Defect engineering over anisotropic brookite towards substrate-specific photo-oxidation of alcohols

TL;DR

This study introduces a defect engineering approach on anisotropic brookite TiO2 photocatalysts, significantly enhancing substrate-specific alcohol oxidation and hydrogen evolution through controlled oxygen vacancies and lattice strain.

Contribution

It presents a novel defect engineering strategy on anisotropic brookite TiO2 to achieve substrate-specific photocatalytic activity, outperforming traditional isotropic nanocrystals.

Findings

Up to 11-fold increase in methanol oxidation rate.

Enhanced hydrogen evolution linked to substrate-specific alcohol oxidation.

Defect engineering creates active sites for alcohol photo-oxidation.

Abstract

Generally adopted design strategies for enhancing the photocatalytic activity are aimed at tuning properties such as the visible light response, the exposed crystal facets, and the nanocrystal shape. Here, we present a different approach for designing efficient photocatalysts displaying a substrate-specific reactivity upon defect engineering. The defective anisotropic brookite TiO2 photocatalyst functionalized with Pt nanocrystals are tested for alcohol photoreforming showing up to an 11-fold increase in methanol oxidation rate, compared to the unreduced one, whilst presenting much lower ethanol or isopropanol specific oxidation rates. We demonstrate that the alcohol oxidation and hydrogen evolution reactions are tightly related, and when the substrate-specific alcohol oxidation ability is increased, the hydrogen evolution is significantly boosted. The reduced anisotropic brookite shows up to twenty-six-fold higher specific photoactivity with respect to anatase and brookite with isotropic nanocrystals, reflecting the different type of defective catalytic sites formed depending on the TiO2 polymorph and its crystal shape. Advanced in-situ characterizations and theoretical investigations reveal that controlled engineering over oxygen vacancies and lattice strain produces large electron polarons hosting the substrate-specific active sites for alcohol photo-oxidation.