Green fabrication of hierarchically-structured Pt/bio-CeO2 nanocatalysts using natural pollen templates for low-temperature CO oxidation

Herein, natural rape pollen was utilized as biotemplates to synthesize hierarchically structured bio-CeO2 and the supported M/bio-CeO2 nanocatalysts (M = Pt, Pd, Au, and Ag). Under the optimal synthetic conditions, the resultant bio-CeO2 could fully maintain the hierarchically porous morphology of the rape pollen template, with a high specific BET surface area of 71 m2 g−1, much higher than the commercial CeO2 (7.7 m2 g−1). Among the different supported M/bio-CeO2 catalysts, the Pt/bio-CeO2 exhibited the best CO oxidation performance with good oxidative catalytic activity and stable performance in five consecutive recycling experiments. In-situ DRIFTS demonstrated that the linearly adsorbed CO-Pt0 was more stable than CO-Ptσ+ (especially at high temperature), and the Pt0 site (51% in the total amount of Pt) was more active than the Ptσ+ site (49%) for CO oxidation. Furthermore, the DFT calculations suggested the varied CO oxidation mechanisms over the supported nanocatalysts which are depending on the loaded metals associated with both geometric and electronic perspectives.