Nanowrinkled Carbon Aerogels Embedded with FeNx Sites as Effective Oxygen Electrodes for Rechargeable Zinc-Air Battery (original) (raw)
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Carbon aerogels for catalysis applications: An overview
Carbon, 2005
Carbon aerogels are nanostructured carbons obtained from the carbonization of organic aerogels, which are prepared from the sol-gel polycondensation of certain organic monomers. These materials have a great versatility both at the nanoscopic level in terms of their pore texture and at the macroscopic level in terms of their form. Thus, the surface area, pore volume, and pore size distribution are tuneable surface properties related to the synthesis and processing conditions, which can produce a wide spectrum of materials with unique properties. In addition, carbon aerogels can be obtained in the form of monoliths, beads, powders or thin films. All these properties make them promising materials for application in adsorption and catalysis. Metal-doped monolithic organic aerogels can be easily prepared by following three main strategies: by addition of the metal precursor to the initial mixture, by ion-exchange or by deposition of the metal precursor on the organic or the carbon aerogel by one of various methods. These metal-doped carbon aerogels have been used as catalysts and as electrodes for electrical double-layer capacitors. This article shows the preparation of metal-doped carbon aerogels, their physico-chemical surface properties and their applications as catalysts in various reactions.
One-Pot Synthesis of Fe-N-Containing Carbon Aerogel for Oxygen Reduction Reaction
Electrocatalysis, 2020
Three-dimensional Fe-N-C aerogel catalysts for the oxygen reduction reaction (ORR) are prepared with resorcinolformaldehyde-melamine and iron precursor using one pot sol-gel process followed by supercritical drying and heat treatment in nitrogen (N2) and then ammonia (NH3) atmospheres. We studied the effect of the synthesis conditions (Fe precursor and Fe content) of organic aerogel and the heat treatment parameters (including temperature and duration) under N2/NH3 atmosphere on the structural properties and ORR catalytic activities of the resulting Fe-N-C aerogel catalysts. The Fe-N-C aerogel catalysts were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and N2-adsorption/desorption, and the ORR activities were studied by the rotating disk electrode method. It was found that the pore structure, the chemical composition and ultimately the ORR performance were largely affected by the nature of iron precursor, iron content and the conditions of heat treatment. The catalysts using Iron (III) acetylacetonate as Fe precursor incorporated with 3 wt% of Fe followed by the HT at 800 °C for 1 h under N2 and then 950 °C under NH3 for 30 min, showed the highest content of active site (Fe-Nx) and largest mesopore volume, resulting in an enhanced catalytic activity and mass-transport property.
Oxygen reduction on an iron?carbonized aerogel nanocomposite electrocatalyst
Journal of Solid State Electrochemistry, 2005
Iron-carbonized aerogel nanocomposite was prepared from highly porous polyacrylonitrile microcellular foams containing a salt of iron, followed by carbonization. The electrochemical reduction of oxygen at this material was studied by using the rotating disk electrode method. In common with Pt/C, iron-carbonized aerogel nanocomposite presented excellent electrocatalytic activity for the oxygen reduction under experimental conditions close to those of a fuel cell cathode, that is, at the catalyst/Nafion interface in acidic solutions.
Electrochimica Acta, 2017
Iron-containing nitrogen-doped carbon aerogels (CAs) were prepared by pyrolysis of organic aerogels of variable composition synthesised from melamine, 5-methylresorcinol and 2,6-dihydroxy-4-methylbenzoic acid. The structure and composition of the catalyst materials were characterised by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, atomic absorption spectroscopy and N 2-adsorption analysis. The electrocatalytic activity of CAs for oxygen reduction reaction (ORR) was evaluated using the rotating disk electrode (RDE) method in alkaline solution and increase of the ORR activity with increasing the nitrogen and iron content was revealed. Low peroxide production on Fe-containing N-doped CA-based catalysts and their high methanol tolerance suggest that these could be suitable cathode catalysts for alkaline fuel cells.
Comparative Study of Two Types of Iron Doped Carbon Aerogels for Electrochemical Applications
Journal of New Materials for Electrochemical Systems, 2013
Iron doped carbon aerogels have been prepared by sol-gel polymerization of potassium salt of 2,4-dihydroxybenzoic acid with formaldehyde followed by an ion-exchange process between K+ doped wet gel and Fe(II) or Fe(III) ion aqueous solutions. The resulted Fe(II) or Fe(III) doped gels have been dried in supercritical conditions with liquid CO2 and then pyrolyzed in high temperature resulting two types of iron doped carbon aerogels. These aerogels were morpho-structural investigated by using BET method, transmission electron microscopy, X-ray diffraction and elemental analysis. Also, these iron doped carbon aerogels (CAD-Fe(2+) and CAD-Fe(3+)) were tested for realization of modified carbon paste electrodes. CAD-Fe(2+) aerogel showed better electrochemical activity than CAD-Fe(3+) and also a good electrocatalytic activity towards H2O2 reduction (expressed by an electrocatalytic efficiency of 404% measured at – 500 mV vs. SCE).
Nanomaterials, 2018
A series of carbon aerogels doped with iron, cobalt and nickel have been prepared. Metal nanoparticles very well dispersed into the carbon matrix catalyze the formation of graphitic clusters around them. Samples with different Ni content are obtained to test the influence of the metal loading. All aerogels have been characterized to analyze their textural properties, surface chemistry and crystal structures. These metal-doped aerogels have a very well-developed porosity, making their mesoporosity remarkable. Ni-doped aerogels are the ones with the largest surface area and the smallest graphitization. They also present larger mesopore volumes than Co-and Fe-doped aerogels. These materials are tested as electro-catalysts for the oxygen reduction reaction. Results show a clear and strong influence of the carbonaceous structure on the whole electro-catalytic behavior of the aerogels. Regarding the type of metal doping, aerogel doped with Co is the most active one, followed by Ni-and Fe-doped aerogels, respectively. As the Ni content is larger, the kinetic current densities increase. Comparatively, among the different doping metals, the results obtained with Ni are especially remarkable.
ChemElectroChem, 2021
Developing high performance nonprecious metal-based electrocatalysts has become a critical first step towards commercial applications of metal-air batteries. Herein, nanocomposites based on Co/Co 2 P nanoparticles encapsulated within hierarchically porous N, P, S co-doped carbon are prepared by controlled pyrolysis of zeolitic imidazolate frameworks (ZIF-67) and poly (cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS). The resulting Co/Co 2 P@NPSC nanocomposites exhibit apparent oxygen reduction reaction (ORR) and evolution reaction (OER) catalytic performance, and are used as the reversible oxygen catalyst for zinc-air batteries (ZABs). Density functional theory (DFT) calculations exhibit that Co 2 P could provide active sites for the ORR and promote the conversion between the adsorbed intermedi-ates, and porous N,P,S co-doped carbon with Co 2 P nanoparticles also improves the exposure of actives sites and endows charge transport. Liquid-state ZABs with Co/ Co 2 P@NPSC as the cathode catalysts demonstrate the greater power density of 198.1 mW cm À 2 and a long cycling life of 50 h at 10 mA cm À 2 , likely due to the encapsulation of Co/Co 2 P nanoparticles by the carbon shell. Solid-state ZABs also display a remarkable performance with a high peak power density of 74.3 mW cm À 2. Therefore, this study indicates the meaning of the design and engineering of hierarchical porous carbon nanomaterial as electrocatalyst for rechargeable metal-air batteries.
Fe-N-Carbon aerogel catalyst for oxygen reduction reaction
EFCF 2021, 2021
Proton exchange membrane fuel cell (PEMFC)s are an excellent energy conversion device for wide application of hydrogen, especially for portable or transportation applications. To reduce the total cost of these devices, non-precious-metal catalysts (NPMCs) have shown promises in replacing platinum-based catalysts. Among NPMCs, iron-nitrogen-carbon (Fe-N-C) catalysts subclass are the most mature. These catalysts are based on nitrogen (N) coordinated iron (Fe) ions embedded in a carbon (C) matrix acting as catalytically active centers. Numerous studies have focused on promoting their catalytic performance towards the oxygen reduction reaction (ORR). Nevertheless, such materials remain less performant than carbon-supported platinum nanoparticles (Pt/C), leading to ca. 3-10 times thicker cathodes, and associated mass transport limitations. Carbon aerogels are ideal candidates to synthesize Fe-N-C catalysts with tuneable mass transport properties thanks to their tridimensional open texture, tailored pore size distribution from micro to macropores and their good electrical conductivity. Herein, we show the promises of Fe-N-C aerogels synthesized a "one pot" sol-gel method comprising formation of a Fe-doped resorcinol (R)-formaldehyde (F)-melamine (M) hydrogel, and followed by carbon dioxide (CO2) supercritical drying, and high temperature pyrolysis under N2 and NH3 atmosphere. By introducing ligands in the synthesis mixture, we modified the chemical environment of the Fe precursor. The resulting changes in morphology, ORR activity and mass transport properties are investigated a rotating disk electrode (RDE) setup and a PEMFC device.
Catalytic graphitization of carbon aerogels by transition metals
2000
Carbon aerogels and Cr-, Fe-, Co-, and Ni-containing carbon aerogels were obtained by pyrolysis, at temperatures between 500 and 1800°C, of the corresponding aerogels prepared by the sol-gel method from polymerization of resorcinol with formaldehyde. All samples were characterized by mercury porosimetry, nitrogen adsorption, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. Results obtained show that carbon aerogels are, essentially, macroporous materials that maintain large pore volumes even after pyrolysis at 1800°C. For pyrolysis at temperatures higher than 1000°C, the presence of the transition metals produced graphitized areas with three-dimensional stacking order, as shown by HRTEM, XRD, and Raman spectroscopy. HRTEM also showed that the metalcarbon containing aerogels were formed by polyhedral structures. Cr and Fe seem to be the best catalysts for graphitization of carbon aerogels.