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Electrocatalytic production of H

Made available in DSpace on 2021-06-25T12:36:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-08-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The modification of carbon-based materials with electroactive organic compounds can improve the oxygen reduction reaction (ORR) efficiency toward H2O2 electrogeneration. The present work sought to evaluate the electrochemical properties of a Printex L6 carbon matrix modified with 1,4-naphthoquinone (NQE) and its application toward the removal of paracetamol in different advanced oxidation processes. The 1.0% NQE-modified material showed 93% selectivity for H2O2 electrogeneration compared to 85% for the unmodified carbon matrix. Density functional theory calculations helped confirm the NQE action as an H+ donor by improving the Delta G of the reaction from -277.11 kJ mol(-1) for PL6C to -986.1 kJ mol(-1) for the NQE-modified material. Applied at 75 mA cm(-2), the modified gas diffusion electrode presented a 30% increase in H2O2 electrogeneration compared to the unmodified electrode. Paracetamol removal followed pseudo-first-order reaction kinetics in the following order: anodic oxidation with H2O2 electrogeneration (AO-H2O2) < AO-H2O2/UVC < electro-Fenton (EF) < photoelectro-Fenton (PEF). The action of the NQE modifier helped enhance the ORR activity and selectivity for H2O2 electrogeneration, thus making the material suitable for environmental application in wastewater treatment. Univ Sao Paulo, Sao Carlos Inst Chem, Ave Trabalhador Sao Carlense 400, BR-13566590 Sao Carlos, SP, Brazil Sao Paulo State Univ, Natl Inst Alternat Technol Detect Toxicol Evaluat, Inst Chem, BR-14800900 Araraquara, SP, Brazil Univ Sao Paulo, Sch Arts Sci & Humanities, Arlindo Bettio 1000, BR-03828000 Sao Paulo, SP, Brazil Sao Paulo State Univ, Natl Inst Alternat Technol Detect Toxicol Evaluat, Inst Chem, BR-14800900 Araraquara, SP, Brazil CNPq: 465571/2014-0 CNPq: 301492/2013-1 CNPq: 302874/2017-8 CNPq: 427452/2018-0 FAPESP: 2014/50945-4 FAPESP: 2015/14669-5 FAPESP: 2017/10118-0 FAPESP: 2017/23464-3 CAPES: 001

Boron-doped diamond (BDD) electrodes are regarded as the most promising catalytic materials that are highly efficient and suitable for application in advanced electrochemical oxidation processes targeted at the removal of recalcitrant contaminants in different water matrices. Improving the synthesis of these electrodes through the enhancement of their morphology, structure and stability has become the goal of the material scientists. The present work reports the use of an ultranano-diamond electrode with a highly porous structure (B-UNCD

The present work investigates the electrocatalytic performance of two different morphologies of boron doped-diamond film electrode (microcrystalline diamond - MCD, and nanocrystalline diamond - NCD) used in electrochemical oxidation for the removal of the antibiotic ciprofloxacin (CIP). A thorough study was conducted regarding the formation of the MCD and NCD films through the adjustment of methane in CH4/H2 gas mixture, and the two films were compared in terms of crystalline structure, apparent doping level, and electrochemical properties. The physicochemical results showed that the NCD film had higher sp2 carbon content and greater doping level; this contributed to improvements in its surface roughness, as well as its specific capacitance and charge transfer, which consequently enhanced its electrocatalytic activity in comparison with the MCD. The results obtained from CIP removal and mineralization assays performed in sulfate medium also showed that the NCD was more efficient than the MCD under all the current densities investigated. The effects of CIP concentration and the evolution of the final by-products, including short-chain carboxylic acids and inorganic ions, were also investigated. The electrochemical performance of the NCD was evaluated in different aqueous matrices, including chloride medium, real wastewater and simulated urine. The application of the NCD led to complete or almost complete CIP degradation, regardless of the medium employed. The kinetic constant rates obtained under the different media investigated were as follows: synthetic urine (0.0416 min−1 – R2 = 0.991)

