Navegando por Autor "Andrade, Tatiana Santos"
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Item High water oxidation performance of W-Doped BiVO4 photoanodes coupled to V2O5 rods as a photoabsorber and hole carrier.(2018) Oliveira, Andreia Teixeira de; Rodriguez, Mariandry del Valle Rodriguez; Andrade, Tatiana Santos; Souza, Helen E. A. de; Ardisson, José Domingos; Oliveira, Henrique dos Santos; Oliveira, Luiz Carlos Alves de; Lorençon, Eudes; Silva, Adilson Cândido da; Nascimento, Lucas Leão; Patrocinio, Antonio Otavio de Toledo; Pereira, Márcio CésarMonoclinic BiVO4 is recognized as a promising photoanode for water oxidation, but its relatively wide bandgap energy (Eg ≈2.5 eV) and poor charge transport limit the light absorption (ηabs) and charge separation (ηsep) efficiencies, thus resulting in low photocurrents. To solve these drawbacks, here the ηabs × ηsep product has been decoupled by combining W‐doped BiVO4 and V2O5 rods (Eg ≈2.1 eV) for simultaneously increasing the light harvesting and the charge separation in photoanodes under back‐side illumination. In this strategy, V2O5 rods maximize the light absorption and hole transport throughout the W‐BiVO4 film, making more holes to achieve the V2O5/W‐BiVO4/H2O interface to trigger the water oxidation reaction with photocurrents as high as 6.6 mA cm−2 at 1.23 VRHE after 2 h reaction. Notably, under back‐side illumination, the W‐BiVO4/V2O5 photoanode exhibited ηabs × ηsep of 74.5 and 93.0% at 0.5 and 1.23 VRHE, respectively, the highest values reported up to date for BiVO4‐based photoelectrodes. This simple strategy brings us closer to develop efficient photoanodes for photoelectrochemical water splitting devices.Item Photoassisted chemical energy conversion into electricity using a sulfite-iron photocatalytic fuel cell.(2021) Sena, Izabela Campos; Sales, Davi de Oliveira; Andrade, Tatiana Santos; Rodriguez, Mariandry del Valle Rodriguez; Silva, Adilson Cândido da; Nogueira, Francisco Guilherme Esteves; Rodrigues, Jairo Lisboa; Mesquita, João Paulo de; Pereira, Márcio CésarPhotocatalytic fuel cells (PFC) are light-assisted devices that convert chemical energy into electricity. However, con ventional PFC produces extremely low photocurrents due to the slow kinetics of the photoanodes to oxidized organic fuels, thus limiting the power generation. Here, an all-inorganic PFC manufactured with heterostructured W-BiVO4/ V2O5 photoanode separated from a platinum cathode by a porous membrane is described. Sulfite ions are used as a fuel anolyte and Fe3+ is the catholyte. Under lighting, the W-BiVO4/V2O5 photoanode is exceptionally efficient for oxidizing sulfite to sulfate, which results in a high photocurrent output. Under optimized conditions, the W-BiVO4/V2O5-Pt cell produces a high short-circuit current of 8.79 mA cm−2 , an open-circuit potential 0.85 V, and a power density of 1.89 mW cm−2 at 4.30 mA cm−2 . The excellent PFC performance is attributed to the photovoltage generated by W-BiVO4/sulfite-sulfate liquid-junctions and efficient charge separation and hole transport in the photoanode bulk promoted by the W-BiVO4/V2O5 junctions. Also, the kinetics of redox reactions are fast, eliminating the use of cocatalysts. Thus, this simple PFC concept can be a viable alternative for electricity generation.Item Production of reduced graphene oxide platelets from graphite flakes using the Fenton reaction as an alternative to harmful oxidizing agents.(2019) Velásquez Piñas, Jean Agustin; Andrade, Tatiana Santos; Oliveira, Andreia Teixeira de; Salomão, Pedro Emílio Amador; Rodriguez, Mariandry del Valle Rodriguez; Silva, Adilson Cândido da; Oliveira, Henrique dos Santos; Monteiro, Douglas Santos; Pereira, Márcio CésarThe conventional chemical methods to produce graphene using strong oxidizing agents produce toxic gases during synthesis; therefore, these methods do not meet the principles of green chemistry. In this work, an alternative top-down method for the synthesis of a few layers of graphene sheets has been produced by a Fenton reaction- (a mixture of Fe2+/H2O2) assisted exfoliation process in water using graphite flakes as a starting material. Based on X-ray diffraction data and Fourier transform infrared (FTIR), Raman spectroscopy, and transmission electron microscopy measurements, it is proposed that the oxidation of graphite by Fenton chemistry facilitates the exfoliation of graphene sheets under mild sonication. Subsequent chemical reduction with ascorbic acid produced a few layers of reduced graphene oxide. Compared to Hummers’ method, the Fenton reagent has similar exfoliation efficiency, but due to the Fenton reagent’s preference to react with the edges of graphite, the chemical reduction can lead to the formation of less defective reduced graphene oxides. Moreover, since Fe and H2O2 are cheap and environmentally innocuous, their use in large-scale graphene production is environmentally friendlier than conventional methods that use toxic oxidizing agents.