Activated Carbon Support Research Articles

Various Morphology of WO₃ Modified Activated Carbon Supported Pd Catalysts with Enhanced Formic Acid Electrooxidation.

Activated carbon support Pd nanoparticles (NPs) modified by various WO₃-shaped catalysts were prepared and applied as an efficient anode catalyst for direct formic acid fuel cells. Three forms of WO₃ (nanosheets, nanoparticles, nanobars) modified activated carbon hybrids were first prepared via different syntheses, and then used as supports to synthesize three types of Pd-WO₃/C catalysts by a NaBH4 reduction method. The morphology, structure, and electrochemical performances of the as-prepared Pd-WO₃/C catalysts were characterized and analyzed. We can see that the noble metal particles loaded with activated carbon modified by WO₃ exhibit small particle size and uniform dispersion from the transmission electron microscope image. The synthesized composite catalysts was used for the formic acid electrooxidation and showed excellent catalytic performance. The oxidation peak current density of the Pd/WO₃-Nanosheets/C (40.04 mA·cm-2 was the highest, approximately 1.2 times that of Pd/C (33.00 mA·cm-2. Additionally, the long-term stability (i-t) test results show that the Pd/WO₃-Nanosheets/C catalyst exhibits superior stability during formic acid electrooxidation. The reason for the increase in performance can be attributed to the following: the large specific surface area of WO₃ decreases the adsorption strength of intermediates such as COad on Pd and prevents the accumulation of poisonous intermediates, thereby promoting the oxidation reaction of formic acid in the direct pathway; the catalyst-support interaction between precious metal Pd and WO₃, substantially improving the catalytic performance of Pd-WO₃/C catalysts.

Sulfonated catalytic esterification of Madhuca indica oil using waste Delonix regia: L16 Taguchi optimization and kinetics

The reported study discusses fuel-grade mahua oil methyl esters production from Madhuca indica oil, utilizing Delonix regia pods as a precursor to develop activated carbon support for preparing sulfonated carbon catalyst by H2SO4 impregnation. Raw pods were found to be thermally stable based on TGA analysis, making it suitable as raw material for catalyst synthesis. The catalyst is characterized using BET, XRD, SEM and FT-IR to check desired properties like surface area, porosity enhancement and doping of required functional groups. MOME production is optimized through L16 Taguchi design. Optimum yield of 97.04% is observed at 50 °C for 1 h with 4% w/w catalyst, methanol:oil of 6:1 and 1000 rpm. Catalyst load (1−4% w/w) affects the reaction most prominently, while methanol to oil molar ratio (3:1–12:1) is insignificant. The optimal product is characterized through ASTM standardized tests and gas chromatography analysis and conforms to acceptable biodiesel properties. The reaction adheres to pseudo-first order kinetics with low EA (4.257 kJ/mol) and high A (174.66 min−1). Catalyst shows appreciable reusability with >85% yield after 4 uses. Cost analysis of catalyst preparation shows that indigenously developed catalyst cuts down biodiesel production costs, thus the production process discussed is lucrative for commercialization.

Facile Approach for Synthesizing High-Performance MnO/C Electrodes from Rice Husk.

Pyrolysis is an effective way to convert biomass into biofuel while obtaining highly porous active carbon materials. In this study, a facile approach, involving hydrothermal and pyrolysis steps, is described for preparing hybrid metal oxide nanoparticle-embedded porous hard carbon matrices (MnO/C) from the biowaste rice husk and organometallic precursors. It was found that the pyrolysis/calcination temperature had a strong influence over the microstructure, especially over the porosity, but also over the carbon content and crystallinity of the nanocomposites; hence, the electrical properties can be controlled. Galvanostatic measurements showed that the nanocomposite obtained at 600 °C exhibited the highest charge/discharge capacity and best stability, delivering an initial discharge capacity of 1104 mA·h·g–1 at a current density of 200 mA·g–1, and retaining a value of 830 mA·h·g–1 after 200 cycles, suggesting excellent cycle stability. A discharge capacity of 581 mA·h·g–1 was obtained even at a current density as high as 2400 mA·g–1, demonstrating superb rate capability. This outstanding electrochemical performance, ascribed to high electrochemical activity of the embedded MnO nanoparticles enhanced by electrical conductivity provided through the high surface area of the active porous carbon support, is discussed in relation to the microstructure of the nanocomposite.

