One Pot Synthesis of CoTiO3-TiO2 Composite Nanofibers and its Application in Dye Degradation

Introduction

Water pollution is a matter of great concern in society. Photocatalysts are applied in order to degrade harmful organic pollutants into non-toxic compounds in water (Zhang et al., 2012). TiO₂ is one of the best-known photocatalysts so far. However, TiO₂ has a notable limitation in that its energy band falls in the ultraviolet zone, which makes it unsuitable to be applied for use in photodegradation under visible light. A lot of effort has been done in this regard in order to extend its activity in the visible region, by making various modifications. Scientists have shown immense curiosity in developing the modified titania; having its wavelength absorption in visible light region. One of the usual procedures is the doping of TiO₂ with elements like carbon, sulfur, and nitrogen; etc. (Chen, Jiang, Geng, Wang, & Yang, 2007; Guan et al., 2019; Ida et al., 2019; Luna, Gatica, Vidal, & Mosquera, 2019; Mahy et al., 2019; Park, Kim, & Bard, 2006; Pylnev & Wong, 2019; Sheydaei, Zangouei, & Vatanpour, 2019; Srisasiwimon, Chuangchote, Laosiripojana, & Sagawa, 2018; Tasbihi et al., 2019; Yoon et al., 2018). An alternative method is to combine TiO₂ with a semiconductor having a small bandwidth (Abdi, Yahyanezhad, Sakhaie, Vossoughi, & Alemzadeh, 2019; Chanhom, Charoenlap, Manipuntee, & Insin, 2019; Hendrix, Lazaro, Yu, & Brouwers, 2019; Ilieva, Nakova, & Tsakova, 2012; Jiang et al., 2018; Mahieu, Puzenat, Geantet, Cardenas, & Afanasiev, 2019; Mao et al., 2017; Ouyang, Chang, & Li, 2012; Ratova, Tosheva, Kelly, & Ohtani, 2019). By joining two semiconductors, a new photocatalytic material with a modified band gap can be developed, which will not merely lengthen the absorption of light to the visible spectrum but will, as well, put a check on the fast merging of electrons or holes during photoactivity.

Metal titanates like nickel titanate, cobalt titanate, ferrite titanate, zinc titanate, copper titanate, and lead titanate are famous functional materials which possess an assortment of uses. The titanate perovskites are the best recommended materials for use in photodegradation. Generally, titanate perovskites having band energy of (>3.0 eV) show photocatalytic activity under UV (ultraviolet) light (Ke, Cheng, Wang, Wang, & Pan, 2014; Zhu, Anzai, Yamamoto, & Yoshida, 2019). By doping the metal titanates, their wavelength can be modified from the UV to the visible light absorption range. CoTiO₃ is an ABO₃-type perovskite oxide, having a narrow band gap semiconductor. Cobalt titanate (CoTiO₃) has been used in various applications such as Li-ion batteries (Jiang et al., 2014), gas sensors (Chuang et al., 2010), magnetic recorders (Toubal, Bensaha, & Yakuphanoglu, 2017) and photocatalysts (Wang, Guo, Wang, & Li, 2016). Cobalt titanate possesses a band width the in visible range (Eg = 2.28 eV). Currently, CoTiO₃ has been used as a catalyst under visible light (Singh et al., 2019). In the last few years, one-dimensional nanomaterials have gotten a tremendous response because of their unique size and shape. Developing materials with 1D (one-dimensional) morphology and nano-size range will not only increase their surface area but will also improve their properties. Therefore, it is believed that 1D nano-structures will exhibit superior thermal, optical, or electrical properties as compared to their nanoparticle counterparts (Choi, Kim, Lim, & Park, 2010; Pan et al., 2012).