Synthesis and characterization of Zr-promoted Ni-Co bimetallic catalyst supported OMC and investigation of its catalytic performance in steam reforming of ethanol

This article presents simple method for the OMC-6%Ni-6%Co (ordered mesoporous carbon containing Ni and Co metallic nanoparticles) catalyst synthesis with high surface area and more proper bimetallic nanoparticle dispersion; prepared successfully by soft template hydrothermal method and different zirconium loadings (0.5, 1, 2 wt %) accomplished by impregnation method, which was known as a desired method for the metal dispersion. The catalysts with/without promoter, were characterized by XRD, FTIR and N₂ adsorption-desorption isotherms, FESEM, EDS, EDS mapping, HRTEM and TPR techniques and investigated in steam reforming of ethanol (SRE) at 250–400 °C. XRD and BET results indicated that zirconium addition more than 0.5% wt, decreased the average mesopore diameter of catalysts, total pore volume and particles size. Also, it was stated that Ni²⁺ and Co²⁺ were caught by the RF/F127 network and further reduced into metallic Ni and Co nanoparticles during the carbonization. The Ni and Co nanoparticles were well-dispersed in the OMC walls. FTIR spectroscopy revealed that F127 left the structure and formed the porous structure. TPR analysis of OMC-6%Ni-6%Co/2%Zr sample, indicated that the sample is reduced easily at low temperatures. FESEM and HRTEM images showed that carbon was precipitated in the CNT form on spent catalyst samples surfaces and confirmed the position of Ni and Co bimetallic nanoparticles on the CNTs tip in the OMC-6%Ni-6%Co/2%Zr sample. 2% Zr-promoted bimetallic catalyst revealed appropriate catalytic performance for SRE, such as high activity, hydrogen yield and proper stability due to the synergistic catalysis of cobalt and nickel. Also, effective factors, such as H₂O/EtOH molar ratio and gas hourly space velocity (GHSV) were investigated on the OMC-6%Ni-6%Co/2%Zr catalyst sample.     

Renewable hydrogen from glycerol steam reforming using Co–Ni–MgO based SBA-15 nanocatalysts

Steam reforming of glycerol was carried out using Si-based mesoporous SBA-15 catalysts. Different mesoporous catalysts- Co-SBA-15, Ni-SBA-15, Co–MgO-SBA-15, Ni–MgO-SBA-15, and Co–Ni-SBA-15 were prepared using a one-pot hydrothermal method. An incipient wetness impregnation method was used only for the bimetallic Co–Ni-SBA-15 catalyst (catalyst designated as Co–Ni-SBA-15-IMPG) to compare its activity to that prepared by the one-pot method. The catalysts were characterized using XRD, TPR, TEM, TGA-DSC, ICP-OES and N₂ adsorption-desorption analytical techniques. A high surface area in the range of 540–750 m²/g was observed depending on the catalyst composition. The glycerol steam reforming (GSR) activity of the catalysts was studied in the reaction temperature range of 450 °C–700 °C for hydrogen production. Results from the GSR studies for continuous 40 h showed that both Co–Ni-SBA-15-IMPG (impregnation) and Co–Ni-SBA-15 (one-pot) were resistant to deactivation, and both yielded 100% glycerol conversion for the entire 40 h. 10%Co–5%Ni-SBA-15 and 10%Co–5%Ni-SBA-15-IMPG produced (70–78) % and (60–78) % H₂ selectivity, respectively. Addition of MgO to Co-SBA-15 and Ni-SBA-15 increased the activity and stability of the catalysts. The catalyst stability performance followed the trend 10%Co–5%Ni > 10%Co–5%MgO >10%Co–5%Ni-IMPG. > 15%Co > 10%Ni–5%MgO >15%Ni-SBA-15. Thermal analyses of the spent catalyst showed a substantial amount of coke deposition which could be the major factor responsible for catalysts deactivation. Bimetallic catalysts prepared by one-pot method (10%Co–5%Ni-SBA-15) and incipient wetness impregnation (10%Co–5%Ni-SBA-15-IMPG) exhibited remarkable GSR activity compared to their monometallic counterparts. The GSR activity was observed in the order: 10%Co–5%Ni-IMPG ≥ 10%Co–5%Ni > 10%Co–5%MgO >15%Co > 15%Ni > 10%Ni–5%MgO.     

