TiO2 nanotubes with laterally spaced ordering enable optimized hierarchical structures with significantly enhanced photocatalytic H2 generation

TL;DR

This study develops TiO2 nanotube arrays with controlled spacing to create hierarchical structures that significantly improve photocatalytic hydrogen production through enhanced surface area and charge transport.

Contribution

It introduces a method to grow self-organized TiO2 nanotubes with defined spacing, enabling hierarchical structures with optimized photocatalytic performance.

Findings

Hierarchical TiO2 nanotube structures outperform conventional arrangements in H2 generation.

Optimized intertube spacing enhances charge transport and surface area.

Layer-by-layer nanoparticle decoration improves photocatalytic efficiency.

Abstract

In the present work we grow self-organized TiO2 nanotube arrays with a defined and controlled regular spacing between individual nanotubes. These defined intertube gaps allow to build up hierarchical 1D-branched structures, conformally coated on the nanotube walls using a layer by layer nanoparticle TiO2 decoration of the individual tubes, i.e. having not only a high control over the TiO2 nanotube host structure but also on the harvesting layers. After optimizing the intertube spacing, we build host-guest arrays that show a drastically enhanced performance in photocatalytic H2 generation, compared to any arrangement of conventional TiO2 nanotubes or conventional TiO2 nanoparticle layers. We show this beneficial effect to be due to a combination of increased large surface area (mainly provided by the nanoparticle layers) with a fast transport of the harvested charge within the passivated 1D nanotubes. We anticipate that this type of hierarchical structures based on TiO2 nanotubes with adjustable spacing will find even wider application, as they provide an unprecedented controllable combination of surface area and carrier transport.