispersion, as well as a high amount of particle incorporation into the Al matrix. A maximum of 37 wt% (22 at%) of Ni is detected via atomic absorption spectroscopy in the Al/Ni coating deposited at −0.1 V from an electrolyte containing 20 g L−1 of Ni NPs. Previous literature show that for bonding application an ideal concentration is around 50 at% of Ni and 50 at% Al. However, this is achieved using high vacuum, time‐consuming processes, and costly techniques like evaporation and magnetron sputtering. The ECD used in this work represents a more cost‐efficient approach which is not reported up to date for the aforementioned application. The reactivity of the coatings is confirmed by Differential scanning calorimetry. Herein, an exothermic reaction is detected upon the mixing of Al and Ni occurring at high temperatures.

Effect of Ce promotion on catalytic activity of Ni-Al catalysts in dry reforming of methane

The Ni-Al, Ni-Ce and Ni-Ce-Al catalysts tested in the dry methane reforming (DRM) were studied. Catalysts were synthesized by solution combustion synthesis and characterized by BET, XRD and TEM. Catalytic activity was studied at 600–900 °C with a 33%CH4:33%CO2:34%Ar (vol.%) fed with total flow rate of 100 ml/ min (3000 h−1). The CH4 and CO2 conversion increased with the increasing of Ce up to 15 wt.%, however, with further increase in Ce content conversion of gases decreased. Carbon was formed as filaments when catalysts worked at high temperature. CeAlO3 species could prevent the formation of filamentous carbon during DRM. Solution combustion synthesis is attractive method of preparation of catalysts, due to high dispersion of Ni particles, thus, surface area is small, diminishing the coke deposition and enhancing the stability.

Microstructure evolution and mechanical properties of 3YSZ/Ni composites with uniform phase distribution prepared by core-shell structure microspheres

Yttrium-stabilized zirconia(3YSZ) microspheres with different size ranges were prepared by sol-gel method, followed by electroless Ni plating on their surfaces. The as-prepared core-shell structure 3YSZ/Ni microspheres were then spark plasma sintered (SPS) into 3YSZ/Ni composites, in which a uniform distribution of ceramic and metal phases was achieved. The underlying correlations among microsphere size, Ni concentration, microstructure, and resultant mechanical properties were experimentally analyzed. Results show that: continuous and smaller microsphere sizes can obtain relatively high-density samples with good mechanical properties, which can be proved by the Minimum Solid Area (MSA) model. 3YSZ sample prepared with the optimized microsphere size range of 0–50 μm exhibits the highest relative density and fracture toughness of 98.8% and 5.51 ± 0.33 MPa·m1/2, respectively. Furthermore, the core-shell structure 3YSZ/Ni microspheres with varying Ni contents exhibited a uniform composite of flakes and particles Ni metal after sintering, among which 3YSZ/10 wt%Ni composites have achieved better mechanical properties, with density, hardness and fracture toughness of 96.9%, 8.61 ± 0.35 GPa, 7.92 ± 0.71 MPa·m1/2, respectively. Firstly, the uniformly dispersed Ni metal flakes or particles provide multiple toughening effects, including crack bridging, pull-out, interfacial debonding, crack deflection, etc. Secondly, due to residual stress, cracks tend to deflect near Ni metal, extending the crack path. Thirdly, the 3YSZ matrix's transition from an intergranular to a transgranular fracture also increases fracture energy consumption. Compared to the pure 3YSZ sample with a wide microsphere size range of 0–100 μm, the fracture toughness of 3YSZ/10 wt%Ni composites with a microsphere size of 0–50 μm is increased by 73.9%.

