Influence of $$\hbox {TiO}_{2}$$ TiO 2 structural properties on photocatalytic hydrogen gas production

Enhanced Photocatalytic Ozonation Using Modified TiO2 With Designed Nucleophilic and Electrophilic Sites

Photocatalytic ozonation is considered to be a promising approach for the treatment of refractory organic pollutants, but the design of efficient catalyst remains a challenge. Surface modification provides a potential strategy to improve the activity of photocatalytic ozonation. In this work, density functional theory (DFT) calculations were first performed to check the interaction between O3 and TiO2-OH (surface hydroxylated TiO2) or TiO2-F (surface fluorinated TiO2), and the results suggest that TiO2-OH displays better O3 adsorption and activation than does TiO2-F, which is confirmed by experimental results. The surface hydroxyl groups greatly promote the O3 activation, which is beneficial for the generation of reactive oxygen species (ROS). Importantly, TiO2-OH displays better performance towards pollutants (such as berberine hydrochloride) removal than does TiO2-F and most reported ozonation photocatalysts. The total organic carbon (TOC) removal efficiency reaches 84.4 % within two hours. This work highlights the effect of surface hydroxylation on photocatalytic ozonation and provides ideas for the design of efficient photocatalytic ozonation catalysts.

H2O2 Exfoliation of TiO2 for Enhanced Hydrogen Production from Photocatalytic Reforming of Methanol

Hydrogen is considered a future energy carrier for clean and sustainable technology. Photocatalytic reforming of methanol produced hydrogen using water and energy from sunlight. This study reported enhanced activity of TiO2 without metal co-catalyst for hydrogen production following H2O2 exfoliation. TiO2 was transformed into peroxo-titania species on the outer layer of the particles, resulting in surface exfoliation. The exfoliation reduced TiO2 crystallite sizes enhanced the surface hydroxyl group and reduced the band gap to 3.0 eV. Hydrogen production from methanol-water mixtures on the TiO2 after four consecutive exfoliations was measured at 300 µmol, significantly higher than the fresh TiO2 (50 µmol).  H2O2 exfoliated TiO2 reduced the pathway for charge migration to the surface.  A high concentration of surface hydroxyl group trapped the charge carriers for efficient hydrogen production. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Photoelectrochemical Enzyme Biosensor Based on TiO2 Nanorod/TiO2 Quantum Dot/Polydopamine/Glucose Oxidase Composites with Strong Visible-Light Response

Although photoelectrochemical (PEC) enzyme biosensors based on visible-light detection would have a high practical value, their development has been limited by the weak visible-light response of available photoactive substrates. Here, to enhance the visible-light response of a photoelectric substrate, a TiO₂ nanorods (NRs)/TiO₂ quantum dots (QDs)/polydopamine (PDA)/glucose oxidase nanocomposite was prepared via hydrothermal synthesis, followed by photopolymerization. TiO₂ QDs with strong light absorption and excellent photocatalytic activity were introduced between the TiO₂ NRs and the PDA. An efficient electron transport interface that formed as a result of the combination of the TiO₂ NRs, TiO₂ QDs, and the PDA could not only transfer electrons quickly and orderly, but also substantially improve the response of the TiO₂ NRs under visible light. Through a series glucose detection, a sensor based on the nanocomposite was found to exhibit superior sensing performance under visible light with a sensitivity of 4.63 μA mM^-1 cm^-2, a linear response over the concentration 0.1-4 mM, and a detection limit of 8.16 μM. This work proposes a biosensor that can detect under visible light, thereby expanding the application range of PEC enzyme biosensors.

Graphene Quantum Dots Improved "Caterpillar"-like TiO2 for Highly Efficient Photocatalytic Hydrogen Production

Photocatalytic water splitting for hydrogen production via heterojunction provides a convenient approach to solve the world crises of energy supply. Herein, graphene quantum dots modified TiO₂ hybrids (TiO₂-GQDs) with a “caterpillar”-like structure exhibit stronger light absorption in the visible region and an enhanced hydrogen production capacity of about 3.5-fold compared to the pristine TiO₂ caterpillar. These results inferred that the addition of GQDs drastically promotes the interfacial electron transfer from GQDs to TiO₂ through C–O–Ti bonds via the bonding between oxygen vacancy sites in TiO₂ and in-plane oxygen functional groups in GQDs. Using a “caterpillar”-like structure are expected to provide a new platform for the development of highly efficient solar-driven water splitting systems based on nanocomposite photocatalyst.

Pd local structure and size correlations to the activity of Pd/TiO2 for photocatalytic reforming of methanol

The interaction between Pd and TiO2 for promoting photocatalytic activity was investigated by tailoring the size of Pd nanoparticles and monitoring the photocatalytic activity of methanol photo-reforming reaction for hydrogen gas production. We show that at 0.6 wt% Pd loading, the catalyst with highly dispersed nanoparticles obtained at 1 °C temperature exhibits superior photocatalytic activity for hydrogen gas production. At different weights of Pd loading, tailoring two sets of catalysts with different structural properties provides correlation between the changes in the Pd local structures and the rate of hydrogen production. The impact of controlling the structural properties of metal nanoparticles on influencing H2 production outweighs the effect of metal loading variation. The differences of Pd/TiO2 activity at the different metal loadings were correlated with the changes in the Pd local structure consequently affecting the electronic transfer and photocatalytic efficiency.