Polydopamine mediated modification of manganese oxide on melamine sponge for photothermocatalysis of gaseous formaldehyde.

It is an urgent need to develop environmentally friendly strategies with low energy consumption for gaseous formaldehyde (HCHO) purification. Herein, a sponge based MS/PDA/MnOx catalyst with plentiful 3D porosities was constructed. The dual-functional PDA layer not only promoted the MnOx loading (25 wt% MnOx in the composite), but also acted as a photothermal converter to absorb photo-irradiation to heat MnOx catalyst (~80 °C after 10 min irradiation). Moreover, the 3D network structure favored the mass transfer and effectively reduced the catalyst agglomeration to expose more active sites. As a result, the obtained MS/PDA/MnOx photothermocatalyst showed highly efficient performance for removal of HCHO within concentration of 40-320 ppm at room temperature under xenon light irradiation. This process followed a pseudo-second-order model, and the reaction rate of the MS/PDA/MnOx was 4.82 times of the MS/MnOx. Finally, a possible photothermocatalysis mechanism was proposed based on the intermediate examination via the in-situ DRIFTS investigation.