Enhanced Visible-Light Photocatalysis Using TiO₂/C₃N₄ Composites for Indoor Air Quality Improvement

As people spend around 70–90% of their time indoors, poor indoor air quality represents a major health concern, mainly due to the emission of volatile organic compounds (VOCs) from multiple sources. Conventional air purification technologies primarily remove particulate matter, whereas photocatalysis degrades pollutants into harmless products. Titanium dioxide (TiO₂) nanoparticles are widely employed as photocatalysts due to their stability, low cost, and non-toxicity. However, their application is limited by UV-light activation and high electron–hole recombination rates. To overcome these limitations, TiO₂–C₃N₄ composites were developed to extend light absorption into the visible region and improve charge separation.

TiO₂–C₃N₄ composites with different mass ratios were synthesized using a simple ball-milling method. The materials were characterized by N₂ physisorption, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Photocatalytic activity was first evaluated under visible light in aqueous medium using a standard organic dye. The most efficient composite was subsequently immobilized and tested in a gas-phase photocatalytic system.

The TiO₂/C₃N₄ composites exhibited low specific surface area and a higher anatase-to-rutile ratio, thereby enhancing photocatalytic performance. The composite containing 0.9 g TiO₂ and 0.1 g C₃N₄ exhibited the highest activity under visible light in liquid medium, achieving 70% degradation. Importantly, this material maintained high photocatalytic efficiency after immobilization and under gaseous conditions, demonstrating its potential for indoor air purification. These results highlight TiO₂–C₃N₄ composites as a promising and cost-effective solution for improving indoor air quality under visible light.