Catalytic Activity Of Carbon Research Articles

Non‐Carbon‐Dominated Catalyst Architecture Enables Double‐High‐Energy‐Density Lithium–Sulfur Batteries

AbstractThe commonly used “catalyst on carbon” architecture as a sulfur host is difficult to jointly achieve high gravimetric and volumetric energy densities for lithium–sulfur (Li–S) batteries due to the contradiction between low tap density/poor catalytic activity of carbon and the easy agglomeration of metal‐based compounds without carbon. Here, a non‐carbon‐dominated catalytic architecture using macroporous nickel/cobalt phosphide (NiCoP) is reported as the sulfur host for Li–S batteries. The macroporous framework, which accommodates a large amount of sulfur, can accelerate the electrochemical reaction kinetics by accelerated e− transport, Li+ diffusion, and superior adsorption and catalytic activity of inherent Ni2P/CoP heterostructures. The high tap density (0.45 g cm−3) and mechanically hard features contribute to the excellent structural and physicochemical stability of the NiCoP@S electrode after the pressing and rolling process. These features enable the Li–S coin cell to exhibit excellent electrochemical performance under conditions of high sulfur loading (10.2 mg cm−2) and lean electrolyte (electrolyte/sulfur of 2 µL mg−1). Inspiringly, the assembled pouch cell can simultaneously deliver a gravimetric energy density of 345.2 Wh kg−1 and an impressive volumetric energy density of 952.7 Wh L−1 based on the entire device configuration.

Comparison of the Catalytic Activity of Carbon, Spinel-Based, and Carbide Materials in the Na-Air Battery

Rechargeable sodium-oxygen batteries have attracted much interest in recent years, owing to their high theoretical specific energy, and the abundance of sodium. The material of which the cathode is constructed influences the performance of the battery. In this study, we show that low-surface-area glassy carbon (GC) cannot operate for more than four consecutive cycles, whereas high-surface-area carbon materials, such as Black Pearl 2000 carbon (BP 2000), significantly increase the number of cyclic- voltammetry runs, without current reduction. NiCo2O4 was previously considered a promising material for the cathode. However, its activity was not compared with the only carbon-based electrode. Here we compare the electrochemical performance of four different NixCoyOz powders to BP 2000, XC72R, and SB carbon. The highest activity was obtained with the use of a powder, which contained 45% NiCo2O4, 10% CoO, 30% metallic nickel and 15% metallic cobalt. We believe that the metallic nickel and cobalt phases are responsible for this high catalytic activity. Accelerated stress tests of XC72R, BP 2000, SB, and TiC powders, after 100 cyclic-voltammetry cycles, revealed that TiC exhibited the greatest loss of reduction peak area (~57%) during the test, indicating the highest loss of catalytic activity. It also exhibited higher loss of oxidation peak area than Vulcan XC72R (~68% vs. ~35%), but lower than BP 2000 (~90%) and SB carbon (~72%). The reason for such a high degradation probably comes from strong surface changes or loss of adhesion of the catalyst powder to the GC electrode during the AST. It was suggested that in most cases, it is the OER process, which exhibits stronger deterioration.

Revealing High Oxygen Evolution Catalytic Activity of Fluorine-Doped Carbon in Alkaline Media.

Oxygen evolution reactions (OER) are important reactions for energy conversion. Metal-free carbon-based catalysts potentially contribute to the catalytic materials for OER. However, it has been difficult to understand the intrinsic catalytic activity of carbon materials, due to catalyst decomposition over the course of long-term reactions. Here, we report high oxygen evolution reaction catalytic activity of F-doped carbon in alkaline media. Intrinsic OER activity was evaluated from a combination of measurements using a rotating disk electrode and O2 sensor. The F-doped carbon catalyst is a highly active catalyst, comparable to state-of-the-art precious-metal-based catalysts such as RuO2.

Catalytic activity of carbon supported-Pt-Pd nanoparticles toward the oxygen reduction reaction

In this work, Pt-Pd catalysts (≈ 35 wt.%, Pt:Pd atomic ratio ≈ 1:2) supported on carbon black, carbon nanofibers and carbon xerogels have been synthesized in order to assess their activity toward the oxygen reduction reaction (ORR). X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis showed low particle and crystallite sizes with good dispersion on carbon supports. Regarding the ORR, the Pt-Pd nanoparticles supported on carbon black displayed the best performance in terms of high diffusional current densities, high specific and mass activities, number of electrons involved in the ORR and enhanced corrosion resistance. The improved performance of this catalyst has been explained from the modification of the Pt-Pt interatomic distance by Pd and the holding/re-reducing of the hydrogen peroxide formed during the ORR, promoting the water formation. In general, the synthesized materials displayed an upgraded corrosion resistance compared with that of the commercial Pt catalyst, suggesting them as suitable candidates to be employed as cathodes in PEMFCs since their Pt content is lower than that of the commercial Pt/C.

