Navegando por Autor "Torres, Juliana Arriel"
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Item Acidic surface niobium pentoxide is catalytic active for CO2 photoreduction.(2019) Silva, Gelson Tiago dos Santos Tavares da; Nogueira, André Esteves; Oliveira, Jessica Ariane de; Torres, Juliana Arriel; Lopes, Osmando Ferreira; Oliveira, Cauê Ribeiro deIn this paper, we report for the first time the significant photocatalytic activity of Nb-based materials for CO2 reduction. Nb2O5 catalysts were prepared through a modified peroxide sol-gel method using different annealing temperatures, showing activity for CO2 photoreduction in all conditions. The activity and selectivity of the Nb2O5 samples were directly related to their surface acidity: high surface acidity prompted conversion of CO2 to CO, HCOOH, and CH3COOH; low surface acidity prompted conversion of CO2 to CH4. The results also indicated that CO is the main intermediate species of the CO2 photoreduction in all conditions. We have uncovered the role played by the surface acidity of Nb2O5 and the mechanism behind its performance for CO2 photoreduction.Item CuO decoration controls Nb2O5 photocatalyst selectivity in CO2 reduction.(2020) Nogueira, André Esteves; Silva, Gelson Tiago dos Santos Tavares da; Oliveira, Jessica Ariane de; Lopes, Osmando Ferreira; Torres, Juliana Arriel; Carmo, Marcelo; Oliveira, Cauê Ribeiro deThe reformation of CO2 through photocatalytic processes to obtain products with high energy value and compatibility with the current energy infrastructure is a compelling strategy to minimize the emission of CO2 into the atmosphere, one of the main greenhouse gases. However, practical application of such a photocatalytic system requires significant efforts for improved CO2 photoreduction performance and product selectivity. Thus, in the present work, CuO nanoparticles were combined with Nb2O5 in order to improve the photocatalytic properties of these semiconductors in the CO2 photoreduction process. Nb2O5/ CuO heterojunctions were prepared via a solvothermal treatment method, while the experimental tools, such as FESEM, HRTEM, and DRS, were employed to evaluate the microstructural and electronic properties. We describe how CuO decoration over Nb2O5 adjusts its selectivity for CO2 reduction to CH4, HCOOH, or H3CCOOH in different contents. An investigation of CO2 photoreduction using different electron donors/scavengers (water, sodium oxalate, and potassium bromate) under ultraviolet radiation revealed that its decoration influences local CO production by modifying the selectivity. CO has been confirmed as the main intermediate for HCOOH and CH3COOH production, and CO2 reduction efficiency increases at low CuO content (2.5% wt), leading to the formation of soluble hydrocarbons, and increases for CH4 in higher amounts (10% wt).Item Enhancing TiO2 activity for CO2 photoreduction through MgO decoration.(2020) Torres, Juliana Arriel; Nogueira, André Esteves; Silva, Gelson Tiago dos Santos Tavares da; Lopes, Osmando Ferreira; Wang, Yanjie; He, Tao; Oliveira, Cauê Ribeiro deHerein we report on the influence of MgO’s basic character in the photoactivity of MgO:TiO2 nanocomposites for the CO2 reduction reaction. TiO2 nanoparticles, decorated with MgO in different mass proportions, were synthesized by the physical mixing of pre-synthesized oxides followed by calcination. The decorated samples presented enhanced photocatalytic activity with higher selectivity for CO, while CH4 was also produced, as well as HCOOH and CH3COOH in a liquid medium in lower proportions. The results indicate that the beneficial MgO influence is only effective at low amounts, whilst a high MgO amount favors an insulating behavior instead of semiconducting, reducing the nanocomposite performance for CO2 photoreduction.Item Evaluation of the activity and selectivity of mesoporous composites of MCM-41 and CuO in the CO2 photoreduction process.