Size effects in plasmonic gold nanorod based Pd-rGO hybrid catalyst for promoting visible-light-driven Suzuki-Miyaura coupling reaction

The studies on the phenomenon of surface plasmon resonance effect by noble metal-based nanoparticles (NPs) have largely been focused on the quantitative enhancement of reaction rates and investigating the mechanistic pathway of the reaction. However, the detailed analysis of the structure-property relation of plasmonic NPs and catalytic performance along with the contribution of absorption vs scattering remains limited. This report focuses on the comparison of the catalytic performance of different aspect ratio of gold nanorods (Au NRs) coupled with Pd-rGO nanocomposite for boosting the product yield of Suzuki-Miyaura coupling reaction under visible light irradiation. The confirmation of the successful synthesis of the Pd/Au NRs@rGO catalyst was done by multiple characterization techniques such as XRD, UV–vis, TEM, XAS, XPS and ICP. Amongst the three different aspect ratios of Au NRs, the superior catalytic performance of medium-sized NRs (length: 56 nm; diameter: 18 nm) with a TON of 50 was achieved under visible light irradiation conditions. A drastic enhancement by a factor of 4.1 was shown by the medium-sized NRs when the reaction results were compared in dark reaction conditions. The obtained enhancement has been ascribed to the higher efficiency of hot electron generation by the SPR effect of Au NRs.