Influence of the sol–gel preparation method on the photocatalytic NO oxidation performance of TiO2/Al2O3 binary oxides

Abstract

In the current work, TiO 2 /Al 2 O 3 binary oxide photocatalysts were synthesized via two different sol-gel protocols (P1 and P2), where various TiO 2 to Al 2 O 3 mole ratios (0.5 and 1.0) and calcination temperatures (150-1000 • C) were utilized in the synthesis. Structural characterization of the synthesized binary oxide photocatalysts was also performed via BET surface area analysis, X-ray diffraction (XRD) and Raman spectroscopy. The photocatalytic NO(g) oxidation performances of these binary oxides were measured under UVA irradiation in a comparative fashion to that of a Degussa P25 industrial benchmark. TiO 2 /Al 2 O 3 binary oxide photocatalysts demonstrate a novel approach which is essentially a fusion of NSR (NO x storage reduction) and PCO (photocatalytic oxidation) technologies. In this approach, rather than attempting to perform complete NO x reduction, NO(g) is oxidized on a photocatalyst surface and stored in the solid state. Current results suggest that alumina domains can be utilized as active NO x capturing sites that can significantly eliminate the release of toxic NO 2 (g) into the atmosphere. Using either (P1) or (P2) protocols, structurally different binary oxide systems can be synthesized enabling much superior photocatalytic total NO x removal (i.e. up to 176% higher) than Degussa P25. Furthermore, such binary oxides can also simultaneously decrease the toxic NO 2 (g) emission to the atmosphere by 75% with respect to that of Degussa P25. There is a complex interplay between calcination temperature, crystal structure, composition and specific surface area, which dictate the ultimate photocatalytic activity in a coordinative manner. Two structurally different photocatalysts prepared via different preparation protocols reveal comparably high photocatalytic activities implying that the active sites responsible for the photocatalytic NO(g) oxidation and storage have a non-trivial nature.

Photocatalytic Activity of Mesoporous Graphitic Carbon Nitride (mpg-C3N4) Towards Organic Chromophores Under UV and VIS Light Illumination

“…Functional materials synthesized by utilizing novel preparation strategies can be promising photocatalytic platforms that harvest renewable solar energy in order to eliminate hazardous industrial contaminants through energy-efficient pathways. Such economic and technological opportunities led to a rapid growth in the research focusing on photocatalytic materials in the recent decades [1][2][3][4][5]. Among such photocatalytic architectures, graphitic carbon nitride (g-C 3 N 4 ) that is the most stable allotrope of carbon nitride at ambient atmosphere stands out as one of the strong contenders in the photocatalytic air and water purification processes owing to its advantageous properties such as being cost-efficient, abundant, non-toxic, metal-free, and stable nature under ambient conditions with a low electronic band gap falling in the visible (VIS) range of the solar spectrum.…”

NOx abatement from stationary emission sources by photo-assisted SCR: Lab-scale to pilot-scale studies

“…Figure 8 shows the effect of the presence/absence of C4H10 on the NOx removal and NO2 selectivity under different reaction temperature. In the absence of C4H10, the reaction principally belonged to photo-oxidation, which has been explored by lots of groups [22,23,31]. In this reaction, the main product was NO2, and their minor products are nitrates or nitrites.…”

“…For a traditional approach, the powder particles photocatalyst has been considered in most of the photocatalytic NOx removal [20][21][22][23]. Despite wide-spread use, this approach suffers from many drawbacks including how to recycle/regenerate the photocatalysts, and poorly exposed to the light source.…”

Absorption, emission, charge transfer resistance and photocatalytic activity of Al2O3/TiO2 core/shell nanoparticles

“…Atmospheric plasma spraying technique has also been employed to prepare Al 2 O 3 -TiO 2 composite [22]. The pollutants degraded include phenol [19,32], nitrophenol [23,31], 2,4-dichlorophenoxyacetic acid (2,4-D) [7], acetaldehyde [16], acetone [22], methyl ethyl ketone [9], benzamide [18], styrene [10], salicylic acid [21], humic acid [33], ammonia [26], nitric oxide [24] and dyes [12,17,20,25,30]. A thin coating of Al 2 O 3 over TiO 2 /Pt enhances the photocatalytic production of hydrogen [34].…”

“…TiO 2 deposited Al 2 O 3 films [14,[16][17][18][19][20] or membranes [21] or flakes [10] or powder [9,22], TiO 2 supported on Al 2 O 3 [23] and TiO 2 /Al 2 O 3 binary oxides [24][25][26] or nanocomposites [7] have been synthesized for application as photocatalysts. Dip-coating [9,18,19,27], atmospheric plasma spraying [22], sol-gel [7,8,10,12,[14][15][16]20,[24][25][26][28][29][30], pyrolysis [21] and wet impregnation [23,31] methods are the largely used synthetic techniques. Atmospheric plasma spraying technique has also been employed to prepare Al 2 O 3 -TiO 2 composite [22].…”