Insights into the Intrinsic Creation of Heterojunction-Based Ordered TiO2 Nanotubes Obtained from the One-Step Anodic Oxidation of Titanium Alloys

María C Nevárez Martínez,Grzegorz Trykowski,Paweł Mazierski,Adriana Zaleska-Medynska,Wojciech Lisowski,Grzegorz Nowaczyk

doi:10.1021/acs.jpcc.0c08621

Abstract

To gain insights into how the presence of the second metal in Ti alloys affects the morphology, crystallinity, chemical structure, and photocatalytic/photoelectrochemical activity of mixed-oxide nanotubes (TiO2–MxOy), five systems were electrochemically synthesized in a fluoride-containing ethylene glycol-based electrolyte by using Ti alloys, with 10 wt % of the second metal, as precursors. The level of self-organization and -orientation in the obtained samples followed the order: Ag < Cu < Mn < V < Co, being the Ti90Ag10_40V sample, the only presenting single Ag nanoparticles embedded in the oxide layer. The highest photocatalytic and photoelectrochemical activities were reported for the Ti90Ag10_40V sample, which can be attained to the heterojunction between the oxides, the formation of single Ag nanoparticles, and the high level of self-organization. Apparently, the intrinsic heterojunction between the oxides depends on the still-needed-to-be-estimated stability of the oxides produced during the anodization of each system.

Highlights

TiO2 is one of the most widely studied materials due to its broad range of applications including photocatalysis, dye-sensitized solar cells, photoelectrochemistry, photovoltaics, and optoelectronic and biomedical devices.[1−3] Most of these purposes demand a high surface area of the material which can be achieved by decreasing the size to the nanometer scale
5.10 toluene-gas-phase not reported 0.07 degradation aThe label of each sample includes as subscripts the weight percent of each of the metals in the precursor alloy. bEG = ethylene glycol. cTi−M stands for the alloy foil precursor for the electrochemical anodization, where M represents the modifying metal; its content was determined by elemental composition through XPS analysis. dPhotocatalytic experiments for a sample prepared under slightly different synthesis conditions (30 V) were reported in our previous work[34] and the phenol photocatalytic degradation presented a rate of 1.45 and 0.362 μmol dm−3 min−1 under UV−vis (λ > 350 nm)
The present article gathers comparative information about five mixed-oxide NT systems produced under the same conditions by electrochemical anodization of Ti−M alloys (M: Ag, Cu, Co, V, or Mn) as precursors to analyze the effect of the second metal in the alloy in the morphology, crystallinity, surface chemistry, and photoelectrochemical properties of the grown NT arrays

Summary

■ INTRODUCTION

TiO2 is one of the most widely studied materials due to its broad range of applications including photocatalysis, dye-sensitized solar cells, photoelectrochemistry, photovoltaics, and optoelectronic and biomedical devices.[1−3] Most of these purposes demand a high surface area of the material which can be achieved by decreasing the size to the nanometer scale. Content of the modifying metal in the surface crystallite sample labela preparation conditions layer ofc Ti−M NTs (wt %). CTi−M stands for the alloy foil precursor for the electrochemical anodization, where M represents the modifying metal; its content was determined by elemental composition through XPS analysis. DPhotocatalytic experiments for a sample prepared under slightly different synthesis conditions (30 V) were reported in our previous work[34] and the phenol photocatalytic degradation presented a rate of 1.45 and 0.362 μmol dm−3 min−1 under UV−vis (λ > 350 nm). The empty space above the electrolyte was flushed with argon

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES