Self-cleaning and de-pollution efficacies of photocatalytic architectural membranes

[Display omitted] •Two photocatalytic architectural membranes were exposed alongside a control sample.•Specimens exposed at three California sites with different weather & pollution levels.•Photocatalytic samples showed excellent self-cleaning performance after two years.•De-NOx efficacy depended on weather, pollution, and type of photocatalytic material.•De-NOx efficacy showed seasonal effects associated with raining/dry periods. Photocatalytic self-cleaning “cool” roofs and walls can maintain high albedos, saving building cooling energy, reducing peak power demand, and mitigating the urban heat island effect. Other environmental benefits result from their de-polluting properties. Specimens from two different photocatalytic architectural membranes and a non-photocatalytic control were exposed alongside vertically, facing west, for two years at three California sites, and retrieved quarterly for testing. Photocatalytic materials showed excellent self-cleaning performance, retaining albedos of 0.74 – 0.75. By contrast, the control material exhibited an albedo loss of up to 0.10, with appreciable soiling observed by scanning electron microscopy. De-pollution capacity was assessed by quantifying NO removal and NOx deposition rates at 60 °C. Efficacy varied with exposure location, weather conditions, and the nature of the photocatalytic material. Seasonal effects were observed, with partial inhibition during the dry season and reactivation during the rainy season.