Direct synthesis of H2O2 over acid-treated Pd/C catalyst derived from a Pd-Co core-shell structure

Abstract Although a wide range of Pd/C catalysts has been developed for the direct synthesis of H2O2, low H2O2 yields remain a challenging issue. In this study, we propose a novel catalyst design involving the formation of Pd@Co(BO3)2 core-shell nanoparticles (NPs) on an activated carbon support followed by the cobalt borate shell etching with H3PO4. The non-noble metal shell efficiently suppressed unfavorable aggregation of Pd NPs, resulting in the formation of small and monodisperse Pd NPs after stripping the cobalt. The use of H3PO4 was also beneficial to obtain a high H2O2 yield by decreasing the metallic nature of Pd and enabling the acid-treated activated carbon to act as a solid acid support. The features of the acid-treated Pd/C catalyst derived from the Pd@Co(BO3)2 core-shell were superior enough for achieving extremely high activity in the direct synthesis of H2O2. The H2O2 productivity of 5721 mmol-H2O2/g-Pd.h with 88.1% H2O2 selectivity reported herein is one of the best values among Pd/C catalysts developed to date. It was also demonstrated that the cobalt borate shell should be completely removed because cobalt accelerated H2O2 decomposition and hydrogenation.

Controlling the Chemical Bonding of Highly Dispersed Co Atoms Anchored on an Ultrathin g-C3N4@Carbon Sphere for Enhanced Electrocatalytic Activity of the Oxygen Evolution Reaction

Controlling the chemical bonding of an active atom and carbon support is an effective strategy for enhancing the electrocatalytic activity of a metal-nitrogen/carbon catalyst. Herein, highly dispersed Co atoms are successfully prepared by using an ultrathin g-C3N4@carbon sphere as the support, and subsequently the well-defined Co-N and Co-O bonds on the atomic level are controllably constructed by adjusting the calcination atmosphere. Results show that highly dispersed Co with Co-O and Co-N bonds exhibits excellent oxygen evolution reaction performance in alkaline media at low and high overpotentials, respectively, and outperform most single-atom catalysts reported to date. DFT calculation, coupled with high-angle annular dark-field scanning transmission electron microscopy and X-ray photoelectron spectrometry techniques, reveals that the high activities mainly originate from the precise O-Co-N and N-Co-N coordination in the ultrathin g-C3N4@carbon sphere support. The enhancement mechanism of chemical bonding provides guidance for the atomic exploration and design of electrocatalysts.

Application of Microwave in Hydrogen Production from Methane Dry Reforming: Comparison Between the Conventional and Microwave-Assisted Catalytic Reforming on Improving the Energy Efficiency

The microwave-assisted dry reforming of methane over Ni and Ni–MgO catalysts supported on activated carbon (AC) was studied with respect to reducing reaction energy consumption. In order to optimize the reforming reaction using the microwave setup, an inclusive study was performed on the effect of operating parameters, including the type of catalysts’ active metal and their concentration in the AC support, feed flow rate, and reaction temperature on the reaction conversion and H2/CO selectivity. The methane dry reforming was also carried out using conventional heating and the results were compared to those of microwave heating. The catalysts’ activity was increased under microwave heating and as a result, the feed conversion and hydrogen selectivity were enhanced in comparison to the conventional heating method. In addition, to improve the reactants’ conversion and products’ selectivity, the thermal analysis also clarified the crucial importance of microwave heating in enhancing the energy efficiency of the reaction compared to the conventional heating.

Non-thermal plasma enhanced dry reforming of CH4 with CO2 over activated carbon supported Ni catalysts

In this paper, the dry reforming of methane and carbon dioxide (DRM) under plasma assisted with nickel (Ni)/activated carbon (AC) catalyst was investigated. In order to determine the synergistic effect of plasma and catalyst, DRM under plasma without catalyst, catalyst alone, and plasma assisted with catalyst was separately studied. The experimental results demonstrated that the highest catalytic activity was achieved when DRM was run under plasma combined with Ni/AC catalyst, and carbon dioxide (64.6%) and methane (65.7%) conversion, as well as the yield of hydrogen (27.9%), carbon monoxide (32.5%) were obtained. Moreover, the AC reduced at 700 °C was regard as the optimum support for DRM, NiC700 under plasma condition exhibited the best performance of DRM ascribed to its mesopores structure, higher specific surface area, and stronger metal-support interaction (SMSI) between Ni and AC support.