(2023) Ceron Geovo, Jose David; Torres, Juliana Arriel; Giroto, Amanda Soares; Rocha, Fernanda Cristina Nogueira da; Garcia, Marília Mariano; Silva, Gelson Tiago dos Santos Tavares da; Souza, Joelma Raimunda de Carvalho; Oliveira, Jessica Ariane de; Oliveira, Cauê Ribeiro de; Nogueira, André EstevesThe conversion of CO2 into valuable chemical feedstock through photocatalysis is considered an effective strategy to mitigate global warming and energy supply problems. Among the challenges for CO2 photoreduction are the design and synthesis of active photocatalysts with high affinity for the CO2 molecule and suitable reduction potentials of valence and conduction bands to promote the reduction of the CO2 molecule. Molecular sieves (MCM-41) with semiconductors, such as copper oxide, are alternatives to the traditional semiconductors (TiO2 and ZnO) with high CO2 adsorption capacity, high specific surface area, and good stability, making them perfect candidates for photocatalysis. Therefore, in this work, mesoporous composite materials based on MCM-41 and CuO were synthesized via the impregnation method. The synthesized materials were chemically, structurally, and morphologically characterized by XRD, SEM, FTIR, XPS, DRS, N2 adsorption and desorption, and atomic absorption spectroscopy techniques, and the photocatalytic activity in the reduction of CO2 was evaluated under visible radiation. We show that MCM-41 and the composite MCM-41/CuO have significant potential for use in the CO2 photoreduction process, where the composition and different active sites in the photocatalysts play an important role in the activity and selectivity of the products formed. The results showed that the MCM-41 and the composite with 1 % (w/w%) CuO presented high selectivity and production of methanol, with 585.88 and 267.05 μmol.gcatalyst -1 , respectively. Thus, the findings demonstrated the versatility of the MCM-41 to form composites with semiconductors, as well as the need to comprehend the main aspects that influence CO2 photoreduction activities and the selectivity of the composites, including their surface, structural, and electrical features.Item Experimental evaluation of the activity and selectivity of pure MnWO4 and doped with rare earth ions in the CO2 photoreduction process.(2022) Peixoto, Julia Caroline; Nogueira, André Esteves; Dias, Anderson; Torres, Juliana Arriel; Cruz, Jean Castro da; Oliveira, Cauê Ribeiro de; Siqueira, Kisla Prislen FélixThe reduction of CO2 to produce useful carbon compounds offers a way to manage the emissions from various industrial sectors. However, selecting efficient systems remain a crucial issue, especially considering the low selectivity of the photocatalysts traditionally used in CO2 photoreduction processes. Here we demonstrate that the modification of MnWO4 with rare earth ions (Europium and Terbium) synthesized by the coprecipitation method can tune the activity and selectivity of the products formed in the process of CO2 photoreduction under UV irradiation. The CO2 photoreduction assays indicated that the photocatalysts presented good activity, resulting in acetate, acetone, acetic acid, ethanol, methane, and methanol products. Doping provided selectivity near 100% for CO2 conversion to methanol and increased the capacity of C2 (e.g., ethanol) production, opening the way for a better understanding of the activity and selectivity of tungstates in the CO2 photoreduction process.Item Microwave-assisted synthesis of Ca1-xMnxMoO4 (x = 0, 0.2, 0.7, and 1) and its application in artificial photosynthesis.(2021) Silva Junior, Roberto Carlos da; Nogueira, André Esteves; Giroto, Amanda Soares; Torres, Juliana Arriel; Siqueira, Kisla Prislen FélixThis work reports, for the first time, to the best of our knowledge, the use of calcium molybdates doped with Mn2+ in the catalytic photoreduction of CO2 to produce compounds with higher added value that have appli cations in different branches of the chemical industry. The molybdates were prepared at 100 ◦C by microwave assisted hydrothermal synthesis and were characterized by X-ray diffraction, Raman vibrational spectroscopy, scanning electron microscopy, and diffuse UV–vis reflectance spectroscopy. The synthesized Ca1-xMnxMoO4 catalysts (x = 0, 0.2, 0.7, and 1) were also calcined at 500 ◦C, in order to investigate possible phase transitions. For x = 0 and 0.2, the samples crystallized in the tetragonal structure (I41/a, #88) and no phase transitions were observed at 500 ◦C. For x = 0.7 and 1.0, the phase produced at 100 ◦C was a hydrated form of manganese molybdate that exhibited triclinic structure (P1, #2) and became monoclinic (C2/m, #12) when calcined at 500 ◦C. The catalysts subsequently investigated were the pure molybdate and the materials with doping contents of 20 and 70 mol% Mn2+, hydrothermally treated at 100 ◦C and after calcination at 500 ◦C. The band gap en ergies ranged from 2.77 to 3.50 eV. In the