Revestimentos de Cu-In com aplicação eletrocatalítica na reação de desprendimento de hidrogênio

Abstract

Hydrogen is considered an alternative to fossil fuels due to its high energy efficiency and the fact that it does not generate carbon dioxide emissions. However, obtaining clean hydrogen is still a challenge due to the high energy cost of water electrolysis and the need for efficient electrocatalysts to reduce this cost. In this context, the aim of this work is to develop and characterize copper-indium coatings in eutectic medium based on choline chloride and urea (at a molar ratio of 1:2) on the surface of 1020 carbon steel and evaluate their electrocatalytic activity in the hydrogen release reaction. The focus is on creating efficient catalysts that can reduce the cost of hydrogen production by water electrolysis. The system was successfully characterized using cyclic voltammetry, revealing two distinct reduction peaks in the regions of -0.8 V and between -1.0 and -1.1 V for the copper and indium species, respectively. Temperature variation affected the process, with the peak at -0.8 V not being evident at 23.5 °C, and the voltammograms at 70 °C showing higher peak currents. The electrodeposits were obtained by means of chronoamperometira and in multilayer electrodeposition, being four layers with a deposition time of 3600 s per layer. The order variations of the layers were: Cu Cu-In Cu Cu In and Cu-In Cu Cu-In Cu. The analysis of the morphology of the multilayer coatings by scanning electron microscopy (SEM) revealed that the temperature and the order of electrodeposition of the Cu and In layers influenced the morphology of the metallic films. The multilayers obtained at 70 ºC exhibited higher coating concentration. Both samples showed nodules and rods in their morphology, however the sample initiated with a Cu-In layer showed lower dispersion compared to the metallic film initiated with a copper layer. The electrolyte properties such as viscosity and diffusion coefficient were also studied. Increasing the temperature reduced the viscosity of the medium and increased the diffusion coefficient of Cu2+ and In3+ species. The electrocatalytic activity of the coatings was evaluated by linearizing the polarization curves obtained by linear sweep voltammetry performed in alkaline KOH 1 mol L−1 solution medium. The copper-indium multilayer coatings showed promise as electrocatalysts in the H2 release reaction in alkaline medium with Tafel slope values in the range of 199.17 and 65.83 mV dec−1.