Eletrodeposição de Snx-In(1−x) e NixMo(1−x) a partir de cloreto de colina e etilenoglicol

Abstract

The objective of this work was to electrodeposit, under potentiostatic control, SnIn and NiMo coatings in a eutectic solvent medium consisting of choline chloride (ChCl) and ethylene glycol (EG) in a 1:2 ratio (1ChCl:2EG). For SnIn coatings, solutions containing 0.025 mol L−1 SnCl2 and/or 0.025 mol L−1 InCl3 were used; for NiMo coatings, 0.4 mol L−1 NiCl2 and 0.025 mol L−1 Na2MoO4.H2O were used. The characterization of the coatings was performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The morphologies of the SnIn coatings at 298 K varied from cubic crystallites to a denser arrangement with interconnected forms from −1.0 V to −1.4 V. At 343 K, irregular layers were observed at −1.4 V. The Sn content was always higher than that of In, increasing slightly with increasing deposition potential, but the temperature did not affect this trend. For the NiMo coatings, the morphology obtained at 298 K resulted in a thin film for both Ni and NiMo, evidenced by the presence of grooves from the surface treatment. At 343 K, nodules formed for Ni, and for NiMo, the morphology was similar to a cauliflower and compact. The temperature facilitated Mo deposition, as indicated by EDS results, which showed a threefold increase in Mo at 343 K, resulting in 4% Mo. Computational simulations were performed for both coatings using density functional theory (DFT). For SnIn, the behavior of the Sn2+ and In3+ ions was evaluated. The results indicated that both cations interacted more strongly with the Cl− ion than with EG and showed no interaction with ChCl. For the NiMo coatings, their application for the hydrogen evolution reaction (HER) was studied. It was observed that the best performance and stability were achieved with the Ni96Mo4 coating, as it exhibited the lowest overpotential and highest exchange current values. Computational simulations were performed for the Ni100 and Ni96Mo4 surfaces, yielding Gibbs energy values of −4.15 and −2.31 kcal mol−1, respectively. These Gibbs energy values agreed with the experimental results, and Ni96Mo4 was found to be the best coating for HER.