Synergic effect of metal and graphene oxide loading on metal titanates for enhanced photocatalytic activity

Abstract

The work done in this thesis focuses on the fabrication of visible light-active photocatalysts (ATiO3 = Ca, Ba, and Sr) based on perovskite oxides metal titanates via the combined effect of metal (plasmonic/transition) and graphene oxide (carbonaceous material). The structural, morphological, chemical composition, optical, and textural properties of the as-fabricated composites were thoroughly examined using a variety of characterization techniques and their efficacy was investigated by conducting the photodegradation studies for several toxic pharmaceutical contaminants, textile dyes and H2 evolution reactions under UV and LED-light exposures. All the developed composites, including Ag/Cu-CaTiO3, Ag-BaTiO3/GO, Fe(III)-SrTiO3-GO, and Cu-CaTiO3-GO, demonstrated superior photocatalytic efficiency than their individual counterparts (pure titanates and their binary composites). The improvement in photocatalytic capabilities attributes to the following merits: (i) suitable morphologies, (ii) increased specific surface areas due to GO and metals (Ag, Cu, Fe), creating more photocatalytic active sites. (iii) enhanced photoexcited charge carrier transit and separation across metal (M), ATiO3, and GO interface contacts, and (iv) a narrower band gap, and expansion in photo-absorption range due to surface-deposited metals. Research on the photocatalysts' reusability were carried out. Recyclability tests revealed that these photocatalysts were stable and reusable, with excellent performance even after numerous cycles of recycling. The key active species involved in the degradation process were affirmed by the scavenger studies. Additionally, the photocatalytic degradation routes were determined using LC-MS analysis, revealing that the ternary hybrids are capable of degrading pollutant molecules into smaller, less hazardous compounds. Finally, based on the outcomes of the LC-MS, band energy calculations and scavenger experiments, the probable photocatalytic mechanism behind the improved photocatalytic activity of the synthesized composites was mapped out. Overall, the current study not only provides an efficient strategy for promoting (ATiO3) the metal titanates photocatalytic activity but also demonstrates the applicability of these as-synthesized photocatalysts in both energy-saving and environmental remediation applications.