Photocatalytic Pavements as an Active CO2 Mitigation Tool: Quantifying the CO2 Removal Potential of TiO2-based Concrete Surface Treatments

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Abstract
The growing pollution from transportation into the environment has created an urgent need for active mitigation tools. Photocatalytic surface treatments for concrete pavements, such as TiO 2 -based surface treatments, offer a promising solution by continuously reducing pollutants using solar energy. While previous research has shown that TiO 2 surface treatments on concrete can reduce CO 2 concentrations through photoreduction, quantifying the CO 2 reduction remains necessary to understand their full potential under realistic conditions. This study presents a novel estimation model trained on experimental data from concrete slabs exposed to different light intensities (0, 23, and 100 W/m 2 ) and CO 2 concentrations (6%, 12%, and 100%) to estimate CO 2 reduction (CDR). Results showed that both higher CO 2 concentrations and higher light irradiance levels led to greater CDR, with maximum reductions of 0.2 g/m 2 per hour under 6% CO 2, 1.6 g/m 2 per hour under 12% CO 2 , and 79.2 g/m 2 per hour under 100% CO 2 , at 100 W/m 2 irradiance. Two models were developed: a linear model, assuming CDR increases linearly with light irradiance, and a conservative model, with CDR plateauing at 100 W/m 2 . Using real sunlight irradiance and traffic data, the model estimates an annual reduction of 5.8–6.8 kg/m 2 with the conservative model, while up to 25.8 kg/m 2 with the linear model. Scaling it to 100 km of road, the TiO 2 surface treatment could remove up to 4.1 M kg of CO 2 annually in cities like Phoenix and 3.7 M kg in Seattle, demonstrating the potential of this technology for large-scale carbon removal.

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