Catalytic steam reforming of JP-10 over Ni/SBA-15

As the only H₂ resource on aircraft from the steam reforming of the jet fuels on board, catalytic steam reforming of JP-10 (one of Jet fuels) over nickel-based catalyst Ni/SBA-15 were first carried out in a fixed bed tube reactor to produce hydrogen on-site or on board. A series of Ni/SBA-15 catalysts with different Ni content (3, 5, 8 and 10.8 wt%) were prepared by a modified incipient wetness impregnation method with addition of sucrose as ligand. And the effect of operation conditions of temperature (630–700 °C), nickel loading, liquid hour space velocity (LHSV = 5, 10, 15 ml/g_cat·h), steam to carbon molar ratio (S/C = 3, 5) on the catalytic activity and selectivity was investigated. It was found that 8Ni/SBA-15 was the optimal catalyst for steam reforming of JP-10 even with a higher LHSV and fuel gas concentration, and approximately 100% conversion of JP-10 with over 80% selectivity to hydrogen under the recommended experimental conditions of 680 °C, S/C of 5, LHSV of 10 ml/g_cat·h. The catalytic activity of 8Ni/SBA-15 dropped slowly to 84% after 6.5 h in the stability test and the carbon deposited was less with just 6% mass loss from TGA measurement (coke deposition rate 0.01g_C/g_cath), which ascribed to possible reasons including confine effect of mesochannel of SBA-15, strengthened structure of mesochannels due to embeded Ni particles, and higher temperature to suppress the main carbon producing reaction.     

A comparative study on the performance of mesoporous SBA-15 supported Pd–Zn catalysts in partial oxidation and steam reforming of methanol for hydrogen production

Using mesoporous SBA-15 (Santa Barbara Amorphous No. 15, a mesoporous material) as support, Pd–Zn nanocatalysts with varying Pd and Zn content were tested for hydrogen production from methanol by partial oxidation and steam reforming reactions. The physico-chemical characteristics of the synthesized SBA-15 support were confirmed by XRD, N₂ adsorption, SEM and TEM analyses. The PdZn alloy formation during the reduction of Pd–Zn/SBA-15 was revealed by XRD and DRIFT study of adsorbed CO. Also, the correlation between Pd and Zn loadings and PdZn alloy formation was studied by XRD and TPR analyses. The metallic Pd surface area and total uptakes of CO and H₂ were measured by chemisorption at 35 °C. The metallic Pd surface area values are in linear proportion with the Pd loading. The formation of PdZn alloy during high temperature reduction was confirmed by a shift in absorption frequency of CO on Pd sites to lower frequency due to higher electron density at metal particles resulted from back-donation. The reduced Pd–Zn/SBA-15 catalysts were tested for partial oxidation of methanol at different temperatures and found that catalyst with 4.5 wt% Pd and 6.75 wt% Zn on SBA-15 showed better H₂ selectivity with suppressed CO formation due to the enhanced Pd dispersion as well as larger Pd metallic surface area. The O₂/CH₃OH ratio is found to play a significant role in CH₃OH conversion and H₂ selectivity. The performance of 4.5 wt% Pd–6.75 wt% Zn/SBA-15 catalyst in steam reforming of methanol was also tested. Comparatively, the H₂ selectivity is significantly higher than that in partial oxidation, even though the CH₃OH conversion is less. Finally, the long term stability of the catalyst was tested and the nature of PdZn alloy after the reactions was found to be stable as revealed from the XRD pattern of the spent catalysts.     

