Synthesis and characterization of a Pd/Ag bimetallic nanocatalyst on SBA-15 mesoporous silica as a plasmonic catalyst

A uniformly dispersed Pd/Ag bimetallic system supported on mesoporous silica SBA-15 was synthesized by a two-step method. Ag/SBA-15 was first synthesized by the microwave-assisted alcohol reduction method, which afforded color-controlled Ag nanoparticles (NPs) with different particle sizes and morphologies. Among them, the smaller yellowish Ag NPs exhibited the highest catalytic activity in H-2 production from ammonia borane (NH3BH3) under dark conditions, while the maximum enhancement under visible light irradiation was attained by blue Ag nanorods. Further decoration of Ag/SBA-15 with Pd NPs was achieved via localized surface plasmon resonance (LSPR)-assisted deposition under visible light irradiation. All Pd/Ag/SBA-15 catalysts showed higher catalytic activities than the inherent Ag/SBA-15 catalysts under both dark and visible-light irradiation conditions, where the Pd/Ag/SBA-15 originated from blue Ag nanorods afforded a maximum enhancement effect. The order of increasing catalytic activity was found to be in accordance with the Ag-LSPR absorption intensity. The LSPR-enhanced photocatalytic activity of the Pd/Ag/SBA-15 was also demonstrated in the Pd-driven Suzuki-Miyaura coupling reaction of aryl halides with boronic acids, where a similar trend in the enhancement of catalytic activity was observed under visible light irradiation.