Suitable Carbon Materials Research Articles

Numerical Analysis on the Use of Carbon Nanostructures as Interlayers to Perovskite Solar Cells Using SCAPS‐1D

AbstractDespite the numerous efforts to optimize the performance of perovskite solar cells (PSCs), challenges persist. Carbon materials are promising candidates for this purpose, but identifying the most suitable carbon material and understanding its role in the PSC among the wide family of carbons remains a challenging task. In this study, SCAPS‐1D software is employed to optimize the use of carbon materials as interlayers to PSCs. The best configuration of the carbon interlayer and the required physicochemical properties of the carbon materials is identified for improved performance. The simulations show that the insertion of thin carbon interlayers of adequate features in n‐i‐p stacked cells (FTO/TiO2/MAPbI3/HTL/Ni) can increase the efficiency of the resulting PSCs by over 2.3 %, while significantly improving the open‐circuit voltage and the fill factor. These results underline that those carbon materials with optical bandgaps ranging from 3 to 3.5 eV offer the best performance as an interlayer to the hole tranport layer, with negligible impact of the thickness of the interlayer. This contribution offers a novel perspective on the use of carbon materials in PSCs and provides new insights into the understanding of the role of carbon materials as interlayers in PSCs.

Evaluation of methane adsorption isotherms at ambient temperature on carbon materials from NLDFT pore size analysis derived from standard N2 and CO2 adsorption isotherms

In this paper, we attempt to estimate CH4 adsorption on carbon materials based on the pore size distribution (PSD) characteristics evaluated from standard nitrogen and carbon dioxide adsorption isotherms using the nonlocal density functional theory (2D-NLDFT), or more precisely, its two-dimensional version (2D-NLDFT). The PSDs of the carbons were calculated by the simultaneous fit of the NLDFT models to the corresponding N2 and CO2 adsorption data. This method is referred to in the literature as the dual gas analysis method which is implemented in SAIEUS software. Essential features of carbon PSDs affecting the shapes of methane adsorption isotherms measured at ambient temperature were identified as related to micro and mesopores carbon structure. We discuss how different micro and mesopore size ranges contribute to methane adsorption isotherms in the low and higher-pressure ranges. The results of the present study may serve as guidance for selecting and designing suitable carbon materials for practical applications such as PSA recovery of CH4 from its mixtures or for methane storage.

Revealing the effect of conductive carbon materials on the sodium storage performance of sodium iron sulfate.

Na2Fe2(SO4)3 (NFS), as a promising cathode for sodium-ion batteries, is still plagued by its poor intrinsic conductivity. In general, hybridization with carbon materials is an effective strategy to improve the sodium storage performance of NFS. However, the role of carbon materials in the electrochemical performance of NFS cathode materials has not been thoroughly investigated. Herein, the effect of carbon materials was revealed by employing various conductive carbon materials as carbon sources. Among these, the NFS coated with Ketjen Black (NFS@KB) shows the largest specific surface area, which is beneficial for electrolyte penetration and rapid ionic/electronic migration, leading to improved electrochemical performance. Therefore, NFS@KB shows a long cycle life (74.6 mA h g-1 after 1000 cycles), superior rate performance (61.5 mA h g-1 at a 5.0 A g-1), and good temperature tolerance (-10 °C to 60 °C). Besides, the practicality of the NFS@KB cathode was further demonstrated by assembling a NFS@KB//hard carbon full cell. Therefore, this research indicates that a suitable carbon material for the NFS cathode can greatly activate the sodium storage performance.

