Highly graphitic Fe-doped carbon xerogels as dual-functional electro-Fenton catalysts for the degradation of tetracycline in wastewater

Fe-doped carbon xerogels with a highly developed graphitic structure were synthesized by a one-step sol-gel polymerization. These highly graphitic Fe-doped carbons are presented as promising dual-functional electro-Fenton catalysts to perform both the electro-reduction of O2 to H2O2 and H2O2 catalytic decomposition (Fenton) for wastewater decontamination. The amount of Fe is key to the development of this electrode material, since affects the textural properties; catalyzes the development of graphitic clusters improving the electrode conductivity; and influences the O2-catalyst interaction controlling the H2O2 selectivity but, at the same time is the catalyst for the decomposition of the electrogenerated H2O2 to OH• radicals for the organic pollutants oxidation. All materials achieve the development of ORR via the 2-electron route. The presence of Fe considerably improves the electro-catalytic activity. However, a mechanism change seems to occur at around −0.5 V in highly Fe-doped samples. At potential lower than −0.5 eV, the present of Feδ+ species or even Fe–O–C active sites favour the selectivity to 2e-pathway, however at higher potentials, Feδ+ species are reduced favoring a O–O strong interaction enhancing the 4e-pathway. The Electro-Fenton degradation of tetracycline was analyzed. The TTC degradation is almost complete (95.13%) after 7 h of reaction without using any external Fenton-catalysts.Grupo RNM-172Universidad de Granada / CBUAMCIN/AEI/10.13039/501100011033/ y "ERDF A way of making Europe” (PID2021-127803OB-I00)Junta de Andalucía (P18-RTJ-2974 y B. RNM.566. UGR20

From Fenton and ORR 2e−-Type Catalysts to Bifunctional Electrodes for Environmental Remediation Using the Electro-Fenton Process

Currently, the presence of emerging contaminants in water sources has raised concerns worldwide due to low rates of mineralization, and in some cases, zero levels of degradation through conventional treatment methods. For these reasons, researchers in the field are focused on the use of advanced oxidation processes (AOPs) as a powerful tool for the degradation of persistent pollutants. These AOPs are based mainly on the in-situ production of hydroxyl radicals (OH center dot) generated from an oxidizing agent (H2O2 or O-2) in the presence of a catalyst. Among the most studied AOPs, the Fenton reaction stands out due to its operational simplicity and good levels of degradation for a wide range of emerging contaminants. However, it has some limitations such as the storage and handling of H2O2. Therefore, the use of the electro-Fenton (EF) process has been proposed in which H2O2 is generated in situ by the action of the oxygen reduction reaction (ORR). However, it is important to mention that the ORR is given by two routes, by two or four electrons, which results in the products of H2O2 and H2O, respectively. For this reason, current efforts seek to increase the selectivity of ORR catalysts toward the 2e(-) route and thus improve the performance of the EF process. This work reviews catalysts for the Fenton reaction, ORR 2e(-) catalysts, and presents a short review of some proposed catalysts with bifunctional activity for ORR 2e(-) and Fenton processes. Finally, the most important factors for electro-Fenton dual catalysts to obtain high catalytic activity in both Fenton and ORR 2e(-) processes are summarized.Ministry of Science and Innovation, Spain (MICINN) Spanish Government PID2021-127803OB-I00Junta de Andalucia B.RNM.566.UGR2

Metal-Carbon-CNF Composites Obtained by Catalytic Pyrolysis of Urban Plastic Residues as Electro-Catalysts for the Reduction of CO2

Metal–carbon–carbon nanofibers composites obtained by catalytic pyrolysis of urban plastic residues have been prepared using Fe, Co or Ni as pyrolitic catalysts. The composite materials have been fully characterized from a textural and chemical point of view. The proportion of carbon nanofibers and the final content of carbon phases depend on the used pyrolitic metal with Ni being the most active pyrolitic catalysts. The composites show the electro-catalyst activity in the CO2 reduction to hydrocarbons, favoring all the formation of C1 to C4 hydrocarbons. The tendency of this activity is in accordance with the apparent faradaic efficiencies and the linear sweep voltammetries. The cobalt-based composite shows high selectivity to C3 hydrocarbons within this group of compounds.This research is supported by the FEDER and Spanish projects CTQ2013-44789-R (MINECO) and P12-RNM-2892 (Junta de Andalucía). J.C.-Q. is grateful to the Junta de Andalucía for her research contract (P12-RNM-2892). A.E. acknowledges a predoctoral fellowship from Erasmus Mundus, Al-Idrissi, programme

Influence of Surface Chemistry on the Electrochemical Performance of Biomass-Derived Carbon Electrodes for its Use as Supercapacitors