Efficient and Stable Ni/SBA-15 Catalyst for Dry Reforming of Methane: Effect of Citric Acid Concentration

Citric acid, one of the representative chelate compounds, has been widely used as an additive to achieve the highly dispersed metal-supported catalysts. This study aimed to investigate the effect of citric acid concentration on the preparation of the highly dispersed Ni catalysts on mesoporous silica (SBA-15) for the dry reforming of methane. A series of Ni/SBA-15 catalysts with citric acid were prepared using the acid-assisted incipient wetness impregnation method, and the Ni/SBA-15 catalyst as a reference was synthesized via the impregnation method. First of all, the citric acid addition during the catalyst synthesis step regardless of its concentration resulted in highly dispersed Ni particles of ~4–7 nm in size in Ni/SBA-15 catalysts, which had a superior and stable catalytic performance in the dry reforming of methane (93% of CO2 conversion and 86% of CH4 conversion). In addition, the amount of coke formation was much lower in a series of Ni/SBA-15 catalysts with citric acid (~2–5 mgcoke gcat−1 h−1) compared to pristine Ni/SBA-15 catalysts (~22 mgcoke gcat−1 h−1). However, when the concentration of citric acid became higher, the more free NiO species that formed on the SBA-15 support, leading to large Ni particles after the stability test. The addition of citric acid is a very clear strategy for making highly dispersed catalysts, but its concentration needs to be carefully controlled.

Hydrocracking of surgical face masks over Y Zeolites: Catalyst development, process design and life cycle assessment

This study highlights the hydrocracking route for the management of surgical face masks, made of polypropylene, into liquid fuels. Hydrocracking experiments were performed at 325 ℃ and 10 bar cold H2 pressure over Ni-loaded HY and steamed HY zeolites. Ni-loaded steamed Y zeolite demonstrated to be the best catalyst leading to considerably high conversion (100 wt%) and selectivity to liquids (85.5 wt%). The increase in the external surface area and mesoporous volume that improved the bulk polymer molecules diffusion, combined with the uniformly dispersed Ni particles and the additionally generated Lewis acidity, were at the origin of the observed behaviour. This catalyst also showed reasonable stability and ability to be thermally regenerated. From the environmental perspective, life cycle assessment shows the benefits of hydrocracking over pyrolysis and incineration.Therefore, our results demonstrate that Ni-loaded steamed Y zeolites could be promising catalysts for the upcycling of surgical face masks to gasoline range fuels, with minimum environmental impacts.

Highly Dispersed Ni over a YSZ Anode Anchored by SiO2 at High Temperature through Low-Temperature Chemical Vapor Deposition

Supported Ni on yttria stabilized zirconia (YSZ) is the most widely used anode for a solid oxide fuel cell (SOFC), where Ni particles are easy to agglomerate at a high temperature of 1400 °C and reductive hydrothermal environments. In this study, Ni particles are successfully dispersed on YSZ through strong interaction between Ni and SiO2. The thin and amorphous SiO2 films, grown by low-temperature chemical vapor deposition (CVD), become spherical particles of nickel silicates uniformly dispersed on the YSZ skeleton after sintering at 1400 °C. Also, the SiO2-anchored Ni particles supported on YSZ (Ni/YSZ-SiO2) are obtained via direct reduction. The electrochemical performance of the Ni/YSZ-SiO2 anode shows a higher power density of approximately 18% than an unmodified Ni/YSZ anode, which resulted from the longer effective TPB area assigned to the highly dispersed Ni particles. The microstructure containing SiO2-anchored Ni particles exhibits high stability under testing and reductive hydrothermal conditions. Accordingly, the method of growing a SiO2 layer via low-temperature CVD is considered as a probable route for the preparation of the Ni/YSZ electrode material with a well-defined microstructure.

Enhanced Low-Temperature CO2 Methanation over Bimetallic Ni–Ru Catalysts

Nickel-based catalysts are the most promising selection for CO2 methanation. But, it is challenging for monometallic Ni to achieve high CO2 conversion at low temperature. This study develops ceria-supported bimetallic Ni–Ru catalysts that are highly efficient for low-temperature methanation. A small amount of Ru (0.2 wt %) addition to Ni enables the intermetal interaction, and enhances the dispersion of Ni particles with a more active surface, consequently boosting the catalytic capacity for hydrogen activation and CO adsorption. The bimetallic Ni–Ru catalysts exhibit a more than 3-fold rate enhancement at low temperature for selective methanation of CO2 relative to the monometallic Ni/CeO2. Operando IR spectroscopy identifies the formate route as the major reaction mechanism over the monometallic Ni, and the presence of Ru in the bimetallic catalysts can induce the *CO-intermediate mechanistic pathway, contributing to the enhanced production of methane.

