Synthesis of Bi2O3 / BiVO4 heteroestruture and evaluation of its photocatalitic potential under solar radiation

Reference Presenter Authors
05-002 Paulo Henrique Eleuterio Falsetti Falsetti, P.H.(Federal Institute of São Paulo); Duque, D.M.(Federal Institute of São Paulo); Mendonça, V.R.(Federal Institute of São Paulo);
The bismuth vanadate (BiVO4) is a n-type semiconductor with a relatively low band-gap energy (Ebg = 2,4 - 2,8 eV), when compared to TiO2 and ZnO (3,2 - 3,4 eV), which makes the semiconductor useful for applications under solar radiation.1 However, it presents low quantum yield due to the high electron (e-) / hole (h+) pairs recombination rate. The formation of heterostructures, a system in which different materials share the same interface, between BiVO4 and Bi2O3 is one good strategy to increase the lifetime of the photogenerated charges.
Therefore, the main goal of the present work was to synthesize Bi2O3 / BiVO4 heterostructured powders via hydrothermal synthesis and to study its performance in the discoloration of a Methylene Blue dye solution in water under solar radiation. The Synthesis2 consisted is disperse n-Bi2O3 powder (nanometer Bi2O3: 90 - 210 nm grains, Sigma / Aldrich, 99.8%) in H2O, further adding NH4VO3 powder (VETEC, 99%), maintaining the Bi:V ratio of 1:1. After the powders dispersion, hydrothermal treatment was carried out at 200 °C for 8 h. XRD analysis of the as-obtained sample showed a mixture of the monoclinic phase of Bi2O3 (JCPDS, n ° 41-1449) and the monoclinic phase of BiVO4 (JCPDS, n ° 83-1699), evidencing the possible formation of the Bi2O3 / BiVO4 heterostructure.
For the photocatalysis experiments, 10 mg of the obtained powder was dispersed in 20 ml of Methylene Blue 10 mg/L. A solution without the powder was tested in the same conditions as blank. The experiment was performed under solar radiation in a sunny day, from 2:00 p.m. to 6:00 p.m.. The beakers with the samples were sealed to avoid evaporation and the temperature was externally controlled.
The analysis showed that the synthesized powder was capable to discolor the solution, resulting in a decrease around 65% in the absorption in 120 min, while the blank experiment resulted in a decrease of 35 % in the same conditions.
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