Tuning the Microstructures of ZnO To Enhance Photocatalytic NO Removal Performances

Abstract

Effective removal of kinetically inert dilute nitrogen oxide (NO, ppb) without NO2 emission is still a challenging topic in environmental pollution control. One effective approach to reducing the harm of NO is the construction of photocatalysts with diversified microstructures and atomic arrangements that could promote adsorption, activation, and complete removal of NO without yielding secondary pollution. Herein, microstructure regulations of ZnO photocatalysts were attempted by altering the reaction temperature and alkalinity in a unique ionic liquid-based solid-state synthesis and further investigated for the removal of dilute NO upon light irradiation. Microstructure observations indicated that as-tuned photocatalysts displayed unique nucleation, diverse morphologies (spherical nanoparticles, short and long nanorods), defect-related optical characteristics, and enhanced carrier separations. Such defect-related surface–interface aspects, especially Vo″-related defects of ZnO devoted them to the 4.16-fold enhanced NO removal and 2.76 magnitude order decreased NO2 yields, respectively. Improved NO removal and toxic product inhabitation in as-tuned ZnO was disclosed by mechanistic exploitations. It was revealed that regulated microstructures, defect-related charge carrier separation, and strengthened surface interactions were beneficial to active species production and molecular oxygen activation in ZnO, subsequently contributing to the improved NO removal and simultaneous avoidance of NO2 formation. This investigation shed light on the facile regulation of microstructures and the roles of surface chemistry in the oxidation of low concentration NO in the ppb level upon light illumination.

Design Strategies for Perovskite-Type High-Entropy Oxides with Applications in Optics

“…As shown in Figure c, the VB values of samples were calculated to be 1.81 eV (10La), 1.90 eV (15La), 2.05 eV (20La), 2.10 eV (25La), and 2.19 eV (30La), respectively. Correspondingly, the conduction band (CB) positions were calculated to be −1.22 eV (10La), – 1.15 eV (15La), – 1.01 eV (20La), – 0.99 eV (25La), and −0.93 eV (30La), respectively, as shown in Figure d . The existence of oxygen vacancies reduces the VB positions (from 2.19 to 1.81 eV) of the samples and the CB positions (from −0.93 to −1.22 eV), which is consistent with the conclusion of our previous first-principles calculations .…”

In situ fabricating a Rh/Ga2O3 photothermal catalyst for dry reforming of methane

“…15,16 Among them, ZnO has been proven to be an environmentally friendly photocatalyst due to its promising characteristics, such as non-toxicity, low price, high stability, and easy preparation, leading to the widespread utilization of ZnO in different photo(thermal) catalytic applications, and certainly, photothermal catalysis of DRM is no exception. 17–19 Moreover, β-Ga 2 O 3 as a wide gap semiconductor has also shown great application prospects in the photocatalytic field because of its excellent stability and simple synthesis process. 20 Unfortunately, the photothermal catalytic efficiency was greatly limited due to its wide bandgap ( E g (ZnO) = 3.37 eV, E g (Ga 2 O 3 ) = 4.59 eV), which leads to a narrow range of light response and low charge mobility of ZnO and Ga 2 O 3 , resulting in photoinduced charge recombination.…”

2D Bismuth-Based Nanomaterials for Photocatalytic Nitrogen Oxide Removal: Progress and Prospects

“…Air pollution has become a prominent global environmental problem, of which nitrogen oxides (NO x , ∼95% NO) are considered one of the most dangerous gaseous pollutants. The burning of fossil fuels, improper treatment of industrial waste gases from nitric acid production, and steady increased motor vehicle emissions have resulted in the emission of large amounts of NO x into the air, causing obvious environmental risks, e.g., acid rain, photochemical smog, PM2.5 solid particles, and deletion of ozone layers. − NO is chemically active because it possesses an unpaired electron, {(σ2s) 2 (σ*2s) 2 (σ2p x ) 2 (π2p y ) 2 (π2p z ) 2 (π*2p y ) 1 }, and reacts with oxygen readily to generate NO 2 . However, the reaction activity significantly descends when the concentration of NO is lower than the ppm level, and it can exist stably in air for a long time.…”