Hydrothermal Synthesis, Photocatalytic Performance, and Phase Evolution from BiOCl to Bi2Ti2O7 in the Bi-Ti-Cl-O System

Photocatalytic Properties of Bi2–xTi2O7–1.5x (x = 0, 0.5) Pyrochlores: Hybrid DFT Calculations and Experimental Study

“…Meanwhile, a deviation exists in the literature regarding the specific surface area of the bismuth titanate pyrochlore (5.75−16.38 m 2 /g), which is caused by different annealing parameters, as well as additional processing steps (hydrothermal treatment) during coprecipitation synthesis. 32,33,38,43 Electronic Properties and Optical Absorption Spectra. The well-optimized crystal structures of BTO models were utilized for further analysis of the electronic structure and optical properties.…”

“…Our results are in line with the S BET = 13.1 m 2 /g for Bi 2 Ti 2 O 7 pyrochlore previously reported by Benčina et al due to identical synthesis methods. Meanwhile, a deviation exists in the literature regarding the specific surface area of the bismuth titanate pyrochlore (5.75–16.38 m 2 /g), which is caused by different annealing parameters, as well as additional processing steps (hydrothermal treatment) during coprecipitation synthesis. ,,, …”

“…Bismuth titanate with a pyrochlore-type structure (BTO), Bi 2 Ti 2 O 7 , is one of the promising photoactive compounds in the visible light range, which was predicted during first-principles calculations. ,− The experimental preparation of BTO in the nanoscale state was presented in papers recently. ,− The authors determined the optical band gap of Bi 2 Ti 2 O 7 to be within the range 2.58–3.28 eV. The observed scatter might be caused by different methods of sample synthesis, which affects the size and morphology of particles, and the different techniques of spectroscopic measurement.…”

“…The observed scatter might be caused by different methods of sample synthesis, which affects the size and morphology of particles, and the different techniques of spectroscopic measurement. Moreover, the known tendency of bismuth titanate to form a nonstoichiometric pyrochlore composition − affected the observed characteristics and sometimes the considered titanate compound “Bi 2 Ti 2 O 7 ”, in fact, had a Bi-deficient composition. , The photocatalytic activity of the prepared BTO samples was investigated by the decomposition of organic dyes rhodamine B, ,− , methyl orange, ,,,, and methylene blue , and for water splitting to produce molecular hydrogen. ,, The high photocatalytic activity of BTO in the visible range was found in comparison with anatase, due to the smaller band gap of the pyrochlore resulting in a greater absorption of light.…”

“…Bi 2 Ti 2 O 7 is a wide-band-gap semiconductor and can independently absorb visible light. Its conduction band (CB) and valence band (VB) have suitable energy levels to create efficient type heterojunction photocatalysts between Bi 2 Ti 2 O 7 and the other semiconductors (e.g., TiO 2 , Bi 4 Ti 3 O 12 , BiOCl, Bi 2 O 3 ). ,,,,− Moreover, Bi 2 Ti 2 O 7 prepared with different morphologies (nanospheres, nanorods, nanoflower-like, etc.) possesses an improvement in photoactivity. ,, One of the well-known problems of Bi 2 Ti 2 O 7 is its low thermal stability, although it is possible to obtain a pure bismuth titanate pyrochlore by soft synthetic methods (e.g., coprecipitation, hydrothermal synthesis) or to stabilize the pyrochlore phase by doping with suitable elements.…”