Synthesis, characterization, and application of bio-templated Ni–Ce/Al2O3 catalyst for clean H2 production in the steam reforming of methane process

A mesoporous γ-alumina was successfully synthesized through an environmentally-friendly method using Fig leaves as a bio-template for the first time in this research. After confirming the formation of porous Al2O3 structure with different characterization techniques, it was used as a supporting material of Ni–Ce particles to effectively enhance the conversion of steam reforming of methane (SRM) process. For this purpose, we optimized Ni content, Ce content, and SRM temperature using bulk and porous structure of Ni–Ce/Al2O3 catalysts. The results of field emission scanning electron microscopy (FESEM), temperature-programmed desorption (H2-TPD), and N2 adsorption/desorption showed the formation of more dispersed Ni particles with smaller sizes on the mesoporous alumina (MAl), especially when they were promoted with CeO2. Besides the efficient influence of CeO2 on Ni particle dispersion, it was enhanced the Ni–Al interaction, increased the activity of the catalysts, and decreased the coke deposition on the catalysts during the SRM process. As a result, 20Ni-3.0Ce/MAl catalyst depicted the highest H2 yield of 96.02% and CH4 conversion of 90.20%, and the lowest produced CO2 to consumed CH4 of 0.52% at 700 °C SRM reaction. This is while the bulky catalyst with equal Ni and Ce contents had 86.09, 92.30, and 0.56 CH4 conversion, H2 yield, and CO2/CH4 molar ratio, respectively at this temperature. Besides, 20Ni-3.0Ce/MAl depicted the highest stability during 12 h continuous SRM reaction at 700 °C with the lowest reduction amounts of 3.97% and 5.12% for CH4 conversion and H2 yield, respectively.

EDTA impregnation assisted synthesis of nickel nanoparticles embedded in activated carbon and its application for dry reforming of methane

In this paper, the catalysts with nanoscale nickel particles embedded in activated carbon were synthesized by Ethylenediaminetetraacetic acid (EDTA) assisted impregnation method. The experimental results revealed that EDTA addition could promote Ni particle dispersion and decrease Ni particle size. Ni particle size was significantly decreased from 18.23 to 4.57 nm when Ni/EDTA ratio was increased from 1:0 to 1:3. Catalytic performance of Ni15-AC-E3 demonstrated that CH4 and CO2 conversion rate under 850 °C were 90.05% and 96.28%, which were decreased by 1.08% and 1.27% after 72 h dry reforming methane (DRM) reaction. Moreover, the characteristic of the used catalyst showed that Ni particle size was only increased from 4.57 to 5.94 nm after the stability test, and NiO was not appeared. Meanwhile, the deposited carbon in the used catalyst was 5.02%. The above results meant that the catalyst prepared by EDTA assisted impregnation method had the ability of suppressing carbon deposition, Ni particle sintering and oxidation during DRM reaction.

High value utilization of waste blast furnace slag: New Ni-CeO2/hBFS catalyst for low temperature CO2 methanation

In the steel industry, large amounts of blast furnace slag (BFS) by-products are inevitably produced and a lot of carbon dioxide is emitted. But at present, slag reuse technology has low added value. In this paper, a high value-added process using blast furnace slag to prepare catalysts for the hydrogenation of carbon dioxide to methane was proposed. Ni-CeO2/hBFS catalyst was prepared by primary wet impregnation using nitric acid modified blast furnace slag (BFS) as a support. CO2 conversion of Ni-CeO2/hBFS catalysts achieved 81.6 % at 350 °C, and the catalyst was not significantly deactivated in a 100 h stability test. The results indicate that: the addition of CeO2 improved the dispersion of Ni particles at high loadings, limited the growth of the Ni particle size and enhanced the synergy between the CO2 adsorption sites, the catalytic active sites and the support, thus improved the catalytic performance at low temperatures. This study provides an effective way for carbon dioxide emission reduction and high-value utilization of blast furnace slag, and developed a Ni-CeO2/hBFS catalyst with superior stability and catalytic performance in long-term operation, thus, the catalyst has great potential for industrial application in the carbon dioxide methanation reaction.

