Effect of the Anodic Titania Layer Thickness on Electrodeposition of Zinc on Ti/TiO₂from Deep Eutectic Solvent

Abstract

Zinc electrodeposition from a deep eutectic mixture of ZnCl2 and choline chloride/ethylene glycol on titanium covered by an anodic titania film of different thicknesses was studied. It was shown that thin titanium dioxide layers work as high resistive media and the rate of zinc deposition decreases with film thickness. Thicker titania layers (23 nm and higher) have opposite properties and the zinc reduction rate starts gradually increasing with thickness. This happens because at the higher voltage necessary to grow thicker anodic films they become more crystalline and consequently more conductive. There is also evidence that in deep eutectic solvent no dense organic layer forms on the titanium/titania electrodes. The application of an AC signal superimposed on a DC potential only marginally increases the amount of zinc deposited and FTIR measurements did not reveal the formation of any chemical bonds between the film and deep eutectic solvent. Zn deposition onto titanium/titania at −1.6 V is characterized by instantaneous three-dimensional nucleation mechanism, which is independent of the titania thickness.

Zinc Nanoparticles Electrodeposited on TiO2Nanotube Arrays Using Deep Eutectic Solvents for Implantable Electrochemical Sensors

“…On the other hand, the annealed nanotube substrate appears to initiate deposition at a higher current density compared to the as-anodized substrate, which could be due to improved charge transfer in the crystalline structure of TiO 2 (anatase) achieved by annealing. 27 This would allow a higher rate of metal nanoparticle deposition due to faster charge transport. The overall measured deposition current density is higher at 40 °C than at RT.…”

“…Current density transient plots at the start of the electrodeposition process can be used to identify the nucleation process of the deposited metal as shown in past works. ,,, In 1983, Scharifker and Hills proposed numerical models for instantaneous and progressive nucleation processes for a diffusion-controlled regime when the current density is converted to a dimensionless form of true( j j max true) 2 . The nucleation mechanism in this model can be either instantaneous or progressive and is assumed to occur at specific locations on the surface.…”

“…In Figure a, the bare Ti substrate demonstrates close-to-immediate initiation of zinc nucleation, which is indicated by the rapid change in the current density due to faster charge transport on the surface of the metal from the initial value toward 0 A when compared to the TiO 2 NTA substrates. On the other hand, the annealed nanotube substrate appears to initiate deposition at a higher current density compared to the as-anodized substrate, which could be due to improved charge transfer in the crystalline structure of TiO 2 (anatase) achieved by annealing . This would allow a higher rate of metal nanoparticle deposition due to faster charge transport.…”

“…According to these findings, electrodeposition using DES electrolytes appears to be a viable method for depositing pure zinc nanocrystals on conductive substrates. Starykevich et al performed zinc electrodeposition on dense TiO 2 substrates with different thicknesses using DES . Electrodeposited zinc can have a diverse morphology, which has a direct influence on the reversibility of the deposited electrode and is argued to be influenced by a multitude of factors predominantly concerning the solid–electrolyte interface as Zheng and Archer stated in their very recent work .…”

“…Starykevich et al performed zinc electrodeposition on dense TiO 2 substrates with different thicknesses using DES. 27 Electrodeposited zinc can have a diverse morphology, which has a direct influence on the reversibility of the deposited electrode and is argued to be influenced by a multitude of factors predominantly concerning the solid−electrolyte interface as Zheng and Archer stated in their very recent work. 28 According to their work, lower electrodeposition current densities could lead to arguably more disordered, moss-like zinc deposits.…”