We introduce a simple and scalable preparation method for colloidal precious metal nanoparticles (NPs) that overcomes the typical restrictions in catalyst synthesis, i.e. the independent control of individual parameters such as size, size-distribution, and particle density (metal loading). Our Co4Cat (Colloids for Catalysts) synthesis concept uses alkaline low-boiling point solvents without the use of additional surfactants. It can be applied to different mono- and multimetallic precious metal NPs as well as different support types. In the presented work, the Co4Cat concept is used to prepare Ir based NPs that are tested as oxygen evolution reaction (OER) catalysts for water electrolysis under acidic conditions. In electrochemical half-cell tests, it is shown that due to the very high surface area, exceptional mass activities can be achieved.

The Co4Cat concept is an advancement of our “toolbox” synthesis approach that was previously applied to Pt based PEM fuel cell catalysts. In the presentation, the general idea as well as the individual synthesis steps are discussed in detail and the electrochemical testing is benchmarked against literature values as well as commercially available OER catalysts.