Porous Au-rich Nanoparticles for Catalytic Applications

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Dealloying of multi-metallic nanoparticles (NPs) has emerged as promising synthetic route to prepare highly active and durable catalysts for heterogeneous and electrochemical reactions like methanol oxidation reaction and oxygen reduction reaction. In particular, porous NPs show high surface area-to-volume ratios and enable to tune its pore confinement and surface curvature which might result in an improvement of the reaction kinetics. The particle diameter and chemical composition of the pristine nano-alloys as well as the dealloying conditions (electrolyte, potential, temperature, etc.) play a very critical role in the design of nanoporous noble metal-rich NPs with advanced functionality. Small bimetallic NPs form core-shell structures during the dealloying process, while for macroscopic alloyed films sponge-like pore structure is produced. The fundamental questions arise what the critical particle size for the formation of nanoporous NPs is and which dealloying parameters controll the lattice strain and chemical distribution inside the nanoporous NPs. In addition, it is not clear to date why the dissolution potential is shifted to higher values by decreasing particle size compared to flat alloyed surfaces. All these fundamental questions will be investigated within the research unit. Our goal is to design dealloyed Au-rich NPs with controlled particle size, pore size and content of less noble metal prepared by dealloying of Ag/Cu from Ag-Au and Cu-Au nano-alloys. We will elucidate the formation mechanism of the porous Au-rich NPs as the function of the particle size and chemical composition of the pristine alloy NPs and will analyze the strain and the chemical distribution of Au and Ag/Cu atoms inside the dealloyed Au-based NPs by applying different (electro)chemical dealloying conditions. Here, the proposed comprehensive study of dealloyed Au-rich NPs will make an important contribution to promote oxidation catalysts for small organic molecules and hopefully boost their application.