Techno-economic comparison of three biodiesel production scenarios enhanced by glycerol supercritical water reforming process

In this study, techno-economic comparison of three different biodiesel production scenarios integrated with glycerol supercritical water reforming (SCWR) process to produce electricity is conducted. In the first scenario, biodiesel is synthesized from acid-pretreated waste cooking oil (WCO) in the presence of alkali catalyst. In the second scenario, biodiesel is obtained from WCO by acid catalyst. In the third scenario, biodiesel is derived from WCO using acid catalyst, followed by hexane extraction of the produced methyl esters. The glycerol evolved from all the above-mentioned pathways is then subjected to the SCWR process in order to produce hydrogen. The produced hydrogen is then combusted to provide thermal energy required by biodiesel production and purification processes as well as to generate electricity. All the developed scenarios are modeled and simulated in Aspen HYSYS software environment. In order to simplify the simulation process, canola-based WCO is considered as triolein with 6 wt% oleic acid (free fatty acid) and, accordingly, the prepared biodiesel is taken into account as methyl oleate. In order to compare the economic profitability of the developed approaches, several economic indicators including net present value (NPV), internal rate of return (IRR), payback period (PBP), discounted payback period (DPBP), and return on investment (ROI) are used. A sensitivity analysis is also carried out to show how variations in feedstock, biodiesel, and electricity prices can affect the NPV of the developed scenarios. According to the results obtained, the highest IRR and ROI values as decision-making parameters are obtained for the first scenario, manifesting its suitability from the techno-economic viewpoint. The economic indicators of the second scenario are also acceptable and very close to the first approach. Overall, upgrading glycerol into hydrogen using SCWR process appears to be an attractive strategy for enhancing the economic viability of biodiesel production plants.     

Hydrogen production by partial oxidation of ethanol over Pt/CNT catalysts

The platinum‐supported catalysts have been prepared by ethylene glycol reduction method, and the catalysts were applied to the partial oxidation of ethanol (POE) for hydrogen production. Four types of support, including CNTs, Al₂O₃, ZrO₂, and CeO₂, were used on POE catalytic performance test. Prior to catalyst preparation, the influence of acidic pretreatment on CNTs purity, surface morphology, and pore structure were investigated. The acid‐treated CNTs and prepared catalysts were characterized with N₂ physisorption, Raman, thermogravimetric, and transmission electron microscopy analysis. The experimental results show that the particle size and metal dispersion of platinum on CNTs, as well as POE activity, depend on pH value of reducing agent and reduction temperature in the stage of catalyst preparation. In the condition pH value of 10 and temperature at 120 °C for catalyst 5 wt% Pt/CNTs preparation, 2 nm platinum clusters were obtained. Using the as‐prepared catalyst to study the effects of POE reaction conditions on the ethanol conversion, hydrogen selectivity, and hydrogen production rate under constant gas hourly space velocity, the corresponding values at the optimum reaction temperature 400 °C and O₂/C₂H₅OH molar ratio of 0.5 were 98.2%, 97.5%, and 202.3 mmol s^?1 kg^?1, respectively. Copyright © 2013 John Wiley & Sons, Ltd.     

Process integration for hydrogen production,purification and storage using iron oxides

Hydrogen production from natural gas using a Ni-based catalyst and its later hydrogen storage with some synthetic and natural iron oxides are presented. The Ni-based catalyst showed high methane conversion, close to the equilibrium one, when producing hydrogen from methane through catalytic partial oxidation (CPO) and wet-CPO with a low steam to carbon ratio (0.5). The solid solution formation observed in the Ni-based catalyst could have enhanced its stability. The iron oxides capacity for hydrogen storage was analysed with reduction–oxidation cycles at 973 K and atmospheric pressure. The natural oxides presented structural modifications, mainly due to sinterization, which negatively affected their storage capacity and stability.     

Investigation of hydrogen storage capacity of multi-walled carbon nanotubes deposited with Pd or V

This work presents the synthesis and characterization of multi-walled carbon nanotubes (multi-walled CNTs) deposited with Pd or V and their hydrogen storage capacity measured by Sievert's volumetric apparatus. The CNTs were grown by the CVD method using LPG and LaNi₅ as the carbon source and catalyst, respectively. Pd was impregnated on the CNTs by the reflux method with hydrogen gas as a reducing agent, while V was embedded on the CNTs by the vapor deposition method. The average metal particle size deposited on the CNTs was around 5.8 nm for Pd and 3.6 nm for V. Hydrogen adsorption experiments were performed at room temperature and at −196 °C under a hydrogen pressure of 65 bar. At −196 °C, the treated CNTs had a maximum hydrogen uptake of 1.21 wt%, while the CNTs deposited with Pd (Pd-CNTs) and CNTs deposited with V (V-CNTs) possessed lower surface areas, inducing lower hydrogen adsorption capacities of 0.37 and 0.4 wt%, respectively. For hydrogen sorption at room temperature, the CNTs decorated with the metal nanoparticles had a higher hydrogen uptake compared to the treated CNTs. Hydrogen adsorption capacity was 0.125 and 0.1 wt% for the Pd-CNTs and V-CNTs, respectively, while the hydrogen uptake of the treated CNTs was <0.01 wt%. For the second cycle, only half of the first hydrogen uptake was obtained, and this was attributed to the re-crystallization of the defect sites on the carbon substrate after the first hydrogen desorption.     

