S-scheme heterojunction CeO2/TiO2 modified by reduced graphene oxide (rGO) as charge transfer route for integrated photothermal catalytic oxidation of Hg0

Abstract

This study explored the photothermal catalytic oxidation of Hg0 by using S-scheme heterojunction CeO2/TiO2 modified by reduced graphene oxide (rGO) at 100-200 °C. The surface properties of self-prepared photothermal catalysts were characterized by BET, SEM, TEM, EDS, XRD, Raman, UV–Vis, XPS, EPR, and UPS. The crystal structure of TiO2 was mainly anatase and the nano-sized CeO2/TiO2 was uniformly distributed on the surface of the rGO sheet. The oxidation efficiency of Hg0 decreased with reaction temperature in the order of Ƞ100 °C = Ƞ150 °C > Ƞ200 °C, implying that the oxidation of Hg0 was controlled by mass transfer governed by adsorption instead of photothermal catalytic reaction. Both photo- and thermos-catalytic reaction mechanisms were involved in the oxidation of Hg0 at 100–200 °C. Moreover, rGO-modified CeO2/TiO2 could tolerate multi-pollutants (SO2 and NO) except for 100 ppm NO, which slightly reduced the oxidation efficiency of Hg0.