Free-standing composite films of multiple 2D nanosheets: Synergetic photothermocatalysis/photocatalysis for efficient removal of formaldehyde under ambient condition

Abstract Thermocatalysis and photocatalysis have been widely investigated to removal of volatile organic compounds (VOCs). However, thermocatalysis needs high-temperature to activate oxygen species, therefore resulting in additional energy consumption. Meanwhile, photocatalysis suffers the rapid charge recombination and the slow surface process. Herein, we combined thermocatalysis and photocatalysis into a free-standing composite film catalyst that was prepared through a facile filtration method using two-dimensional graphene oxide (GO), manganese oxide (MnOx) and polymeric carbon nitride (CN) nanosheets as building blocks. The superior photothermal effect of GO rapidly enhanced the film temperature to ~85 °C, and then initiated the MnOx thermocatalysis. Furthermore, the increased temperature also promoted the charge diffusion and the surface reaction process of CN photocatalyst. Impressively, with the synergetic photothermocatalysis and photocatalysis, this composite film catalyst presented improved performance for catalytic oxidation of gaseous formaldehyde at ambient condition under xenon light irradiation, compared with the individual thermocatalyst and photocatalyst, as well as the photothermocatalyst. In addition, cycling experiments demonstrated the film catalyst possessed good durability. This investigation associates photothermocatalysis with photocatalysis for improving formaldehyde catalytic degradation, hopefully providing a new and efficient strategy not only for VOCs removal, but also for other catalytic applications.