Recycling Properties of Iridium Nanoparticles Anchored on Graphene as Catalysts in Alcohol Oxidation

In this paper, we describe the synthesis, characterization, and recycling properties of iridium nanoparticles (IrNPs) anchored on graphene (IrNPs@GNPs) as a catalyst for alcohol oxidation. The formation of this hybrid material (comprising metal nanoparticles on graphene) is achieved in a single step under mild conditions. Graphene serves not only as a support for metal nanoparticles but also plays a critical role in controlling nanoparticle growth and nucleation while enhancing stability by preventing sintering. The IrNPs exhibit a spherical morphology with a small average size distribution (2.1 nm). The IrNPs@GNPs is an efficient catalytic material in the conversion of alcohols to the corresponding carbonyls in a sustainable manner, as supported by quantitative sustainability metrics. Oxidation reactions proceed at room temperature, using water as the solvent and atmospheric oxygen as the terminal oxidant. We detail the catalytic activity, substrate scope, and reuse/recycling of this hybrid material. Furthermore, we identify the primary deactivation pathway of the catalyst and present a regeneration protocol that restores its initial activity. The reuse and recyclability of iridium nanoparticles on graphene represent a significant advancement in the sustainable application of iridium-based catalysts.