Transições de fase e funcionalização química em nanoestruturas de MoS2 : aplicações em energias renováveis

• Autor(a) principal: Santos, Felipe Conceição dos
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações do Mackenzie
• Texto Completo: http://dspace.mackenzie.br/handle/10899/26508
• topic: MoS2; transições de fase; funcionalização química; CNPQ::ENGENHARIAS::ENGENHARIA DE MATERIAIS E METALURGICA

The eminent scarcity of fuels based on fossil resources, as well as serious environmental damage arising from their utilization, imposes us a need to search for more sustainable alternatives in the energy field. The use of hydrogen as a fuel presents itself as a promising solution, having as a main challenge the substitution of platinum for catalysts that provides energetic viability to electrochemical technologies. The transition metal dichalcogenides (TMDs), especially the molybdenum disulfide (MoS2), is pointed as a potential substitute for the metal catalysts due to the high catalytic activity observed for MoS2 when presented in the metallic phase (1T). However, the 1T phase is thermodynamically metastable, and it is essential to develop strategies to stabilize the metal phase of MoS2 without compromising its catalytic properties. The present work describes a study of the stability of the 1T’ phase (distorted metallic) in MoS2 nanostructures prepared by chemical exfoliation with nbutillithium. Initially it is presented the synthesis of a material with mixed character (1T’/2H-MoS2) as well as the impact of the presence of semiconducting domains in the stability of the 1T’ phase and in the material’s catalytic properties. Additionally, surface chemical functionalization of 1T’-MoS2 with organic molecules were studied as a tool to promote the metallic phase stabilization. The results indicated that the presence of semiconducting domains possess a great negative impact both in the 1T’ phase stability and in the electrocatalytic performance of the material in the hydrogen evolution reaction (HER). The chemical modification of the surface of MoS2 presented itself as a pretty efficient strategy to stabilize the 1T’ phase and prevent 1T’-MoS2 oxidation.