H2 generation from steam gasification of swine manure over nickel-loaded perovskite oxides catalysts

In this study, nickel-loaded perovskite oxides catalysts were synthesized via the impregnation of 10%Ni on XTiO3 (X = Ce, Sr, La, Ba, Ca, and Fe) supports and employed in the catalytic steam gasification of swine manure to produce H2-rich syngas for the first time. The synthesized catalysts were characterized using BET, H2-TPR, XRD, HR-TEM, and EDX analysis. Briefly, using perovskite supports resulted in the production of ultrafine catalyst nanoparticles with a uniform dispersion of Ni particles. According to the catalytic activity test, the gas yield showed the increment as 10% Ni/LaTiO3 < 10% Ni/FeTiO3 < 10% Ni/CeTiO3 < 10% Ni/BaTiO3 < 10% Ni/SrTiO3 < 10% Ni/CaTiO3. Meanwhile, zero coke formation was achieved due to the oxygen mobility of prepared catalysts. Also, the increase in the H2 production for the applied catalysts was in the sequence as 10% Ni/CeTiO3 < 10% Ni/FeTiO3 < 10% Ni/LaTiO3 < 10% Ni/BaTiO3 < 10% Ni/SrTiO3 < 10% Ni/CaTiO3. The maximum H2 selectivity (∼48 vol%) obtained by10% Ni/CaTiO3 was probably due to the synergistic effect of Ni and Ti on enhancing the water-gas shift reaction, and Ca on creating the maximum oxygen mobility compared to other alkaline earth metals doped at the A place of perovskite. Overall, this study provides a suitable solution for enhanced H2 production through steam gasification of swine manure along with suggesting the appropriate supports to prevent Ni deactivation by lowering coke formation at the same time.

Enhancement of hydrogen and carbon nanotubes production from hierarchical Ni/ZSM-5 catalyzed polyethylene pyrolysis

Pyrolytic catalysis technology has been considering a promising strategy to convert waste plastics into high-value products from economic and environmental perspectives. The design of efficient catalysts plays a key role in product distribution. In this study, Ni-supported hierarchical ZSM-5 (designated as Ni/ZSM-5-M) was developed for the pyrolytic catalysis of polyethylene (PE) to produce carbon nanotubes (CNTs) and hydrogen by using two-stage fixed bed reactor. Results showed that the Ni/ZSM-5-M catalyst generated the highest carbon material yield of 43.8 wt% and the maximum hydrogen production of 5.2 wt% about 26.27 mmol/gPE. In order to understand the correlation between catalysts structure and products, the essential structural characteristics of as-prepared catalyst were characterized by the comprehensive approach such as SEM, TEM, XRD, TPR and so on. The results indicated that alkali treatment introduced a hierarchical structure and significantly improved the dispersion of Ni particles, producing a catalyst surface area of 356 m2/g and average Ni particle size of ∼14.8 nm, which further enhancing catalytic activity for the production of hydrogen and CNTs. The Ni/ZSM-5-M catalyst produced a higher yield of carbon deposits (43.8 wt%), including over 66% high-value CNTs (289 mg/gPE) and hydrogen yield (5.2 mg/gPE). This study suggests alkali modification method to prepare Ni/ZSM-5-M catalyst is a promising way to promote the production of valuable CNTs and hydrogen from waste plastics.

Dry reforming of methane over silica zeolite-encapsulated Ni-based catalysts: Effect of preparation method, support structure and Ni content on catalytic performance

Dry reforming of methane (DRM) is a prospective technology for efficient utilization of CH4 and CO2, with the essential challenge being the design and synthesis of efficient catalysts. In this research, serial encapsulated Ni-based catalysts (xNi@S-1, x = 5, 7, 10) by silica zeolite (S-1) were prepared successfully. The effects of support structure, preparation method and Ni content upon the catalytic performance for DRM were investigated and diverse characterizations were utilized for revealing structural features of as-prepared catalysts. Encapsulated 7Ni@S-1 catalyst prepared using the one-pot hydrothermal method could acquire more homogeneously dispersed metallic Ni particles and more Ni species including Ni0, NiO, 1:1/2:1 Ni phyllosilicates that could facilitate forming stable Ni0 sites and Ni2+-O2- ion pairs for adsorption and activation of CH4 and CO2, respectively. Hence, 7Ni@S-1 still maintained the highest CH4 and CO2 conversions of 57.9% and 88.6% and H2/CO molar ratio of 0.90 after 52 h stability tests.