Evaluación de la actividad fotocatalítica de nanoestructuras de T-Nb2O5 obtenidas por el método sol-gel
Evaluación de la actividad fotocatalítica de nanoestructuras de T-Nb2O5 obtenidas por el método sol-gel
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Antecedentes: La fase T del pentóxido de niobio (Nb2O5) absorbe energía en la región del ultravioleta lo que lo hace un material promisorio en aplicaciones fotocatalíticas. Objetivo: En este trabajo se sintetizó, caracterizó y evaluó la actividad fotocatalítica, en la degradación de Rodamina B, del T-Nb2O5. Metodología: Las muestras fueron preparadas por el método sol-gel siguiendo dos procedimientos diferentes (NH4OH y H2O); los materiales fueron sinterizados a temperaturas de 650 °C y 750 °C y caracterizados por DRX, MEB y espectroscopias IR e UV-vis. Resultados: El NH4OH modifica el tamaño cristalino, la energía de banda gap y la porosidad del T-Nb2O5, además inhibe el crecimiento de nanopartículas de Nb2O5 en el proceso sol-gel, por lo tanto se ve modificada la cinética para la degradación de Rodamina B. La actividad fotocatalítica de las nanoestructuras es dominantemente determinada por el equilibrio de absorción y la cinética de la reacción. Conclusión: Los resultados de caracterización estructural, morfológica, vibracional y óptica permiten inferir que se obtuvo la cristalización del T-Nb2O5 y que a 750 °C el material exhibió una mayor eficiencia en la actividad fotocatalítica.
Palabras clave: caracterización, catalizador, fotocatálisis, pentóxido de niobio, sol-gel.
Abstract
Background: T phase of Niobium pentoxide (Nb2O5) absorbs energy in the ultraviolet region which makes it a promissory material in photocatalytic applications. Objective: In this work the T-Nb2O5 was synthesized, characterized and its photocatalytic performance for degradation of Rhodamine B was evaluated. Methods: The samples were made by the sol-gel method following two different procedures (NH4OH and H2O); the materials were sintered at 650 °C and 750 °C temperatures and later characterized by XRD, SEM, IR and UV-vis spectroscopy. Results: NH4OH modifies the T-Nb2O5 crystalline size, band-gap energy, and porosity, besides inhibiting the growth of Nb2O5 nanoparticles in sol-gel process, and therefore the kinetics for Rhodamine B degradation are modified. The photocatalytic activity of the nanostructures is dominantly determined by adsorption equilibrium and reaction kinetics. Conclusions: The results of structural, morphological, vibrational and optic characterization allow to conclude that the crystallization of T-Nb 2 O 5 was achieved, and that the material treated at 750°C showed an increased efficiency in the photocatalytic activity.
Key words: characterization, catalyst, photocatalysis, niobium pentoxide, sol-gel.
Resumo
Antecedentes: A fase T do pentóxido de nióbio (Nb₂O₅) absorve energia na região do ultravioleta tornando-se um material promissor para aplicações catalíticas. Objectivo: Neste estudo foi sintetizado, caracterizar e avaliar a actividade fotocatalítica na degradação de Rodamina B, o T-Nb2 O5 . Metodologia: As amostras foram preparadas pelo método de sol-gel, seguindo dois procedimentos diferentes: (NH4 OH e H2 O). Finalmente as amostras foram sinterizados a temperaturas de 650 °C e 750 °C para logo ser caracterizadas por: DRX, SEM e espectroscopia de IV e UV-VIS. Resultados: O uso do NH4 OH modifica o tamanho dos cristalitos, a energia da banda e a porosidade do T-Nb2 O5 , também inibe o crescimento de nanopartículas Nb2 O5 no processo sol-gel, por conseguinte, a cinética de degradação de Rodamina B. A é modificado. Conclusão: Os resultados da caracterização estrutural, morfológica, vibracional e óptico permitem inferir que foi obtido a cristalização da T-Nb2 O5. Assim, as amostra em 750 °C apresentam uma maior eficiência na actividade fotocatalítica.
Palavras-chave: caracterização, catalisador, fotocatálise, pentoxido de niobio, sol-gel.
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