Green synthesis of AgI nanoparticle-functionalized reduced graphene oxide aerogels with enhanced catalytic performance and facile recycling

AgI nanoparticle-functionalized self-assembled reduced graphene oxide aerogels are constructed using vitamin C as the reducing agent. The obtained aerogels can be used as efficient catalysts for organic dye degradation, reduction of 4-nitrophenol, and synthesis of bis(indolyl)methane. A set of characterizations, including FESEM, TEM, XRD, XPS, Raman, FTIR, optical absorption, and photoluminescence techniques, confirm that the aerogel is formed from ultra-dispersed AgI nanocrystals and the self-assembly of reduced graphene oxide nanosheets into porous hydrogel structures. The obtained aerogels exhibit high photocatalytic degradation ability toward an organic dye (rhodamine-B) because of the high visible light-driven catalytic activity of AgI and the high specific surface area of graphene nanosheets with three-dimensional interconnected pores. The well-wrapped reduced graphene oxide nanosheets on AgI nanostructures could promote the transfer of photo-generated electrons, which not only effectively inhibits the recombination of electrons and holes but also suppresses the photocorrosion of AgI; this promotes the photocatalytic activity and stability. Moreover, these nanostructures show the best catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol in the presence of NaBH₄ as a reducing agent. Furthermore, the AgI-reduced graphene oxide aerogel nanocomposites are active catalysts for the synthesis of bis(indolyl)methane under solvent-free conditions. The nanocomposites exhibit excellent catalytic activity and remarkable durability. This study brings a novel approach to the development of multi-responsive reduced graphene oxide aerogels via the co-assembly of various semiconductor nanocomponents for a variety of applications that involve sustained catalytic activity.