performance tests, the productions of CO and CH4 after 6 h of irra diation were in the ranges 2.41–19.74 and 0.21–0.82 μmol g− 1 , respectively. The doped x = 0.2 sample treated at 100 ◦C exhibited the best performance, producing the highest amounts of CO and CH4. The results indicated that the doping of CaMoO4 with Mn2+ improved the performance of this ceramic for the purpose of artificial photosynthesis. Furthermore, our results support a deep discussion about the role of doping content and crys talline structure of the molybdates on the photocatalytic activity.Item Rapid microwave-assisted hydrothermal synthesis of CuBi2O4 and its application for the artificial photosynthesis.(2020) Ribeiro, Lucas da Silva; Pinatti, Ivo Mateus; Torres, Juliana Arriel; Giroto, Amanda Soares; Lesse, Fabiana; Silva, Elson Longo da; Oliveira, Cauê Ribeiro de; Nogueira, André EstevesStrategies for CO2 reforming for hydrocarbon production using ultraviolet or visible radiation are promising to mitigate environmental impacts from other human activities. Semiconductors act as photocatalysts for light-to-fuel conversion, but a rigorous control of their structure and morphology is crucial for high efficiency and selectivity. Thus, CuBi2O4 semiconductors have been synthesized by the microwave-assisted hydrothermal method and studied for the CO2 photoreduction process. This method produced crystalline materials with controlled morphology using low temperatures and short processing time. Moreover, the semiconductors showed excellent catalytic performance and selectivity, approximately 90% in the conversion of CO2 to CH4. Therefore, our new synthesis approach was adequate for CuBi2O4 preparation, providing an essential indication of activity in the CO2 photoreduction process.Item Redução de CO2 em hidrocarbonetos e oxigenados : fundamentos, estratégias e desafios.(2021) Silva, Gelson Tiago dos Santos Tavares da; Lopes, Osmando Ferreira; Dias, Eduardo Henrique; Torres, Juliana Arriel; Nogueira, André Esteves; Faustino, Leandro Augusto; Prado, Fernando Siqueira; Patrocinio, Antonio Otavio de Toledo; Oliveira, Cauê Ribeiro deThe development of renewable energy sources (e.g., solar and wind) moves foward, the tendance for replacing fossil fuels increases. However, these technologies have as primary barriers to industrial processes’ efficiency and especially storage. Thus, CO2 reduction routes using these energy sources could chemically store part of the energy as fuels or chemicals, offering alternatives to current oil and gas industry. This process is inspired by photosynthesis, e.g., photochemical or electrochemical processes, using homogeneous or heterogeneous catalysts. Nevertheless, this reaction is thermodynamically unfavorable and has very slow kinetics, given the high stability of the CO2 molecule and the complexity of the redox reactions involved. Therefore, this review addresses this process’s kinetic and thermodynamic challenges, and the fundamental concepts of the photo(electro)chemical processes for CO2 reduction, besides presenting and discussing the materials with the potential to act as catalysts. The main reaction mechanisms and advances in the understanding of such processes are discussed, as well as future perspectives.Item Role of Cu0 - TiO2 interaction in catalyst stability in CO2 photoreduction process.(2022) Torres, Juliana Arriel; Cruz, Jean Castro da; Nogueira, André Esteves; Silva, Gelson Tiago dos Santos Tavares da; Oliveira, Jessica Ariane de; Oliveira, Cauê Ribeiro deThe application of copper-based semiconductors for CO2 photoreduction has been limited by the poor stability of these catalysts in aqueous solutions due to parallel oxidation reactions. Thus, here we discussed the role of the Cu0-TiO2 interaction in catalyst stability, where the semiconductor acts as a charge separator and support for Cu0. Cu0 nanoparticles were deposited on the surface of TiO2 by reducing copper nitrate using a sodium borohydride solution. The metallic copper presents a higher selectivity in CO production (82.32%), while pure TiO2 presents a selectivity for CH4 (62.44%). However, with the heterostructure formation, the photocatalysts activity increases and the selectivity changes with copper amount variation over TiO2. In addition to the obtained C1 products (CH4, CO, and CH3OH), products containing two or more carbons (C2+) were also generated, such as acetic acid (C2H4O2), acetone (C3H6O), and isopropanol (C3H8O). H2 was also produced, although the selectivity for products derived from the photoreduction of CO2 was significantly greater. The sample TiO2/Cu 30% was significantly stable, which indicated the importance of an adequate heterojunction in the catalyst activity. These results demonstrate the synergistic effect between different copper species over TiO2, in which both materials play a role in the catalytic event.Item The effect of SnO2 surface properties on CO2 photoreduction to higher hydrocarbons.