GABRIEL DE ALMEIDA SILVESTRIN

GABRIEL DE ALMEIDA SILVESTRIN

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Hydrogen mitigation
2024 - DE MICHELI, LORENZO; SILVESTRIN, G.; SOUZA, R.F.B. de; NETO, A.O.; GIOVEDI, C.
In the context of discussions surrounding the hydrogen economy, particularly its green aspects, ensuring safety in the production and storage of hydrogen is paramount. This is especially crucial when hydrogen mixes with air, comprising between 6% and 30% in volume, as it poses potential risks of explosions. A proven method to mitigate these dangers is the utilization of Passive Autocatalytic Recombiners (PARs). These devices facilitate the recombination of hydrogen with oxygen on active catalytic surfaces, leading to the generation of water vapour and heat [1], reducing significantly the risk of explosions. PARs are typically composed of materials like stainless steel, alumina, and silica, which support active catalytic elements such as platinum or palladium. To combat catalyst deactivation resulting from water accumulation, researchers have explored the use of hydrophobic materials [2], among which graphene stands out. Recent studies have demonstrated that graphene could be successfully applied directly on surface, [3], using a non-thermal plasma system. This method resulted in the production of a material with few layers and hexagonal structural defects, making it attractive due to its simplicity, low cost, and scalability. In this sense, graphene is a promising option fto be applied as hydrophobic coating in catalysts for PARs. This work investigated the formation of films of graphenoid materials doped with platinum or palladium on a sintered porous metal filter in a single step. X-ray diffraction experiments revealed high amorficity, with percentages of approximately 49.6% and 60.0% for materials containing platinum or palladium, respectively. The D1/G band ratios were 2.9 and 1.6 for materials with platinum or palladium, indicating the presence of structural defects. Contact angle measurements demonstrated strong hydrophobicity for both materials, with values of 124º and 119º, respectively. Catalytic tests showed that the palladium-based converter was able to remove 17% of the injected hydrogen, while the material containing platinum achieved a removal of around 23%, confirming the effectiveness of these coatings in converting hydrogen into water. The experimental results indicated that coating porous steel filters with graphene doped with catalytic metals represents a promising strategy to ensure safety and efficiency in converting hydrogen into green energy systems. This approach has significant implications for sustainability and corporate social responsibility practices.
Innovative deposition of platinum-graphene on alumina for passive autocatalytic recombiners to improve nuclear safety
2024 - SILVESTRIN, G.; SOUZA, R.F.B. de; NETO, A.O.; DE MICHELI, L.; GIOVEDI, C.
Innovative lead-carbon battery utilizing electrode-electrolyte assembly inspired by PEM-FC architecture
2024 - SOUZA, RODRIGO F.B. de; SILVESTRIN, GABRIEL A.; CONCEICAO, FELIPE G. da; MAIA, VICTORIA A.; OTUBO, LARISSA; NETO, ALMIR O.; SOARES, EDSON P.
This study explores the innovative integration of a lead‑carbon battery with an electrode-electrolyte assembly inspired by Proton Exchange Membrane Fuel Cell (PEM-FC) architecture. The lead‑carbon material, synthesized with a 40 % mass ratio using the Flash Joule Heating Method, exhibits predominant Pb0 and PbO phases, as observed in lattice parameter fringes, with additional detection of the PbO2 phase. The resulting Carbon-Lead Acid Battery (CLAB) demonstrates a specific capacity of 11.2 mAh g−1. The incorporation of carbon enhances nanoparticle stability, yielding a highly stable battery performance over 100 cycles, with discharge potential variations of <2 %. This innovative CLAB assembly not only showcases stable performance and also introduces the potential for constructing flexible lead batteries, expanding technological applications. The study provides comprehensive insights into the synthesis, performance, and prospects of this novel lead‑carbon battery architecture, emphasizing its significance in the realm of energy storage solutions.
Enhanced carbon monoxide tolerance of platinum nanoparticles synthesized through the Flash Joule Heating Method
2024 - NANDENHA, JULIO; SILVESTRIN, GABRIEL; OTUBO, LARISSA; ANDRADE, DELVONEI A.; SOUZA, RODRIGO F.B. de; ANTOLINI, ERMETE; NETO, ALMIR O.
Was employ the Flash Joule Heating Method (FJHM) to synthesize carbon-supported Pt nanoparticles. In this method, an aqueous solution of the Pt precursorH2PtCl6·6 H2O is introduced into a reactor containing Vulcan XC 72 carbon. Subsequently, the mixture undergoes 50 cycles of discharges at 100 coulombs per discharge. Comparative XRD analysis with a commercially prepared Pt/C BASF, utilizing a reduction deposition method, reveals an expansion in the interplanar spacing of the platinum crystal lattice in the FJHM-prepared Pt/C catalyst (FJHM-Pt/C). This expansion suggests the emergence of structural defects, a finding confirmed by TEM images displaying distinct step-like features on the FJHM-Pt/C surface. Cyclic voltammogram analysis demonstrates a noteworthy increase in the oxidation pre-peak at 0.5 V for FJHM-Pt/C compared to Pt/C BASF. When employing pure H2 as fuel, the single proton exchange membrane fuel cell (PEMFC) utilizing Pt/C BASF as the anode catalyst exhibits a higher maximum power density (MPD) than its FJHM-Pt/C counterpart. Conversely, in the presence of CO, the PEMFC with FJHM-Pt/C as the catalyst demonstrates a superior MPD compared to the cell equipped with commercial Pt/C as the anode. These findings underscore enhanced CO tolerance, highlighting the potential advantages of the FJHM preparation method.
Effective phosphate removal from water by electrochemically mediated precipitation with coffee grounds biocarbon obtained by non-thermal plasma method
2023 - SILVESTRIN, G.A.; GONCALVES, M.H.; GODOI, C.M.; MAIA, V.A.; FERREIRA, J.C.; GUILHEN, S.N.; NETO, A.O.; SOUZA, R.F.B. de
This study investigates the use of biocarbon electrodes, produced from coffee grounds through plasma pyrolysis, in the electrochemically mediated precipitation process for phosphorus removal in a flow reactor. The structural and electrochemical properties of biocarbon were analyzed using X-ray powder diffraction (XRD), Raman spectroscopy, and cyclic voltammetry. The results show that biocarbon consists of both graphene oxide and lignocellulose with surface OH groups that facilitate the breakdown of water, a key step in the electrochemically mediated precipitation process for phosphorus removal. The addition of graphite to the biocarbon paste was found to be necessary to obtain a response from the biocarbon in cyclic voltammetry. The Gr75BC25 electrode achieved higher phosphorus removal rates than other tested electrodes, particularly at low flows, due to the functional groups present in biocarbon enhancing the breakdown of water. However, electrodes with a greater amount of biocarbon exhibit lower rates of phosphorus removal and higher consumption of electrical power, which can be attributed to their higher electrical resistivity. Thus, to optimize its use, it is important to balance the benefits of increased phosphorus removal rates with the trade-off of increased energy consumption and decreased phosphorus removal at higher levels of biocarbon. The results suggest that biocarbon produced from coffee grounds by plasma pyrolysis has the potential to be used as an effective electrode material for electrochemically mediated precipitation processes.