International audience; While it remains a challenging task, having a fundamental understanding of the influence of water matrix composition is of central importance for the removal of pollutants in electrochemical treatment processes. This work studied the effect of the complexity of different water matrices on the removal of endocrine disruptors using different electrochemical advanced oxidation processes (EAOPs) based on H2O2 electrogeneration. The study helped improve the understanding of synthetic and real urban wastewater, and the effective mechanisms for the treatment of pollutants in these effluents. The results obtained showed that, regardless of the medium applied, there was an increase in pollutants mineralization in the following order, based on the EAOPs method employed: electrochemical oxidation with H2O2 electrogeneration (EO-H2O2) < electro-Fenton (EF) < photoelectro-Fenton (PEF). Despite the slower degradation kinetics of the EO-H2O2 process, its wider pH range makes it suitable for implementation. Aside the degradation/mineralization performance of the EO-H2O2 process, a time-course analysis was conducted on the nitrogen and chloride-based ions in the solution investigated since their presence is vital for determining the final use of the treated effluents based on the parameters of water quality. These parameters include the established maximum concentration levels of the compounds in the water matrix allowed for human consumption or the legal limits of discharge for wastewater treatment facilities. The findings help shed light on the role of coexisting species in water matrix, since this affects the efficiency and competitiveness of EAOPs. Clearly, having detailed knowledge of the water matrix composition will help one to have a better understanding of EAOPs, and this will enable to obtain higher degradation levels in water treatment processes.

Made available in DSpace on 2021-06-25T12:28:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-12-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Carbon-based catalysts are widely used in oxygen reduction reactions (ORR) via 2e- H2O2 electrogeneration. The direct comparability of the structural proprieties of different carbon matrices applied on ORR, however, has never been tested. Here, we evaluate how the electrochemical and structural properties of different carbon-based materials, including carbon Printex XE2B (PXE2BC), Printex L6 (PL6C), carbon derived from lignin (LIGC), graphite (GRA) and glassy carbon (GC), affect on ORR. All the materials were characterized by Raman spectroscopy, X-ray photoelectron spectrometry (XPS), elementary analysis, field emission gun scanning electron microscopy, surface area measurements and electrochemical assays for the evaluation of ORR. Notably, the morphology, the size of the particles and the types of functional groups present in the structure of carbon materials were keys in the efficiency of ORR. The carbon materials PL6C and PXE2BC with high surface area and oxygenated functional groups in their structure displaced the ORR potential, facilitating the reaction. Carbon materials with less surface area, such as GRA, LIGC and GC, and whose main functional groups in their structures were non-oxygenated or nitrogenated, were less active in ORR. The displacement of the potential and the efficiency of H2O2 generation were directly dependent on the electrochemical and structural characteristics of the materials used as catalysts. These results are particularly relevant regarding a proper choice of carbon catalyst can increase the efficiency of ORR. (C) 2020 Elsevier Inc. All rights reserved. Univ Sao Paulo, Sao Carlos Inst Chem IQSC, Ave Trabalhador Sao Carlense 400, BR-13566590 Sao Carlos, SP, Brazil Sao Paulo State Univ, Natl Inst Alternat Technol Detect Toxicol Evaluat, Inst Chem, Araraquara, SP, Brazil State Univ Campinas Unicamp, Fac Mech Engn, Rua Mendeleyev 200, BR-13083860 Campinas, SP, Brazil Fed Univ Sao Carlos UFSCar, Dept Chem, Rodovia Washington Luiz Km 235, BR-13565905 Sao Carlos, SP, Brazil Fed Univ ABC UFABC, Lab Eletroquim & Mat Nanoestruturados LEMN, Ctr Ciencias Nat & Humanas CCNH, Rua Santa Adelia 166, BR-09210170 Santo Andre, SP, Brazil Univ Estadual Campinas, Brazilian Water Res Ctr BWRC, BR-13083970 Campinas, SP, Brazil Sao Paulo State Univ, Natl Inst Alternat Technol Detect Toxicol Evaluat, Inst Chem, Araraquara, SP, Brazil CNPq: 465571/2014-0 CNPq: 301492/2013-1 CNPq: 302874/2017-8 CNPq: 427452/2018-0 FAPESP: 2011/14314-1 FAPESP: 2014/50945-4 FAPESP: 2016/19612-4 FAPESP: 2016/01937-4 FAPESP: 2016/08760-2 FAPESP: 2017/10118-0 FAPESP: 2017/23464-3 CAPES: 001 CAPES: 88887126/2017/00

