Carbon-rich materials with three-dimensional ordering at the angstrom level

Carbon-rich materials, which contain over 90% carbon, have been mainly synthesized by the carbonization of organic compounds. However, in many cases, their original molecular and ordered structures are decomposed by the carbonization process, which results in a failure to retain their original three-dimensional (3D) ordering at the angstrom level. Recently, we successfully produced carbon-rich materials that are able to retain their 3D ordering at the angstrom level even after the calcination of organic porous pillar[6]arene supramolecular assemblies and cyclic porphyrin dimer assemblies. Other new pathways to prepare carbon-rich materials with 3D ordering at the angstrom level are the controlled polymerization of designed monomers and redox reaction of graph. Electrocatalytic application using these materials is described

Electrochemical behavior of pt- a d pd-supported activated carbons with different functionalities

Due to their relatively low price, high surface area and versatile physic-chemical properties, conductive carbon materials are considered among the most promising supports of electroactive species and/or catalysts for different electrochemical devices, like supercapacitors, fuel cells, batteries, sensors, etc. [1]. However, in these applications, carbon supports are usually subjected to oxidation and/or corrosion processes, which can be promoted by the supported electroactive species and/or catalysts [2]. In this sense, although the surface functionalities of carbons seem to play a key role on their electrochemical response and stability, their influence in the presence of electroactive catalysts is still controversial. Particularly, the effect of phosphorous groups has been never reported. In this work, the influence of different oxygen and phosphorous functionalities on the electrochemical behavior of Pt- and Pd-supported activated carbons (ACs) has been studied. Various ACs showing similar surface areas (ca. 1400-1500 m2/g) and a rich variety of surface chemistry, with oxygen and phosphorous-like surface groups, were obtained by physical (CO2) (HAG800 support) or chemical (H3PO4) (HA3500 support) activation of olive stone. The ACs were used as support of Pd, Pt and Pd/Pt catalysts (Fig 1a), with nominal loadings of 0.5-1.0 wt%, by using the incipient-wetting impregnation method. The samples were characterized by N2 and CO2 adsorption, TEM, XRD, XPS, TPD experiments and different electrochemical techniques. Although the supported metals promote carbon electroxidation and/or corrosion (see the higher oxidation currents for the metalloaded sample – Fig 1b), the presence of surface phosphorous groups (HA3500-M samples) results in lower oxidation currents than in the case of P-free samples (HAG800-M samples) (Fig. 1.b). These results are in agreement with the oxidation resistance induced by phosphorous groups in oxidizing gas phase at high temperatures [3], and may support the statement that these phosphorous groups could enhance the durability of carbon-supported metal electrocatalysts for different electrochemical applications.Universidad de Málaga. Campus de Excelencia Andalucía Tech

Effect of carbon surface on degradation of supercapacitors in a negative potential range

The stability of supercapacitors is the key factor for their use under high temperature, high voltage and long-term durability. To improve the supercapacitor stability, there is a need to understand the degradation mechanism. In this work, the degradation sites in a carbon electrode at negative potential range are investigated in two common organic electrolytes: 1 M Et4NBF4 dissolved in propylene carbonate and in acetonitrile. To elucidate the common factor over a wide range of carbon materials, we examined eight kinds of carbon materials including activated carbons, carbon blacks, zeolite-template carbon (high surface area and a large amount of carbon edge sites) and graphene mesosponge (high surface area and a little amount of carbon edge sites). Their surface structures are distinguished into two regions: carbon basal planes and edge sites by nitrogen physisorption and high-sensitivity temperature-programmed desorption up to 1800 °C. Unlike the degradation at positive potential range, initial degradation reactions at negative potential range occur mainly on the carbon basal planes rather than the edge sites. This finding is corroborated by the theoretical calculation.This work was supported by JSPS KAKENHI (grant Nos. 17H01042 and 19H00913); the Dynamic Alliance for Open Innovation Bridging Human, Environment, and Materials program; and the Network Joint Research Centre for Materials and Devices. R. T. acknowledges the China Scholarship Council for the financial support. MINECO and FEDER (CTQ2015-66080-R MINECO/FEDER) are acknowledged for financial support

Binderless thin films of zeolite-templated carbon electrodes useful for electrochemical microcapacitors with ultrahigh rate performance