Activity and selectivity of Co(Ni)Mo sulfides supported on MgO, Al2O3, ZrO2, TiO2, MCM-41 and activated carbon in parallel hydrodeoxygenation of octanoic acid and hydrodesulfurization of 1-benzothiophene

Mo, CoMo and NiMo sulfide catalysts were prepared using MgO, Al2O3, ZrO2, TiO2, MCM-41 and activated carbon supports. The catalysts were tested in parallel hydrodeoxygenation (HDO) of octanoic acid and hydrodesulfurization (HDS) of 1-benzothiophene. For all supports, NiMo catalysts were more active in both HDO and HDS than Mo and CoMo catalysts. HDO activity of NiMo catalysts decreased with type of support in the following order TiO2 > C > ZrO2 > Al2O3 > MCM-41 > MgO. The products of HDO were linear C7 and C8 hydrocarbons. Some isomerization and cracking activity was observed only with MCM-41 support. HDS activity of NiMo catalysts decreased in the following order C > ZrO2 > TiO2 > Al2O3 > MgO > MCM-41. HDO/HDS selectivity was influenced by the active phase and the support type and it was the highest over the NiMo/TiO2 catalyst.

Size, nanostructure, and composition dependence of bimetallic Au–Pd supported on ceria–zirconia mixed oxide catalysts for selective oxidation of benzyl alcohol

A bimetallic Au–Pd catalyst supported on ceria–zirconia with Au:Pd molar ratio 0.8 has been synthesized using a simultaneous deposition–precipitation method and oxidized at 250, 450, and 700 °C in order to modify its particle size, nanostructure, and composition. Combined X-ray energy dispersive spectroscopy (XEDS) and X-ray photoelectron spectroscopy (XPS) analysis clearly evidence that the bimetallic Au–Pd catalyst oxidized at 250 °C is made up of a mixture of monometallic Au and Pd and bimetallic Au–Pd nanoparticles with Au:Pd ratios varying over a wide range. Increasing oxidation temperature leads to a stronger interaction between Au and Pd. Meanwhile, a slight increase of particle size and a narrowing of the Au:Pd ratio in the bimetallic nanoparticles take place. Compared with titania and activated carbon supports, the resistance against sintering at high temperatures of Au–Pd metal particles supported on ceria–zirconia is proven to be higher. A synergistic effect has been observed for selective oxidation of benzyl alcohol on these catalysts. The catalytic activity decreases only slightly after oxidation at 450 °C. However, oxidation at 700 °C results in much lower catalytic activity. Migration of Pd onto Au particles during oxidation of benzyl alcohol enhances the catalytic activity of a physical mixture of monometallic Au and Pd supported on ceria–zirconia catalysts. This fact, jointly with an analysis of the intrinsic activity, reveals the influence of the actual nature of Au–Pd interactions in the bimetallic particles, which points to higher activity of Au@Pd or AuPd@Pd nanostructures on ceria–zirconia supports.

Magnetite Nanorods Stabilized by Polyaniline/Reduced Graphene Oxide as a Sensing Platform for Selective and Sensitive Non‐enzymatic Hydrogen Peroxide Detection

AbstractIn this study, magnetite nanorods stabilized on polyaniline/reduced graphene oxide (Fe3O4@PANI/rGO) was synthesized via a wet‐reflux strategy. The possible formation of Fe3O4@PANI/rGO was morphologically and structurally verified by field emission scanning electron microscopy (FE‐SEM), Fourier transform infrared (FT‐IR) spectroscopy, Raman spectroscopy, X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). Furthermore, the thermal stability of Fe3O4@PANI/rGO was measured by a thermogravimetric analyzer (TGA); the composite had good thermal stability owing to the ceramic nature of Fe3O4. The Fe3O4@PANI/rGO has been applied as a potential sensing platform for electrochemical detection of hydrogen peroxide (H2O2). By the combined efforts of extended active surface area, active carbon support, more catalytic active sites and high electrical conductivity, the Fe3O4@PANI/rGO exhibited an improved performance toward the non‐enzymatic detection of H2O2 in 0.5 M KOH with a fast response time (5 s), high sensitivity (223.7 μA mM−1 cm−2), low limit of detection (4.45 μM) and wide linear range (100 μM–1.5 mM). Furthermore, the fabricated sensor exhibited excellent recovery rates (94.2–104.0 %) during real sample analysis.

