Stepwise construction of Pt decorated oxygen-deficient mesoporous titania microspheres with core-shell structure and magnetic separability for efficient visible-light photocatalysis

Photocatalytic materials modified with carbon quantum dots for the degradation of organic pollutants under visible light: A review

In recent years, carbon quantum dots (CQDs) have received widespread attention owing to their non-toxicity, sustainability, excellent photostability, and intrinsic photoluminescence properties. In particular, CQDs have attracted considerable interest for visible-light-driven photocatalysis because of their excellent electron transfer characteristics and high light capture efficiency. Many studies have reported CQDs/photocatalyst composite systems constructed to make full use of the solar spectrum, improving the ability of photocatalytic materials to degrade organic pollutants. Here, we review the recent research on CQDs-based photocatalysts, and their ability to remove environmental pollutants, with a special emphasis on degradation mechanisms. Several improvements in the catalytic response of CQDs to visible light are also included. In addition, we discuss the aspects that should be considered to construct composite materials based on CQD characteristics and the potential applications of CQD-based photocatalysts for efficient utilization of visible light.

Galvanic Deposition of Pt Nanoparticles on Black TiO2 Nanotubes for Hydrogen Evolving Cathodes

A galvanic deposition method for the in-situ formation of Pt nanoparticles (NPs) on top and inner surfaces of high-aspect-ratio black TiO2 -nanotube electrodes (bTNTs) for true utilization of their total surface area has been developed. Density functional theory calculations indicated that the deposition of Pt NPs was favored on bTNTs with a preferred [004] orientation and a deposition mechanism occurring via oxygen vacancies, where electrons were localized. High-resolution transmission electron microscopy images revealed a graded deposition of Pt NPs with an average diameter of around 2.5 nm along the complete nanotube axis (length/pore diameter of 130 : 1). Hydrogen evolution reaction (HER) studies in acidic electrolytes showed comparable results to bulk Pt (per geometric area) and Pt/C commercial catalysts (per mg of Pt). The presented novel HER cathodes of minimal engineering and low noble metal loadings (μg cm-2 range) achieved low Tafel slopes (30-34 mV dec-1 ) and high stability in acidic conditions. This study provides important insights for the in-situ formation and deposition of NPs in high-aspect-ratio structures for energy applications.

Nanocage-Shaped Co3- x Zrx O4 Solid-Solution Supports Loaded with Pt Nanoparticles as Effective Catalysts for the Enhancement of Toluene Oxidation

Nanocage-shaped Co_{3- x} Zr_x O₄ solid-solution supports and the corresponding platinum loaded nanocomposites, yPt/Co_{3- x} Zr_x O₄ (x =0.27, 0.50, 0.69; y = 0.5, 1.0, 2.0 wt.%), are successfully fabricated via a Cu₂ O nanocube hard template method and a glycol reduction method, respectively. The hollow nanocage structures obviously improve surface areas; moreover, the Zr doping forms the Co_{3- x} Zr_x O₄ solid-solution supports, and the corresponding yPt/Co_{3- x} Zr_x O₄ catalysts promote the enhancement of catalytic performance. Catalytic activity toward toluene combustion is enhanced for the 2.0 wt% Pt/Co_2.73 Zr_0.27 O₄ catalyst. The catalysts are characterized using multiple techniques. Pt nanoparticles are uniformly dispersed across the Co_2.73 Zr_0.27 O₄ nanocage surface. The 2.0 wt% Pt/Co_2.73 Zr_0.27 O₄ catalyst exhibits the highest catalytic activity among all the samples and demonstrates good stability, with 90% toluene conversion obtained at a temperature of 165 °C. The same catalyst accomplishes full toluene oxidation at 180 °C, at a weight hourly space velocity of 36 000 mL h^-1 g^-1 . The apparent activation energy (E_a ) over the yPt/Co_2.73 Zr_0.27 O₄ samples are significantly lower than those over the Co_{3- x} Zr_x O₄ supports, with the 2.0 wt% Pt/Co_2.73 Zr_0.27 O₄ catalyst exhibiting the lowest E_a value. These findings demonstrate the potential of the 2.0 wt% Pt/Co_2.73 Zr_0.27 O₄ catalyst as a promising catalyst toward atmospheric toluene removal.