(2023) Torres, Juliana Arriel; Nogueira, André Esteves; Silva, Gelson Tiago dos Santos Tavares da; Oliveira, Cauê Ribeiro deSeveral photocatalysts have been developed for applications in reduction reactions, including tin oxide-based semiconductors. Although its band structure is unfavorable for CO2 reduction reactions, strategies to modify its surface properties directly impacted its activity and selectivity during these reactions. Here, we analyze the influence of heat treatment and decoration of SnO2 with gold nanoparticles on the gas phase CO2 photoreduction process. In both cases, a deleterious effect was observed during reactions under UV radiation (with a drop of 59.81% and 51.45% in CH4 production for SnO2_150°C and SnO2/Au_cop, respectively, compared to SnO2_cop), which is directly related to the availability of surface hydroxyl groups that play a crucial role in CO2 adsorption. Under visible radiation, the gold plasmonic resonance took place in the production of methane (0.33 μmolg 1 for SnO2/Au_cop and 0.29 μmolg 1 for SnO2/Au_150°C), with small amounts of carbon monoxide (0.06 μmolg 1 for SnO2/Au_cop and 0.03 μmolg 1 for SnO2/Au_150°C). These results demonstrate that, though the SnO2 band structure does not indicate a good semiconductor for CO2 reduction, its surface characteristics are responsible for its catalytic activity.Item The facile microwave-assisted coprecipitation route to obtain polyoxoniobate (Na7 (H3O) Nb6O19·14H2O) nanorods modified with copper for CO2 photoreduction.(2023) Sousa, Joelma Raimunda de Carvalho; Torres, Juliana Arriel; Ribeiro, Lucas da Silva; G. Filho, José B.; Santos, Fabiana Lesse dos; Malgioglio, Nicholas; Gorup, Luiz Fernando; Pinto, Alexandre Henrique; Nogueira, André EstevesThe CO2 reduction by solar means has been discussed as an alternative to emission abatement, a fundamental topic for sustainable, carbon-free production in the future. However, the choice of efficient systems, starting with the catalysts, is still a critical issue, especially due to the poor activity of available options. Polyoxometalates have been extensively studied as promising photocatalysts due to their semiconducting properties. Nevertheless, the synthetic conditions of polyoxoniobate are stringent due to the low reaction activity of Nb species, the lack of soluble precursors, and the narrow pH range. Unlike the literature, in the present study, we report a simple polyoxoniobate synthesis method. This synthesis method has some remarkable features, such as low processing time and temperature and good activity and selectivity in the CO2 photoreduction process. The results revealed an outstanding efficiency for the CO2 reduction reaction with a high selectivity of CO2 to CO conversion (92.5%). Furthermore, C2 compounds (e.g., acetate) were produced in the liquid phase of the reaction system. Our findings are significant for indicating the potential of polyoxoniobate for CO2 photoreduction, which opens a way to control competitive reactions with synthesis, leading to higher selectivity.Item Unveiling CuO role in CO2 photoreduction process - catalyst or reactant?(2020) Nogueira, André Esteves; Silva, Gelson Tiago dos Santos Tavares da; Oliveira, Jessica Ariane de; Torres, Juliana Arriel; Silva, Mitchell González Soares da; Carmo, Marcelo; Oliveira, Cauê Ribeiro deWe systematically investigated CO2 photoreduction catalyzed by CuO from different synthetic methods (solvothermal, coprecipitation and solid-state reaction) to understand which mechanism is prevailing for this reaction. The results showed that CuO acts as a reactant during CO2 reduction through copper carbonate formation rather than a catalyst, but the as-formed Cu2(OH)2CO3 (malachite) is active as catalyst for the same reaction. Significant CO2 conversion was observed during the CuO carbonation process, reducing to lower conversion levels after complete conversion to copper carbonate.