CO Adsorption Performance of CuCl/Activated Carbon by Simultaneous Reduction–Dispersion of Mixed Cu(II) Salts

CO is a toxic gas discharged as a byproduct in tail gases from different industrial flue gases, which needs to be taken care of urgently. In this study, a CuCl/AC adsorbent was made by a facile route of physically mixing CuCl2 and Cu(HCOO)2 powder with activated carbon (AC), followed by heating at 533 K under vacuum. The samples were characterized by X-ray powder diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), N2 adsorption/desorption, and scanning electron microscopy (SEM). It was shown that Cu(II) can be completely reduced to Cu(I), and the monolayer dispersion threshold of CuCl on AC support is 4 mmol·g−1 AC. The adsorption isotherms of CO, CO2, CH4, and N2 on CuCl/AC adsorbents were measured by the volumetric method, and the CO/CO2, CO/CH4, and CO/N2 selectivities of the adsorbents were predicted using ideal adsorbed solution theory (IAST). The obtained adsorbent displayed a high CO adsorption capacity, high CO/N2, CO/CH4, and CO/CO2 selectivities, excellent ad/desorption cycle performance, rapid adsorption rate, and appropriate isosteric heat of adsorption, which made it a promising adsorbent for CO separation and purification.

Electron Microscopy Study of Degradation Mechanisms in Platinum Group Metal-Free Catalysts

Commercial low-temperature polymer electrolyte membrane fuel cells (PEMFCs) rely on expensive platinum-based catalysts to drive the oxygen reduction reaction at the cathode. In order to overcome cost barriers limiting market penetration in both transportation and stationary applications, significant efforts are being made to develop suitable platinum group metal-free (PGM-free) catalysts. The latest classes of PGM-free catalysts show very promising mass activity, but the poor durability of these carbon-based materials is still a significant challenge that must to be addressed. In this effort, advanced analytical electron microscopy methods were employed to study the degradation pathways of PGM-free catalysts which were submitted to accelerated stress tests. Catalysts provided by four different suppliers were tested concurrently in a specially designed segmented fuel cell. Polarization curves were recorded both before and after a durability stress test which involved 10k square wave cycles between 0.95 – 0.60 V in air. Analytical electron microscopy performed across a wide length scale (sub-nanometer to micron) will be presented which links the observed performance losses with changes to the atomically dispersed active sites, carbon support, and ionomer distribution. The advantages and disadvantages of different catalyst precursors (metal organic frameworks, cyanamide/polyaniline, etc.) will also be discussed from a durability standpoint. This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office under the Electrocatalysis Consortium (ElectroCat). Microscopy was performed as part of a user project at ORNL’s Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility

Removal of Copper Ions from Wastewater Using Magnetite Loaded On Active Carbon (AC) and Oxidized Active Carbon (OAC) Support

The magnetite Fe3O4 was supported on active carbon AC (Fe3O4 /AC) and oxidized active carbon OAC (Fe3O4 /OAC). It was prepared by co-precipitation method and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), surface area measurements (BET) and vibrating sample magnetometer (VSM) techniques. Fe3O4 /AC and Fe3O4 /OAC were used as adsorbents for removal of Cu (II) ions from wastewater. The effect of adsorption parameters such as contact time, the pH of the solution, the weight of adsorbent and the initial concentration of Cu(II) ions was elucidated to achieve the process’s optimal operational conditions. It was found that the removal percentage of the Cu(II) ions was reached to 96.15 % after 30 min. The adsorption process fitted very well the pseudo-second-order model and the adsorption equilibrium data could be well described by the Langmuir isotherm.

Impregnation of ZnO onto a Vegetal Activated Carbon from Algerian Olive Waste: A Sustainable Photocatalyst for Degradation of Ethyl Violet Dye

This study is aimed at developing a simple and low-cost method to fabricate ZnO-loaded porous activated carbon (AC-ZnO) prepared from the Algerian olive-waste cakes and utilize it as a photocatalyst for the degradation of Ethyl Violet dye. The synthesized AC-ZnO material was characterized using powder X-ray diffraction, BET surface area measurements, Raman microscopy, thermogravimetric analysis, UV-visible diffuse reflectance spectroscopy, and zeta potential measurements. The degradation efficiency was evaluated with Ethyl Violet (EV) dye in aqueous solution under UV irradiation supplied by a Xenon arc lamp through a Pyrex glass filter (cutoff 280 nm), and the degraded products were identified by using electrospray ionization mass spectroscopy. Additional experiments were carried out under N2 flow and with isopropyl alcohol to examine the role of superoxide and hydroxyl radicals, respectively. The amount of ●OH radical formed on irradiated AC-ZnO was tested with terephthalic acid which can act as a chemical trap for the ●OH radicals. The results from this study indicate that the AC-ZnO is a potential catalyst for the pollutant removal and the ●OH radicals are the key species for the degradation of EV. Further, this study opens up an opportunity to produce cheaper activated carbon support from olive wastes for environmental remediation applications.

