A plasmonic AuPd bimetallic nanoalloy decorated over a GO/LDH hybrid nanocomposite via a green synthesis route for robust Suzuki coupling reactions: a paradigm shift towards a sustainable future

Abstract

Exploiting the advantageous science of layered architectures, herein graphene oxide (GO) and a ZnCr-layered double hydroxide (LDH) have been united together and further modified by Au–Pd noble metal nanoparticles (NPs) to design a highly efficient novel GO/LDH@AuPd hybrid photocatalyst. The synthesis of this hybrid composite was carried out via the in situ nucleation of the ZnCr LDH over the surface of GO sheets, subsequently followed by the photo-deposition of bimetallic alloyed NPs and the reduction of graphene oxide (GO) to reduced graphene oxide (RGO) under light illumination. The successful formation of a GO/LDH@AuPd hybrid material was evidenced via XRD, UV-vis spectroscopy, TEM and XPS analysis. Here XPS techniques were employed to assess the electronic contribution of LDH towards the electron density on the noble metal through the GO surface during the photoreduction process. TEM images confirmed that bimetallic NPs are well dispersed on the LDH as well as over the GO surface. Moreover, the significant quenching of the PL intensity and the smaller arc radius of EIS measurements of an active AuPd alloyed sample demonstrate effective charge separation leading to superb photocatalytic activity. Here, an energy saving and green synthesis method was adopted by utilizing (i) visible-light active Zn–Cr-LDH nanoplates, (ii) SPR-effective gold NPs, (iii) the channelling features of GO, (iv) the charge heterogeneity of the AuPd alloy and (v) the efficiency of palladium towards the C–C coupling reaction, which made the catalyst more powerful in terms of enhancing the photocatalytic Suzuki coupling reaction compared to various chemical agents at high temperatures. The existence of Au enhances the abilities of Pd synergistically together with GO/LDH in the presence of visible light, boosting Suzuki coupling reactions. The Suzuki coupling product yield, i.e., biphenyl, is around 99.5% over the GO/LDH@AuPd composite, which is about 1.9 times higher than a single metal loaded GO/LDH composite. The enhanced catalytic activity resulted from the electron transfer pathways of LDH → Au → Pd and LDH → RGO → Au → Pd in the hybrid nanoarchitecture. We believe that this novel approach can lead to stable heterogeneous photocatalysts for other reactions with high activities.