Preparation of Bi-based heterostructures through the one-pot method with the potential to photocatalytic applications

Eduardo Henrique Dias,Osmando Ferreira Lopes,Gelson Tiago Dos Santos Tavares Da Silv,Caue Ribeiro

doi:10.30609/jeti.v4i01.11438

Abstract

This paper describes a facile one-pot method to obtain Bi-based heterostructures by calcination process and evaluate the physical-chemical properties. The increase in the temperature treatment changed the sample’s phase crystalline, the synthesis method proposed was able to obtain (BiO)2CO3, α-Bi2O3, and β-Bi2O3 pure phases and (BiO)2CO3/α-Bi2O3 and α-Bi2O3/β-Bi2O3 heterostructures. Additionally, the annealing temperature also influences the morphology, optical, and photocatalytic properties. The temperature increases decreased the sample’s bandgap, and the above 350ºC, the samples became active under visible radiation. The photocatalytic performance of the samples was evaluated under UV and visible radiation on the MB degradation, it was observed that under UV radiation, the (BiO)2CO3 phase exhibited higher performance than the Bi2O3 phase. Therefore, we can confirm that the increases in the temperature harmed the photocatalytic performance under UV radiation. On the other hand, synthesized samples above 300°C showed the best performance under visible radiation, due to the bandgap reduction and the electron/hole pair lifetime increasing.

Highlights

On the other hand, when the sample was treated at 350oC it was observed a mixed-phase between (BiO)2CO3 and β-Bi2O3 in the crystalline tetragonal phase (JCPDS: 27-0050) because the (BiO)2CO3 was partially decomposed in β-Bi2O3 according to the following reaction: (BiO)2CO3 → Bi2O3 + CO2
The (BiO)2CO3 sample was completely decomposed when calcinated at 370oC, it was observed the formation of β-Bi2O3
The analysis of the derivative thermogravimetry (DTG) curves showed that the decomposition temperature of Bi2O2CO3 occurs at 356°C in close agreement with the XRD results

Summary

Introduction

Of organic molecules by direct or indirect oxidation, through the generation of radicals (OH, O2).[3,4]. Metal oxides such as TiO2 and ZnO are the most popular materials used as photocatalysts.[5,6,7,8] These materials are activated only under UV radiation, so they have low efficiency driven by solar radiation, making large-scale applications inviable.[9] there has been a growing interest in developing functional materials capable of absorbing a larger part of the solar spectrum, as active catalysts under visible radiation, as this represents 43% of sunlight, against only 5% for UV radiation.[10]. Bismuth compounds are interesting and can be promising candidates even in different forms, i.e., BiOX has been used in carbon dioxide photoreduction,[11] Bi2S3 has been applied to boost the hydrogen photogeneration,[12] Bi2O3 has been used as gas sensors, solid oxide fuel cells, optical coatings, and ceramic glass manufacturing,[13] and BiVO4 has been studied for oxygen evolution and organic pollutant degradation.[14]

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Conclusion