Otimização dos processos de síntese para obtenção do compósito a- MoO3/C3N4 e estudo de sua atividade fotocatalítica

Abstract

MoO3 is an n-type semiconductor with unique properties such as photocatalytic efficiency and different morphologies, thus attracting considerable attention and being studied both alone and in association with other semiconductors with the aim of further improving its properties. C3N4 is another photocatalyst that has attracted attention due to its low bandgap (2.7 eV), allowing absorption of visible light to generate more electron-hole pairs. of the αMoO3/C3N4 hybrid material. The work was divided into three stages. In the first stage, using the spray-pyrolysis synthesis method, syntheses were performed at different precursor concentrations (0.1M, 0.2M and 0.3M), temperatures (600 °C to 1000 °C) and atomizer power (70% and 100%), the flow rate, in turn, was fixed at 3 L/min, the different parameters were used in order to obtain -MoO3 in a single step. Once MoO3 synthesis was optimized, the next step was to use the ultrasonic method (step 2) at different times (5 min, 10 min and 15 min) on the selected sample and analyze the results obtained. With the time for the synthesis with the best results, stage 3 was started, in which the coupling of MoO3 and C3N4 was performed using sonochemical method, obtaining the hybrid material composite MoO3/C3N4. The optimization of the parameters necessary to obtain -MoO3 particles was investigated by X-ray diffraction (XRD). The influence of the parameters involved in the synthesis of α-MoO3 by spray pyrolysis, as well as the effect of the ultrasonic method on morphology, photocatalytic activity and optical properties were investigated by X-ray diffraction (XRD), spectroscopy in the UV-Visible region (UV-Vis), photocatalytic activity, photoluminescence (FL) and field emission scanning electron microscopy (SEM-FEG). The response used to optimize the material after the ultrasonic method was the photocatalytic degradation of methylene blue. The X-ray diffractograms showed the obtainment of an orthorhombic phase -MoO3 with a space group of 62 Pbnm as well as the presence of a hydrated phase in the analyzed samples. The composite samples analyzed presented band gap energy values of 3.09 eV. The MOCN 1 sample showed the best photocatalytic activity, reaching 100% degradation in 300 min. Through micrographs, it was possible to observe the influence of the synthesis parameters and the ultrasonic process itself on the morphology of the samples, variations that influenced the photocatalytic activity and photoluminescence of the samples.