Aurivillius family of layered perovskites, BiREWO 6 (RE = La, Pr, Gd, and Dy): Synthesis, characterization, and photocatalytic studies

Current trends on dry photocatalytic oxidation technology for BTX removal: Viable light sources and highly efficient photocatalysts

One of the main gaseous pollutants released by chemical production industries are benzene, toluene and xylene (BTX). These dangerous gases require immediate technology to combat them, as they put the health of living organisms at risk. The development of heterogeneous photocatalytic oxidation technology offers several viewpoints, particularly in gaseous-phase decontamination without an additional supply of oxidants in air at atmospheric pressure. However, difficulties such as low quantum efficiency, ability to absorb visible light, affinity towards CO2 and H2O synthesis, and low stability continue to limit its practical use. This review presents recent advances in dry-phase heterogeneous photodegradation as an advanced technology for the practical removal of BTX molecules. This review also examines the impact of low-cost light sources, the roles of the active sites of photocatalysts, and the feasible concentration range of BTX molecules. Numerous studies have demonstrated a significant improvement in the efficiency of the photodegradation of volatile organic compounds by enhancing the photocatalytic reactor system and other factors, such as humidity, temperature, and flow rate. The mechanism for BTX photodegradation based on density functional theory (DFT), electron paramagnetic resonance (EPR) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) investigations is also discussed. Finally, the present research complications and anticipated future developments in the field of heterogeneous photocatalytic oxidation technology are discussed.

Layered Perovskites BaLnnInnO3n+1 (n = 1, 2) for Electrochemical Applications: A Mini Review

Modern humanity is facing many challenges, such as declining reserves of fossil energy resources and their increasing prices, climate change and an increase in the number of respiratory diseases including COVID-19. This causes an urgent need to create advanced energy materials and technologies to support the sustainable development of renewable energy systems including hydrogen energy. Layered perovskites have many attractions due to their physical and chemical properties. The structure of such compounds contains perovskite layers divided by layers with different frameworks, which provide their properties' features. Proton-conduction layered perovskites open up a novel structural class of protonic conductors, potentially suitable for application in such hydrogen energy devices as protonic ceramic electrolysis cells and protonic ceramic fuel cells. In this mini review, the special features of proton transport in the novel class of proton conductors BaLn_nIn_nO_3n+1 (n = 1, 2) with a layered perovskite structure are observed and general regularities are discussed.

Local structure and ionic transport in acceptor-doped layered perovskite BaLa2In2O7

Materials with perovskite or perovskite-related structure have many applications because of theirs different physical and chemical properties. These applications are extremely diverse and cover different fields including hydrogen energy. Layered perovskites with Ruddlesden-Popper structure constitute a novel class of ionic conductors. In this paper, the effect of acceptor doping on the local structure and its relationship with transport properties were shown for layered perovskites based on BaLa2In2O7 for the first time. The geometric factor (the increase in the unit cell volume due to the increase in the ionic radii of cations) plays major role in the area of small dopant concentration (x  0.15). The concentration factor (the increase in the oxygen vacancy concentration) is more significant in the area of big dopant concentration (x  0.15). The acceptor doping is a promising way of improving the oxygen-ionic conductivity of layered perovskite BaLa2In2O7.

Oxygen Ion and Proton Transport in Alkali-Earth Doped Layered Perovskites Based on BaLa2In2O7

Inorganic materials with layered perovskite structures have a wide range of physical and chemical properties. Layered perovskites based on BaLanInnO3n+1 (n = 1, 2) were recently investigated as protonic conductors. This work focused on the oxygen ion and proton transport (ionic conductivity and mobility) in alkali-earth (Sr2+, Ba2+)-doped layered perovskites based on BaLa2In2O7. It is shown that in the dry air conditions, the nature of conductivity is mixed oxygen–hole, despite the dopant nature. Doping leads to the increase in the conductivity values by up to ~1.5 orders of magnitude. The most proton-conductive BaLa1.7Ba0.3In2O6.85 and BaLa1.7Sr0.15In2O6.925 samples are characterized by the conductivity values 1.2·10−4 S/cm and 0.7·10−4 S/cm at 500 °C under wet air, respectively. The layered perovskites with Ruddlesden-Popper structure, containing two layers of perovskite blocks, are the prospective proton-conducting materials and further material science searches among this class of materials is relevant.

An investigation on the promoting effect of Pr modification on SO2 resistance over MnOx catalysts for selective reduction of NO with NH3

Pr-modified MnOx catalyst was synthesized through a facile co-precipitation process, and the results showed that MnPrOx catalyst exhibited much better selective catalytic reduction (SCR) activity and SO2 resistance performance than pristine MnOx catalyst. The addition of Pr in MnOx catalyst led to a complete NO conversion efficiency in 120-220 °C. Moreover, Pr-modified MnOx catalyst exhibited a superior resistance to H2O and SO2 compared with MnOx catalyst. After exposing to SO2 and H2O for 4 h, the NO conversion efficiency of MnPrOx catalyst could remain to 87.6%. The characterization techniques of XRD, BET, hydrogen-temperature programmed reduction (H2-TPR), ammonia-temperature programmed desorption (NH3-TPD), XPS, TG and in situ diffuse reflectance infrared spectroscopy (DRIFTS) were adopted to further explore the promoting effect of Pr doping in MnOx catalyst on SO2 resistance performance. The results showed that MnPrOx catalyst had larger specific surface area, stronger reducibility, and more L acid sites compared with MnOx catalyst. The relative percentage of Mn4+/Mnn+ on the MnPrOx-S catalyst surface was also much higher than those of MnOx catalyst. Importantly, when SO2 exists in feed gas, PrOx species in MnPrOx catalyst would preferentially react with SO2, thus protecting the Mn active sites. In addition, the introduction of Pr might promote the reaction between SO2 and NH3 rather than between SO2 and Mn active sites, which was also conductive to protect the Mn active sites to a great extent. Since the presence of SO2 in feed gas had little effect on NH3 adsorption on the MnPrOx catalyst surface, and the inhibiting effect of SO2 on NO adsorption was alleviated, SCR reactions could still proceed in a near-normal way through the Eley-Rideal (E-R) mechanism on Pr-modified MnOx catalyst, while SCR reactions through the Langmuir-Hinshelwood (L-H) mechanism were suppressed slightly.

Preparation of Bi3Fe0.5Nb1.5O9/g-C3N4 heterojunction photocatalysts and applications in the photocatalytic degradation of 2,4-dichlorophenol in environment

The energy band relationship and the active substances were studied to determine photocatalyst accords with the Z-type transfer mechanism.