Controlled nanozeolite deposits are prepared by electrochemical techniques on a macroporous carbon support and binderless thin film electrodes of zeolite-templated carbon are synthesized using the deposits as templates. The obtained film electrodes exhibit extremely high area capacitance (10–12 mF cm−2) and ultrahigh rate capability in a thin film capacitor.We thank the Generalitat Valenciana, and FEDER (PROMETEO/2009/047) and the Spanish Ministry of Economy and Competitiveness (Projects PRI-PIBJP-2011-0766, CTQ2012-31762 and MAT2010-15273). A.B.M. thanks the Spanish Ministry Science and Innovation for a Ramón y Cajal fellowship (RyC 2009-03913). This research was also supported by Strategic International Cooperative Program, Japan Science and Technology Agency (JST)

Estudio de la capacidad electroquímica mediante carbones nanomoldeados

The template carbonization technique enables the production of porous carbons and carbon-based composites with precisely designed, controlled pore structures. The resulting templated carbons are therefore useful to investigate and understand the relation between carbon nanostructure and electrocapacitive properties. In this short review paper, we introduce our works on electrochemical capacitance using zeolite-templated carbons and carbon-coated anodic aluminum oxide.La técnica de nanomoldeo mediante carbonización de plantillas sólidas infiltradas permite la preparación y el diseño de materiales carbonosos porosos, tanto puros como compuestos, donde las estructuras porosas son fácilmente definibles y controlables. Los carbones nanomoldeados resultantes son muy útiles como materiales modelo para estudiar las relaciones entre la nanostructura del carbón y sus propiedades electrocapacitivas. En este trabajo, realizamos una breve revisión de nuestros estudios sobre la capacidad electroquímica utilizando carbones nanomoldeados obtenidos como réplica de una zeolita o por recubrimiento de óxido de aluminio anodizado.This research was partially supported by the Strategic International Cooperative Program, Japan Science and Technology Agency (T.K.) and MINECO (Spanish-Japanese project PRI-PIBJP-2011-0766); and a Grant-in-Aid for Scientific Research (B), 26286020 (H.N.). This research was partially supported also by Nano-Macro Materials, Devices and System Research Alliance and by Network Joint Research Center for Materials and Devices

Insight into the origin of carbon corrosion in positive electrodes of supercapacitors

While activated carbons are used as electrode materials in commercial supercapacitors, they are not stable under high voltage operation especially at a positive-electrode side, and this limits the working voltage of supercapacitors to about 2.8 V in organic electrolytes. Thus, revealing the specific carbon chemical structures causing the corrosion is of great significance to come up with ideas of avoiding the corrosion reactions and eventually to achieve high energy density by expanding the working voltage. In this work, a variety of carbon materials are analyzed with many characterization techniques such as X-ray diffraction, Raman spectroscopy, N2 adsorption, magnetic susceptibility measurement, and temperature programmed desorption up to 1800 °C, to find out the origin of corrosion reactions in an organic electrolyte. While carbon crystallinity and porosity are not directly related to the positive-electrode corrosion, a good correlation is found between the corrosion charge and the number of carbon edge sites terminated by H and oxygen-functional groups which are decomposed and release CO. It is thus concluded that the H-terminated edge sites, phenol, ether and carbonyl groups are electroactive sites for the carbon materials used in the positive electrode of supercapacitors.This work was supported by JSPS KAKENHI (grant no. 15H01999 and 17H01042); the Dynamic Alliance for Open Innovation Bridging Human, Environment, and Materials program; and the Network Joint Research Centre for Materials and Devices. R. T. acknowledges the China Scholarship Council for the financial support. MINECO and FEDER (CTQ2015-66080-R MINECO/FEDER) are acknowledged for financial support

Comportamiento electroquímico de carbones activados con presencia de grupos superficiales de fósforo

Debido a su elevada superficie específica y una combinación única de conductividad, estabilidad y gran versatilidad química-estructural, los carbones activados (CAs) se emplean como electrodos en diversas aplicaciones electroquímicas. En estas aplicaciones, los heteroátomos presentes en su superficie, tales como oxígeno y nitrógeno, juegan un papel muy importante. La presencia de grupos superficiales estables de fósforo ha sido menos estudiada, pero parece inducir efectos positivos en las propiedades electroquímicas de los materiales carbonosos, aumentando su conductividad, capacidad y/o actividad electrocatalítica en diversas reacciones. Además, se ha propuesto que dichos grupos aumentan la resistencia a la oxidación electroquímica del material en medio acuoso, lo que supone una prometedora aproximación para aumentar la densidad de energía de los supercondensadores en este medio. No obstante, a pesar de todas estas ventajas, no existen estudios que justifiquen las causas ni los mecanismos de tales efectos. En este trabajo se presenta un estudio sobre el efecto de los grupos superficiales de fósforo en la capacidad y la estabilidad electroquímica de un carbón activado.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Enhanced electro-oxidation resistance of carbon electrodes induced by phosphorus surface groups

