Interface engineering of MnO/CoO S-scheme heterojunctions to enhance the photothermal catalytic degradation of toluene.

Transition metal oxides have high photothermal conversion capacity and excellent thermal catalytic activity, and their photothermal catalytic ability can be further improved by reasonably inducing the photoelectric effect of semiconductors. Herein, MnO/CoO composites with S-scheme heterojunctions were fabricated for photothermal catalytic degradation of toluene under ultraviolet-visible (UV-Vis) light irradiation. The distinct hetero-interface of MnO/CoO effectively increases the specific surface area and promotes the formation of oxygen vacancies, thus facilitating the generation of reactive oxygen species and migration of surface lattice oxygen. Theoretical calculations and photoelectrochemical characterization demonstrate the existence of a built-in electric field and energy band bending at the interface of MnO/CoO, which optimizes the photogenerated carriers' transfer path and retains a higher redox potential. Under UV-Vis light irradiation, the rapid transfer of electrons between interfaces promotes the generation of more reactive radicals, and the MnO/CoO shows a substantial improvement in the removal efficiency of toluene (74.7%) compared to single metal oxides (53.3% and 47.5%). Moreover, the possible photothermal catalytic reaction pathways of toluene over MnO/CoO were also investigated by in situ DRIFTS. The present work offers valuable guidance toward the design and fabrication of efficient narrow-band semiconductor heterojunction photothermal catalysts and provides deeper insights into the mechanism of photothermal catalytic degradation of toluene.