Given the benzene removal photocatalytic results, de-NOx tests were carried out only with the specimens thermally treated at 450 °C / 2h. Results are reported in Figure . A photocatalytic de-NOx plot is displayed in Figure . Cu-G1.0/450 confirmed to be the most active (under white-light exposure) photocatalyst, with a FQE value of 3.3×10 -3 molecules.photon -1 that is more than twice the removal rate of the commercial anatase-based photocatalyst (K7000, FQE = 1.5×10 -3 molecules.photon -1 ), Figure . Indeed, all of the synthesised photocatalysts were shown to be more active than K7000 -unmodified Ti/450, being a mixture of anatase and rutile TiO2 polymorphs has been shown to be photocatalytically active against isopropanol degradation . [Anatase and rutile, also as nanoparticles , when in form of a heterojunction are able to absorb visible light .] Those results are confirmed by the initial (first 2 min of reaction) pseudo-first order kinetic constant k'app data, reported in Figure . Cu-G1.0/450 was that having the higher initial de-NOx rate, this being equal to 6.8×10 -2 h -1 (versus 5.4×10 -2 h -1 of Cu-G0.5/450). This is more than twice as higher than the k'app rate constant of unmodified titanias (K7000 = 3.1×10 -2 h -1 ; Ti/450 = 2.9×10 -2 h -1 ). However, for a photocatalyst to be effective in NOx removal, parameters as selectivity for the formation of ionic species and conversion of NO are also important, as NO2 is more hazardous to human beings than NO . If from the one hand all of the tested photocatalysts showed to possess very good selectivity toward the formation of ionic species (values ranging from 91% in Cu-G0.5/450 to 100% in K7000, Figure ), from the other, Cu-G1.0/450 was that showing the highest NO conversion percentages amongst the whole series, 24% against 9% of K7000, Figure . Thus, TiO2 surface modification with 1mol% CuxO, and 1 wt% graphene (Cu-G1.0/450) showed promise to de-NOx properties, limiting the formation of NO2, and improving the selectivity to the reaction for N2 evolution. Furthermore, similarly to the benzene removal photocatalytic tests, Cu-G1.0/450 proved itself to be recyclable also in consecutive photocatalytic experiments, as displayed in Figure . Moreover, with the available data, we can fairly speculate that NOx abatement mainly followed the NO oxidation path by O2 •-species (formed by the photogenerated electrons in reductive reactions with oxygen from the environment) . concentration ~13%) . Methyl radical may also be detected, depending on the reaction condition, as DMPO-OCH3  spin-adduct (relative concentration: 7%). The oxygen-centred spin-adduct DMPO-OR  (relative concentration ~10%) comes from the decomposition of DMSO solvent . The intensity of the EPR signal reflected the character of photocatalyst, the highest signal was monitored for reaction systems with Ti/450, for the copper-and copper-graphene-decorated titania materials intensity was lower due to electron transfer to CuO conduction band and reduction of Cu(II).