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

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

Influence of catalyst structure on PEM fuel cell performance – A numerical investigation

Abstract The effect of the catalyst microstructure on a 5 cm2 PEM fuel cell performance is numerically investigated. The catalyst layer composition and properties (i.e. ionomer volume fraction, platinum loading, particle radius, electrochemical active area and carbon support type), and the mass transport resistance due to the ionomer and liquid water surrounding the catalyst particles, are incorporated into the model. The effects of the above parameters are discussed in terms of the polarization curves and the local distributions of the key parameters. An optimum range of the ionomer volume fraction was found and a gain of 39% in the performance was achieved. As regards the platinum loading and catalyst particle radius, the results showed that a higher loading and a smaller radius leads to an increase in the PEMFC performance. Further, the influence of the electrochemical active area produces an overall increase of 22% in current density and this was due to the use of a new material developed as support for Pt particles, an iodine doped graphene, which has better electrical contacts and additional pathways for water removal. Using this parameter, the numerical model has been validated and good agreement with experimental data was achieved, thus giving confidence in the model as a design tool for future improvements of the catalyst structure.

The improved hydrodechlorination catalytic reactions by concerted efforts of ionic liquid and activated carbon support

Modified and stabilized palladium nanoparticles were prepared successfully by using an ionic liquid, 1-butyl-3-methylimidazolium trifluoroacetate.

Enhancing the sugars production yieldby supporting H3PW12O40 heteropoly acid on activated carbon for use as catalyst in hydrolysis of cellulose

In this work, two catalysts were produced to be used in hydrolysis of cellulose reactions to obtain glucose, a raw material used in the production of bioethanol. The heteropoly acid, H3PW12O40 (HPW), reported as strong and thermally stable acid, was supported on activated carbon (AC) in a ratio varying from 1:1 to 2:1 to produce the catalysts AC-HPW (1:1) and AC-HPW (2:1). The catalysts were tested in cellulose hydrolysis evaluating some reaction variables and the results show the remarkable dependence of reaction temperature, amount and acidity of the catalyst. The results indicate the advantage of supporting HPW on carbonaceous material for using as catalyst in hydrolysis of cellulose, showing better conversion rate into sugars comparing with unsupported HPW. Keywords: heteropoly acid; activated carbon support; hydrolysis of cellulose.

Pd Nanoparticle Catalysts Supported on Nitrogen-Functionalized Activated Carbon for Oxyanion Hydrogenation and Water Purification

We provide an efficient, sustainable, low-cost, and potentially scalable method to prepare N-functionalized activated carbon (AC) for Pd-based catalysis with improved performance for water purification. N-functionalized AC supports were realized via “soft nitriding”, that is, low temperature heating of a urea–AC mixture, and Pd nanoparticles with a significantly increased number of surface Pd(0) sites were achieved on the supports. Moreover, Pd nanoparticles were preferentially loaded near the (treated) AC exterior surface. N-functionalization improved nitrite and bromate hydrogenation kinetics but not for chlorite and chlorate, suggesting that different mechanisms determine the reaction activity of these oxyanions.

Enhancement of the Stability of Au-Cu/AC Acetylene Hydrochlorination Bimetallic Catalyst with Melamine Treated Support

This paper highlights the experimental and theoretical studies on the Melamine treated Active Carbon (MAC) support for an Au-Cu bimetallic catalyst in acetylene hydrochlorination reaction. Compared to the original Active Carbon (AC) loaded with the same amount of 0.1wt% Au and 1.0wt% Cu, MAC supported catalyst(MACH), wherein Carbon/C6H6N6 mass ratio was 5:3, exhibited excellent catalytic activity. The initial conversion of acetylene increased from 77.5% to 82.7% at 150℃ and atmospheric pressure. The gas hourly space velocity (GHSV) was 120h-1 under a feed volume ratio VHCl/VC2H2 of 1.05. As polymerization of acetylene on the catalyst was the main cause of deactivation, accelerated deactivation test was carried out. The result indicated MACH performed good anti-coking capacity. Based on the characterization by using BET, XRD, SEM, TGA, TPD and XPS techniques, the variation of O1s XPS spectra of the synthesized catalysts was observed that was in line with DFT results. It is postulated that the better stability and the better dispersion of gold actions were ascribed to the additional metal and the modified substrate. The electron transmission from the auxiliary and the elevated groups on the catalyst surface partially inhibited the reduction of the Au3+ active species. Meanwhile, the stronger adsorption energy of HCl was also beneficial to catalytic activity and stability.