The following are available online at https://www.mdpi.com/1996-1944/12/15/2458/s1, Figure S1. N2 adsorption and desorption isotherms at 77K of CK-series samples. Figure S2: High resolution XPS deconvoluted spectra in the corresponding regions: (a) C1s, (b) O1s, (c) N1s and (d) S2p3/2 for the activated carbons prepared from Custard apple tree wood (CK-Serie). Figure S3: High resolution XPS deconvoluted spectra in the corresponding regions: (a) C1s, (b) O1s, (c) N1s and (d) S2p3/2 for the activated carbons prepared from Fig tree wood (FK-Serie). Figure S4: High resolution XPS deconvoluted spectra in the corresponding regions: (a) C1s, (b) O1s, (c) N1s and (d) S2p3/2 for the activated carbons prepared from Olive tree wood (OK-Serie).first_page settings Open AccessFeature PaperArticle Influence of Surface Chemistry on the Electrochemical Performance of Biomass-Derived Carbon Electrodes for its Use as Supercapacitors by Abdelhakim Elmouwahidi 1 [OrcID] , Esther Bailón-García 1, Luis A. Romero-Cano 2 [OrcID] , Ana I. Zárate-Guzmán 3, Agustín F. Pérez-Cadenas 1,* [OrcID] and Francisco Carrasco-Marín 1 [OrcID] 1 Research Group in Carbon Materials, Inorganic Chemistry Department, Faculty of Sciences, University of Granada, Campus Fuente Nueva s/n. 18071 Granada, Spain 2 Facultad de Ciencias Químicas, Universidad Autónoma de Guadalajara, Av. Patria 1201, Zapopan, Jalisco C. P. 45129, Mexico 3 Centro de Investigación y Desarrollo Tecnológico en Electroquímica (CIDETEQ) S.C., Parque Tecnológico Sanfandila, Pedro Escobedo, Querétaro 760703, Mexico * Author to whom correspondence should be addressed. Materials 2019, 12(15), 2458; https://doi.org/10.3390/ma12152458 Received: 28 June 2019 / Revised: 31 July 2019 / Accepted: 1 August 2019 / Published: 2 August 2019 (This article belongs to the Special Issue Element-Doped Functional Carbon-based Materials) Download PDF Browse Figures Cite This Paper Abstract Activated carbons prepared by chemical activation from three different types of waste woods were treated with four agents: melamine, ammonium carbamate, nitric acid, and ammonium persulfate, for the introduction of nitrogen and oxygen groups on the surface of materials. The results indicate that the presence of the heteroatoms enhances the capacitance, energy density, and power density of all samples. The samples treated with ammonium persulfate show the maximum of capacitance of 290 F g−1 while for the melamine, ammonium carbamate, and nitric acid treatments, the samples reached the maximum capacitances values of 283, 280, and 455 F g−1 respectively. This remarkable electro-chemical performance, as the high specific capacitances can be due to several reasons: i) The excellent and adequate textural characteristics makes possible a large adsorption interface for electrolyte to form the electrical double layer, leading to a great electrochemical double layer capacitance. ii) The doping with hetero-atoms enhances the surface interaction of these materials with the aqueous electrolyte, increasing the accessibility of electrolyte ions. iii) The hetero-atoms groups can also provide considerable pseudo-capacitance improving the overall capacitance.This work was supported by FEDER and Spanish MINECO (grant number CTQ-2013-44789-R); and Junta de Andalucía (grant numbers P12-RNM-2892, RNM172)

Heteroatom Doped High Porosity Carbon Nanomaterials as Electrodes for Energy Storage in Electrochemical Capacitors: A Review

At present it is indispensable to develop and implement new/state-of-the-art carbon nanomaterials as electrodes in electrochemical capacitors, since conventional activated carbon based supercapacitor cells cannot fulfil the growing demand of high energy and power densities of electronic devices of the present era, as a result of the rapid developments in this field. Functionalized carbon nanomaterials symbolize the type of materials with huge potential for their use in energy related applications in general and as an electrode active material for electrochemical capacitors in particular. Nitrogen doping of carbons has shown promising results in the field of energy storage in electrochemical capacitors, gaining attention of researchers to evaluate the performance of new heteroatoms functionalised materials such as sulphur, phosphorus and boron lately. Literature is widely available on nitrogen doped materials research for energy storage applications; however, there has been a limited number of review works on other functional materials beyond nitrogen. This review article thus aims to provide important insights and an up-to-date analysis of the most recent developments, the directions of future research, and the techniques used for the synthesis of these functional materials. A critical review of the electrochemical performance including specific capacitance and energy/power densities is made, when these single doped or co-doped active materials are used as electrodes in electrochemical capacitors

Supercapacitors (electrochemical capacitors)