In order to enhance hydrogen peroxide (H2O2) electrogeneration, a catalyst based on less than 1 wt% of Pd nanoparticles dispersed onto commercially available Printex L6 carbon black (PCL6) is proposed and synthetized. The material was characterized by physico-chemical and electroanalytical methods, demonstrating high activity with a 320 mV lower onset potential compared to pristine PCL6 and high stability after 5000 potential cycles. Its performance places it among the most efficient bi- and monometallic electrocatalysts for H2O2 production. When testing the accumulation of H2O2, a 1.69-fold molar increase was observed for Pd1%/PCL6 compared to PCL6. Different electrochemical advanced oxidation processes based on H2O2 generation have been performed to oxidize and remove pollutants as exemplarily shown on methyl paraben in Na2SO4 solution as model pollutant. A boron-doped diamond electrode was used as anode while Pd1%/PCL6 was tested in a rotating ring disk electrode (RRDE) and gas diffusion setup. Pollutant degradation followed a pseudo-first-order reaction kinetic in the following order: anodic oxidation along with H2O2 generation (AO-H2O2)

This short review presents a critical overview of the most recent works published in the literature related to the use of electrochemical advanced oxidation processes (EAOPs) for the treatment of antibiotics present in synthetic and real wastewaters. The first section focuses on novelties within the traditional EAOPs, including electrochemical oxidation and electrochemical Fenton-based processes. The second section is devoted to new electrochemical technologies, including heterogeneous electro-Fenton, electrochemically activated persulfate processes, and combined processes. Future perspectives about these processes are also presented to aid the continuous evolution of research in the area.

The inefficiency of conventional water treatment methods in the treatment of recalcitrant herbicides has led to the search for new, efficient and eco-friendly mechanisms for degrading these organic pollutants. Electrochemical advanced oxidation processes (EAOP) have emerged as a promising alternative due to their high degree of efficiency in degrading organic pollutants. This work investigates the removal of Tebuthiuron (TBH) in synthetic and real wastewater using different EAOPs in a flow-by reactor. The degradation/mineralization experiments were performed using boron-doped diamond electrode as anode and gas-diffusion electrode (GDE) as cathode for the in situ electrogeneration of hydrogen peroxide (H2O2). For the analysis conducted in synthetic medium, TBH degradation was found to fit well in a pseudo-first-order kinetic reaction with increasing k1 values according to the following order of efficiency: anodic oxidation (AO, 3.1 × 10−5 s−1)

Made available in DSpace on 2018-12-11T17:32:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-07-01 This paper compares the results of two preparation routes for the production of carbon (Vulcan XC 72R) modified with vanadium nanostructured electrocatalysts for hydrogen peroxide (H2O2) electrogeneration using the following mass proportions of vanadium on carbon (V/C): 1, 3, 5, 7, 10, and 13%. Best results for H2O2 electrogeneration were obtained using a V/C sol-gel method (SGM) with 3%, highest ring currents. For oxygen reduction reaction (ORR), using the V/C SGM with 3% and V/C polymeric precursor method (PPM) with 7%, the results of ring currents measured are very high when compared to Vulcan XC 72R. X-ray diffraction (XRD) analysis mainly showed the V2O5 phase. X-ray photoelectron spectroscopy (XPS) results of the V/C PPM 7% and V/C SGM 3% samples highlight the predominance of the V2O5 phase and, for the latter catalyst, a more oxidized carbon surface. For the most promising electrocatalysts, the contact angle was evaluated, showing that the anchoring of the metal in the carbon surface increases the hydrophilicity of the materials. The prepared materials are promising for peroxide electrogeneration mainly due to the synergetic effect of vanadium oxide nanoparticles and acid oxygen species of the carbon, contributing to enhancing catalyst hydrophilicity. LEMN Centro de Ciências Naturais e Humanas (CCNH) Universidade Federal do ABC (UFABC), Rua Santa Adélia 166, Bairro Bangu Instituto de Química Universidade Estadual Paulista (UNESP) Instituto de Química de São Carlos Universidade de São Paulo, Caixa Postal 780 Instituto de Química Universidade Estadual Paulista (UNESP)