Вплив гетероатомів азоту та кисню на каталітичну активність вуглецевих нанопоруватих матеріалів типів КАУ й СКН у реакції розкладання пероксиду бензоїлу

Вплив гетероатомів азоту та кисню на каталітичну активність вуглецевих нанопоруватих матеріалів типів КАУ й СКН у реакції розкладання пероксиду бензоїлу

Sonochemical synthesis of carbon supported Sn nanoparticles and its electrochemical application

A sonochemical approach was employed to prepare Vulcan carbon XC-72R supported by Sn nanoparticles at room temperature in the presence of ethylene glycol. The reduction of metallic Sn ion and ethylene glycol takes place and in turn the glycolate ion as formed acts as a stabilizing agent. Transmission electron microscope, X-ray diffraction, and X-ray photoelectron spectroscopy have illustrated that the metallic Sn nanoparticles are successfully embedded on the carbon. The significantly observed reduction over potential for oxygen reduction reaction displays a higher catalytic activity of carbon supported by Sn nanoparticles due to the large surface area of the modified electrode.

Influence of pre-treatment on the catalytic activity of carbon and its Co-based catalyst for oxygen reduction reaction

Impact of carbon pre-treatment on the catalytic activity and selectivity of its own and its relevant non-precious metal Co-based catalyst (carbon-supported cobalt diethylenetriamine, CoDETA/C) for oxygen reduction reaction is investigated. Three pre-treatment methods involving thermal treatment, H2O2-oxidation and KOH-activation are used in this paper. Electrochemical activity demonstrated by cyclic voltammograms and rotating ring disk electrode technique in O2-saturated electrolyte shows that pre-treatment step has a significant effect on the catalytic activity and selectivity of carbon and its Co-based catalyst: (1) for carbon sample, a KOH-activation gives the highest activity in acid medium, while a H2O2-oxidation in alkaline solution; and (2) for its Co-based catalyst, the as-ground gives the highest activity and selectivity in acid solution, while a KOH-activation in alkaline medium. Raman spectra indicate that pre-treatment can decrease the disorder of carbon matrix. X-ray diffraction shows that face-centered cubic α-Co phases are present and pre-treatment of carbon can decrease the size of metal Co dispersed on the catalyst surface.

Preparation of Sulfonated Carbons from Rice Husk and Their Application in Catalytic Conversion of Glycerol

Sulfonated carbons were prepared from carbonized rice husk and further treatment with sulfuric acid (TC-6M, sulfuric acid 6 mol L–1 under reflux, TC-L, concentrated 96% sulfuric acid under reflux, TC-V, vapor of concentrated 96% sulfuric acid). The catalytic activity of carbons was evaluated in esterification of glycerol with acetic acid (AA) and etherification of glycerol with tert-butyl alcohol (TBA). Only the TC-L carbon showed a significant amount of sulfur in its composition (2.2 mmol g–1). This catalyst also had the highest total acidity (5.8 mmol g–1) and improved the best catalytic performance in glycerol esterification and etherification. In the esterification reaction of glycerol, 90% conversion was observed after 5 h of reaction, with selectivities of 11%, 52%, and 37% to mono-, di-, and tri-glycerides, respectively. In the etherification of glycerol, after 4 h of reaction a conversion of 53% was achieved, with 25% selectivity to di- and tri-tert-butylglycerol. Thus, the use of sulfonated carbons in glycerol conversion proved to be an interesting alternative to add value to the production chains of rice and biodiesel by using their byproducts: rice husk and glycerol.

Studies on a Customized Carbon Catalyst in Biodiesel Production from Waste Sunflower Oil

In this study, transesterification of waste sunflower oil with high free fatty acid was studied in a combined heterogeneous and homogeneous catalytic system. Production of hetero-carbon catalyst and their characteristics were done. The effects of the heterogeneous carbon on the homogeneous acid and base catalyzed transesterification reaction were analyzed. Parameters, such as reaction temperature, reaction time, and excess methanol, affecting the reaction were optimized to obtain a high yield of biodiesel. The results clearly showed that the introduction of customized carbon reduced both acid and base catalyst consumption. It was observed that carbon alone is not responsible for catalyzing the transesterification reaction but the addition of carbon reduces the homogeneous catalyst consumption. It was found that the catalytic activity of carbon with acid catalyst was found to have maximum performance. The highest conversion of waste sunflower oil was found to be 82% with acid catalyst at the following optimized process conditions: Combination of 1.5 wt% H2SO4, 5 wt% carbon, 90 minutes reaction time at 65°C, and 100% excess methanol.