ZnCo2O4/CNT composite for efficient supercapacitor electrodes

Due to their combination of enhanced electrical conductivity and high-performance electron and ion transport channels, binary metal oxides with well-morphological optimized electrode materials have been attracted the greatest research attention for high-performance supercapacitor applications. An easy co-precipitation method is used to synthesize ZnCo 2 O 4 nanoparticles using NaOH and Urea as precipitation agents. To facilitate electrical conductivity, suitable carbon material such as carbon nanotube (CNT) has been added to make a composite material. The three-electrode system was preferred for estimating specific capacitance of prepared material and optimally efficient ZnCo 2 O 4 /CNT electrode delivered a moderate 888 F/g capacitance at 1 A/g in 3 M KOH and after 5000 charge discharge cycles 94.72% of cycling stability retained at 5 A/g. This paper presents a little price and simple procedure for preparation of ZnCo 2 O 4 /CNT electrode that promotes creative sprit for energy storage applications.

Ni(PO3)2/CNTs hybrid architecture via phthalocyanine modulated self-assemblies for efficient hydrogen evolution reaction

Reasonable design and facile synthesis of high-efficiency non-noble electrocatalysts for hydrogen evolution reaction (HER) in water splitting are crucial for renewable and clean energy technologies. Increasing the number of active sites via nanostructuring is a fundamental method to promote the HER activity of the catalysts. However, the balance between the exposed active sites and the stability cannot be well maintained due to the aggregation of nanoscale catalysts. Therefore, it is imperative to combine effective active compounds with suitable carbon materials to stabilize nanomaterials. Hence, a hybrid architecture with Ni(PO3)2 nanoparticles ladened on the carbon nanotubes (Ni(PO3)2/CNTs) was elaborately designed and synthesized by pyrolyzing the nickel phthalocyanine (NiPc)/CNTs assemblies and subsequent phosphidation. The π-π interaction between NiPc and CNTs is conductive to the tight attachment of the active species to the substrate, while the inlaid structure effectively prevents the corrosion/aggregation of Ni(PO3)2 nanoparticles and ensures the stability of the catalyst. Accordingly, Ni(PO3)2/CNTs displayed excellent HER performances with remarkable stability both in 1.0 M KOH and 0.5 M H2SO4 with overpotentials of 71 mV and 87 mV at 10 mA cm−2, respectively. The Tafel slopes of Ni(PO3)2/CNTs in alkaline and acid medium were 65 mV dec-1 and 46 mV dec-1, respectively, both exposed a Volmer-Heyrovsky mechanism during the HER. The present work will shed new light on the exploitation of non-noble metal high-efficiency HER electrocatalysts.

Theoretical studies about C2H2 semi-hydrogenation on the carbon material supported metal cluster catalysts: Influences of support type and cluster size on the catalytic performance

The support type and cluster size of the supported catalysts strongly affect their catalytic performance toward the targeted reaction. This study is designed to investigate the influences of support type and cluster size on C2H4 selectivity and activity of C2H2 semi-hydrogenation; density functional theory calculations were utilized to illustrate C2H2 semi-hydrogenation mechanism on the catalysts with the different carbon material supported different sizes of metal clusters. The results show that for the different carbon material supported single-atom Cu or Pd catalysts, the support types greatly affect C2H4 selectivity and activity, among them, GDY support shows excellent catalytic performance. On the other side, as to the Mn/GDY (M=Cu, Pd) catalysts with different cluster sizes, the activity of Pdn/GDY is generally better than that of Cun/GDY; while the selectivity of Cun/GDY is better than that of Pdn/GDY. Interestingly, Pd1/GDY presents excellent C2H4 selectivity and activity for C2H2 semi-hydrogenation, attributing to its moderate Mulliken charge of metal atoms. This study could provide valuable structure clue for the obtaining of highly-efficient supported catalysts with suitable carbon material support and cluster size.

Selective construction of fused heterocycles by mild oxidative C-H functionalization using non-metallic catalysis

Summary Under non-metallic catalysis and conditions with no external energy input, there remain to date significant unmet challenges in precise C-H functionalization with controllable sites and numbers. Here, by establishing a hierarchical, porous, low N-doped graphitic carbon/hexafluoroisopropanol (HFIP) catalyst system, we report selective construction of structurally novel π-extended N,O-heterocycles from tetrahydroquinoxalines and 2-naphthols via oxidative aryl C-H bifunctionalization at room temperature. There is good substrate and functional group compatibility, as well as excellent step and atom efficiency, and the reaction uses an accessible catalyst and a naturally abundant oxidant. Mechanistic study reveals that the in situ-formed catalyst-O2 species stabilized by HFIP enables a decent substrate oxidation to match the coupling processes. The work highlights the potential practicality of a strategy merging suitable carbon material and HFIP in further development of oxidative transformations under sustainable catalysis.

