X‐Ray Photoelectron Spectroscopy Study of Ni and Ni–SiO ₂ Coatings Electrodeposited From Deep Eutectic Solvent

ABSTRACT Ni and nanocomposite Ni–SiO 2 coatings with nanostructured Ni crystalline characteristics were electrodeposited at 8 mA cm −2 from an environmentally friendly deep eutectic solvent (DES)–based electrolyte containing 0 and 30 g/L of SiO 2 nanoparticles. X‐ray photoelectron spectroscopy study was performed on the coatings to study the effect of the addition of SiO 2 nanoparticles into the DES‐based electrolyte on the interactions of reducing Ni with electrolyte residual water and/or electrolyte species during electrodeposition. The presence of nickel chloride was detected in the Ni coating due to the precipitation of electrolyte decomposition by‐products species on the cathode surface. However, nickel chloride was not observed in the Ni–SiO 2 composite coating. Ni hydroxide and oxide were detected in both Ni and Ni–SiO 2 nanocomposite coatings. However, their amount decreased when SiO 2 was present in the electrolyte. These observations can be related to the interference of the particles with the reactions happening on the cathode surface other than Ni 2+ reduction. Agitated SiO 2 nanoparticles in the electrolyte during electrodeposition could cause a decrease in the formation of nickel hydroxide, nickel oxide, and electrolyte decomposition by‐products at the cathode surface.