Process simulation and life cycle analysis of biodiesel production

Biodiesel is a renewable and sustainable biofuel. There are various production processes to produce biodiesel from different kinds of raw materials. In this study, the environmental impacts of biodiesel production from non-edible Jatropha oil and waste cooking oil (WCO) were investigated and compared using systematic life cycle assessment. The results show that crops growing and cultivation of non-edible Jatropha curcas lead to higher environmental impacts compared to WCO process. However, biodiesel production process from Jatropha oil has better performance because the WCO process needs to consume variety of chemicals and requires a large amount of energy for the pretreatment of raw WCO and further chemical conversion to biodiesel. Results also indicate that the collection mechanism of WCO has significant contributions towards environmental impacts. In general, biodiesel production from Jatropha oil shows higher impacts for damage categories of climate change, human health and ecosystem quality whereas biodiesel production from WCO has more severe environmental impacts for resource category. The total environmental impact is 74% less in case of using WCO as raw material compared to non-edible Jatropha oil.     

Microwave deposition of Pt catalysts on carbon nanotubes with different oxidation levels for formic acid oxidation

Platinum (Pt) nanoparticles are uniformly deposited on carbon nanotubes (CNTs) with different oxidation levels using a pulse microwave-assisted polyol (MP) method. The CNTs are chemically oxidized using nitric acid for different periods of time (1−3 h). The MP route is capable of depositing uniform Pt nanoparticles with grain size of 2.67–2.95 nm over the surface of CNTs, forming Pt@CNT catalysts for formic acid electro-oxidation. The oxygen functionalities assist in the deposition of Pt crystals over the oxidized CNTs. The Pt@CNT catalyst with high oxidation level shows positive effects on the ratio of direct (dehydrogenation) to indirect (dehydration) oxidation, CO tolerance, and long-term stability. The improved anti-poisoning ability is attributed to the facts that the surface oxygen functionalities facilitate the direct pathway of HCOOH oxidation and strip the Pt-CO_ads occupied sites.     

Preparation,characterization and hydrogen storage studies of carbon nanotubes and their composites: A review

Current challenge for researchers worldwide is to construct a reliable, efficient, and affordable medium that can store hydrogen reversibly at ambient temperature and pressure for on-board applications. Carbon nanotubes (CNTs) and their composites are considered as leading source of solid-state reversible hydrogen storage medium owing to its unique characteristics including high surface area, nanoporous structure, tuneable properties, low mass density, cage like structure, chemical stability, dissociation of hydrogen molecule, and easy synthesis method. Nanocrystalline metal or metal oxide or hydride is doped/embedded into pristine CNTs via in-situ reduction, wetness impregnation, high-energy ball milling and sputtering method. Characterization techniques of pristine and composites are utilized to study morphological, thermal, qualitative, quantative, and elemental analysis. Nanocomposite hydrogen uptake capacity is frequently measured by volumetric and gravimetric methods. Multifold enhancement of hydrogen storage of composites compared to pristine CNTs is attributed to activation, acidification, purification, ball milling and spillover of physisorbed hydrogen by metal catalyst onto CNTs via spillover mechanism. Hydrogen uptake of CNTs and composites follow monotonous dependence on hydrogen pressure. Composites not only present high hydrogen uptake as compared to pristine CNTs but also shows significant cyclic stability upon successive adsorption–desorption cycles.     