Room Temperature Oxidative C−H Functionalization for Selective Construction of Fused Heterocycles by a Low N-Doped Graphitic Carbon/HFIP Catalyst System

Under metal-free catalysis and external energy input-free conditions, there remain to date significant unmet challenges in precise C−H functionalization with controllable sites and numbers. Here, by establishing a low N-doped hierarchical porous graphitic carbon/hexafluoroisopropanol (HFIP) catalyst system, we demonstrate, for the first time, a direct construction of structurally novel π-extended N,O-heterocycles from tetrahydroquinoxalines and 2-naphthols via selective oxidative aryl C−H bifunctionalization at room temperature, proceeding with the striking features of good substrate and functional group compatibility, excellent step and atom-efficiency, and the use of easily accessible and reusable catalyst and naturally abundant oxidant. Mechanistic study reveals that the in situ formed catalyst-O2 species stabilized by HFIP enables a decent oxidation of substrates to match the coupling processes. The work highlights the potential practicality of the strategy merging suitable carbon material and hexafluoroisopropanol in further development of oxidative C−H functionalization reactions under sustainable catalysis.

Electrocatalytic hydrogen production using the designed hexaphenanthrene iron, cobalt and ruthenium(II) cage complexes as cathode (pre)catalysts immobilized on carbonaceous substrates

Hexaphenanthrene iron, cobalt and ruthenium(II) macrobicyclic complexes, the molecules of which have been designed for their efficient immobilization on carbon materials, such as activated carbon (AC), reduced graphene oxide (RGO) and carbon paper (CP), were tested as the cathode electro(pre)catalysts for hydrogen production in a PEM MEA water electrolysis cell. They were found to possess the good performances of hydrogen production. The use of the suitable carbon materials of a high surface area, AC and RGO, as the substrates for their efficient immobilization, as well as the addition of Nafion® as a polymer electrolyte, allowed to substantially increase an electrocatalytic activity of the corresponding clathrochelate-containing CP-based cathodes. Chemical design of the above metal-encapsulating cage molecules allowed a substantial decrease in a consumption of these metals by using their adsorbed monolayers. The high adsorptive capacities of the suitable carbon materials resulted in a substantial increase in a surface concentration of their electrocatalytically active centers, and, therefore, in that of an electrocatalytic activity of the obtained hybrid clathrochelate-containing carbon-based cathode materials.

New types of the hybrid functional materials based on cage metal complexes for (electro) catalytic hydrogen production

Abstract Successful using of cage metal complexes (clathrochelates) and the functional hybrid materials based on them as promising electro- and (pre)catalysts for hydrogen and syngas production is highlighted in this microreview. The designed polyaromatic-terminated iron, cobalt and ruthenium clathrochelates, adsorbed on carbon materials, were found to be the efficient electrocatalysts of the hydrogen evolution reaction (HER), including those in polymer electrolyte membrane (PEM) water electrolysers. The clathrochelate-electrocatalayzed performances of HER 2H+/H2 in these semi-industrial electrolysers are encouraging being similar to those for the best known to date molecular catalysts and for the promising non-platinum solid-state HER electrocatalysts as well. Electrocatalytic activity of the above clathrochelates was found to be affected by the number of the terminal polyaromatic group(s) per a clathrochelate molecule and the lowest Tafel slopes were obtained with hexaphenanthrene macrobicyclic complexes. The use of suitable carbon materials of a high surface area, as the substrates for their efficient immobilization, allowed to substantially increase an electrocatalytic activity of the corresponding clathrochelate-containing carbon paper-based cathodes. In the case of the reaction of dry reforming of methane (DRM) into syngas of a stoichiometry CO/H2 1:1, the designed metal(II) clathrochelates with terminal polar groups are only the precursors (precatalysts) of single atom catalysts, where each of their catalytically active single sites is included in a matrix of its former encapsulating ligand. Choice of their designed ligands allowed an efficient immobilization of the corresponding cage metal complexes on the surface of a given highly porous ceramic material as a substrate and caused increasing of a surface concentration of the catalytically active centers (and, therefore, that of the catalytic activity of hybrid materials modified with these clathrochelates). Thus designed cage metal complexes and hybrid materials based on them operate under the principals of “green chemistry” and can be considered as efficient alternatives to some classical inorganic and molecular (pre)catalysts of these industrial processes.