International audienceRapid development of the technologies based on electric energy in the last decades have stimulated intensive research on efficient power sources. Electrochemical energy conversion and storage systems are based on Faradaic reactions (charge transfer) and electrostatic attraction of ions at the electrode/electrolyte interface. The latter might be an interesting solution for applications requiring moderate energy density, high power rates, and long cycle life. Electrochemical capacitors (ECs) store the charge in a physical manner, hence, their energy density is moderate. At the same time, the lack of electrochemical reactions ensures very high power and long cycle life compared to batteries. Activated carbons with their versatile properties (like specific surface area, well-developed and suitable porosity, heteroatoms in the graphene matrix) are the most popular materials in EC application. This chapter provides a comprehensive overview of the carbon-based materials recently developed, with special attention devoted to those obtained by biomass carbonization and activation. Electrochemical properties demonstrated by such carbons are discussed in respect to their physicochemical characteristic

Recent advances in hydrothermal carbonisation:from tailored carbon materials and biochemicals to applications and bioenergy

Introduced in the literature in 1913 by Bergius, who at the time was studying biomass coalification, hydrothermal carbonisation, as many other technologies based on renewables, was forgotten during the "industrial revolution". It was rediscovered back in 2005, on the one hand, to follow the trend set by Bergius of biomass to coal conversion for decentralised energy generation, and on the other hand as a novel green method to prepare advanced carbon materials and chemicals from biomass in water, at mild temperature, for energy storage and conversion and environmental protection. In this review, we will present an overview on the latest trends in hydrothermal carbonisation including biomass to bioenergy conversion, upgrading of hydrothermal carbons to fuels over heterogeneous catalysts, advanced carbon materials and their applications in batteries, electrocatalysis and heterogeneous catalysis and finally an analysis of the chemicals in the liquid phase as well as a new family of fluorescent nanomaterials formed at the interface between the liquid and solid phases, known as hydrothermal carbon nanodots

Influence of Surface Chemistry on the Electrochemical Performance of Biomass-Derived Carbon Electrodes for its Use as Supercapacitors

Activated carbons prepared by chemical activation from three different types of waste woods were treated with four agents: melamine, ammonium carbamate, nitric acid, and ammonium persulfate, for the introduction of nitrogen and oxygen groups on the surface of materials. The results indicate that the presence of the heteroatoms enhances the capacitance, energy density, and power density of all samples. The samples treated with ammonium persulfate show the maximum of capacitance of 290 F g−1 while for the melamine, ammonium carbamate, and nitric acid treatments, the samples reached the maximum capacitances values of 283, 280, and 455 F g−1 respectively. This remarkable electro-chemical performance, as the high specific capacitances can be due to several reasons: i) The excellent and adequate textural characteristics makes possible a large adsorption interface for electrolyte to form the electrical double layer, leading to a great electrochemical double layer capacitance. ii) The doping with hetero-atoms enhances the surface interaction of these materials with the aqueous electrolyte, increasing the accessibility of electrolyte ions. iii) The hetero-atoms groups can also provide considerable pseudo-capacitance improving the overall capacitance

Electrodos basados en carbón obtenidos a partir de residuos agrícolas y geles de carbono para supercondensadores y electro-reducción de oxígeno

En la presente Tesis Doctoral se han preparado y caracterizado diferentes series de materiales basados en carbono, tanto carbones activados como materiales compuestos óxido metálico - xerogel de carbón. Estos materiales se obtuvieron mediante activación con KOH y H3PO4 de diferentes residuos agrícolas tales como maderas de olivo, higuera y chirimoya, además se ha empleado como material de partida un residuo de la industria oleícola, el alperujo, subproducto obtenido durante el sistema continuo de extracción de dos fases y que consiste de una mezcla de alpechín y orujo. Se trata de un residuo altamente contaminante que, según las actuales normativas medioambientales, debe ser separado antes de destinarlo a cualquier uso como la obtención de energía. Por otra parte, se han sintetizado también materiales compuestos óxidos metálicos - xerogel de carbón, seleccionándose los óxidos: TiO2, ZrO2 y V2O5. Los materiales preparados han sido caracterizados química y texturalmente, y empleados como electrodos de condensadores electroquímicos para el almacenamiento de energía eléctrica en forma electrostática, y en la reacción de electro-reducción de O2.Tesis Univ. Granada. Programa Oficial de Doctorado en QuímicaEste Trabajo de Investigación ha sido financiado por la Junta de Andalucía, a través del Grupo de Investigación RNM-172 y del Proyecto de Excelencia P12- RNM-2892; y también por el Ministerio de Economía y Competitividad y fondos FEDER a través del Proyecto Retos CTQ2013-44789-R. Igualmente, Abdelhakim Elmouwahidi agradece al Programa ERASMUS MUNDUS la concesión de una beca Al Idrisi, Acción 2, Lote 1