Electrocatalytic Oxidation of Cyanide on Copper-doped Cobalt Oxide Electrodes

[EN] Copper and copper oxides are well-known excellent catalysts in several chemical processes, but their low mechanical and electrochemical stability restrict their direct utilization as electrodes in electrolytic processes. In this work, the incorporation of copper into cobalt oxide (CuxCo3-xO4) is presented as an excellent approach to obtain highly active and robust copper-based electrocatalysts. Particularly, the electrocatalytic performance of Ti-supported CuxCo3-xO4 electrodes (with 0 <= x <= 1.5) has been studied for the oxidation' of cyanide in alkaline media. Cyclic voltammetry and electrolysis runs show an outstanding effect of Cu on the activity, efficiency and kinetics of spinel CuxCo3-xO4 electrodes for CN(-)electro-oxidation. Despite being active oxides with high activity towards water oxidation, copper saturated (x=1.0) and oversaturated (x=1.5) spinels exhibit unprecedented 100% current efficiencies for the electro-oxidation of CN- in aqueous electrolyte. In situ surface enhanced Raman spectroscopy (SERS) reveals the specific adsorption of CN- ions on surface Cu species to be involved in the electrocatalytic oxidation mechanism. This electrocatalytic activity has been attributed to surface Cu(II) in the spinel lattice. Furthermore, the CuxCo3-xO4 electrodes also display high electrochemical stability. Therefore, they are considered excellent candidates for the sustainable electrochemical elimination of highly toxic cyanides.Financial support from the Spanish Ministerio de Economia y Competitividad and FEDER funds (MAT2016-76595-R, IJCI-2014-20012) and from the Generalitat Valenciana (PROMETEO2013/038) is gratefully acknowledged.Berenguer, R.; La Rosa-Toro, A.; Quijada, C.; Morallon, E. (2017). Electrocatalytic Oxidation of Cyanide on Copper-doped Cobalt Oxide Electrodes. Applied Catalysis B Environmental. 207:286-296. https://doi.org/10.1016/j.apcatb.2017.01.078S28629620

Improving the power performance of urine-fed microbial fuel cells using PEDOT-PSS modified anodes

© 2020 The Authors The need for improving the energy harvesting from Microbial Fuel Cells (MFCs) has boosted the design of new materials in order to increase the power performance of this technology and facilitate its practical application. According to this approach, in this work different poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT-PSS) modified electrodes have been synthesised and evaluated as anodes in urine-fed MFCs. The electrochemical synthesis of PEDOT-PSS was performed by potentiostatic step experiments from aqueous solution at a fixed potential of 1.80 V (vs. a reversible hydrogen electrode) for different times: 30, 60, 120 and 240 s. Compared with other methods, this technique allowed us not only to reduce the processing time of the electrodes but also better control of the chemical composition of the deposited polymer and therefore, obtain more efficient polymer films. All modified anodes outperformed the maximum power output by MFCs working with the bare carbon veil electrode but the maximum value was observed when MFCs were working with the PEDOT-PSS based anode obtained after 30 s of electropolymerisation (535.1 µW). This value was 24.3% higher than using the bare carbon veil electrode. Moreover, the functionality of the PEDOT-PSS anodes was reported over 90 days working in continuous mode

Synthesis and in situ FTIRS characterization of conducting polymers obtained from aminobenzoic acid isomers at platinum electrodes

The electrochemical homo-polymerization of o-, m- and p-aminobenzoic acids has been performed on Pt electrodes in perchloric acid aqueous medium by cyclic scanning of the potential. Different limit potentials were employed to obtain thin polymeric films. When the switching potential was extended beyond the respective monomer oxidation peak, a rather degraded material was obtained. In situ FTIR spectroscopy has been used to characterize the redox response of films synthesized at the lower potential limits. Characteristic absorption features related with benzenoid and quinoid rings and different types of C–N bonds suggest the presence of redox processes similar to those undergone by the parent compound polyaniline. In addition, the existence of a chemical interaction between –COOH and –NH– groups in the reduced state of the three homopolymers studied can be suggested. Carbon dioxide has been detected at potentials higher than 1.0 V (RHE) irrespective of the polymeric material, thus indicating its degradation.Ministerio de Ciencia y Tecnología (MAT2001-1007) (MAT2004-01479); Generalitat Valenciana (Grupos04/75

Electrochemical behaviour of aqueous SO2 at polycrystalline gold electrodes in acidic media. A voltammetric and in-situ vibrational study. Part II. Oxidation of SO2 on bare and sulphur-modified electrodes