Agricultural Waste Derived Catalysts for Low Temperature SCR Process: Optimization of Preparation Process, Catalytic Activity and Characterization

ABSTRACT Carbon-based catalytic materials have received significant attention for low temperature flue gas denitrification (DeNOx) process, due to their physicochemical properties and ease of modification. To improve the DeNOx efficiency, preparation of biochar catalyst supports was conducted that included the acid treatment of the agricultural wastes rice straw, corn cobs and lotus leaves. Taguchi experimental design (34) was employed to screen suitable carbon materials and optimize the preparation parameters of the biochar. All of the acid-modified and unmodified samples were evaluated to determine their performance and they were characterized by using SEM, BET and FT-IR analysis. The experimental and characterization results showed that acid modification of the biochars improved their DeNOx performance, which may have been due to the changes in the physical and chemical properties of the carbon material following the acid treatment. The optimum combination in the acid modification procedure was found to be the use of lotus leaf carbon treated with an acid/mass ratio of 1.50 and a pyrolysis temperature of 800°C. The biochar prepared using these optimum preparation parameters were then employed as a carrier to support an active catalyst component (MnOx). The lotus leaf biochar supported 10 wt% manganese catalyst prepared using ultrasonic impregnation method exhibited nearly 90% NOx conversion at 250°C at a high space velocity of 45, 000–1, and it exhibited strong resistance to H2O. Additional studies showed that higher redox capacity and suitable surface acidity were two of the deciding factors in the improved low temperature SCR performance of the 10% Mn/LBC catalysts.

English

The most important target of this study is to develop a method to compare the materials’ degradation due to thermal fatigue and temperature variation between the carbon nanotube wire and unidirectional carbon fiber/epoxy composite (UCFEC). In the presented study, by using experimental results data, thermal fatigue life of carbon nanotube wire and unidirectional carbon fiber/epoxy was compared after being exposed to temperature variation in space. This process was done by using a new analytical method that models the material strength deterioration as a function of temperature variation in low Earth orbit thermal cycles. Based on the relations that were obtained by using recommended analytical method, the carbon nanotube wire offered less thermal fatigue strength degradation equal to 6.608% after being subjected to 1,200,000°C temperature variation in comparison with unidirectional carbon fiber/epoxy composite thermal fatigue strength degradation. Therefore, it seems that carbon nanotube wire shows better thermal fatigue resistance. The results of this comparison may be used to determine the suitable carbon material for space missions based on thermal fatigue life.   Key words: Carbon nanotube, low earth orbit, thermal cycles, temperature variation, material degradation.

Rapid “Mix‐and‐Stir” Preparation of Well‐Defined Palladium on Carbon Catalysts for Efficient Practical Use

AbstractA facile direct deposition approach for the preparation of recyclable Pd/C catalysts simply by stirring a solution of tris(dibenzylideneacetone)dipalladium(0) with a suitable carbon material was evaluated. An extraordinarily rapid catalyst preparation procedure (<5 min) under mild conditions and its excellent performance in cross‐coupling and hydrogenation reactions were demonstrated. The key point for catalyst design is the direct deposition of Pd0 centers onto the highly accessible surface area and the avoidance of ill‐defined PdII/Pd0 states.

