TiO2 Concrete Coatings for NOx Reduction

ISEF Category: Environmental Engineering

Subcategory: Pollution Control  ·  Difficulty: Intermediate  ·  Setup: Home Setup  ·  Time: 1 to 2 Months

The Hook

Air pollution does not only come from tailpipes and smokestacks. Some building surfaces can help clean the air too. That means a concrete tile can act a bit like a passive air filter if the coating is designed well. You can test that idea with simple sensors and a light source.

What Is It?

Photocatalysis sounds fancy, but the idea is simple. A photocatalyst is a material that uses light to speed up a chemical reaction without being used up itself. In this project, titanium dioxide, or TiO2, does the work. Under UV light, TiO2 can help break down nitrogen oxides, which are a group of air pollutants often called NOx.

Think of the coating like a tiny cleanup crew on a wall or sidewalk. The TiO2 particles sit in the paint binder on the tile surface. When light hits them, they help turn NOx into less harmful compounds. Your job is to test whether different coating recipes, surface coverage, or light conditions change how much NO2 drops inside a sealed chamber.

This topic sits at the border of chemistry, materials, and pollution control. You are not just asking whether the coating works. You are asking how well it works, under what conditions, and which design gives the best result.

Why This Is a Good Topic

This makes a strong science fair topic because you can measure a clear before-and-after signal, change one variable at a time, and compare real coating designs. It connects to a real problem, since NOx pollution affects air quality near roads and buildings. You can learn about photocatalysis, sensor calibration, controls, and experimental design without needing a professional lab.

Research Questions

• How does TiO2 loading in a paint binder affect the rate of NO2 drop in a sealed chamber under UV light?
• What is the effect of UV intensity on the NO2 reduction rate of a TiO2-coated tile?
• Does the type of binder change how well a TiO2 coating reduces NOx?
• To what extent does coating thickness change the amount of NO2 removed from the chamber air?
• Which surface texture, smooth or rough concrete, leads to faster NOx reduction?
• How does repeated light exposure change the performance of the same coated tile over multiple trials?

Basic Materials

• Concrete tiles or ceramic tiles with similar surface area.
• Sunscreen-grade TiO2 powder.
• Household paint binder or clear acrylic medium.
• Small disposable cups or weighing boats for mixing.
• Digital kitchen scale with 0.1 g accuracy.
• Cheap NO2 sensor or air quality sensor with NO2 readout.
• UV lamp or UVA light source.
• Airtight clear plastic container or sealed chamber.
• Small fan for air mixing inside the chamber.
• Painter's tape or labels for sample coding.
• Smartphone camera for documentation.
• Nitrile gloves, dust mask, and safety glasses.

Advanced Materials

• Analytical balance.
• UVA radiometer or UV light meter.
• Laboratory-grade NO2 sensor or electrochemical gas sensor.
• Data logger for continuous sensor output.
• UV-transparent chamber materials.
• Surface profilometer or microscopy access for coating texture checks.
• X-ray diffraction access for confirming TiO2 phase.
• Scanning electron microscopy access for coating morphology.
• Controlled humidity chamber.
• Computer with statistics software for sensor and trial analysis.

Software & Tools

• Google Sheets: Organizes trial data, makes graphs, and tracks sensor changes over time.
• ImageJ: Measures coating coverage, surface uniformity, and photo documentation quality.
• Python: Cleans sensor data, compares trials, and runs statistical tests.
• NIH ImageJ plugins: Helps extract repeatable measurements from images of coated samples.
• R: Fits models, compares conditions, and checks whether differences are statistically meaningful.

Experiment Steps

1. Define the one performance metric you will track, such as percent NO2 drop or decay rate in the chamber.
2. Choose one coating variable to change first, such as TiO2 amount, binder type, or surface texture.
3. Design a control set that separates light effects, sensor drift, and natural gas loss from real photocatalysis.
4. Plan a chamber layout that keeps air mixing, sample placement, and sensor position consistent across trials.
5. Build a calibration plan that turns sensor output into a comparable numerical signal.
6. Decide how you will repeat trials, summarize variation, and test whether any coating beats the control.

Common Pitfalls

• Using a sensor that drifts with humidity or temperature, which can look like NO2 removal when none happened.
• Letting the chamber leak, which lowers gas levels and hides the coating effect.
• Comparing coatings with different surface coverage, which makes the binder or texture look more important than the TiO2.
• Skipping a dark control, which leaves you unable to tell whether light caused the change.
• Mixing the chamber air poorly, which creates local concentration pockets and noisy sensor data.

What Makes This Competitive

A competitive version goes beyond a simple yes or no test. You compare multiple coating formulas, include strong controls, and show that your sensor data is calibrated and repeatable. You also get stronger if you test a real design question, like whether binder chemistry, surface roughness, or UV dose changes performance. Careful statistics and a clear explanation of limitations make the project feel like real environmental engineering.

Project Variations

• Test TiO2 coatings on brick, ceramic, and concrete to see how surface porosity changes NOx removal.
• Compare TiO2 mixed into paint versus TiO2 brushed on as a top layer to see which coating form lasts longer.
• Add humidity or airflow as a second factor to study how real outdoor conditions change photocatalytic performance.

Learn More

• PubMed: Search for review articles on TiO2 photocatalysis, NOx removal, and building surface pollution control.
• NOAA Air Resources Laboratory: Look for background on nitrogen oxides, atmospheric chemistry, and air quality basics.
• NASA Earth Observatory: Read accessible articles on air pollution sources and atmospheric chemistry.
• USGS Water and air quality resources: Use background pages on environmental monitoring and contaminant behavior.
• MIT OpenCourseWare: Search for environmental engineering, chemistry, or materials science lecture notes that explain photocatalysis and surface reactions.
• Journal of Photochemistry and Photobiology: Search the journal for papers on TiO2, photocatalysis, and environmental cleanup.