Optimized Spacing between TiO₂ Nanotubes for Enhanced Light Harvesting and Charge Transfer

Abstract

We investigate two distinctly different anodic TiO2 nanotubular morphologies, spaced and close‐packed arrays. While the close‐packed tubular arrays are formed in ethylene glycol, spaced nanotubes (NTs), which have a regular gap between individual NTs, grow in a diethylene glycol or dimethyl sulfoxide‐based electrolyte. Depending on the electrolyte used for anodization, the morphology, crystal structure, and chemical composition of the resulting nanotubular layer vary from one another. This influences the electrochemical and photoelectrochemical activity of the NTs. Overall, we find that spaced NTs can not only provide enhanced charge‐transfer characteristics but can also show beneficial light absorption characteristics when used as a photo‐ or light‐harvesting electrode.

Effect of different hole scavengers on the photoelectrochemical properties and photocatalytic hydrogen evolution performance of pristine and Pt-decorated TiO2 nanotubes

“…In order to estimate the band gap for the TiO2 nanotube layers the data was plotted as (Iph hv) 1/2 vs. hv (h is the Planck constant, v is the frequency of the light) using the data from the photocurrent spectra of the TiO2 nanotubes in the hole scavenger free (Fig 2c) and in the MeOH-containing (Fig 2d) electrolytes. The obtained band gap values for nanotubes of different lengths and in different electrolytes are all in range of 3.02-3.13 eV, which roughly is consistent with the previously reported values for anodic TiO2 nanotubes [2]. Table 1 IPCE spectra of the 4.58 µm thick TiO2 nanotube layers (selected because of the highest IPCE in the Na2SO4 electrolyte) were taken to compare different hole scavengers (Fig.…”

“…In this respect, titanium dioxide (TiO2) has acquired wide attention from researchers, due to the high photocatalytic activity, outstanding photocorrosion resistance, nontoxicity, and economic viability of this material [1]. Nanotubular TiO2 geometries are especially attractive for photocatalytic applications due to their high surface area combined with directionality to light and charge management [2]. TiO2 nanotubes can be prepared by various methods, which can be roughly divided into templating, hydrothermal, and anodic self-organization approaches [3].…”

Laser-Assisted Synthesis and Oxygen Generation of Nickel Nanoparticles

“…Such behavior is due to the fact that the oxygen evolution reaction (OER) dominates the total response and as a result the photoactivity is simply hidden [ 72 ]. Therefore, with a simple, quick, and easy step, the obtained current densities can be boosted by over an order of magnitude where, in case of structural optimizations [ 35 ], or doping [ 72 ], only a few percent increase is often observed.…”

“…Moreover, we provide an example of modification with created colloid, using it to enhance the efficiency of oxygen production in the TiO 2 -based electrode by over an order of magnitude. Due to the easily adjustable TiO 2 nanotubes (NTs) morphology, facile production, high surface area, and stability [ 33 , 34 , 35 , 36 , 37 , 38 , 39 ], together with nickel nanoparticles, they have become a very strong, yet eco-friendly, duet for further research. The electrochemical properties of hybrids composed of Ni nanoparticles electrodeposited onto titania nanotubes were shown for example by Chen et al using nickel sulphate as NPs precursor [ 40 ].…”

The Effect of Laser Re-Solidification on Microstructure and Photo-Electrochemical Properties of Fe-Decorated TiO2 Nanotubes

“…However, its tubular structure synthesized by anodization is most frequently examined due to perpendicular orientation of hollow cylinders regarding the metal substrate reducing the charge recombination and the scalability of the fabrication process [15,21]. Additionally, the geometrical parameters of titania nanotubes (TiO 2 -NTs) could be easily optimized during the synthesis, giving rise to the specific surface and light absorption of the resulting material [14,22]. The advantage of the direct contact between the electrode material and the current collector, as well as well-developed surface area, has been used in prototype supercapacitors when the further hydrogenation via cathodic polarization or plasma treatment in hydrogen atmosphere is applied.…”