Ethanol steam reforming on Ni/CaO catalysts for coproduction of hydrogen and carbon nanotubes

Catalytic steam reforming of ethanol is considered as a promising technology for producing H₂ in the modern world. In this study, using a fixed‐bed reactor, steam reforming of ethanol was performed for production of carbon nanotubes (CNTs) and H₂ simultaneously at 600°C on Ni/CaO catalysts. Commercial CaO and a synthetic CaO prepared using sol‐gel were scrutinized for ethanol's catalytic steam reforming. Analysis results of N₂ isothermal adsorption indicate that the CaO synthesized by sol‐gel has more pore volume and surface area in comparison with the commercial CaO. When Ni was loaded, the Ni/CaO catalyst shows an encouraging catalytic property for H₂ production, and an increase in Ni loading could improve H₂ production. The Ni/CaO catalyst with sol‐gel CaO support has presented a higher hydrogen production and better catalytic stability than the catalysts with the commercial CaO support at low Ni loading. The highest hydrogen yield is 76.8% at Ni loading content of 10% for the Ni/sol‐gel CaO catalyst with WHSV of 3.32/h and S/C ratio of 3. The carbon formed after steam reforming primarily consists of filamentous carbons and amorphous carbons, and CNTs are the predominant type of carbon deposition. The deposited extent of carbon on the used Ni/CaO catalyst lessen upon more Ni loading, and the elongated CNTs are desired to be formed at the surface of the Ni/sol‐gel CaO catalyst. Thus, an efficient process and improved economic value is associated with prompt hydrogen production and CNTs from ethanol steam reforming.     

Highly coke resistant Ni–Co/KCC-1 catalysts for dry reforming of methane

Nanofibrous KCC-1 supported Ni–Co bimetallic catalysts were investigated for dry reforming of methane for syngas generation. Monometallic catalysts such as Ni/KCC-1 and Co/KCC-1, and a series of bimetallic Ni–Co/KCC-1 catalysts were prepared by impregnation and co-impregnation method, respectively. All the catalysts were characterized by XRD, FT-IR, HR-SEM, FE-SEM, XPS, FT-Raman, BET, UV–Visible DRS and AAS techniques. Monometallic nickel supported catalyst contains NiO as an active phase, whereas bimetallic nickel catalysts contain Ni₂O₃, and NiCo₂O₄ on the surface. In the case of cobalt loaded catalysts, spinel Co₃O₄ is the dominant active species, apart from NiCo₂O₄. The addition of cobalt in Ni/KCC-1 has a pronounced effect on the crystallite size, surface area and active species. The hydrogen pretreatment of the catalyst produces bimetallic Ni–Co alloy on the surface. The catalytic activities of the bimetallic catalysts towards dry reforming of methane are better than monometallic catalysts. Mesoporous silica-based KCC-1 offers easy accessibility to the entire surface moieties due to its fibrous nature and the presence of channels, instead of pores. The 2.5%Ni-7.5%Co/KCC-1 showed the maximum CH₄ and CO₂ conversion along with a remarkably low H₂/CO ratio. The life-time test confirms the high thermal stability of the catalysts at 700 °C for 8 h, with less deactivation due to coke formation. The spent catalysts were characterized by XRD, TGA, FT-Raman, and FE-SEM to understand the structural and chemical changes during the reaction. The insignificant D band and G band of graphitic carbon in FT-Raman spectra for the highly active 2.5%Ni-7.5%Co/KCC-1 and 5%Ni–5%Co/KCC-1 catalysts along with TGA results containing 12% weight loss confirms the minimum coke deposition, formation of amorphous carbon and highest coke resistance. The fibrous support restricts the sintering and aggregation of nickel particles as well the deposition of coke. The addition of amphoteric cobalt increases the activity and stability of the catalysts. Ni–Co/KCC-1 with high coke resistance seems to be a promising catalyst for dry reforming of methane.     

Morphological variation of electrodeposited nanostructured Ni-Co alloy electrodes and their property for hydrogen evolution reaction

Nanostructured nickel-cobalt alloys of the content of Co varying from 0% to 75% for hydrogen evolution reaction were fabricated by galvanostatic electrochemical deposition processes. With the incorporation of Co into Ni matrix, the morphologies of Ni-Co alloys are changed from nanocones to lamellar structure and finally evolved to a mixed shape of nanocone structure and lamellar structure. Among these Ni-Co alloys, the optimal Ni-60%Co alloy exhibits outstanding electrocatalytic activity with a small hydrogen overpotential of ?180 mV and follows Volmer-Tafel mechanism. Better performance of Ni-60%Co can be attributed to the synergetic combination of Ni and Co and unique complex mesh structure which provides the enlarged exposure of catalytically active sites. In addition, Ni-60%Co alloy also displays good electrochemical stability under 10 h galvanostatic test. With prominent electrochemical properties, Ni-60%Co alloy has a certain advantage in the catalytic hydrogen evolution material.     

Hydrogen production from catalytic reforming of the aqueous fraction of pyrolysis bio-oil with modified Ni–Al catalysts

Hydrogen production from renewable resources has received extensive attention recently for a sustainable and renewable future. In this study, hydrogen was produced from catalytic steam reforming of the aqueous fraction of crude bio-oil, which was obtained from pyrolysis of biomass. Five Ni–Al catalysts modified with Ca, Ce, Mg, Mn and Zn were investigated using a fixed-bed reactor. Optimized process conditions were obtained with a steam reforming temperature of 800 °C and a steam to carbon ratio of 3.54. The life time of the catalysts in terms of stability of hydrogen production and prohibition of coke formation on the surface of the catalyst were carried out with continuous feeding of raw materials for 4 h. The results showed that the Ni–Mg–Al catalyst exhibited the highest stability of hydrogen production (56.46%) among the studied catalysts. In addition, the life-time test of catalytic experiments showed that all the catalysts suffered deactivation at the beginning of the experiment (reduction of hydrogen production), except for the Ni–Mg–Al catalyst; it is suggested that the observation of abundant amorphous carbon formed on the surface of reacted catalysts (temperature programmed oxidation results) may be responsible for the initial reduction of hydrogen production. In addition, the Ni–Ca–Al catalyst showed the lowest hydrogen production (46.58%) at both the early and stabilized stage of catalytic steam reforming of bio-oil.     

Supporting high-loading Ni on SBA-15 as highly active and durable catalyst for ammonia decomposition reaction

Although supported Ni is generally considered the most active non-noble metal catalyst for decomposing NH₃ to produce CO_x-free H₂, its activity is not sufficient. Herein, supporting high-loading Ni on SBA-15 is explored to alleviate the low intrinsic activity issue of Ni. SBA-15 supports with tunable textual properties are synthesized to support Ni catalyst for NH₃ decomposition. Characterization shows that Ni catalyst with a loading close to 40 wt% supported on SBA-15 with the largest specific surface area (Ni/SBA-15-80) exhibits a NH₃ decomposition performance much better than those reported on other Ni-based NH₃ decomposition catalysts, resulting from its favorable textural properties and high Ni loading. In addition, Ni/SBA-15-80 shows excellent catalytic stability, with no activity degradation over an 80-h NH₃ decomposition test. This work reveals the importance of textural properties of support and Ni loading to NH₃ decomposition performance and can provide a new idea for synthesizing high-performance NH₃ decomposition catalysts.     

Simultaneous production of hydrogen and carbon nanotubes from biogas: On the design of combined process

We introduced a novel combined process of CO₂ methanation (METH) and catalytic decomposition of methane (CDM) for simultaneous production of hydrogen (H₂) and carbon nanotubes (CNTs) from biogas. In this process, biogas is catalytically upgraded into CH₄-rich gas in METH reactor using Ni/CeO₂ catalyst, and the obtained CH₄-rich gas is subsequently decomposed into H₂ and CNTs in CDM reactor over CoMo/MgO catalyst. Among the three different process scenarios proposed, the combined process with a steam condenser equipped between METH and CDM reactors could greatly improve a CNTs productivity. The CNTs production yield increased by more than 2.5-fold, maximizing at 9.08 gCNTs/gCat with a CNTs purity of 90%. The deposited carbon product was characterized as multi-walled carbon nanotubes (MWCNTs) with a surface area of 136.0 m²/g, comparable with commercial CNTs of 199.8 m²/g. The remarkable I_G/I_D ratio of 2.18 confirms a superior portion of graphitic carbon in the synthesized CNTs upon the commercial CNTs with I_G/I_D = 0.74. Notably, the CH₄ conversion reached 94.5%, while the CO₂ conversion achieved 100%, resulting in the H₂ yield and H₂ purity higher than 90%. This combined process demonstrates a promising route for production of high quality CNTs and high purity H₂ with complete CO₂ conversion using biogas as abundant renewable energy resources. In addition, the test of raw biogas showed no deactivation of catalyst, justifying the implementation of the developed process for real biogas without purification.     

