Navegando por Autor "Nogueira, Francisco Guilherme Esteves"
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Item Bismuth vanadate photoelectrodes with high photovoltage behave as photoanode and photocathode in photoelectrochemical cells for water splitting.(2018) Santos, Wayler Silva dos; Rodriguez, Mariandry del Valle Rodriguez; Khoury, Julia M. O.; Nascimento, Luiza A.; Mesquita, João Paulo de; Silva, Adilson Cândido da; Nogueira, Francisco Guilherme Esteves; Pereira, Márcio CésarUsing dual-photoelectrode photoelectrochemical (PEC) devices based on earth-abundant metal oxides for unbiased water splitting is an attractive means of producing green H2 fuel, but is challenging, owing to low photovoltages generated by PEC cells. This problem can be solved by coupling n-type BiVO4 with n-type Bi4V2O11 to create a virtual p/n junction due to the formation of a hole-inversion layer at the semiconductor interface. Thus, photoelectrodes with high photovoltage outputs were synthesized. The photoelectrodes exhibited features of pand n-type semiconductors when illuminated under an applied bias, suggesting their use as photoanode and photocathode in a dual-photoelectrode PEC cell. This concept was proved by connecting a 1 mol% W-doped BiVO4/Bi4V2O11 photoanode with an undoped BiVO4/Bi4V2O11 photocathode, which produced a high photovoltage of 1.54 V, sufficient to drive standalone water splitting with 0.95% efficiency.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 Synthesis, structural characterization, and thermalproperties of the poly (methylmethacrylate) / 𝛿 FeOOH hybrid material : an experimental and theoretical study.(2016) Corrêa, Silviana; Lacerda, Lívia Clara Tavares; Santos, Maíra dos Santos; Rocha, Marcus Vinícius Juliaci; Nogueira, Francisco Guilherme Esteves; Silva, Adilson Cândido da; Pereira, Márcio César; Brito, Angela Dayana Barrera de; Cunha, Elaine Fontes Ferreira da; Ramalho, Teodorico de CastroThe 𝛿-FeOOH/PMMA nanocomposites with 0.5 and 2.5 wt.% of 𝛿-FeOOH were prepared by grafting 3 (trimethoxysilyl)propyl methacrylate on the surface of the iron oxyhydroxide particles.TheFTIR spectra of the 𝛿-FeOOH/PMMA nanocomposites showed that the silanemonomers were covalently attached to the 𝛿 FeOOHparticles. Because of the strong interaction between the PMMA and 𝛿-FeOOH nanoparticles, the thermal stability of the 𝛿-FeOOH/PMMA nanocomposites was improved compared to the pure PMMA.The SEM analysis conferred the size agglomerate of particles regarding the morphology of samples.The theoretical study enabled a better understanding of the interaction of the polymer with the iron oxyhydroxide.The DFT-based calculations reinforce the radical trapping mechanism of stabilization of nanocomposites; that is, Fe3+ species might be able to accept electrons coming from the organic phase that decomposes via radical unzipping.The radical scavenge effect delays the weight loss of polymer.