Adilar Gonçalves dos Santos Júnior

The genus Shewanella is renowned for its metabolic versatility and role in extracellular electron transfer (EET). This study characterizes Shewanella sp. (REG000848), a lineage isolated from the South Atlantic Blue Amazon. Phylogenomic metrics (ANI < 85% and dDDH < 27%) reveal that REG000848 is a genetically divergent lineage, exhibiting unique adaptations to marine stressors. The strain demonstrated exceptional physiological resilience, maintaining growth at temperatures up to 45°C, salinity levels of 12% NaCl, and a pH range of 4.5–10.0, significantly exceeding the thresholds of the model S. oneidensis MR-1. Genomic analysis identified a robust Mtr respiratory machinery, with multiple paralogs of the MtrB/PioB family and deca-heme cytochromes (MtrC and OmcA), providing the framework for its bioelectrogenic potential. Pangenomic analysis defining REG000848 as a specialized ecotype within the Southern Blue Amazon. In Microbial Fuel Cells (MFCs), the lineage achieved an immediate Open-Circuit Voltage (OCV) of 250 mV, suggesting a biofilm-independent electron transfer mechanism. These findings underscore the South Atlantic as a strategic reservoir of genetic resources, positioning Shewanella sp. (REG000848) as a promising bio-platform for sustainable energy and industrial biotechnology in processes that are usually stressful for most microorganisms.

Niobium-based oxides are being increasingly evaluated as materials for energy storage applications. Additionally, the use of these oxides as cathodes in aqueous electrolytes has shown promise. Based on this, the pseudocapacitive behavior of protonic niobate nanowires in an aqueous acidic electrolyte (1 M H₂SO₄) was evaluated for the first time. The material was obtained in two simple sequential steps. First, hydrothermal synthesis resulted in sodium niobate; second was ionic exchange (in two concentrations of 2 M and 0.1 M HNO₃), where the protonic niobate was obtained. The resulting protonic niobate was characterized by FEG-SEM, the results demonstrated that the morphology of the oxide was concentration-dependent in the ionic exchange step, and EDS analysis was used to validate the procedure. Using DRX, Raman spectroscopy, and FTIR analysis, the transformation of sodium niobate to protonic niobate was evidenced. The electrochemical tests demonstrated that the protonic niobate presented pseudocapacitive behavior when employed as the cathode in 1 M H₂SO₄, and the ionic exchange in 2 M HNO₃ promoted a better specific capacitance, reaching 119.8 mF·cm⁻² at a 1 mA·cm⁻² current density.

The growing demand for sustainable energy storage solutions has prompted the exploration of eco-friendly materials for supercapacitor applications. In this study, we present a simple two-step synthesis of nanoscale carbon spheres using a modified Stöber method, employing black wattle tannin extracted from Acacia mearnsii as a carbon precursor, in comparison with the conventional resorcinol precursor. Morphological characterization revealed that highly homogeneous nanoscale spheres were obtained. Physicochemical characterizations indicated that the tannin-derived spheres exhibited residual silica content due to incomplete template removal, which increased series resistance and limited the material's performance. Although inferior to resorcinol-derived spheres, which achieved a specific surface area of 2093 m2g−1, the tannin-derived material still exhibited a high surface area of 457 m2g−1 and a specific capacitance of 66.3 F g−1 in aqueous H2SO4 electrolyte, with well-defined morphology achieved without an activation step. By using an environmentally friendly precursor, we successfully produced a material with a homogeneous and well-defined structure, high surface area, and obtained through a simple two-step process of polymerization and carbonization without additional activation. These findings may open new directions for future research.

Com o intuito de evitar ou minimizar a corrosão por pite dos aços inoxidáveis é possível aprimorar a capacidade protetiva da camada passiva dessas ligas, e um dos métodos para se obter esse resultado é o tratamento superficial de passivação química. Nesse contexto foi investigado o efeito do tratamento de passivação química com ácido nítrico na resistência à corrosão por pite e no acabamento superficial dos aços inoxidáveis ferrítico AISI 430 e austenítico AISI 316L em meio contendo cloreto. Para isso duas condições superficiais foram utilizadas para cada material: superfície lixada e superfície passivada quimicamente conforme a norma ASTM A967/967M. O acabamento superficial foi caracterizado pela avaliação da rugosidade média e análise visual por microscopia óptica. O comportamento frente à corrosão foi avaliado através de ensaios de polarização anódica cíclica em 0,6 M NaCl conforme norma ASTM G61 e a morfologia dos pites foi caracterizada por microscopia óptica. De acordo com os resultados, a resistência à corrosão por pite dos aços inoxidáveis AISI 430 e AISI 316L submetidos ao tratamento de passivação tiveram os potenciais de pite e de repassivação aumentados em relação ao valor obtido com a superfície lixada, ou seja, tiveram sua resistência à corrosão por pite melhorada.