Open AccessSelective Removal of Photocatalytically Active Anatase TiO 2 Phase from Mixed‐Phase TiO 2 ‐ZnO Nanocomposites: Impact on Physicochemical Properties and Photocatalytic Activity
Author(s) -
Me Nambath Gayathri,
Tatiparti Sankara Sarma V.,
Mukherji Suparna
Publication year - 2020
Publication title -
energy and environmental materials
Language(s) - English
Resource type - Journals
ISSN - 2575-0356
DOI - 10.1002/eem2.12078
Subject(s) - anatase , photocatalysis , crystallinity , rutile , materials science , nanocomposite , chemical engineering , phase (matter) , nuclear chemistry , nanotechnology , chemistry , composite material , organic chemistry , catalysis , engineering
TiO 2 ‐ZnO nanocomposites were synthesized by varying Ti:Zn molar ratio from 1:0.1 (TZ‐1:0.1) to 1:1 (TZ‐1:1). With increase in Zn content, from TZ‐1:0.1 to TZ‐1:0.2, anatase transformed to rutile phase. TZ‐1:0.3, which contained a blend of phases, including rutile and anatase TiO 2 , ZnO, and zinc titanates, exhibited the narrowest bandgap (2.5 ± 0.1 eV), and showed the highest photocatalytic activity. TZ‐1:1 was predominated by zinc titanates. All the nanocomposites exhibited narrower bandgaps compared to pure TiO 2 nanoparticles, facilitating visible light activity. This study was designed to explore whether a method targeting the removal of a specific crystalline phase (anatase) influenced the properties and photocatalytic activity of the nanocomposite. Selective dissolution not only removed anatase phase, but also led to significant loss of crystallinity, widened the bandgap, and adversely affected photocatalytic performance, in nanocomposites that contained >80% anatase phase (TZ‐1:0.1 and TZ‐1:0.2). However, in nanocomposites that contained less of anatase phase (TZ‐1:0.3 and TZ‐1:1), the morphology, bandgap, crystallinity, and the extent of photocatalytic activity at the end of 240 min remained largely unaffected. Photocatalytic activity in TZ‐1:0.3 and TZ‐1:1 originated from a blend of phases comprising of less photocatalytically active phases, such as rutile TiO 2 , ZnTiO 3 , and Zn 2 TiO 4 , rather than from the anatase phase. The Ti:Zn molar ratio controlled the phases present in TiO 2 ‐ZnO nanocomposites, which, in turn, controlled the physicochemical properties and visible light activity. Thus, in nanocomposites that contained a mix of several phases, the properties and photocatalytic activity were not dependent on anatase phase.