Abstract
Self-organized anodic double layer TiO
2
nanotube arrays (TNTAs) were sensitized by an electrochemical anodization process on a Ti sheet with a two-step anodization method. The prepared sample, followed by hydrothermal treatment with Nd(NO
3
)
3
and/or Gd(NO
3
)
3
and/or PtCl
4
solution at 180 °C for 2 h, produced Nd-Pt-TNTAs, Gd-Pt-TNTAs, Nd-Gd-Pt-TNTAs and Pt-TNTAs. The morphological and structural properties were studied by SEM, XRD and Raman spectra techniques. The hydrogen evolution reaction (HER) performance on Lanthanides-Pt-TNTAs was investigated using the Tafel linear polarization technique. The calculated values of the activation energy are in good agreement with the trend in catalytic activity. The excellent performance of doped TNTAs with low activation energy (E
a
) is due to the formation of an excitation energy level below the conduction band of TiO
2
from the binding of electrons with oxygen vacancies decreasing the excitation energy resulting in robust electrocatalytic activity. The very low value of E
a
for Nd-Gd-Pt-TNTAs (2.02 kJ/mol) compared to other electrochemical catalysts used for hydrogen evolution reactions containing titanium nanotubes was achieved for the first time. This makes the Lanthanides -Pt-TNTAs prepared in the present work optimal catalysts for electrodes and promising for applications in fuel cells or as water splitting materials.
Highlights
Synthesis of self-organized anodic double layer TiO
2
nanotube arrays (TNTAs) on a Ti sheet with a two-step anodization method.
Nd, Gd, Pt were deposited on anodic TNTAs arrays by hydrothermal method.
The HER mechanisms on Lanthanides-Pt-TNTAs in acidic media has been discussed.
The order of catalytic activity based on the values of activation energy was Nd-Gd-Pt-TNTAs > Gd-Pt-TNTAs > Nd-Pt-TNTAs > Pt-TNTAs > undoped TNTAs.