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Projeto de investigação
Center of Physics and Engineering of Advanced Materials
Financiador
Autores
Publicações
Enhanced borohydride oxidation kinetics with Au@MOF-808 nanocomposite electrocatalysts with ultra-low Au loading
Publication . Belhaj, Ines; Becker, J. Alexander; Viana, Alexandre M.; Gusmão, Filipe M. B.; Chaves, Miguel; Pereira, Eulália; Sljukic, Biljana; Balula, Salete S.; Silva, Luis Cunha; Santos, Diogo M. F.
ABSTRACT: The highly stable metal-organic framework (MOF) composed of[Zr6O4(mu 3-OH)4(OH)6(H2O)6(BTC)2]& sdot;nH2O units (MOF-808) was modified by incorporating gold (Au) nanoparticles and functional groups to enhance electrocatalytic activity for the borohydride oxidation reaction (BOR). Three composite materials (Au@MOF-808, Au@MOF-808-NH2, and Au@MOF-808-SH) were prepared by the incorporation of Au in structurally related MOFs, MOF-808, MOF-808-NH2, and MOF-808-SH, respectively. These composite materials were evaluated as anodic electrocatalysts for BOR in alkaline media using cyclic voltammetry and chronoamperometry. Among the prepared materials, Au@MOF-808-NH2 exhibited the highest BOR activity, with an apparent activation energy of 15.3 kJ mol-1, a reaction order of 0.6, an anodic charge transfer coefficient of 0.63, and a number of exchanged electrons of 4.4. The latter was significantly below the theoretical eight-electron value, indicating the presence of alternative reaction pathways. Notably, this material achieved a high mass-specific BOR peak current of 4.23 A mu gAu-1, demonstrating outstanding electrocatalytic efficiency despite the ultralow noble metal loading. These results underscore the potential of Au@MOF-808-NH2 as a cost-effective and scalable anodic electrocatalyst for high-performance direct borohydride fuel cells.
CrFeVWX (X = Ta or Ti) High-Entropy Alloy: A Theoretical and Experimental Comparative Investigation on Phase Stability
Publication . Martins, Ricardo; Valadares, Vasco; Pereira, André; Pereira Gonçalves, Antonio; Neves, Filipe; Sá, Ana; Luz, Paulo P. da; Monteiro, Bernardo; Galatanu, Andrei; Monnier, Judith; Villeroy, Benjamin; Dias, Marta
ABSTRACT: Materials capable of withstanding extreme environments open promising opportunities for nuclear fusion reactors. In this study, equiatomic CrFeTaVW and CrFeTiVW high-entropy alloys are investigated as interlayer materials between W and CuCrZr. Monte Carlo and Molecular Dynamics simulations predicted a bcc-type structure for both systems. Additionally, the Monte Carlo simulation predicts lower potential energy and a more stable structure for both systems than Molecular Dynamics. For CrFeTaVW, the chemical segregation values are lower in MC than in the MD simulation, whereas for CrFeTiVW, the opposite trend is observed, with MC indicating stronger segregation values. After simulation, the high-entropy alloys were prepared by planetary ball milling, consolidated by spark plasma sintering, and analyzed using X-ray diffraction, scanning electron microscopy, and thermal diffusivity. The experimental results for the milled powders confirmed the formation of a bcc structure in both alloys. The consolidated material revealed a bcc-type structure and an Fe2Ta Laves phase for the CrFeTaVW HEA, while the CrFeTiVW HEA exhibits two different bcc-type structures. The values of CrFeTaVW and CrFeTiVW thermal diffusivity are between 3.5 and 7 mm2/s, which is consistent with the expected values for high-entropy alloys. Overall, the findings indicate that these HEAs have promising properties that can be used in extreme environments.
Unidades organizacionais
Descrição
Palavras-chave
Physics of Strong Interactions and Correlations,Condensed Matter Physics,Nanostructured materials and nanotechnology,Engineering of Advanced Materials and Processes,
Contribuidores
Financiadores
Entidade financiadora
Fundação para a Ciência e a Tecnologia, I.P.
Programa de financiamento
Financiamento do Plano Estratégico de Unidades de I&D - 2019
Número da atribuição
UID/CTM/04540/2019