Precisely Controlled Bimetallic Nanocatalysts on Mesoporous Silica Nanoparticle Supports for Highly Efficient and Selective Nitrate Reduction

Abstract

Monodisperse bimetallic nanocatalysts homogeneously supported on mesoporous silica nanoparticles are demonstrated as highly active reducing catalysts for controlled nitrate transformation. For this, we finely controlled catalyst size, and composition based on new synthetic conditions. Specifically, atomic clusters of Mreducing/Cu nanocatalysts (Mreducing = Pd, Pt) were further grown by additional Mreducing impregnation (Mreducing/Cu/Mreducing type). Reaction kinetics were observed to be affected by the ratio of Mreducing to Cu, for which Pd−rich Pd/Cu/Pd nanocatalysts showed better performance than Cu−rich analogs. Product selectivity (ammonium vs. nitrogen) was highly correlated with the morphology of nanocatalysts, where nitrogen gas (dominant) selectivity was observed with an increase in Pd particle size. Lastly, MSN−Pd/Cu/Pd catalyst are highly stable with no catalyst deterioration over the multiple reactions (10 times) with the consistent high reaction rates and N2 selectivity. Overall, this research furthers our understanding of catalytic nitrate reduction as a function of precisely controlled nanocatalyst(s) size and composition.