Rose-like N-doped Porous Carbon for Advanced Sodium Storage

Carbon materials have been widely applied in the energy storage devices, however, the preparation of suitable carbon materials for sodium-ion batteries (SIBs) is still a challenge. In this paper, N-doped porous carbon material (NDPCs) with rose-like structure has been successfully prapared through pyrolysis of the as-prepared polyimides in-situ. The NDPCs shows rose-like structure derived from 2D nanosheets, an expanded interlayer distance of 0.387nm, a high specific surface area of 215.7m2g−1 and the electrochemical performances for Na-ion batteries are systematically investigated. A high reversible specific capacity of 240mAhg−1 at a current density of 100mAg−1 is attained and a specific capacity of 224mAhg−1 is remained even after 100 cycles. Remarkably, even at a high current density of 3.2Ag−1, the reversible specific capacity of 104mAhg−1 can be observed. This excellent performance of NDPCs electrode may be ascribed to its superior structure, since the micropore/mesopore might efficiently shorten the diffusion distance of Na-ion and the enlarged interlayer spacing of 0.38nm is significant for Na-ion insertion/extraction. Significantly, the approach to prepare carbon materials from PI may be generalized to other polymers.

Pre-Treated Carbide-Derived Carbon for Enhanced Electrode Performance

Various kinds of carbonaceous materials have been extensively studied for use as the electrodes in energy storage devices for transportation and renewable energy storage applications. Capacitive electrodes (CEs) are used in a broad range of systems related to both energy and water infrastructures across the globe. Carbide-derived Carbon (CDC), a suitable carbon material for supercapacitor applications, has been presented due to its simple preparation and easy control of structures and properties such as graphitization and porosity. CDCs produced by binary and ternary carbides showed significantly improved electrochemical capacity as various electrodes for supercapacitor and lithium ion battery. In this work, we demonstrate significantly improved electrochemical capacitance of a CDC by controlling pore texture and crystallization through the introduction of pre-treatment at high temperature for supercapacitor application. By tailoring the pore texture and graphitic structure of CDCs as pre-vacuum treatment from carbide, the electrode showed a high increase of capacitance under wide range of various scan rates from 2 mV/s ~ 100 mV/s.

Structure optimization of cathode microporous layer for direct methanol fuel cells

Abstract To obtain the cathode microporous layer (CML) with high mass transfer performance and high electronic conductivity, a pore-forming technology was introduced to optimize CML microstructure for direct methanol fuel cells. In this paper, the effects of carbon material type, carbon material loading and pore-forming agent loading in CML on fuel cell performance were discussed systematically. The results indicated that the optimized CML consisted of carbon nanotubes and ammonium oxalate with the loading of 1.5 and 3.5 mg cm−2 respectively. The fuel cell performance was improved by 30.3%, from 224 to 292 mW cm−2 at 80 °C under 0.3 MPa O2. Carbon nanotube was found to be the most suitable carbon material for the CML due to its great specific surface area and small particle size, resulting in increasing the number of the hydrophobic sites and the contact area between the support and the catalyst layer. The carbon material and pore-forming agent loading directly influenced the pore distribution and the contact resistance of membrane electrode assembly. The water removal capacity and the gas mass transfer property of diffusion layer were improved by optimizing the amount of micropore and macropore structures.

Carbon materials as electrodes for electrosorption of NaCl in aqueous solutions

Different porous carbons (MWCNT, a carbon aerogel, an activated carbon cloth and a chemically activated carbon) were evaluated as electrode material for the electrosorption of NaCl. The results obtained from the chronoamperometric experiments were correlated to the surface area and the size of the pores present in each carbon. These results indicate that all the surfaces are equivalent for the electrosorption process, demonstrating that both, mesopores and micropores, are equally effective. Nevertheless, the kinetics of the process is influenced by the pore size distribution of the carbon, although it is rather fast for all the carbons studied. The chemically activated carbon seems to be the most suitable carbon material for electrosorption of NaCl due to the combination of a high surface area and an appropriate pore size distribution.