# Boosting the Mechanical Strength and Photocatalytic Activity of 3D-Printed Titania Aerogels by Atomic Layer Deposition and Heat Treatment

## TL;DR

This paper shows how to strengthen and improve the photocatalytic performance of 3D-printed titania aerogels using atomic layer deposition and heat treatment.

## Contribution

The study introduces ALD of TiO2 layers to enhance both mechanical strength and photocatalytic activity of 3D-printed aerogels.

## Key findings

- ALD TiO2 coatings improve mechanical properties of 3D-printed aerogels.
- ALD coatings increase photocatalytic activity by enhancing interface area and nanoparticle interconnection.
- Thermal postprocessing fully crystallizes ALD TiO2, boosting hydrogen evolution rate over tenfold.

## Abstract

Titania aerogels
are highly porous materials optimal
for photocatalysis
due to their high surface area. Further spatial structuring by 3D
printing improves gas diffusion in the aerogel, leading to a higher
photocatalytic activity. However, the aerogel’s mechanical
properties are reduced in comparison to non-3D printed aerogels. We
hereby present an approach based on atomic layer deposition (ALD)
of subnanometer-thin TiO2 layers to compensate for that
detrimental effect. The ALD-deposited TiO2 consists of
amorphous and anatase phase, with the anatase phase likely crystallizing
on the aerogel’s crystallites. Nanoindentation measurements
confirm that the TiO2 ALD-coatings improve the aerogel’s
mechanical properties. Additionally, it enhances the photocatalytic
properties of the TiO2 aerogel, which we attribute to the
increased interface area and improved interconnection of the nanoparticle
network. By further thermal postprocessing, it is possible to fully
crystallize the ALD-deposited TiO2, which shows a complementary
effect on photocatalytic performance, improving hydrogen evolution
rate by more than 1 order of magnitude from 6.35 to 125 μmol
g–1 h–1. The combination of 3D
structuring of aerogels with ALD coatings demonstrated in this work
could be extended in the future to a wide range of materials where
the interplay between mechanical and catalytic properties is vital.