Evaluation of N-doped graphene role in the visible-light driven photodegradation of sulfamethoxazole by a TiO2-silver-graphene composite

[Display omitted] •SMX was effectively photodegraded by TiO2Ag-NGr under visible light irradiation.•VB XPS data prove the decreased band gap observed for TiO2Ag-NGr sample.•XPS analysis provided the chemical species at the composites surface.•Efficient charge separation was facilitated by the presence on nitrogen-doped graphene in the composite.•The SMX was mainly degraded by the photogenerated holes h+. The present work reports on the evaluation of nitrogen-doped graphene role in the efficient degradation of sulfamethoxazole, under visible light or sunlight exposure. The catalyst is a TiO2Ag-based nanocomposite that incorporates the nitrogen-doped graphene via a two-step procedure (one hydrothermal followed by a thermal treatment). The presence of nitrogen-doped graphene in the composite led to a very good extension of the photocatalytic activity of TiO2Ag towards the visible range through narrowing the bandgap of TiO2Ag-NGr to 2.5 eV compared to 3.07 eV the TiO2Ag material. This led to an almost 100% photodegradation efficiency when exposed to direct sunlight, within one hour. The corroboration of the X-ray photoelectronic spectroscopic data (XPS) with the experimental results of the involved reactive species provide the proposed mechanism of the photodegradation process, together with the elucidation of the graphene role in the composite.