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.
Highlights
Zirconia with a high negative conduction band potential is capable of generating holes with very strong oxidation power and currently being explored as a potential third generation photocatalyst
Zirconia precursor pyrolyzed at various temperatures in air/reduced atmosphere resulted in nanocrystalline white and black zirconia respectively, exhibiting visible light photocatalytic activity towards degradation of methylene blue
White zirconia with pure monoclinic crystal structure exhibited a slight increase in degradation efficiency with the decrease in pyrolysis temperature
Summary
The degradation of MB dye solution was carried out in visible light for 900R and 900R_12 (see supplementary information Figure S14b) samples exhibiting a degradation efficiency of 66 and 73%, respectively This substantiated the detrimental effect of tetragonal crystal structure for the catalytic activity. The exhibition of similar photocatalytic degradation efficiency by 1400A and 900R_12 proves that the oxygen vacancies (in 900R_12) played a minimal role in the catalytic activity It was observed from the PL spectra that the intensity of 900R was higher than that of the 900A and 1400A (see supplementary information Figure S6). This indicates that there was a high rate of electron-hole recombination in 900R samples. In black zirconia, while the presence of defects assist in increasing the photocatalytic activity, the presence of tetragonal phases on the contrary, even in small amounts can contribute to the opposite effect
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
