Smog-eating Photocatalytic Coating | 23 Mar 2026

Source: IE

In a step towards tackling Delhi’s worsening air pollution, the Delhi government has partnered with IIT Madras to test “smog-eating” photocatalytic coatings on urban surfaces to neutralize severe urban air pollutants across the city's infrastructure. 

• Smog-eating Photocatalytic Coatings: The project focuses on deploying photocatalytic coatings powered by Titanium dioxide (TiO₂), a stable, relatively inexpensive, and commercially available material. 
  • When exposed to sunlight, TiO₂ acts as a catalyst, generating surface electrons that react with and dismantle critical air pollutants like Nitrogen dioxide (NO₂) and Volatile Organic Compounds (VOCs).  
  • Applied on surfaces like roads, buildings, and pavements, these coatings work continuously as a passive air-cleaning system.  
• Impact on Secondary Pollutants: While this technology does not directly filter existing primary particulate matter (like PM2.5/PM10), it is crucial for preventing the formation of Secondary Particulate Matter and highly toxic Ground-Level Ozone by actively destroying their chemical precursors. 
• Environmental Challenges: While they are cost-effective, stable, and scalable, the real-world efficacy of this technology faces hurdles such as reduced sunlight intensity during peak smog, shifting wind dynamics, and heavy dust accumulation, which can block sunlight and require periodic cleaning. 
  • Large-scale use of “smog-eating” coatings may lead to nitrate runoff into urban drainage systems, which can increase nutrient levels in water bodies like the Yamuna.  
    • This may trigger eutrophication (algal blooms), highlighting the need for environmental safeguards and careful implementation. 
• Comparative Analysis: Unlike centralized, energy-intensive, and largely ineffective technological interventions like Smog Towers or weather-dependent Cloud Seeding, photocatalytic coatings represent a decentralized, zero-energy, passive mitigation strategy.  
  • The technology is not a standalone solution but works as a continuous background process, complementing measures like Graded Response Action Plan (GRAP).