The electrochemical oxidation of SO2 on polycrystalline gold electrodes has been studied by means of cyclic voltammetry and in situ vibrational techniques. On bare gold electrodes, SO2 is irreversibly oxidised on forward scans at 0.6 V/RHE, featuring a diffusion-limited peak. Oxidation is inhibited by the formation of chemisorbed oxygen. A SO2 anodic current rise occurs on the reverse scan in parallel with the reduction of the metal oxide layers. As shown by FT-IR, oxidation proceeds to yield a mixture of soluble S(VI) species as stable reaction products. From vibrational spectra and results from the irreversible adsorption method, it follows that no strongly adsorbed S-O-like residues are present onto the gold surface in the region 0.3-0.5 V/RHE. On sulphur-modified electrodes improved electrocatalysis is manifested by the shift of the diffusion-limited peak to lower potentials. The best performance is observed at a sulphur coverage of 0.5. At higher coverage, sulphur adlayers impart lower catalytic efficiency and eventually show strong poisoning properties. This behaviour is exhibited by sulphur adlayers generated either in situ by SO2 reduction or ex situ by sulphide adsorption/oxidation in acidic or alkaline media

Preparation and Characterization of Antimony-Doped Tin Dioxide Electrodes. Part 1. Electrochemical Characterization.

Antimony and antimony-platinum doped tin dioxide electrodes supported on titanium have been prepared by thermal decomposition. Ti/SnO2-Sb electrodes have a cracked-mud structure, typical of oxide electrodes prepared by thermal decomposition. The introduction of platinum in the oxide layer has a packing effect in the coating morphology. The electrochemical characterization of these electrodes has been performed in acid medium, and a relation between the roughness factor (measured from electrode capacitance) and electrochemical porosity (related to the voltammetric charge) has been established. The mechanism for the oxygen evolution reaction has been determined by Tafel measurements indicating that the electrodes prepared are nonactive electrodes. The electrocatalytic activity strongly depends on geometric factors, since the activity toward oxygen evolution increases with the electrochemical porosity. Anodic stability of Ti/SnO2 electrodes has been checked with accelerated service life tests. The introduction of platinum in the oxide coating increases the service life by 2 orders of magnitude

Electrochemical behaviour of aqueous SO2 at polycrystalline gold electrodes in acidic media: a voltammetric and in situ vibrational study: Part 1. Reduction of SO2: deposition of monomeric and polymeric sulphur

The electro-reduction of SO2 has been monitored by using cyclic voltammetry, FT-IR spectroscopy and SER spectroscopy. Prior to the bulk reduction, SO2 is reduced to yield a monomeric sulphur adlayer at a maximum coverage of about 0.25. The sulphur adlayer undergoes a reversible redox surface process at E<0.0 V (RHE), which implies a change in the frequency of the Au---S stretching mode from 270 to 300/310 cm−1. In the potential region encompassing the bulk reduction voltammetric peak, infrared spectra display a band at 2585 cm−1 attributable to a S---H vibration from a soluble species. Accordingly, H2S or H2Sx were proposed as tentative bulk reduction products. In positive sweeps a broad anodic wave develops between 0.2 and 0.6 V that leaves polymeric sulphur species adsorbed at multilayer level, with a S---S stretching mode at 460 cm−1 and a S---S---S bending vibration at 218 cm−1. Multilayer sulphur can be removed reductively under a sharp cathodic peak. According to literature of the S(-II)/Au system, removal proceeds to yield soluble S(-II) species, via intermediate polysulphides

