When benzene was used as model gas,

When benzene was used as model gas, its concentration exiting through the outlet was measured using a VOC-72 M gas analyser (Environment SA, FR), that is based on gas chromatography and photoionisation detector. The inlet gas mixture (prepared mixing gas cylinders containing synthetic air and benzene) was allowed to flow into the chamber until it stabilised at a concentration of ~ 260 μg.m−3(~80 ppb). This concentration was chosen because the World Health Organisation recommends an exposure to total VOCs < 300 μg.m−3during 8 h/day [53]. The mixture of air with that concentration of benzene was guaranteed using two mass flow controllers with a flow rate of 150 mL.min−1. The photocatalytic experiments were assessed by placing the photocatalyst inside the reactor and covering the glass window. Once the desired NOx/benzene concentration was reached and it attained a stable level into the reactor, the window glass was uncovered, the lamp turned on, and the photocatalytic reaction started.Photocatalytic activity for de-NOx abatement and benzene removal was reported as formal quantum efficiency (FQE) [54], defined as the number of molecules degraded per incident photon.