A simple and fast method for the preparation of super active Pd/CNTs catalyst toward ethanol electrooxidation

For the first time, galvanic reduction by zinc sheet is used as a new strategy to prepare modified electrodes. In this work, glassy carbon electrode (GCE) was modified by decoration of Pd nanostructures on carbon nanotubes (Pd/CNTs). In this method, deposited PdCl₂ on CNTs was directly reduced to metallic Pd nanostructure using a zinc sheet in HCl (2% w/w) solution. This approach offers a number of advantages including being very fast, simple and green; and modified electrodes show high activity. The prepared catalyst is characterized by Field Emission Scanning Electron Microscopy, X-Ray Diffraction and energy-dispersive X-ray and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). In addition, electrochemical measurements show that the performance as well as the stability of the as-prepared catalyst for ethanol oxidation is outstanding. The Pd/CNTs catalyst shows higher mass current density, which is 7.9 times as high as that of commercial Pd/C.     

Highly dispersed NiCu nanoparticles on SBA-15 for selective hydrogenation of methyl levulinate to γ-valerolactone

Copper and nickel nanoparticles highly dispersed on an ordered mesoporous silica support (SBA-15) were prepared by a glycol-assisted impregnation method and tested for the catalytic transfer hydrogenation reaction of methyl levulinate to γ-valerolactone (GVL). Characterizations by high resolution transmission electron microscopy, X-ray diffraction, N₂ sorption, H₂ temperature-programmed reduction and X-ray absorption spectroscopy confirm that the highly dispersed nanoparticles were well-anchored to the mesopores of SBA-15 with the strong interaction. Comparing to a catalyst synthesized by a conventional aqueous impregnation method, our catalyst shows a higher conversion and greater selectivity towards GVL of reaction at 140–170 °C using 2-propanol as a solvent and a hydrogen donor. Results showed that NiCu/SBA-15 (EG) had much better activity, providing 91.3% conversion of ML with 89.7% selectivity towards GVL in 3 h at 140 °C. The high compositional homogeneity, uniform distribution of the nanoparticles in the mesoporous channels and the strong interaction between the metal nanoparticles and SBA-15 contribute to the superior catalytic performance. This catalyst also demonstrates superb stability over the course of 5 reaction cycles without significant loss in catalytic activity and selectivity towards GVL formation.     

Investigations of a platinum-ruthenium/carbon nanotube catalyst formed by a two-step spontaneous deposition method

Platinum (Pt) is a popular catalyst for hydrogen oxidation on the anode side of solid polymer fuel cells (SPFC). It increases the electrode activity, which catalyzes the reaction of the fuel cell. There are two methods commonly used to produce hydrogen for SPFC: fuel reforming and methanol decomposition. Both of these methods produce carbon monoxide, which is considered to be a poison for SPFC because it deactivates Pt easily. Adding ruthenium (Ru) to a Pt catalyst is an efficient way to improve the inhibition of carbon monoxide (CO) formation and reduce the Pt loading requirement.This study introduces a method to synthesize a bimetal catalyst that is suitable for SPFC. To improve the electrocatalyst activity, a new process with two spontaneous deposition steps is adopted. In the first step, Ru is deposited on the wall of carbon nanotubes (CNTs) to obtain Ru/CNTs. Pt is then added in the second deposition step to form Pt-Ru/CNTs. The morphology and microstructure of catalysts are characterized with microscopes, and the performance of membrane electrode assembly is evaluated by cyclic voltammetry method. Experimental results have proved that even with a lower Pt loading, this home-brewed bimetal catalyst performs a compatible electrocatalytic activity, and is capable of resisting attack from CO when a syngas (H₂ + 20 ppm CO) is provided.