Browsing by Subject "NOx abatement"

Now showing 1 - 3 of 3

Open Access
Enhanced photocatalytic NOx oxidation and storage under visible-light irradiation by anchoring Fe3O4 nanoparticles on mesoporous graphitic carbon nitride (mpg-C3N4)
(Elsevier, 2019) Irfan, Muhammad; Sevim, M.; Koçak, Yusuf; Balcı, Merve; Metin, Ö.; Özensoy, Emrah
Several mesoporous graphitic carbon nitride (mpg-C3N4) photocatalysts were synthesized by using a hard-templating method comprising thermal polycondensation of guanidine hydrochloride over silica spheres at three different temperatures (450, 500 and 550 ℃). After structural characterization of these mpg-C3N4 photocatalysts, they were tested in NO(g) photo-oxidation under visible (VIS) light. The effects of polycondensation temperature on the structure and photocatalytic performance of mpg-C3N4 in NO photo-oxidation were studied. The results revealed that polycondensation temperature has a dramatic effect on the photocatalytic activity of mpg-C3N4 in NO photo-oxidation, where mpg-C3N4 synthesized at 500 ℃ (mpg-CN500) showed the best performance in NOx abatement as well as a high selectivity towards solid state NOx storage under VIS light illumination. Photocatalytic performance of the mpg-CN500 was further enhanced by the anchoring of 8.0 ± 0.5 wt.% Fe3O4 nanoparticles (NPs) on it. Fe3O4/mpg-CN500 photocatalyst showed both high activity and high selectivity along with extended reusability without a need for a regeneration step. Enhanced photocatalytic NOx oxidation and storage efficiency of Fe3O4/mpg-CN500 photocatalyst was attributed to their mesoporous structure, high surface area and slow electron-hole recombination kinetics, efficient electron-hole separation and facile electron transfer from mpg-CN500 to Fe3O4 domains enhancing photocatalytic O2 reduction, while simultaneously suppressing nitrate photo-reduction and decomposition to NO2(g).
Open Access
Enhancement of photocatalytic NOx abatement on titania via additional metal oxide NOx-storage domains: Interplay between surface acidity, specific surface area, and humidity
(Elsevier, 2020) Çağlayan, Mustafa; Irfan, Muhammad; Ercan, Kerem Emre; Koçak, Yusuf; Özensoy, Emrah
In this work, we propose a simple and effective preparation procedure to obtain ternary mixed oxides composed of titania (TiO2, P25), alumina (γ-Al2O3) and calcium oxide (CaO) functioning as efficient photocatalytic NOx oxidation and storage (PHONOS) catalysts that are capable of facile NOx abatement under ambient conditions in the absence of elevated temperatures and pressures with UVA irradiation. In this architecture, titania was the photocatalytic active component and CaO and/or γ-Al2O3 provided NOx storage domains revealing dissimilar specific surface areas (SSA) and surface acidities. We show that photocatalyst formulation can be readily fine-tuned to achieve superior photocatalytic performance surpassing conventional P25 benchmark in short (1 h) and long term (12 h), as well as humidity-dependent photocatalytic tests. We demonstrate the delicate interplay between the surface acidity, SSA and humidity and provide detailed mechanistic insights regarding the origin of photocatalytic activity, selectivity and deactivation pathways.
Open Access
TiO2-Al2O3 binary mixed oxide surfaces for photocatalytic NOx abatement
(Elsevier, 2014) Soylu, A. M.; Polat, M.; Erdogan, D. A.; Say, Z.; Yıldırım, C.; Birer, Ö.; Ozensoy, E.
TiO2-Al2O3 binary oxide surfaces were utilized in order to develop an alternative photocatalytic NOx abatement approach, where TiO2 sites were used for ambient photocatalytic oxidation of NO with O2 and alumina sites were exploited for NOx storage. Chemical, crystallographic and electronic structure of the TiO2-Al2O3 binary oxide surfaces were characterized (via BET surface area measurements, XRD, Raman spectroscopy and DR-UV-Vis Spectroscopy) as a function of the TiO2 loading in the mixture as well as the calcination temperature used in the synthesis protocol. 0.5 Ti/Al-900 photocatalyst showed remarkable photocatalytic NOx oxidation and storage performance, which was found to be much superior to that of a Degussa P25 industrial benchmark photocatalyst (i.e. 160% higher NOx storage and 55% lower NO2(g) release to the atmosphere). Our results indicate that the onset of the photocatalytic NOx abatement activity is concomitant to the switch between amorphous to a crystalline phase with an electronic band gap within 3.05-3.10 eV; where the most active photocatalyst revealed predominantly rutile phase together and anatase as the minority phase.