Ce(0.6)Zr(0.3)Y(0.1)O(2) nanorod supported gold and palladium alloy nanoparticles: high-performance catalysts for toluene oxidation

Current progress on catalytic oxidation of toluene: a review

Toluene is one of the pollutants that are dangerous to the environment and human health and has been sorted into priority pollutants; hence, the control of its emission is necessary. Due to severe problems caused by toluene, different techniques for the abatement of toluene have been developed. Catalytic oxidation is one of the promising methods and effective technologies for toluene degradation as it oxidizes it to CO₂ and does not deliver other pollutants to the environment. This paper highlights the recent progressive advancement of the catalysts for toluene oxidation. Five categories of catalysts, including noble metal catalysts, transition metal catalysts, perovskite catalysts, metal-organic frameworks (MOFs)-based catalysts, and spinel catalysts reported in the past half a decade (2015-2020), are reviewed. Various factors that influence their catalytic activities, such as morphology and structure, preparation methods, specific surface area, relative humidity, and coke formation, are discussed. Furthermore, the reaction mechanisms and kinetics for catalytic oxidation of toluene are also discussed.

Carbon deposits during catalytic combustion of toluene on Pd–Pt-based catalysts

Carbon is easily deposited on a catalyst during the catalytic combustion of toluene, resulting in catalyst deactivation.

Preparation of a Series of Pd@UIO-66 by a Double-Solvent Method and Its Catalytic Performance for Toluene Oxidation

This paper reports on the preparation, characterization, and catalytic properties of the Pd@UIO-66 for toluene oxidation. The samples are prepared by the double-solvent method to form catalysts with large specific surface area, highly dispersed Pd⁰ (Elemental palladium) and abundant adsorbed oxygen, which are characterized by X-ray Photoelectron Spectroscopy (XPS), Brunauer-Emmett-Teller (BET) and Transmission Electron Microscopy (TEM). The results show that as the Pd content increases, the adsorbed oxygen content further increases, but at the same time Pd⁰ will agglomerate and lose some active sites, which will affect its catalytic performance. While 0.2%Pd@UIO-66 has the highest concentration of Pd⁰, the result shows it has the best catalytic activity and the T₉₀ temperature is 210 °C.

Porous hollow CoInOx nanocubes as a highly efficient catalyst for the catalytic combustion of toluene

Porous hollow HC-CoInOx nanocubes were synthesized via a SiO2 template strategy involving a cobalt-based metal-organic framework derived from a Prussian Blue analogue. As a heterogeneous catalytic material for the catalytic combustion of toluene, the hollow HC-CoInOx nanocubes displayed superior catalytic performance (T90 = 178 °C) and greatly reduced the activation energy for toluene oxidation due to their large surface area, the formation of surface dangling bands and oxygen vacancies, and increased number of weak acid sites. In comparison, the C-CoInOx sample (without the introduction of a SiO2 template) required a higher reaction temperature to achieve the same conversion of toluene (T90 = 345 °C). Especially, the insertion and coating of SiO2 in CoIn-PBA nanocubes greatly improves their thermal stability, and the nanocubic shape of the porous hollow HC-CoInOx sample can remain intact after roasting at 450 °C, while the nanocubic shape of the C-CoInOx sample without the introduction of SiO2 is partially damaged and suffers from serious aggregation under the same firing conditions. Simultaneously, the porous hollow HC-CoInOx nanocubes also exhibited excellent cycling and thermal stability for the catalytic combustion of toluene to CO2 and H2O.

Nanocatalysts for Electrocatalytic Oxidation of Ethanol

The use of ethanol as a fuel in direct alcohol fuel cells depends not only on its ease of production from renewable sources, but also on overcoming the challenges of storage and transportation. In an ethanol-based fuel cell, highly active electrocatalysts are required to break the C-C bond in ethanol for its complete oxidation at lower overpotentials, with the aim of increasing the cell performance, ethanol conversion rates, and fuel efficiency. In recent decades, the development of wet-chemistry methods has stimulated research into catalyst design, reactivity tailoring, and mechanistic investigations, and thus, created great opportunities to achieve efficient oxidation of ethanol. In this Minireview, the nanomaterials tested as electrocatalysts for the ethanol oxidation reaction in acid or alkaline environments are summarized. The focus is mainly on nanomaterials synthesized by using wet-chemistry methods, with particular attention on the relationship between the chemical and physical characteristics of the catalysts, for example, catalyst composition, morphology, structure, degree of alloying, presence of oxides or supports, and their activity for ethanol electro-oxidation. As potential alternatives to noble metals, non-noble-metal catalysts for ethanol oxidation are also briefly reviewed. Insights into further enhancing the catalytic performance through the design of efficient electrocatalysts are also provided.

Fe-doped CeO2 nanorods for enhanced peroxidase-like activity and their application towards glucose detection

Surface defects of Fe-doped CeO₂ nanorods were found to be active sites for increasing peroxidase mimetic activity.

Ultrasensitive Gold Nanostar-Polyaniline Composite for Ammonia Gas Sensing

Gold in the form of bulk metal mostly does not react with gases or liquids at room temperature. On the other hand, nanoparticles of gold are very reactive and useful as catalysts. The reactivity of nanoparticles depends on the size and the morphology of the nanoparticles. Gold nanostars containing copper have rough surfaces and large numbers of active sites due to tips, sides, corners, and large surface area-to-volume ratios due to their branched morphology. Here the sensitivity of the gold nanostar-polyaniline composite (average size of nanostars ∼170 nm) toward ammonia gas has been investigated. For 100 ppm ammonia, the sensitivity of the composite increased to 52% from a mere 7% value for pure polyaniline. The gold nanostar-polyaniline composite even showed a response time as short as 15 s at room temperature. The gold nanostars act as a catalyst in the nanocomposite. The stability and sensitivity at different concentrations and the selectivity for ammonia gas were also investigated.