Lead ion adsorption from aqueous solutions in modified Algerian montmorillonites

The adsorption of lead (II) ions on three Algerian montmorillonites (sodium, non-sodium, and acidic-activated) was studied. Transmission electron microscopy coupled with energy dispersive X-ray analysis, X-ray fluorescence and physical adsorption of gases were used to characterize the clays. This characterization has shown than the activation with acid increases the surface area as a consequence of the rupture of the laminar structure. The effect of the pH in the lead adsorption capacity was analyzed. The results show that adsorption is strongly depended on the pH. At low pH values, the mechanism that governs the adsorption behavior of clays is the competition of the metal ions with protons. Between pH 2 and 6, the main mechanism is an ion exchange process. The kinetics of the adsorption is tested with respect to pseudo-first-order and second-order models. The adsorption process, gives a better fit with the Langmuir isotherm, being the monolayer capacity ranging between 18.2 and 24.4 mg g(-1). The adsorption of lead decreased in the order Acidic-M-2 > M-2 > M-1. Thermodynamic parameters such as Delta H, Delta S, and Delta G were calculated. The adsorption process was found to be endothermic and spontaneous. The enthalpy change for Pb(II) by M-1 adsorption has been estimated as 60 kJ mol(-1), indicating that the adsorption of Pb(II) by all montmorillonites used corresponds to a physical reaction. The adsorption capacity of washed Acidic-M-2 was very high compared to M-2 and M-1.This study has been financed by the AECID (projects AECID-PCI A/019533/08 and A/023858/09) and Ministerio de Ciencia e Innovacion (project MAT2010-15273). The National Agency for the Development of University Research (CRSTRA), the Directorate General of Scientific Research and Technological Development (DGRSDT) of Algeria.Zehhaf, A.; Benyoucef, A.; Berenguer, R.; Quijada Tomás, C.; Taleb, S.; Morallon, E. (2012). Lead ion adsorption from aqueous solutions in modified Algerian montmorillonites. Journal of Thermal Analysis and Calorimetry. 110(3):1069-1077. https://doi.org/10.1007/s10973-011-2021-8S106910771103Patterson JW. Industrial wastewater treatment technology. New York: Butterworth-Heinemann; 1985.Adebowale KO, Unuabonah IE, Olu-Owolabi BI. The effect of some operating variables on the adsorption of lead and cadmium ions on kaolinite clay. J Hazard Mat. 2006;34:130–9.Vogel C, Adam C, Unger M. Heavy metal removal from sewage sludge ash analyzed be thermogravimetry. J Therm Anal Calorim. 2011;103:243–8.Adebowale KO, Unuabonah IE, Olu-Owolabi BI. 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Hazard Mater. 2006;136:654–62.Mahbouba R, El Mouzdahir Y, Elmchaouri A, Carvalho A, Pinto M, Pires J. Characterization of a delaminated clay and pillared clays bynadsorption of probe molecules. Colloids Surf A. 2006;280:81–7.Gok ASzcan, zcan A. Adsorption of lead(II) ions onto 8-hydroxy quinoline-immobilized bentonite. J. Hazard Mater. 2009;161:499–509.Schoonheydt RA, Pinnavaia T, Lagaly G, Gangas N. Pillared clays and pillared layered solids. Pure Appl Chem. 1999;71:2367–71.Stoch L, Bahranowski K, Budek L, Fijal J. Mineral Pol. 1977;8:31–7.Srivastava SK, Tyagi R, Pant N, Pal N. Studies on the removal of some toxic metal ions, Part II. Removal of lead and cadmium by montmorillonite and kaolinite. Environ Technol Let. 1989;10:275–82.Orumwense FFO. Removal of lead from water by adsorption on a kaolinitic clay. J Chem Technol Biotechnol. 1996;65:363–9.Chantawong V, Harvey NW, Bashkin VN. Adsorption of lead nitrate on Thai kaolin and ballclay. Asian J Energy Environ. 2001;2:33–48.Lapides I, Yari S. Thermo-X-ray-diffraction analysis of dimethylsulfoxide-kaolinite intercalation complexes. J Therm Anal Calorim. 2009;97:2–19.Echeverría JC, Zarranz I, Estella J, Garrido JJ. Simultaneous effect of pH, temperature, ionic strength, and initial concentration on the retention of lead on illite. Appl Clay Sci. 2005;30:103–15.Naseem R, Tahir SS. Removal of Pb(II) from aqueous/acidic solutions by using bentonite as an adsorbent. Water Res. 2001;35:3982–6.Donat R, Akdogan A, Erdem E, Cetisli H. Thermodynamics of Pb2+ and Ni2+ adsorption onto natural bentonite from aqueous solutions. J Colloid Interface Sci. 2005;286:43–52.Cicmanec P, Bulánek R, Frolich K. Thermodynamics of CO probe molecule adsorption on Cu–FER-zeolite comparison of TPD, FTIR, and microcalorimetry results. J Therm Anal Calorim. 2011;105:837–84.Zamzow MJ, Eichbaum BR, Sandgren KR, Shanks DE. Removal of heavy metals and other cations from wastewater using zeolites. Sep Sci Technol. 1990;25:1555–69.Ouki SK, Cheeseman C, Perry R. Effects of conditioning and treatment of chabazite and clinoptilolite prior to lead and cadmium removal. Environ Sci Technol. 1993;27:1108–16.Brigatti MF, Lugli C, Poppi L. Kinetics of heavy-metal removal and recovery in sepiolite. Appl Clay Sci. 2000;16:45–57.Bektas N, Agım BA, Kara S. Kinetic and equilibrium studies in removing lead ions from aqueous solutions by natural sepiolite. J Hazard Mat. 2004;112:115–22.Juang RS, Lin SH, Tsao KH. Mechanism of sorption of phenols from aqueous solutions onto surfactant-modified montmorillonite. J Colloid Interface Sci. 2002;254:234–41.Alberga L, Holm T, Tiravanti G, Petruzzelli D. Electrochemical determination of cadmium sorption on kaolinite. Environ Technol. 1994;15:245–54.Tiller KG, Gerth J, Brümmer G. The sorption of Cd, Zn and Ni by soil clay fractions: procedures for partition of bound forms and their interpretation. Geoderma. 1984;34:1–16.Stadler M, Schindler PW. The effect of dissolved ligands upon the sorption of Cu(II) by Ca-montmorillonite. Clays Clay Miner. 1993;41:680–92.Belbachir M, Bensaoula A. US Patent 2001;No. 6, 274, 527 B1.Lozano-Castelló D, Suárez-García F, Cazorla-Amorós D, Linares-Solano A. Porous texture of carbons. In: Beguin F, Frackowiak E, editors. Carbons for electrochemical energy storage and conversion systems. Florida: CRC Press; 2009. p. 115–62.Cazorla-Amorós D, Alcañiz-Monge J, Linares-Solano A. Characterization of activated carbon fibers by CO2 adsorption. Langmuir. 1996;12:2820–4.Cazorla-Amorós D, Alcañiz-Monge J, de la Casa-Lillo MA, Linares-Solano A. CO2 as an adsorptive to characterize carbon molecular sieves and activated carbons. Langmuir. 1998;14:4589–96.Gu B, Schmitt J, Chen Z, Liang L, McCarthy JF. Adsorption and desorption of different organic matter fractions on iron oxide. Geochim Cosmochim Acta. 1995;59:219–29.Kul AR, Koyunchu H. Heavy metal removal from municipal solid waste fly ash by chlorination and thermal treatment. J. Hazard Mater. 2010;179:332–9.Ho YS, McKay G. Pseudo-second order model for sorption processes. Process Biochem. 1999;34:451–65.Sing K, Everet D, Haul R, Moscou L, Pierotty R, Rouquerol J, Siemieniewska T. Reporting physisorption data for gas/solid systems with special reference to the determination of surface area and porosity. Pure Appl Chem. 1985;57:603–19.Temuulin J, Jadambaa Ts, Burmaa G, Erdenechimeg Sh, Amarsanaa J, MacKenzie KJD. Characterisation of acid activated montmorillonite clay from Tuulant (Mongolia). Ceram Int. 2004;30:251–5.Noyan H, Onal M, Sarikaya Y. The effect of sulphuric acid activation on the crystallinity, surface area, porosity, surface acidity, and bleaching power of a bentonite. Food Chem. 2007;105:156–63.Huang FC, Lee FJ, Lee CK, Chao HP. Effects of cation exchange on the pore and surface structure and adsorption characteristics of montmorillonite. 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Preparation and Characterization of Antimony-Doped Tin Dioxide Electrodes. Part 2. XRD and EXAFS Characterization.

