Surface-Confined Photodeposition of Noble Metal Nanoclusters on TiO₂ in a Fluidized Bed for the Catalytic Oxidation of Formaldehyde

Noble metal nanoclusters/oxides have been attracting close attention in heterogeneous catalysis due to their unique physical and chemical properties. However, due to the effect of the Schottky heterojunction, the deposited particles are easy to aggregate, and the size is difficult to control. In this work, we report a surface-confined photodeposition process to load ultrafine noble nanoclusters on semiconductor oxides, e.g., titanium oxide (TiO2), in a fluidized bed (F method). Different from the traditional photodeposition in solution (L method), the metal precursors which are absorbed on the semiconductor are difficult to migrate via the F method, therefore effectively inhibiting the agglomeration of nanoparticles. Noble metal nanoclusters with a uniform size smaller than 2 nm are obtained. In the model reaction of the catalytic oxidation of formaldehyde (HCHO), Pt/TiO2 with an ultralow loading amount (0.08 wt% Pt) showed excellent performance for the catalytic oxidation of HCHO at room temperature, which is benefited from the small and uniform size of nanoclusters. This work brings an effective strategy in the fabrication of size-controlled noble metals on oxide supports for heterogeneous catalysis.