Desenvolvimento de nanofibras eletrocatalíticas por Solution Blow Spinning para a reação de evolução do oxigênio

Abstract

Hydrogen (H2) as fuel has been considered as the most promising source of renewable energy to meet growing global demand. Among H2 production methods, water splitting can produce high purity H2 and in a sustainable way. This occurs through two half reactions, that is the Hydrogen Evolution Reaction (HER) and the Oxygen Evolution Reaction (OER). However, the OER is a slow reaction due to the various steps involved in the process. For this reason, there is a great call for the development of nanocatalysts based on earth-abundant metals (Ni, Cu, Co, Fe, Ca) for the OER. Among the most varied types of nanostructures, nanofibers (one-dimensional structures, 1D) are presented as efficient supports for catalysis due to their high surface area. In this work, Solution Blow Spinning (SBS) method was used to produce solid and hollow nanofibers of some metal oxides (Ca3Co4O9-δ, NiO, CuFe2O4, CoFe2O4 e NiFe2O4) based on non-noble metals with potential to be used as electrocatalysts of the OER in alkaline medium. A series of morphological, structural, elemental and electrochemical characterization techniques were performed to provide detailed compression on the influence of morphological parameters on the performance of each catalyst. Hollow fibers with average diameter on range 200 - 257 nm and highly rough surface were obtained. It was observed that the performance for the OER is dependent on the morphological characteristics of these materials (diameter, crystallite size, tubular wall thickness and roughness). With superior activity to 1D, 2D and 3D materials of the same composition reported in the literature. From general results, when compared with nanoparticles, it was concluded that the structure of the fibrillar morphology of nickel-oxide puts an important rule in the overall performance of the electrocatalyst. Also influenced by route of synthesis, which contributed to the formation of a greater amount of active species for the OER on the surface of electrode, reflecting directly in the electrochemically active area (ECSA).