Several antimony and platinum doped tin dioxide electrodes supported on titanium have been characterized by X-ray diffraction (XRD) and X-ray absorption spectroscopy (EXAFS) techniques. Ti/SnO2-Sb electrodes show a rutile-type nanostructure with a distorted unit-cell because of the substitution of the Sn(IV) ion by Sb(V). The presence of platinum on the electrode coating modifies the lattice parameters of the SnO2 cell due to an amorphization of tin oxide layers. The structural modifications on the different electrode after anodic polarization-deactivation have been analyzed

Preparation and Characterization of Antimony-Doped Tin Dioxide Electrodes. Part 2. XRD and EXAFS Characterization

Several antimony and platinum doped tin dioxide electrodes supported on titanium have been characterized by X-ray diffraction (XRD) and X-ray absorption spectroscopy (EXAFS) techniques. Ti/SnO2−Sb electrodes show a rutile-type nanostructure with a distorted unit-cell because of the substitution of the Sn(IV) ion by Sb(V). The presence of platinum on the electrode coating modifies the lattice parameters of the SnO2 cell due to an amorphization of tin oxide layers. The structural modifications on the different electrode after anodic polarization−deactivation have been analyzed

Preparation and Characterization of Antimony-Doped Tin Dioxide Electrodes. 3. XPS and SIMS Characterization.

Several antimony- and antimony-platinum-doped tin dioxide electrodes supported on titanium have been characterized by X-ray photoelectron spectroscopy (XPS) for surface analysis and secondary-ion mass spectrometry (SIMS) for in-depth profile analysis. The surface analysis of the freshly prepared electrodes indicates that the Sb/Sn ratio in the electrode surface is similar to the nominal composition in the precursor solution, but the amount of Pt is higher than this nominal composition. The presence of platinum also produces the segregation of Sb near the electrode surface. The anodic polarization treatment of the electrode produces changes in its chemical state. The growth of a passivating hydroxide in the outer layer is the main cause of the deactivation of Ti/SnO2-Sb electrodes. The introduction of platinum in the layer prevents the hydroxide formation and modifies the deactivation mechanism of the electrode. The growth of an isolating TiO2 between the support and the active oxide produces the deactivation of Ti/SnO2-Sb-Pt electrodes