Navegando por Autor "Silva, Gelson Tiago dos Santos Tavares da"
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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 Insights into the role of CuO in the CO2 photoreduction process.(2019) Nogueira, André Esteves; Oliveira, Jessica Ariane de; Silva, Gelson Tiago dos Santos Tavares da; Oliveira, Cauê Ribeiro deThe CO2 photoreduction process to produce light hydrocarbons is known to be infuenced by the presence of CuO nanoparticles, but the actual role of this material, whether as a catalyst or a reactant, has not yet been revealed. In this work, we investigate the role of CuO nanoparticles produced by a solvothermal method as a catalyst in CO2-saturated water reaction media under UV light, considering the efects of diferent electrolytes (Na2C2O4, KBrO3, and NaOH) and temperatures on nanoparticle phase and activity. The electrolyte strongly infuenced product selectivity (NaOH led to evolution of CH4, Na2C2O4 to CO, and KBrO3 to O2) and induced CuO phase change. A long-term analysis of these processes indicated that during the initial steps, CuO acted as a reactant, rather than as a catalyst, and was converted to CuCO3.Cu(OH)2, while the as-converted material acted as a catalyst in CO2 photoreduction, with conversion values comparable to those reported in the literature.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 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.