Enhancement of nitric oxide removal by ammonia on a low-rank coal based carbon by sulphuric acid treatment

This work presents a study of the effect of wet sulphuric acid treatment and gas-phase treatment with SO 2 + O 2 + H 2O on the catalytic activity of a low-rank coal-based carbon for the nitric oxide reduction with ammonia. Carbons were characterized by N 2 adsorption, TPD, and FTIR in order to assess how the surface chemistry and the texture of carbons change after the treatments. A great amount of oxygenated functional groups both CO 2 and CO evolving ones are produced by liquid-phase sulphuric acid treatment. However, the amount of those groups after gas-phase treatment with SO 2 + O 2 + H 2O is lower, in particular the CO 2 evolving groups. The catalytic activity of carbons was examined in a fixed bed reactor at 150 °C in a gas flow containing NO, O 2, N 2 and NH 3, the effluent concentration being monitored continuously during the reaction. The obtained results indicate that an appropriate balance between the type of oxygen functional groups and surface area available to the reactant gas are required to reach high levels of NO conversion.

Catalysis of methane decomposition over elemental carbon

Catalytic decomposition of methane is an attractive method for CO/CO 2-free production of hydrogen, particularly, for fuel cell applications. Over 30 different samples of elemental carbon, including a variety of activated carbons (ACs), carbon blacks (CBs), nanostructured carbons (including, carbon nanotubes and fullerenes C 60/70), graphites, glassy carbon and synthetic diamond powders, were screened for the catalytic activity in methane decomposition reaction. It was found that the catalytic activity of carbons is mostly determined by their origin, structure and surface area.

Catalytic decomposition of hydrogen peroxide in alkaline solutions

Catalytic activity of carbon, platinum-supported on high-area carbon, platinum, lead ruthenate, and ruthenium oxide towards hydrogen peroxide decomposition in alkaline solution is investigated using the rotating disk electrode technique. The heterogeneous rate constant for peroxide decomposition on these catalysts is determined from the slope of log( i L) versus time, where i L is the diffusion-limiting current corresponding to the concentration of peroxide at a given time. The order of catalytic activity is found to be platinum>lead ruthenate>ruthenium oxide>carbon. A general reaction mechanism for the peroxide decomposition on these catalysts is also proposed.

Carbon as a catalyst in oxidation reactions and hydrogen halide elimination reactions

Carbon catalyses many reactions, mainly oxidation reactions with oxygen and with halogens, e.g. SO 2 + 1 20 2 → SO 3 , or CO + Cl 2→ COCl 2. It is known, however, that different carbons behave quite differently in the reduction of oxygen on fuel cell cathodes. Therefore the catalytic activity of carbons has been studied in other reactions. A convenient test reaction is the oxidation of dilute aqueous sulphurous acid. It became apparent that all catalytically active carbons contain small quantities of nitrogen, and inactive carbons such as wood charcoal or carbon blacks can be rendered highly active by treatment with N H 3 or HCN at elevated temperatures. Photoelectron spectra indicate that the catalytic activity increases parallel to the incorporation of a nitrogen species which is pyridine-like, i.e. incorporated in the aromatic layers. Treatment with NH 3 at 900 °C leads also to massive gasification of the carbons, increasing their surface area. Other reactions studied included the oxidation of aqueous oxalic acid and of methanol to formaldehyde. A quite different type of reaction is the elimination of hydrogen chloride from 1-chloroalkanes, e.g. 1 -chlorobutane. Again, activity changes in parallel to nitrogen content. Reaction products are olefins, dimers of the alkyl groups, and a polymer on the catalyst surface. The formation of alkyl dimers, e.g. n-octane in the case of n-butylchloride, suggests that radicals are involved in the reaction.

174. Remarkable catalytic activity of carbon activated with sulfuric acid for the reduction of nitric oxide

174. Remarkable catalytic activity of carbon activated with sulfuric acid for the reduction of nitric oxide

The Catalytic Activity of Carbons from Aromatic Hydrocarbons and Some Derivatives

The Catalytic Activity of Carbons from Aromatic Hydrocarbons and Some Derivatives