Unravelling platinum nanoclusters as active sites to lower the catalyst loading for formaldehyde oxidation

Abstract

Minimizing the use of precious metal remains a challenge in heterogeneous catalysis, such as platinum-based catalysts for formaldehyde oxidation. Here we report the catalyst system Pt/TiO2 with low platinum loading of 0.08 wt%, orders of magnitude lower than conventional catalysts. A volcano-like relationship is identified between reaction rates of formaldehyde and platinum sizes in a scale of single-atoms, nanoclusters and nanoparticles, respectively. Various characterization techniques demonstrate that platinum nanoclusters facilitate more activation of O2 and easier adsorption of HCHO as formates. The activated O facilitates the decomposition of formates to CO2 via a lower reaction barrier. Consequently, this size platinum with such low loading realizes complete elimination of formaldehyde at ambient conditions, outperforming single-atoms and nanoparticles. Moreover, the platinum nanoclusters exhibit a good versatility regardless of supporting on “active” FeOx or “inert” Al2O3 for formaldehyde removal. The identification of the most active species has broad implications to design cost-effective metal catalysts with relatively lower loadings.