The electro-oxidation of carbon materials enormously degrades their performance and limits their wider utilization in multiple electrochemical applications. In this work, the positive influence of phosphorus functionalities on the overall electrochemical stability of carbon materials has been demonstrated under different conditions. We show that the extent and selectivity of electroxidation in P-containing carbons are completely different to those observed in conventional carbons without P. The electro-oxidation of P-containing carbons involves the active participation of phosphorus surface groups, which are gradually transformed at high potentials from less-to more-oxidized species to slow down the introduction of oxygen groups on the carbon surface (oxidation) and the subsequent generation of (C*OOH)-like unstable promoters of electro-gasification. The highest-oxidized P groups (–C–O–P-like species) seem to distribute the gained oxygen to neighboring carbon sites, which finally suffer oxidation and/or gasification. So it is thought that P-groups could act as mediators of carbon oxidation although including various steps and intermediates compared to electroxidation in P-free materials.Financial support by the Spanish Ministerio de Economía y Competitividad, for the MAT2013-42007-P, P09-FQM-5156R, CTQ2012-36408, JCI2011-10566, JCI-2012-12664 and the Joint Spanish-Japanese (PRI-PIBJP-2011-0766) projects, FEDER and the Junta de Andalucía are gratefully acknowledged

The carbonization of aromatic molecules with three-dimensional structures affords carbon materials with controlled pore sizes at the Ångstrom-level

分子構造により細孔径を制御したカーボンを開発. 京都大学プレスリリース. 2021-05-24.Carbon materials with controlled pore sizes at the nanometer level have been obtained by template methods, chemical vapor desorption, and extraction of metals from carbides. However, to produce porous carbons with controlled pore sizes at the Ångstrom-level, syntheses that are simple, versatile, and reproducible are desired. Here, we report a synthetic method to prepare porous carbon materials with pore sizes that can be precisely controlled at the Ångstrom-level. Heating first induces thermal polymerization of selected three-dimensional aromatic molecules as the carbon sources, further heating results in extremely high carbonization yields (>86%). The porous carbon obtained from a tetrabiphenylmethane structure has a larger pore size (4.40 Å) than those from a spirobifluorene (4.07 Å) or a tetraphenylmethane precursor (4.05 Å). The porous carbon obtained from tetraphenylmethane is applied as an anode material for sodium-ion battery

Preparación de micro-supercondensadores mediante electrosprayado de materiales carbonosos nanoestructurados

Los materiales carbonosos nanoestructurados presentan excelentes propiedades eléctricas, texturales y estructurales, que pueden ser aprovechadas para la fabricación de microcondensadores de elevada potencia y energía, fundamentales en el desarrollo de dispositivos electrónicos portátiles. Sin embargo, el reducido tamaño de sus partículas dificulta su procesado en láminas delgadas, impidiendo un control adecuado de la forma y el espesor de capas finas de estos materiales. Los procedimientos basados en la preparación directa de materiales carbonosos sobre el colector de corriente condicionan la composición y estructura del electrodo, lo que provoca un aumento de los costes de producción. Por ello, es necesario el desarrollo de nuevos procedimientos de fabricación de capas finas que permitan la completa implementación de estos dispositivos. En este sentido, destaca la técnica de electrosprayado. Esta técnica está basada en las fuerzas electrohidrodinámicas. Cuando un líquido fluye a través de un capilar y se aplica un campo eléctrico (este campo eléctrico se suele establecer entre el capilar y un colector de corriente plano), el correspondiente menisco se deforma en un cono, conocido como cono de Taylor. Cuando el voltaje del campo eléctrico alcanza un determinado valor límite, las fuerzas electrohidrodinámicas superan la tensión superficial del líquido, produciendo la salida de un chorro de pequeño diámetro. Generalmente, ese chorro rompe formando un espray, formado por gotas de tamaño nanométrico altamente cargadas. En este trabajo se propone el uso de la técnica de electrosprayado para el depósito controlado de una lámina delgada y continua de un material carbonoso nanoestructurado, directamente sobre el colector de corriente. Las láminas delgadas resultantes fueron caracterizadas como electrodos en supercondensadores con un electrolito acuoso.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec