Unveiling the role of defects in optimizing photocatalytic CaTiO3 nanoparticles

Abstract

The photocatalytic activity of defect-induced Calcium Titanate (CaTiO₃) particles, synthesized via the hydrothermal method without any template or surfactant, has been examined. Defect engineering was attained by changing the annealing temperature from 100°C to 800 °C. Various characterization techniques were employed to analyze their structural, morphological, and optical properties. X-ray diffraction analysis by Rietveld Refinement documented that all the CaTiO₃ particles have an orthorhombic Pbnm crystal structure. The photocatalytic activity was estimated by inspecting the photodegradation of Rhodamine B (RhB) under UV light, which revealed that the process tracks pseudo-first-order kinetics. Photo degradation mechanism was further confirmed via High Performance Liquid Chromatography (HPLC) and Total Organic Carbon (TOC) measurements. Our findings demonstrated that CaTiO₃ particles annealed at a low-temperature range, particularly at 100 °C, exhibit high photocatalytic efficiency and hydroxyl radicals and holes are identified as the active species in this sample. This enhanced performance is correlated to the presence of defects within the samples. Transmission Electron Microscopy and X-ray Photoelectron Spectroscopy exposed surface-disordered features in samples annealed at lower temperatures. The O1 s spectra from XPS analysis exhibited peaks corresponding to oxygen vacancy-related defect sites at 531.3 eV with the relative intensity of these peaks diminished with thermal treatment. Additionally, Raman spectroscopy detected disordered crystal characteristics in these samples. This work offers new insights into the photocatalytic performance of bare CaTiO₃ particles. It lays the foundation for developing cost-effective synthesis and annealing processes for photocatalytically active materials.