NEW DELHI: In a significant step toward addressing Delhi’s chronic air quality crisis, the Delhi government has signed a Memorandum of Understanding (MoU) with the Indian Institute of Technology Madras (IIT Madras) to test innovative photocatalytic “smog-eating” surfaces.
The six-month pilot study, formalised on March 13, 2026, aims to evaluate whether titanium dioxide (TiO₂)-based coatings can passively break down harmful pollutants like nitrogen dioxide (NO₂) and volatile organic compounds (VOCs) directly on urban infrastructure such as roads, buildings, and pavements.
The project, fully funded by the Delhi government, is led by Professor Somnath C Roy from the Department of Physics at IIT Madras. It marks a shift from temporary pollution-control tactics to science-driven, infrastructure-embedded solutions that require no additional energy or behavioural changes from residents.
What Are Smog-Eating Surfaces and How Do They Work?
At the heart of the initiative is photocatalysis using TiO₂, a stable, commercially available, and inexpensive material often compared to sand in its chemical stability. When exposed to sunlight (specifically ultraviolet rays), TiO₂ generates electrons on its surface that produce highly reactive oxygen species, such as hydroxyl radicals and superoxide radicals. These radicals oxidise and break down pollutants like NO₂ and VOCs, major contributors to Delhi’s smog into harmless by-products such as nitrates, water, and simpler compounds like nitrogen and oxygen.
Professor Roy explained the process in detail: “When sunlight hits TiO₂, it generates electrons which come up on the surface. These electrons react with pollutants like NO₂ and break them down into simpler [substances], such as nitrogen and oxygen.” He added that “Sunlight alone cannot break these molecules,” underscoring the catalytic role of the material. The technology operates as a “continuous background process” and “will not replace other pollution-control measures. It will work alongside them.”
Applications under testing include mixing TiO₂ into concrete and asphalt, applying it as surface coatings on roads, buildings, glass panels, and metal structures, or mounting dedicated photocatalytic panels on rooftops and street-light poles—similar to solar panels but focused on air purification. Laboratory tests will first simulate Delhi’s real-world conditions in a specialised smog chamber using actual traffic and pollution data, before moving to field trials.
Delhi’s Air Pollution Crisis: Why This Matters Now
Delhi continues to grapple with severe air pollution, recording zero “good” air quality days throughout 2025 according to AQI.in data. Vehicular emissions remain a primary source of NO₂, pushing the city’s Air Quality Index into unhealthy, severe, or hazardous categories for extended periods. Traditional episodic measures have offered only short-term relief, prompting the government to explore long-term, scalable innovations embedded in everyday urban infrastructure.
Environment Minister Manjinder Singh Sirsa highlighted the urgency: “Through this study, we aim to find the best, long-lasting, and affordable ways to put ‘smog-eating’ coatings on roads, buildings, and city surfaces. It can work in our favour if the study can provide evidence-based findings that such coatings or materials can cut NO₂ & other pollutants.” He further stressed, “It is essential to find innovative scientific solutions for cleaning Delhi’s air,” noting the city’s growing population and rapid urbanisation. Under Chief Minister Rekha Gupta’s leadership, the focus remains on achieving cleaner air “without blanket bans.”
Previous Government Efforts to Curb Pollution
Over the years, the Delhi government and the Commission for Air Quality Management (CAQM) have deployed a range of measures under the Graded Response Action Plan (GRAP), which escalates restrictions based on AQI levels. These have included odd-even vehicle rationing schemes during severe pollution episodes, bans on firecrackers and construction activities, deployment of anti-smog guns and water sprinklers for dust suppression, stricter enforcement of vehicle emission norms, promotion of electric mobility, and mechanical road cleaning. While these interventions have provided temporary relief, particularly during winter smog peaks they have not delivered sustained improvements, as evidenced by the absence of “good” air days in 2025.
Professor Roy emphasised that the new technology is complementary: it will function continuously alongside existing controls, with considerations for real-world challenges such as dust accumulation (requiring periodic cleaning, perhaps monthly) and varying sunlight exposure.
What Comes Next: Pilot Outcomes and Scalability
The study will assess not only pollutant reduction efficiency but also practical factors like cost-effectiveness, durability, optimal TiO₂ concentration, and integration methods. Field trial locations in Delhi are yet to be finalised and will depend on laboratory results. Professor Roy noted: “Based on our preliminary results, we will make recommendations, and the Delhi government will decide in which areas exactly the pilot will be conducted.” If successful, deployment could be scaled to high-traffic zones, particularly during peak smog months later in 2026.
This collaboration represents a proactive, evidence-based approach to urban air purification. As Delhi seeks sustainable solutions beyond episodic restrictions, the success of these smog-eating surfaces could offer a blueprint for other polluted cities across India and beyond transforming ordinary infrastructure into silent guardians of public health.
Global Context and Precedents
Photocatalytic TiO₂-based “smog-eating” surfaces are not entirely new and have been tested and deployed in several countries with varying degrees of success. In Europe, pilot projects on roads and pavements in Italy (Bergamo), France (Paris), Belgium (Antwerp), and the Netherlands have demonstrated measurable reductions in NOx levels, with some studies reporting decreases in ambient air pollution near treated surfaces.
Iconic buildings such as Rome’s Jubilee Church (Dives in Misericordia) feature TiO₂ coatings that effectively decompose NOx and VOCs while maintaining the structure’s appearance and preventing dirt accumulation. In Mexico City, the Torre de Especialidades hospital is covered with photocatalytic tiles on its façade; long-term field tests confirmed significant reductions in surrounding pollution levels.
Japan has led commercial adoption since the 1990s, incorporating photocatalytic materials in construction projects for self-cleaning and air-purifying surfaces, including applications in urban areas like Tokyo. Other trials in the United States (e.g., Chicago and Orlando) and Milan’s Palazzo Italia have also explored the technology.
While real-world results can vary depending on factors such as sunlight exposure, surface area, dust accumulation, and traffic patterns, these international experiences provide valuable data on durability, maintenance needs, and integration methods, insights that the Delhi-IIT Madras pilot can build upon to tailor the solution for local conditions.
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