Dominating role of crystal structure over defect chemistry in black and white zirconia on visible light photocatalytic activity

Abstract

Nanometric powder particles of white zirconia were synthesized through precursor route by the pyrolysis of zirconium (IV) butoxide at varied temperatures in air ranging from 900–1400 °C and were predominantly monoclinic in nature. To control the defect chemistry, the precursor was also pyrolyzed in a reduced atmosphere at 900 °C, eventually resulting in black zirconia. The stabilization of tetragonal phase and observed color change from white to black in samples pyrolyzed under reduced atmosphere was attributed to the creation of oxygen vacancies and disorder. The black and white zirconia produced delineated the influence of crystal structure and oxygen vacancies on the photocatalytic performance. Furthermore, zirconia synthesized at lower temperatures (600 and 800 °C) in air confirmed the detrimental role of tetragonal phase on the degradation behavior of methylene blue dye. High photocatalytic degradation rate for white zirconia was attributed to the presence of increased density of nano-sized pores and low recombination rate of electron-hole pairs as confirmed by PL measurements. Interestingly, black zirconia exemplified relatively limited activity albeit presence of oxygen vacancies. This negative effect was attributed to the presence of tetragonal phase and possibly, the insufficient creation of new energy states near valence and conduction band towards Fermi energy level.

Design of nanoscaled heterojunctions in precursor-derived t-ZrO2/SiOC(N) nanocomposites: Transgressing the boundaries of catalytic activity from UV to visible light

“…The area under the peak gives a relative oxygen vacancy of 52% (assuming negligible amount of OH adsorption) on the surface of ZrO 2 . The presence of oxygen vacancies is also confirmed through EPR analysis (g value of 1.992) 51 (Fig. S6).…”

“…This separation combined with the reduced band gap helps in harnessing visible light for photocatalysis 59,60 . Albeit the detrimental contribution t-ZrO 2 towards photocatalytic activity 51 , the formation of heterojunctions as well as the retention of nanodomains of t-ZrO 2 with an average size of 10 nm in an amorphous matrix is believed to enhance the catalytic activity. The degradation mechanism and the heterojunction formation are exemplified in Figs.…”

Rod-Shaped Carbon Aerogel-Assisted CdS Nanocomposite for the Removal of Methylene Blue Dye and Colorless Phenol

“…To clearly determine the kinetics of degradation of MB by the synthesized catalysts, the obtained experimental data were fitted with the pseudo-first-order model, ln(C0/C) = kt, where C0 represents the initial conc., C signifies the conc. at time t, and k represents the first-order rate constant ( Figure 10) [41]. All plots of ln(C0/C) against time demonstrated a linear fit, and the slope of the linear regression is equal to the first-order apparent rate constant (K).…”

“…To clearly determine the kinetics of degradation of MB by the synthesized catalysts, the obtained experimental data were fitted with the pseudo-first-order model, ln(C 0 /C) = kt, where C 0 represents the initial conc., C signifies the conc. at time t, and k represents the first-order rate constant ( Figure 10) [41]. To clearly determine the kinetics of degradation of MB by the synthesized catalysts, the obtained experimental data were fitted with the pseudo-first-order model, ln(C0/C) = kt, where C0 represents the initial conc., C signifies the conc.…”

Photodegradation activity of yttrium-doped SnO2 nanoparticles against methylene blue dye and antibacterial effects

“…This progress respites the photocatalytic activity might also increase since the coupling of NMs with dissimilar bandgap supporting the electron-hole charge separation as in the instance of metal oxide (MO) per several heterojunctions. The photocatalytic performance of the as-prepared 4% Y:SnO 2 PCs was compared with recently reported PCs with different semiconductor metal oxides/metal and auxiliary nanocomposites, as shown in Table 1 (Rashad et al 2014;Wang et al 2018;Patil et al 2018;Benzaouak et al 2018;Teeparthi et al 2018).…”